Join Date: Jul 2005
Location: Auburn, WA, USA
Re: Dead battery
I've been curious about this for some time now, so since this thread came up I figured I would do some testing. My battery will drain down in 2 weeks to the point where it will not start reliably. It is 3 years old, and I'm sure near end of life, so I just keep it on the Battery Tender.
There is always a little drain on the battery, the BC has to keep its clock running, so it is using some current (which is why you have to reset the clock after disconnecting the battery). I have also noticed a bit of a spark when connecting the battery, again indicating there is some current drain.
Armed with my digital meter (everyone has one now, right? they are so cheap these days), I set out to measure the static current drain. This might be useful to others who are trying to find a problem. When the battery is first connected, there is a load of about 0.29A (290mA), then after about 2 seconds it drops to 0.10A and then several seconds later it drops to 0.04A and stays at that point. I assume when power is first applied, the BC powers up and initializes (290mA), enters an idle state (100mA), then finally a standby state where it just keeps the clock running (40mA). Some of that load may be the alarm system as well. At 40mA load, it would take a looong time to run a good battery down!
Some other numbers of interest:
Key in the R position, but everything off: 0.20A
(part, or maybe all, of this load is an accessory relay I have installed)
Stereo playing, normal volume: 1.00A
Key in R, GPS on: 0.44A
Dash light and wing lights on: 1.28A
Trunk light: 0.30A
So, with everything off, if you see a load of much more than 0.04A, something is drawing current that shouldn't be. Your measurements may vary a bit depending on the battery voltage and condition of the battery connections, but they should be close to these numbers.
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