This FAQ (Frequently Asked Questions) document is now maturing somewhat. The maintainer is currently William Burrow (aa126@fan.nb.ca). Please include the word "FAQ" in your message subject line. The purpose of the document is to gather the collective wisdom of the bikecurrent bicycle mailing list in one place. Bikecurrent is a mailing list all about electricity for bicycles, especially bicycle lighting.
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Portions of content and overall document Copyright 1998-2004 by William Burrow.
The most current copy of the this FAQ may be found at:
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Now featuring tags to indicate New and Updated sections.
NEW! Now there is also a collection of Reviews available excerpted from the bikecurrent list.
Also, check your local Radio Shack (Tandy in the UK) and electronics and hobby stores. Usually found listed in the Yellow Pages of your telephone directory.
The voltage from a battery or power source is the potential difference available and is measured across the power source terminals. The actual voltage may differ under a load, depending on what the source is.
The current is the amount of flow in the circuit. It is measured in line with the circuit, never across any component in the circuit.
The resistance is the amount resistance to current flow in the circuit. The relationship between voltage, current and resistance is called Ohm's Law, and often expressed as:
Volts = Amps x Resistance or V = I x R where V is volts I is current R is resistance
Power (Watts) = Amps x Voltage or P = I x V where P is power I is current V is volts
Note that power can also be expressed as volt-amps, or VA, which is more correct for AC circuits. Both Watts and VA are identical for DC circuits. Also note that one can rearrange units from Ohms Law algebraically and substitute them into the equation for power. This is generally not needed for bicycle lighting systems, as we often know the power consumed and voltage of the system.
Amp-hours = Amps x time (hours)
Q. How much current is my 10 watt light drawing on my 12V sealed lead acid battery lighting system?
A. Knowing from the battery section that a 12V sealed lead acid battery supplies about 13.6V fully charged and the equation for DC power, then we have:
V = 13.6V W = 10W Power = Amps x Volts ==> Amps = Power / Volts Amps = 10VA / 13.6V (note the V's cancel) Amps = ~0.74A About 3/4 of an amp current draw.
Q. I installed a new 10W halogen bulb in place of the 2.4W bulb in my headlight, but it does not look all that much brighter after a short while of use, what could be wrong?
A. It might be possible there is a voltage drop between the battery and the bulb. Check the connections to be sure they are clean and mate firmly. Note that the section on lights and bulbs specifically mentions that halogen lamps operate most efficiently in a narrow voltage band. By checking the voltage at the light bulb while it is on, you find 12.0V. Knowing your battery is fully charged, you check it and find it is 13.0V while the light is running. What resistance is your wiring offering to the current?
Givens:
delta V = 13.0V - 12.0V = 1.0V
V = 13.0V
W = 10W
delta V = I x R ; Ohm's Law
P = I x V ==> I = P / V ; Figure out current drawn by the system
from the power and voltage given
Substitute current drawn into Ohm's Law and rearrange for resistance:
delta V = ( P / V ) x R ==> ( delta V ) / ( P / V ) = R
==> R = ( delta V ) / ( P / V )
R = 1.0 V / ( 10 VA / 13.0V )
R = 1.0 V / ( 0.77 A )
R = 1.3 ohms
This is a rather inadequate section of wire for the purpose because of
the voltage drop between one end of the wire and the other, and should be
replaced with a heavier gauge of wire.
| Wire Gauge | % power lost | Diameter (mm) | Area (mm^2) |
|---|---|---|---|
| 14 | .2% | 1.6 | 2.0 |
| 16 | .3% | 1.27 | 1.27 |
| 18 | .5% | 1.0 | 0.79 |
| 20 | .8% | 0.80 | 0.50 |
| 22 | 1.3% | 0.64 | 0.32 |
| 24 | 2.1% | 0.51 | 0.20 |
For good performance, 18 AWG wire at 0.5% loss would be recommended. Stranded zip cord for lamps has been recommended on the list, so long as one can tell one wire from the other (usually just a ridge down one side is sufficient).
Also note that smaller wire (higher AWG numbers) may suffer from heating due to current passing through them, thus raising the resistance of the wire.
http://www.intl-light.com/handbook/
Charge capacity is measured in coulombs:
- 1 ampere [A] = 1 coulomb of electrical charge
passing a given point in a
wire or circuit per 1 second.
= 1 coulomb / 1 second
- 1 ampere = 1,000,000 microamperes [uA]
= 1,000 milliamperes [mA]
= 0.001 kiloampere [kA]
= 0.000 001 megaampere [MA]
- 1 ampere-hour [AH] = 3,600 coulombs
= 1,000,000 uAH
= 1,000 mAH
= 0.001 kAH
= 0.000 001 MAH
Work is measured in joules, it is a unit rarely used in electronics.
Power (or the rate of work) is measured in watts:
- 1 watt [W] = 1 joule of energy transferred
(or work done) per 1 second
= 1 joule / 1 second
- 1 watt = 1 ampere * 1 volt
- 1 watt = 1,000,000 microwatts [uW]
= 1,000 milliwatts [mW]
= 0.001 kilowatt [kW]
= 0.000 001 megawatt [MW]
Energy (or capacity for work) is measured in joules:
- 1 joule = 1 volt * 1 coloumb
- 1 joule = 1 watt * 1 second = ( 1 joule / 1 second ) * 1 second
- 1 watt-hour [WH] = 3,600 joules
= 1,000,000 uWH
= 1,000 mWH
= 0.001 kWH
= 0.000 001 MWH
There are other types, but this section is not complete yet.
