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Battery drains?

The battery on my friend’s van goes dead if she doesn’t run the van for two or more weeks.
This doesn’t sound right to me.
Is it possible her battery is slowly being drained?


Yes, very possible…It’s called a parasitic drain…Alarm systems, remote door locks, defective electronics, a hidden courtesy light that stays on all the time (hood, trunk, glove-box) are the usual culprits…

If you don’t find a courtesy light that is not going out, the next suspect is any aftermarket audio equipment. Amplifiers that are not properly installed and never turn off are common.

Alarms and remote CD changers are intended to stay on all the time, but should not draw enough current to drain the battery in two weeks unless they are defective. Six months maybe, but not two weeks.

If the problem is not obvious by inspection, your friend will need a ammeter that reads around a 100 mA current flow. You disconnect the positive battery terminal and connect the ammeter in series. Then have a cup of coffee while you wait for the computers to go back into sleep mode (assuming the van is a late model vehicle). Then you should have something in the range of a 30-60 mA drain to keep all the computers and clock running in sleep mode. A strong battery should be able to support that drain for at least six months. If the drain is over 100 mA, you start pulling fuses or disconnecting accessories until the drain drops down where it belongs.

If you pull out every fuse in the fuse box and you still have a drain (remember where each fuse goes) then suspect that the drain might be a bad diode in the alternator.

A failing battery might go dead after a couple of weeks of inactivity, but that is not the way batteries normally fail.

There very well could be a current drain causing the trouble. Have a shop check the condition of the battery and the charging system to make sure those things are ok. Then have the current checked while the van is parked. Normal current draw should be between 15-25 milliamps when things are in the sleep mode.

This is a great product for anything that has a battery and does not get used all the time, car, motorcycle, lawnmower …