Originally Posted by Forchetto
Not really into HID mods ...
Decosse is probably our man.
HIDs not my thing either - I prefer to optimize the incandescents with
a) Improved wiring with relays to avoid voltage drop to the lamp
b) more efficient bulb of standard wattage
c) improved lens/reflector.
Back to the original problem - battery simply not sufficiently charged adequately to provide the 5A required for the light bulb, even if only for a few minutes.
The LED draws minimal current which is why that test is irrelevant
Originally Posted by Ripper
Your battery only provides 4.8 Amps for one hour. However this would not prevent the bulb from lighting up since the battery should be able to provide 9.6 Amps for 30 minutes but because this is outside the battery's recommended rating there is a risk of damage to the battery.
A reasonable generality for the illustration at hand - however 4.8Ah rating does not really mean the battery will supply 4.8A for one hour - nor will it supply 9.6A for 30 mins.
The way Ah rating is calculated is from the maximum current the battery is capable of constantly supplying over a period of 20 hrs before it depletes to 80% depth of discharge; for a 4.8Ah battery that means it would sustain 240mA for 20 hrs.
The math however is not linear and there is a significant difference from supplying 5A vs 240mA - so although it sounds like a simple ratio, in the real World, you would never get anywhere close to one hour at 5A load.
That being said however, a 5A load should easily be able to be sustained by a 4.8Ah battery for at least a reasonable period of time: if it does not even light, then the battery is sagging excessively suggesting it has insufficient charge state.