See Yahoo! for more links related to batteries.
For information about NiMH batteries as applied to digital cameras (including many tips and links to other resources), check out the Batteries for AA-compatible digital cameras document.
Secondary cells are typically rechargeable cells, good for many use many times. They are not fully discharged typically, in order to preserve their life time. Sealed Lead Acid, and NiCad batteries are examples of secondary cells.
An amp-hour is a compound unit obtained by multiplying the current in amps drawn from the battery by the period of time (for rating purposes, usually 20 hours) until the battery must be recharged (in the case of rechargeable batteries).
Nomenclature: Note that the amp-hour rating from a battery is often referred to by the single letter: C.
Example: A 4.0 Ah SLA battery has C=4.0. Fractional quantities are often referred to when speaking of current drain on a battery, so that for a battery with C=4.0 Ah, a C/10 current drain would refer to a current drain of 0.4 A (amps).
See also section 3.26 for the capacity of a battery pack made of multiple cells.
Folks on this mailing list from time to time post questions of the form:
I have a 20 watt lamp, and I'm powering it from a 12 volt 4 amp hour sealed lead acid battery. I calculate that it should run for 4Ah/1.7A = 2.3 hours. But when I find I only get 1.5 hours of run time. What's wrong with my battery?
The answer to questions like this is that the actual capacity of a lead acid battery DRASTICALLY decreases as you start putting high loads on it. The rated capacity is measured at a load of C/20. That is, measured by drawing a current in amps equal to one twentieth of the amp hour number of the battery. When you start drawing high loads, the total capacity you can get out of the battery drops.
One fellow in Grizzly Peak Cyclists used a 6.5 amp hour sealed lead acid battery to power a 50 watt lamp. His bulb drew 50VA/12V = 4.2 amps, meaning he was putting a load on the battery of about .6C (where C = 6.5 amp-hours). At this load, the ACTUAL expected amp hour capacity of a "6.5 amp-hour" capacity battery is more like 4 amp-hours. Thus, he could expect his battery to power that lamp for just UNDER one hour (4Ah/4.2A = ~0.95 hr or so).
Current Capacity Amps Usable
(Amps) (Hours) Amp-hrs
------- ------- ---- -------
C/20 20 hr 0.05 1.0
C/10 9 hr 0.10 0.90
C/5 4 hr 0.20 0.80
C/2 1.3 hr 0.50 0.65
1C 33 min 1.0 0.56
2C 12 min 2.0 0.40
Multiply values in the last two columns by however many amp hours your battery actually is to get the numbers for your lead acid battery.
By examining this table, you can see that if you drain a sealed lead acid battery at a rate of C/2, you will get out of it only 65% of the rated amp hours. If you drain the battery at a rate of 2C, you'll only get 40% of the official rated amp hours out of it.
This is excerpted from a table in a brochure put out by Power Sonic, a maker of sealed lead acid batteries, and of sealed lead acid battery chargers.
Note that Power Sonic has a nice graph depicting how load affects a battery (in straight lines on log graph "paper"!)
Hawker Energy (Gates) Cyclon cells
These cells have significantly better performance than ordinary sealed lead acid batteries (SLA's). They come in single 2 volt cells, in D size rated at 2.5 amp hours, and X size (somewhat larger than D size, but shaped like a D size cell) rated at 5.0 amp hours. The 5.0 amp hour cells can be had, Glenn tells me, for $8.00 each. Meaning a 6 volt 5 AH Cyclon battery pack will cost you $24.00 in batteries to make up (the batteries have tabs you can solder to make the three cell pack).
The following table shows the degree of "degradation" of available amp hour capacity as Hawker Cyclon cells (a 5.0 amp hour one in this case) is drained at higher and higher current levels.
At the extreme right in this table I show for comparison (for some of the table entries) the % degradation of amp hour capacity at that fraction of C current drain for an ordinary technology SLA battery.
Amps
fract disch AH % of Comparision to ordinary Relative
C rate Capacity rated (PowerSonic) SLA battery performance
---- ----- ------ ------- ------------------------ -----------
.1 0.5 5.0 100 (90% for ordinary SLA) 110%
.2 1.0 4.8 96 (80% for ordinary SLA) 120%
.42 2.1 4.3 86
.78 3.9 3.9 78
1.00 5.0 3.75 75 (56% for ordinary SLA) 134%
1.40 7.0 3.5 70
2.00 10.0 3.3 66 (40% for ordinary SLA) 165%
According to Varta's NiMH data, one gets the following discharge capacity vs current:
Current %Capacity
------- ---------
0.2C 100%
0.5C 95%
1C 93%
2C 88%
Also, see Duracell's performance data sheets at:
(Disclaimer: neither Duracell nor Varta batteries are endorsed by the FAQ holder)
I finally figured out how to get an Ah rating out of the Duracell graphs for 5 alkaline D-cells driving different wattage 6V bulbs. The charts show service hours vs discharge resistance and service hours vs discharge current, so if we do R=V^2/P to get an equivalent resistance for the bulb (using a nominal 6V) and divide it across 5 cells, we get the equivalent resistance/cell. We can then find the expected service life to 4V (.8V/cell) and correspond that to an equivalent constant discharge current using the second chart. By multiplying the service life and equivalent constant discharge amperage, we get the Ah life for the battery at different wattages. Here is what it yields (I apologize for the abbreviated column headings, but I don't want the chart to scroll):
Ohms/ Service Watts Ohm/6V cell (hours) mA mAh ----- ------ ------ ------ -- --- .5 72 14.4 220 75 16500 .7 51 10.3 160 100 16000 1 36 7.2 100 160 16000 1.5 24 4.8 70 200 14000 2 18 3.6 45 280 12600 3 12 2.4 30 380 11400 5 7.2 1.4 12 800 9600 7 5.1 1.0 8.5 950 8075(Sorry, the discharge resistance graph doesn't go below 1 Ohm/cell.)
