jkb242

My battery died over night and discharged unexpectedly to 2.3v across the battery while connected. Charging seem to very slow so I begin checking for a drain or short. With everything off inside the car and the battery partially charged to around 8v, measured 3.2 amps drain which steady decrease in current over the next several seconds to around 200ma over several seconds. Within about two minutes, the current was reduced to around 30ma. Never seen anything like thus before. After several minutes of removing and reconnecting the battery the current never reached above minimal. Any ideas of a component in the vehicle that would duplicate this type of characteristics?

Thanks!

Gumby22

1) Check the sides of the battery case - if they’re bulged out (feel them if you’re not sure - there will be a noticeable convex curve to the case), it has at least one burst cell and needs replacement. If you smell hydrogen gas (rotten egg smell) at all, replace the battery.

2) If you’re trying to recharge from that low of a voltage, disconnect the battery from the car. The modules are trying to communicate with each other and it will slow the charge of the battery. Again, if you smell hydrogen gas at all during charging, replace the battery.

3) Under normal conditions (meaning battery is fully charged and there’s no parasitic drain), it can take up to an hour for primary communication to cease and up to 4 hours for all the modules to totally power down.

You will not get accurate results with the battery at 8 volts because it’s not enough power for the modules to function properly, and on low power, modules can do very weird things. First fully charge the battery, or replace it, then conduct a drain test. Check it after an hour - most of the time they’re at or below 25mA by then - if not, give it another hour and check again. If it’s still above 25mA, proceed to pulling fuses from the engine bay fuse box to isolate the circuit.

jkb242

That makes sense and fits the characteristics described. I replaced the battery just felt had been too deeply discharged for any long term reliability. Before connecting the new one I performed these checks again with normal readings. Was unaware that the quiescent state took that long. Thanks for pointing this out.