Martin it is largely academic if an Edison type bulb is 100% current source. When testing a lipo between 4.2 and 3.1 V or a lead acid between 14.7 and 10.7 it is good enough (tm)
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8 years ago
Martin
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8 years ago
Off a 220V line, the difference in charging current between one and two car batteries in series is just 3%.
In the bush, that's a pretty cheap, rugged, calibrated current source.
Cheers, James Arthur
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8 years ago
Indeed, Martin, I once used a small incandescent bulb as a rough constant current regulator for a string of red LEDs running from a 12V battery on my bike.
The bulb was mounted on the handlebars and normally ran dull red. This was a useful indication that the rear lights were on, and also provided a battery charge indicator - it would go out when the battery needed charging but the LEDs were still operating.
Cheers
-- Syd
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8 years ago
Me?
Probably a good load for measuring reserve capicity for a lead acid.
Lipo or li-ion may be another thing, they usually run a converter which keeps constant power. Which means increasing current as voltage drops.
It depends upon the application.
Cheers
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8 years ago
On a sunny day (Fri, 27 Nov 2015 10:33:53 -0500) it happened Martin Riddle wrote in :
No the other Martin, sorry because I lost the original article, then remembered his words about arguing in school about it, so just wanted to reply.
I got some new RC lipos (single cell) and need to measure some discharge curves. I found that using a 12 V car headlight works just fine (on a 3.8 V lipo). But need a low voltage cutoff to protect the batteries from getting damaged. Bit over 2 amp, simpler than a heatsink with some transistor. And then to log the voltage every minute... until cutoff.