Of course, trying to see with a 6 Volt bulb at 4 Volts is another problem entirely. :) So is trying to figure out battery capacity using these graphs with constant-power (PWM input) usage instead of constant-resistance (a close approximation of driving the bulb directly) or constant-amperage usage.
Bruce N. Ingle <ingle_bruce@micro-e.com>
Mechanical Engineer, MicroE, Inc.
There's a chart at http://www.homepower.com/hp/sitesfrm.htm that gives these figures:
Temperature (F)
104 32 -20
--- --- ---
Capacity Lead Acid Gel Cell 108% 87% 40%
Sintered NiCad 98% 90% 78%
This agrees with other information I've seen.
One fact to note is that during discharge the NiCad reaction is exothermic (generates heat) while the lead-acid reaction is endothermic. This will help keep NiCads warmer at any ambient temperature. Also, while no figures are available, it should be noted that alkaline primary cells do very poorly in the cold. Lithium primaries are better than alkalines in the cold.
Lead Acid vs NiCd batteries Copyright 1997 Marty Goodman
Folks often ask me about which battery to get with their bicycle lighting systems: Lead Acid or NiCd batteries. This is intended as a "canned" first response to such questions.
The two most common technologies of rechargeable battery used in bicycle headlight systems are Sealed Lead Acid ("SLA") and Nickel-Cadmium ("NiCd"). Low to medium price ($70 to $150) systems will feature SLA batteries, and medium to high priced systems ($140 to $400) will feature the NiCd batteries.
The short version of my advice:
If you do a great deal of night riding, such as many nightly commutes per week, you should get a NiCd battery-based system. If you do only occasional night rides, you'll likely do fine with a SLA-based system. But in either case, you will probably be VERY wise to invest in a third-party battery charger, and NOT use the battery charger supplied with the system you buy.
Long version of my advice:
(a) battery characteristics
Lead Acid batteries are about 2 to 4 times less expensive at time of purchase than are NiCd batteries.
However, NiCds, IF PROPERLY CARED FOR (this is a key operative qualification!) can be recharged 3 to 5 times as many times before they wear out as can be SLA batteries.
Cost of a high quality third party charger for either system is roughly the same ($45 to $90). Note that SLA batteries require a DIFFERENT charger from that required by NiCd batteries.
Overall, NiCd batteries are at least as inexpensive, and probably actually somewhat LESS expensive a source of power than SLA batteries IF you are using them frequently, over the course of their total life. However, if you are using the battery infrequently, for, say, 20 rides per year, then the more expensive NiCd will probably die due to its shelf life expiring before you use all its available charges.
NiCd batteries are, overall, about 30% lighter for a given amount of power capacity than SLA batteries. A significant, but not utterly overwhelming difference.
SLA batteries retain nearly their full charge for two months or more just sitting on the shelf, unattached to a charger. NiCd batteries lose about 1% of their charge per day when sitting on the shelf, due to internal "self-discharge".
NiCd batteries have a flatter voltage vs time curve during discharge than do SLA batteries. This means your lights will remain relatively more constantly bright during the entire useful discharge life of the battery with a given lighting system than would be the case for a SLA battery of comparable amp hour capacity and voltage.
BOTH NiCd AND SLA batteries can be severely damaged by being deeply discharged to down below 75% of their rated voltage. With either system one must never run the battery "into the ground", letting ones lights go from yellow to orange to dim orange. TURN YOUR LIGHTS OFF when they get noticeably yellow, else you risk permanently damaging your battery.
Many ignorant folks claim NiCd batteries are subject to "charge memory". This is false. As used by cyclists for night lighting applications, there is NO "charge memory" problem with NiCd batteries. PERIOD. I can give you a detailed explanation of the myth of "charge memory", and why so many folks make such utterly ignorant and false statements about it, if you wish to get in touch with me about this.
Some manufacturers who supply SLA batteries with their lighting systems (such as VistaLite with its VL4xx systems) choose the Hawker Industries (formerly called "Gates") Cyclon type SLA batteries. This particular make and model of SLA battery is significantly superior to ALL other SLA batteries. If you are replacing a SLA battery in your existing lighting system, get a Hawker Industries Cyclon battery pack (available in 2.5 amp hour and 5.0 amp hour six volt modules). These offer greater usable battery capacity for a given amp hour rating, are able to withstand deep discharge somewhat better than ordinary SLA batteries, and they last thru more recharge cycles than ordinary SLA batteries. Interestingly, the retail price for a Hawker Cyclon SLA battery is not all that different from the price of a similar ordinary SLA battery. Power Sonic (headquarters in Redwood City, CA) sells Hawker Cyclon batteries. Locally in Berkeley, Al Lashers can order and sell these batteries.
Permission is explicitly given to Sheldon Brown to post this essay on his web site. Permission is given to reproduce this in printed and electronic publications that are NOT FOR PROFIT. Reproduction in any FOR PROFIT publication is explicitly PROHIBITED without consent of the author.
When hooked in series (head to tail) the volts do add up. Amp-hours do not add up. In the example where you have 10, 1.2V, C-cells connected to yield 12V, you *do* however get 10 times as many watt-hours as you would with one cell. A 12 volt bulb with the same power rating would take 1/10 as many amps as a 1.2 volt bulb.
