power drain

[Just Bill]

basic old car electrical system, no new type memory radio or stuff that is on with key off(it does have an alternator). Battery runs down sooner than I think it should. Measured 9.1ma draw at the battery. Any suggestions???

Bill

[chevynut]

Welcome to the site Bill.

9.1 ma seems like a tiny current draw, and it shouldn't kill the battery very quickly but I suppose it shouldn't be there. For example, if your battery capacity is 50 AH, it would take well over 7 months to completely discharge at that rate. How fast does it discharge?

Disconnect the alternator and see if you still have current draw as it could be a leaky diode. But depending on how fast it discharges you might have a bad battery.

[Just Bill]

We know the batt is not really good, but after a long charge, it only lasted about a week. 9ma certainly is not enough to finish off a good batt quickly, I agree, but this car sometimes sits for several months(trailer queen). My next task was to disconnect the alternator. Thanks.

[mech393]

if the alternator is fine I would do a three minute charge test and if it goes over 15.5 volts after three minutes then id replace the battery , but the battery should be the first thing and then check the other components.

[rustay56]

if the alternator is fine I would do a three minute charge test and if it goes over 15.5 volts after three minutes then id replace the battery , but the battery should be the first thing and then check the other components.

I don't know this test Mech393, could you elaborate on this please.

Regards Andrew.

[mech393]

you take a battery and hook up a battery charger and volt meter and you run the charger at 40 amps or as close as you can get to it and check the voltage at three minutes the battery shouldn't go past 14.5 if its good if it goes past or up to 15.5 or higher then it sulfated usually it gets to 15.5 before the three minutes is up , but when the battery is sulfated the voltage goes up trying to push the amperage through the resistance of the sulfated cells of the battery.

[markm]

I have found the source of many of these issues to be modern radios wit electronic memory.

[chevynut]

A radio's memory has very, very little power draw, a few milliamps at most. With today's non-volatile FLASH memory it could be virtually nothing. If it's hooked up wrong and the stereo is always powered, then I can see where that's a problem. I can leave my Porsche sitting for many weeks in the winter with a good battery and it won't go anywhere near dead. Same with my Silverado.

If a radio is draining a good battery, there's something wrong with the radio or it's wired wrong.

[rustay56]

Mech393 Thanks for that explanation.