Note: Gates cell info is at the end.
I did some tests of the two bulbs that are sitting around my place.
The incandescent is a standard large round hi/low beam car headlight for
1970's cars. (cost $4.50)
The halogen is a small rectangular low beam unit that is common on
early 1980's cars (cost $15.00)
Remember that there can be a large difference in efficiency. I did not try
to measure that because it is hard to capture all of the light and measure
it. However, the halogen is a bright white light compared to the dingy
incandescent and probably is significently more efficient.
Results: The results of the tests indicate that halogen bulbs are much
better, esp. so if you are working at low voltages. In the case of my
friends bike light, he runs the 12V halogen from a 7.2 V battery pack;
and it works great.
Data: Doing a voltage vs current measurement gave the following:
Halogen ==> V = 4.145 * I - 8.866 (correlation = 0.9997)
Incandescent V = 7.289 * I - 9.436 (correlation = 0.9987)
In both cases the DC power vs voltage is linear. So the lower the voltage
the less power you get. The halogen is still quite usefull at 7.2 V (22.5W)
while the incandescent is color shifted towards the red and draws 16.4W.
So if you are considering making your own lighting system then get a car
halogen lamp, build a battery pack for something like 10V (nicads) and
you will have a nice 35W light. Strings of nicads can be used to make
7.2V, 8.4V, 9.6V, 10.8V, 12.0V. It would be better to have a 8.4V
string with 2 in parallel (14 batteries total, 29W power, aprox 90 min
life with 3 A-H batteries) than to have a 12V string (49W, 35 min with
10 batteries). Using only 7 batteries for the 8.4V would give a life of
In reality neither battery pack will last that long because the discharge
is faster than the 10 hour nominal rate. However, it is fairly easy to make
a 14 cell battery pack and it lasts a lot longer than the 10 cell 12V pack.
This will mean that you have to make your own custom charger (pretty easy
because it is just constant current).
I ran across some interesting nicads a while ago. They are rated to be
charged in 1.5 hour but the "standard" charger that the racers use charges
them at 4.5A in about 20 min! They only use the batteries a handfull of
times before throwing them out.
Currently I am using a gel-cell but when I look at these numbers I have to
admitt that a 8.4V system with a halogen bulb looks very good. Other
advantages of the halogen bulb are the reduced size and weight. They are a
lot easier to mount and don't bounce as much.
Gates Cyclon Batteries
I got the info on these a while ago and took a look at them. They are not
cheap but they are good. Basically the acid is stored in the paper seperators.
The cell can not explode, leak and are a lot better in these ways:
- last 3 years without recharging or cell dammage
- at -40C they can put out 50% of charge compared to 30% for lead acid
- lower internal resistance, very fast recharge
- typical 8 to 10 year life in float use, 200 to 2000 cycles
- charger is simple (2.35V / cell; no current limit ==> 1 hour recharge)