How long a 10 cell pack lasts depends on the power of your lamp, naturally.
Steve J Kurt <kurtsj@mtco.com> adds:
Just as an added note: the amp-hour rating indicates how many hours the cell can supply a given current into some particular load. The voltage times the Ah gives the watt-hours (a measure of energy) that the cell can provide. When you hook a number of cells in series, make sure they all have the same Ah rating. Since they are hooked together in series, they will all be delivering/carrying the same current. The goal is to get them to run out of energy at the same time. If one runs out of energy before the others, the remaining cells will still force current through the discharged cell. Not such an awful thing if you are using primary (non-rechargeable) cells like alkalines. It is a bad thing when using secondary (rechargeable) cells like NiCad or NiMH's, since this can damage the cell severely.
You can add Ah only when you hook batteries or cells in parallel. In this case the voltages must be matched. If they are even slightly different, then there will be large currents flowing between the batteries, which may cause them to overheat and/or catch fire. Isolation diodes (a.k.a. "or'ing" diodes) are often used when batteries are used in parallel. In other cases, if paralleled NiCad are charged in parallel, they can be used in parallel if you don't change the configuration.
Going back to the issue of figuring out run times by looking at the amp-hour rating. You need to know how many amps your load is drawing. For instance, I use 6 D NiCad cells rated at 4.4 amp-hours. My light draws 2 amps, therefore I should get about 2.2 hours of use. In practice, I get closer to 2 hours, but it's close enough. How do you figure out how much current your load uses?? Well, I can hook up my meter and find out. Otherwise, you need to look at the voltage and wattage of the load. My light is rated at 6v and 15W. Since power (watts) = voltage x current, the light should use (15/6)A, or 2.5 amps. I've measured the voltage and current of the light, and it doesn't use 15W. However, it is close enough to give you a close idea of what sort of run time to expect.
For NiCad batteries, try Radio Shack, one of the electronics houses listed in this FAQ or elsewhere, or the NiCad Lady.
Also, try these two hobby sources (NOTE: the FAQ holder does not endorse these or other suppliers):
Note that a simple PWM or chopper does not regulate the voltage in any way, it merely makes the apparent voltage to the bulb lower to act as a dimmer. Also note that this is not an efficient way to dim a light bulb, as you can see from the efficiency curve in the graph in Section 6.2.
A very highly efficient method of voltage regulation is possible using the PWM technique, however. By using analog or microprocessor circuits, it is possible to achieve a high degree of regulation. NiteRider's digital lights use such a circuit. Willie Hunt has also designed such a device and made it available for sale. For more information and ordering information see his LVR information page. Similar devices are also available from electronics supply houses, though they typically have lower rated efficiencies than Willie Hunt's device, around 85% or less, compared to 99% or better for the LVR.
Also see Steve Kurt's note in section 3.21 on why the PWMs available from electronics supply houses have typically lower rated efficiencies and why.
The advantages of using a regulator can be summed up as:
Below about 5 deg C (40 deg F), batteries are not able to accept a full charge. Especially not NiCads, which can be a serious fire or explosion hazard when charged cold. Move your battery inside your house or apartment for one to three hours (depending on the size of your battery) to warm up before charging. Avoid charging your batteries in a cold, unheated garage in the winter, as they will not warm up sufficiently. If you can find or make a temperature compensating charger, by all means use that.
Batteries, especially NiCad batteries, are capable of putting out incredible amounts of current. When a short circuit develops for whatever reason in the circuit between the battery and the lamp(s), the battery will deliver a considerable amount of current. Not only that it will get hot. Hot enough to start a fire (in the wires, the bag the battery is in, etc.).
To be effective, the fuse should be placed as close as possible to the battery. It does not really matter which side of the battery you put the fuse on, though some people have a preference. Simple blade fuse holders can be had from Radio Shack and a spare blade fuse taped to the holder for easy replacement on the road.
The issue really is, what size fuse do you need, found in the next section.
For example, a single 20W bulb in a 12V system draws about 1.5A (see the DC circuit section). Double that is about 3A. If the only fuses available are 2A, 3A, 5A and higher, then a 3A fuse would be appropriate.
It is recommended that battery packs (not necessarily cells) be charged separately to extend the life of the packs.
Packs that are not the same capacity and voltage should never be placed in parallel. There is a risk that one of the packs will run out before the other and be destroyed in the process.
As ever the answer to this question (put it in the FAQ somebody :-) is CPC: http://www.cpc.co.uk/
(all plus VAT and small order charge of up to a fiver if you spend less than 30 quid (it's not hard to spend more than this usually :-)) [Prices in UK Pounds Stirling - wab]
[Section 3.13] glosses over the distinction between a PWM chopper and a PWM switching power supply (this is what is being referred to as having efficiencies of 85% or less). A PWM chopper simply turns power on for a while, then turns it off. This is repeated over and over, and at a rather high frequency (at least above the flicker frequency of 30Hz). The output is useful only for light bulbs, or perhaps heating elements.
By contrast, a switching power supply uses inductors and capacitors to store energy, and provide a rather smooth DC output voltage. Great for computers, radios, and all manner of electronics. The act of storing energy tends to involve a number of sources of losses, which is why they are less efficient.
...use the spray for cleaning car battery terminals. This then needs to be cleaned using distilled water or first tap and next distilled. Finally, the device needs to dry.
