Parasitic draw

Pda1122 · December 9, 2018

09 gmc 2500 6.0
Connecting amp meter between neg battery connections I first get a .32 amp draw that goes away after 20 seconds. Drops down to .18. Is this normal? Is it the interior light/radio turning off? I also hear a noise coming from the passenger side door when first connecting. Kinda like power lock noise but only has crank windows/manual lock. Battery goes dead after every 2-3 weeks. Only has 40,000 miles on it but will try to do some alternator testing today. Maybe check grounds and make sure they are nice and clean. I checked a couple weeks ago and battery was getting 14+ volts while running.

Dealer put a new starter in and couldn’t find anything else wrong. I just charged the battery and after having it sit an hour it’s reading 12.81v and the other battery is reading 12.85v. I’m guessing the “other” battery on the driver side only powers the plow? I’ve seen the starting battery so dead it was at 4v and wouldn’t even power the interior lights! I’ll have to test the cold cranking later making sure it doesn’t get under 10v. So just go unplugging fuses? What’s a good amp draw? Around .018 if using 10 amp meter?

diyer2 · December 9, 2018

IMO

You will have some small amount of draw, normal.

Put battery maintainers on it.

A battery will lose power siting on the bench, the warmer the faster the power/voltage loss.

thedcorvette · December 9, 2018

2-3 weeks isn’t normal though, most vehicles can sit for months. Could be a bad battery or one that’s going, but something is grounded somewhere in there

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Supreme Pizza · December 9, 2018

I have many newer vehicles, and without exception - they all end up with nearly dead batteries if I let them sit for a month or two. The security system, the clock, the computer that senses the keyfob signals, and all the other gizmos draw a small amount of power 24/7. The older vehicles (1950's) seem to maintain battery power longer than the newer stuff, due to the lack of electronics.

I have gotten in the habit of disconnecting the batteries on the vehicles that I don't use regularly. In addition, I charge all of the vehicle batteries once per month to keep them topped up.

However, as he said above - ALL car batteries lose power over time, even on a work bench.

4 hours ago, diyer2 said:

A battery will lose power siting on the bench

carkhz316 · February 14, 2019

Okay, is it .180 or .018 AMPS? 180 milliamps is way too much, whereas 18 millliamps is acceptable. It sounds like you need to continue performing your parasitic draw test to isolate the draw. Pull and replace fuses one by one with your Ammeter installed in series (easiest DIY way) while monitoring the current draw.