In answer to your question about how NiCd batteries fail:
My understanding is that principly they fail in one of two ways: The first is gradual. Their capacity gradually decreases bit by bit with each recharge over time, until it drops below a level that's acceptable for the application in question. Arbitrarily that level is often listed as 85% of original capacity, but of course if you are in an application where the batteries when charged have two or three times the capacity you need the definition of "dead" may be more generous. This is seldom the case for night bicycle lighting, however, where we usually want nearly full capacity for issues of run time and weight. There the 85% rule probably is more or less correct.
However, NiCd batteries also fail in a second way: They grow "dentrites" internally, which internally short out the battery. Dendrites gradually grow, but it's only when they actually complete the internal short circuit that you notice them. Thus, they can produce what appears to be a sudden failure of the battery. This will be experienced typically with a battery that has sat on the shelf too long. It's not usually something you encounter DURING the operation of an already working battery. It's typically seen when you try to charge up a pack that has been sitting on the shelf, and discover it won't take ANY charge at all. At that point, you'll find that one or more cells in the battery pack will have a ZERO pole to pole resistance... behaving as if it's totally shorted out (which, of course, it IS... internally).
There is a debate about whether and how to try to rejuvinate internally shorted NiCd batteries. Some argue for zapping the batteries with a fat capacitor or blast from some high current source, to vaporize the dentrites. Others take a more pessimistic attitude, arguing that even when you vaporize the dentrite's connection, most of the dentrite remains, and it will soon again grow and short out the cell. I've experienced both in a few isolated experients with zapping shorted NiCd's: On occasion I've gotten reasonable extra use out of cells I've zapped, and on other occasions I've found that the repaired, zapped cell very quickly fails again. To what extent, if any, this is related to exactly how one zaps the battery in the first place I have no idea.
---marty
In message: <0.700001764.1200242557-1463792126-1013062744@topica.com> Thang Vu <tv_4@yahoo.com> writes about what is NiCad memory (edited with suggestions from Jonathan Edelson):
Some on the list have recommended storing unused batteries in the freezer. If you do this, be sure that they warm up before you use them. Never charge a cold battery, doing this is a fire hazard and may damage the battery. See section 3.16.
e.g. Four AA NiCad batteries of 2000mAh each in series make a 4.8V nominal pack with 2000mAh charge capacity for a total of 9600mWh energy capacity.
On the other hand, the same batteries in parallel make a battery pack of 1.2V nominal at 8000mAh charge capacity for a total of 9600mWh. Note that the energy (Wh) in the two packs is the same. This makes it easy to double check, just measure the voltage and work your way back to Ah or the number of cells.
If the pack has some batteries in parallel, then those parallel packs in series, first work out the capacity for each parallel pack. Similarly, work out the capacity of series packs (which is trivial) then the capacity for the series packs in parallel for the converse.
Note: The list recommends against wiring batteries in parallel. Many do make packs of parallel cells, though, carefully matching cells to avoid potential damage.
Li-Ion batteries usually will not discharge below 2.50V, since that is when safety circuitry will open making the battery appear dead. Allowing a Lithium Ion battery to discharge to 1.50V or lower will cause damage to the battery that will prevent safe recharging. Do not attempt to recharge such batteries.
Note that lithium Ion and Lithium Ion Polymer batteries are similar, but the latter use a gel based electrolyte.
Based on an article from the Battery University on Charging Li-Ion batteries.
Typically, Li-Ion batteries only last 2-3 years and for about 300-500 cycles. Charging a partially discharged pack is better than fully discharging the battery completely. However, some packs with fuel gauge circuitry will require a full discharge about every 30 charges to recalibrate the circuitry.
Heat and high charge levels (storing the battery unused at full charge) will shorten the life of the battery. Store Li-Ion batteries at 40% charge or so in a cool place (do not freeze). Avoid storing in a hot car or in your laptop while running off mains power. Some laptop manufacturors recommend leaving the battery in the laptop to prevent damage to the battery pack.
Avoid buying Li-Ion batteries in advance or as old stock, even at clearance prices - they won't be a bargain. Be sure to check the manufacturing date, Lithium batteries start to age as soon as they are made.
Based on an article from the Battery University on prolonging the life of Li-Ion batteries.
Charging 12V SLA batteries is a known technology nowadays. Simply go to the Mouser Electronics web site and order yourself a Power-Sonic model PSC-12500A [PSC-6250A for 6V -wb] "wall wart", Mouser Electronics Stock number 547-12500A ($40). Plug it into your battery every night and forget it. My batteries last about 2 years this way, with 5-day/week usage.
From: Marty Goodman MD KC6YKC <MARTYGOODMAN@delphi.com>
To summarize what both I and Glenn noted in this thread on the VistaLite VL4xx charger matter:
Most makers of lead acid batteries note (often on the battery) that their batteries can be happily INDEFINITELY be connected to a regulated source of about 6.9 volts. (Glenn quotes one maker who expresses this as 6.81 - 7.05 volts). [13.5 - 13.8V for 12V batteries -wb]
They also note that for faster charging the battery can be connected to a regulated voltage source of about 7.2 volts (Glenn's example was a recommendation in the range of 7.35 to 7.65) [14.4V for 12V batteries -wb] for some limited period of time (typically 24 to 48 hours). If LEFT connected to such a higher voltage source, tho, beyond this time, the battery will be injured.
Thus, the kind of VistaLite charger that puts out about 7.5 or more volts is a BATTERY COOKER if left attached to the battery for more than a day or so.
Thus, also, comes my recommendation for a simple, tinkerers' battery charger consisting of nothing more than an unregulated DC supply that puts out about 10 or so volts (and that can supply no more than about a half amp or so, to intrinsically limit initial current to the battery) hooked to a simple linear voltage regulator (such as an LM317) to yield a source of regulated 6.9 volts. This can be hooked to the battery and left connected to it indefinitely.
It is a decent charger.
More fancy, sophisticated chargers are available thru third party outlets (PowerSonic, A&A engineering, etc.). These are smart enough to charge the battery at a lower voltage if it's really low, then go to a higher voltage to complete charging quickly and fully, then drop back to a lower voltage when the battery is full, going into a trickle charge state where only low current is applied. OR (in some cases) shutting down entirely, but monitoring the battery voltage and giving it a bit of a goose when needed to keep it fully charged.
Smart SLA chargers can be purchased from Power Sonic, at a cost of about $50 to $80 for chargers appropriate to existing bicycle lighting systems. You have to add your own cable, of course, to attach the charger to your particular system. Tinkerers should note that a proper trickle charger for SLA batteries is a regulated power supply set to 6.90 to 6.95 volts for a "6 volt" SLA battery, and to 13.8 to 13.9 volts for a "12 volt" SLA battery.
All of the above applies ONLY to lead acid battery technology, NOT to NiCds, where other considerations apply.
Also note, that one can build a smart SLA charger using various ICs from companies such as Unitrode. A datasheet for Unitrode's U3906 chip can be found here.
This is not a problem with Vistalite light sets equipped with NiCad battery packs.
With the exception of the Nite Rider Digital Pro 6 and Xcell Pro (formerly called NiteHawk) lighting systems, virtually [all] bicycle lighting systems on the market supply inexcusably cheap, often quite destructive to the battery type of chargers. The problem is that with most supplied chargers, they charge the battery rather slowly (require 10 or more hours to provide a full charge) THEN then keep JAMMING current into the battery after it's full, heating it up and ultimately destroying it. MANY cyclists have destroyed their $140 replacement cost NiCd water bottle battery by leaving it hooked up to the charger for some days or weeks.
While NOT a "smart" charging system, the NiteRider Xcell Pro and Digital Pro 6 systems do have a reasonably safe "set it and forget" charging system, tho only when used with their supplied battery. Their system charges the battery at a modest rate for 10 hours, then a timer switches over to a 3 times slower charging rate for maintenance of the battery. Their system is not a "smart charger" in that it DOES NOT in ANY WAY sense actual battery condition.
To more quickly charge SLA or NiCd batteries (full charge in 2 to 4 hours), one needs a "smart charger". Such a charger senses battery condition during charging, pours current into the battery as long as the battery needs it, senses when the battery is full, and then cuts back to a much reduced current flow (or pulses of current at intervals) to keep the battery filled without harming it.
NiCd batteries really benefit from a proper smart charger. Unfortunately, one has to press into service chargers made for other purposes if one wants a smart charger for one's bicycle lighting system. Or make one oneself from scratch. I've done both, successfully. Certain DeWalt and Black and Decker power tool chargers can be converted into very effective smart chargers for bicycle lighting system batteries. The DW9106 and DW9104 in particular are good choices. (NOTE: ALL the DeWalt chargers have 110 volts AC at BOTH battery terminals. Touching the exposed terminals while charging may result in a LETHAL shock.) Some cam-corder and cell phone 6 volt NiCd battery chargers may be suitable as smart chargers for 6 volt NiCd bicycling batteries. I've built from scratch two smart chargers for my battery systems using a Maxim MAX 713 smart charger controller chip. Both work very well. Some have used the more modern 2002 NiCd smart charger controller chip made by Maxim, Benchmarq, and Unitrode. Contact Marty for details if interested.
The reason I and others have been recommending DeWalt (and Black and Decker) brand power tool chargers for use with bicycle NiCd battery packs is that we KNOW they are negative delta V - sensing smart chargers. They connect to the battery with ONLY TWO WIRES... the plus and minus of the battery.
MANY ... most, I believe... other power tool battery charger systems on the market (I don't know about Bosch specifically) use a TEMPERATURE SENSOR inside the battery, and can only properly charge batteries with the exact right kind and wiring of temperature sensor (thermistor) inside the battery pack. Such chargers, which are UNACCEPTABLE for charging anything other than the specific make and model of battery pack they were designed to be used with, are often identified by the fact that they connect to their battery pack with THREE or more contacts, NOT the two used by the Black and Decker / DeWalt chargers.
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A bicycle generator is a mechanical device that generates electricity from the rotational energy acting upon it, typically from a bicycle wheel. One part of the generator rotates (the rotor) and the other part stays still (the stator). The rotor is made up of permanent magnets of some type and the stator is made up of coils of wire. The magnetic field of the turning rotor passes through the coils of the stator, inducing electricity which is then drawn off and used to power the light.
There are several other FAQs that cover generators as well.
Axa, Union and Nordlicht are all 3W and well regarded. Union also make a roller dynamo which has low drag. FER make a 3W spoke dynamo. Early ones (I am told, I have no direct experience) wear out there pulley-belt drive train and cannot be repaired. Later ones are supposed to be better. There is a 6W (12V) FER expected soon. There are simple units available that switch over automatically to dry cells when you stop. I have tried the Pifco unit and it works well.
The rest of this section is not done yet.
Awful ASCII rendering of a graph.
A
nice, alternative, graphical rendering by the FAQ author provided
courtesy of Myra Van Inwegen on her website. Note:
this graph depicts curves derived from the equations below, but may not
show all curves from the following formulae.
The curves depicted follow the following relationships (so you can plug them into a graphing calculator or draw them yourself):
Life = v ^ -12 where v is variation in voltage
Luminous flux = v ^ 3.5 and ^ is the symbol for raise to
Efficiency = v ^ 2 power of
As can be seen by the graph, a slight undervoltage to the bulb dramatically increases its expected lifespan, while an overvoltage to the bulb similarly shortens the life of the bulb. Conversely, undervoltage decreases the light output and efficiency of the bulb, while overvoltage to the bulb increases the efficiency and light output of the bulb.
From this, it can be seen that for a sacrifice in lifespan, greater light output and efficiency can be achieved. Also, it can be seen that the bulb puts out significantly less light and is less efficient at lower than rated voltages.
It's not that there's no interest in non-bulb light sources. The trouble is that none of the current alternatives are suitable for a headlamp. Keep looking because someday you'll find something, but be aware of the problems and what your looking for.
All the alternatives I've seen have one or more of the following problems:
Most of us use red LED tail lights. I also have a flashing green electro-luminescent belt. These are both used as "be seen" lights rather than headlamps. High lumen/watt, non-white colors and wide viewing angles are a plus for marker lights.
Headlamps have a different set of requirements. They should be white (or at least close) with a tight beam. A beam requires a compact light source (or large optics). So far the alternatives are, at best, competitive with the average bulb and worse than the best bulb systems (e.g. with a PWM regulator). The alternatives are slowly gaining, I suspect a 2W LED headlamp will be better than a 2W bulb in a year or two, but for higher power it will be a while.
OK. people I _know_ can supply these bulbs, have a good range and are happy to ship to the US for GBP 1.50 (~$2) are:
US. suppliers who can probably help are:
P.S. Caving supplies isn't the only specialist supplier in the UK by any means (as another poster suggested!). Ones who definitely stock these bulbs (and probably have 10W in stock are:)
Others in the US who may be able to help:
Mark Siminoff suggests:
Peter White Cycles carries some types of 2.4W generator bulbs, including the HS3 bulb with notched flange:
Marty Goodman suggests that higher quality HOT (overvolted) MR-11 bulbs can be had from original equipment manufacturors such as: NiteRider, NightSun, or VistaLite.
The astute reader will notice that the four 1.5V alkaline AA batteries that are typically used in the Micro II add up to 6V. However, due to the internal resistance of alkaline batteries under load, in fact only about 4.8V to 5.2V are supplied to the bulb. This can be verified with a simple voltmeter.
Using alternative batteries, such as NiCads, does not damage the bulb either, because NiCads are actually rated at 1.25V, and so supply only about 5V under load. Users have also reported successfully using Lithium batteries, though the FAQ holder has no actual data concerning these.
Though in the past Cateye advertised the availability of an external battery pack for the Micro II lamp, to date none is available. However, Cateye has announced the release of a new Micro halogen lamp with a 6W bulb and a rechargeable pack.
In conclusion, if the user fabricates and uses an external pack, either a PWM regulator should be used to regulate the voltage to 5V, or the pack should be created only to supply up to 5V.
MR11 are the little (they look like they would almost fit into a 35mm film can) bulb + reflector combination in use in lots of systems, like VistaLite 500, NiteRider, Specialized Proview, etc. They come in 6 and 12V versions. MR16 are bigger version of the same - maybe 2" lens diameter [they are 50mm - ed]. I think they also come in 6V and 12V versions. I think they are mainly used in NightSun products.
You can also get 6V 5W or 6W MR11 bulbs from VistaLite and NiteRider, but again you'd need a lamp housing to put them it, and anyway they use different connectors from the NightSun ones.
The FAQ holder notes:
The MR-16 bulb is commonly available in stores in the lighting section in 20W and 50W versions both with spot beam and flood beam. The spot beam is the most useful for homebrew bicycle lights. It is also possible to find a 10W version if you know of a good source for these bulbs.
The MR-11 bulb is not commonly available, and must be ordered through a bike shop. The selection of wattages is much better. Some bulbs are custom made for specific bicycle lighting companies and are available only from that company. Note that some custom bulbs have different connectors and may not be interchangable with your lamp assembly. See the next question for two interchangeable brands of lamps.
NiteRider's 6 volt bulbs ARE interchangeable with the 6 volt bulbs used in the VistaLite VL5xx series. BUT, you must first remove the metal heat reflector that's added to the bulb and glued to it on NiteRider MR11 bulbs. Similarly, to use a VistaLite VL5xx bulb in a 6 volt NiteRider system, you need to get such a heat reflector (from a dead NiteRider bulb) and glue that to the bulb with silicone sealant. Be sure NOT to use a 6 volt VistaLite bulb in a 12 volt (13.2 volt) NiteRider system!
In halogen bulbs, the halogen cycle causes tungsten that boils off the surface of the bulb element to be redeposited onto the element. This prolongs the operating life of the element and keeps the bulb from blackening (at normal operating temperatures).
Frank Krygowski <frkrygow@cc.ysu.edu> writes in rec.bicycles.tech <3CCDD7F4.9DE32EF3@cc.ysu.edu>:
But the general idea is, as you move from Standard (or Vacuum) to Krypton to Halogen, you're generally getting more light from the same amount of electricity. And not only are Standard bulbs dimmer to begin with, they gradually darken the inside of their glass as the bulb ages, so the light drops off with time. Halogen bulbs are worth the money. Assuming your light can stand the higher temperatures at which they run.
Some links to other pages on light bulbs:
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The following brands claim to make cyclocomputers that can be used in pouring rain or used even fully submerged:
The Vetta can also be worn on the wrist, then snapped off and used on the bike.
While it is recommended not to use cyclocomputers in the rain that are not rated for wet use, the following units gave their owners little complaint or only required drying out with a hair dryer to get working again:
It was also suggested that for otherwise waterproof units, that the contact points be sealed with silicone compound. This is available in small tubes from auto parts counters. Vaseline was suggested as an alternative, since the silicone compound resembled vaseline in texture. In addition, vaseline was noted to reduce corrosion on the contacts significantly.
Finally, it was suggested that wireless computers might be more immune to water penetration overall.
>>> Marty:
When I get my Screamer next month, I'm going to install two Cateye Astrale computers on it. I'd like to run both computers off the same pick-ups, which will mean splicing the wires. I recall that you did this for Zach's Screamer. Do you have any tips as to how best to go about splicing the co-ax wires on the Astrale harness?
FWIW, when I've spliced Avocet wires in the past, I've simply twisted the strands of wires together, smeared non-corrosive RTV on 'em to keep things waterproof, and covered the splice with heat-shrink stuff. I've never tried to solder anything, as I'm [not confident of my soldering skills]. <<<
Marty's reply:
Richard,
CatEye sensor wires on the Astrale and most other of their modern cycling computers are by far THE most difficult sensor wires to splice that I've dealt with (and I've spliced a half dozen or more different brand and model type cycling computer sensor wires in my day).
It's actually CatEye's very very high quality of construction that causes this: They are made of VERY finely stranded copper, with EACH STRAND shellacked with insulating coats. These strands are intermingled with fine nylon thread strands. The result is a very strong, thin, flexible wire that can handle high frequency pulses cleanly.
While the wire may LOOK like its bare when you strip it, IT'S NOT! You will NOT make contact by twisting the strands together.
My technique involves at least modest soldering skill. I first cut the nylon strands off and out of the way. Then I put a glob of solder on the tip of my (high quality Weller WCTPN temperature-controlled soldering station) soldering iron. I then bathe the strands of the CatEye wire in that solder glob until the varnish boils off and I see the strands get tinned. Only THEN can I work with the strands in terms of twisting them, soldering them, etc.
The more I learn about splicing cycling computer sensor wires, the better and more knowledgeable I get about doing it, but the more reluctant I am to actually DO a splice if there's an alternative.
I've learned that with reed switch pickups (all cycling computers except higher end Avocets, and even those on their cadence sensor) open circuit is truly INFINITE resistance, and a "closed" circuit (closed switch) is seen by the cycling computer for anything less than about 600,000 ohms. What this perhaps obscure techno babble means is that even a VERY VERY high resistance short between the two sensor wires... of the kind that can occur is a poorly weather protected splice gets just a little wet... will cause the cycling computer to see a permanent short on the sensor line, and "lock up".
I learned this the hard way, after an extensive splicing job on Zach's Rans SCREAMER went bad after he rode it in the rain. Eventually (with excellent help from more knowledgeable folks on BikeCurrent list, as well as some effective testing and deduction of my own) I understood just what was the problem, and painstakingly re-did most of the many splices (we had three computers, in two locations, sharing two different pickups for cadence and speed) in a fashion designed to thwart that problem.
My technique for splicing now involves a number of tricks aimed at preventing such nasty high resistance shorts: I cut the wires to quite differing lengths (by a distance of 2 or more inches) so that the two splices for the two sensor wires wind up distant from each other. This greatly increase the path needed for a short to form between the two wires. I use heat shrink tubing after soldering the joint. I use either plasti-dip or silicone sealant (or both) to seal the ends of the heat shrink tubing. I use heat shrink tubing again over both wires, to make the joint look a little more pleasing, and to add strength to that joint, and I AGAIN use plasti-dip and/or silicone sealant on that second sheath of heat shrink, globbing the wires with this weather sealant then putting the heat shrink over that and shrinking it down, then making sure the ends of the heat shrink are solidly plugged with the weather sealant goop.
As you can see from reading the above, my technique is painstaking and time-consuming. SO much so that I tend to recommend to folks, whether they're considering attempting to do a splice themselves or paying me to do the splice for them, to consider (if it's possible with available wire run lengths) just running two separate cables and sensors. For making a really RELIABLE splice, that won't fail when used in the pouring rain repeatedly, is not a trivial matter.
For those technically interested, the sensors on the CatEye (and all other cycling computers that use a reed switch and single rotating magnet) MUST be designed to be sensitive to a very high resistance short... to have what we'd call in electronics a "very high impedance input"... because sensors electronics that would register only a real dead short draws more power from the cycling computer, too much so to be consistent with running a cycling computer off a tiny coin sized battery for years at a time. We've had discussions on BikeCurrent about possible tricks to get around this, but the bottom line is that these high impedance sensors for the reed switch are the simplest and least expensive by far solutions to the problem of a reliable sensor that doesn't draw too much power.
Anyway, the summary of the above is: you CAN splice computer sensor wires, but to do a good, weather-proof job is tricky, and requires at least moderate skill. And patience. And time. And you need to know what you're up against, and deal with it accordingly.
The Echowell J-12 has a countdown type distance display that may be just as useful, though Marty Goodman <MARTYGOODMAN@delphi.com> writes that this computer only displays speed with whole numbers rather than tenths.
Judy Colwell <Judy.Colwell@stanford.edu> writes that the Trek Radar is difficult to setup and use. It also has a reliability problem with respect to the placement of the magnet and pickup.
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