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Stroked Smoke
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100 Posts
Discussion Starter #1
My batteries seem to get a little low after a week or so. I do not drive the truck daily. It seems to charge fine. I put a meter in series with the batteries and have around .2 to .25 draw on them. From the reading I have done here that seems to be about normal. I have had the batteries tested and they passed the load test. The truck seems to start after a week or so, but rolls over slow. Finally here is my question - I have mismatched batteries in the truck, can that cause them to drain? Neither of them are very new one is 1000 cca and the other is a red top 850 cca.

Thanks,

Tim
 

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Genius, when I drink
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1,295 Posts
First I would check all of your battery connections even the grounds, makes sure everything is clean and tight. If that does not 'fix' things then I would disconnect the batteries in between drives and see if the issue is still there. If it is it would indicate that with the batteries are this issue. If that is not the issue I am not sure where to look next.
 

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PSN Pretender
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1,926 Posts
The rule of thumb for a parasitic draw is that .005 amps or less IS acceptable.

You have a draw, to pinpoint your draw you can start pulling fuses until the draw goes away, then diagnose that particular circuit. But you must leave your meter hooked up in series with your battery cable for at least 45 minutes. There are modules on the vehicle that will stay active after the key is turned off, after a while they will turn them selves off. Also do not open the door during this period or you will have to start over. A good practice is to open both doors and close the latch with a screwdriver, this is so the GEM module thinks the doors are shut and will "go to sleep" and you can further diagnose your problem if you need to move inside your cab.

Dont forget that the alternator can draw battery's down also, so you might have to disconnect it to check.

If you are worried that the other battery is causing your draw just disconnect it and re-check current draw.

Good Luck
 

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Need a ride.
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553 Posts
Cardinal rule of thumb, always replace both batteries, never just the one thats bad. The bad one will pull down the load of the new one.
 

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Stroked Smoke
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100 Posts
Discussion Starter #5
Thanks for the info. I am out of town right now, but will try that when I get back.
 

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Buffalo Diesel
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280 Posts
If you can swing it, I'm very happy with my Walmart batteries, $75 each. 3 yr free replacement, 9 year pro-rated.

I'd trace down the problem first though.
 

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Stroked Smoke
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100 Posts
Discussion Starter #7
I waited the time and used a better meter this time. The draw was 2 mA
(.002). Apparantly the meter I used first was not that accurate.

I had a trickle charge on them all week until around 4. I did all my testing and around 7 decided to have the batteries tested again. They both passed, but said they had low charge voltage. They both dropped to high 10 volts with load and came back to just over 12. I am thinking that the batteries might be the culprit. I am a believer in replacing both, but unfortunately my truck had mismatched batts when I bought it.

Thanks for all the help.
 

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Steamfighter
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1,094 Posts
My batteries , no load , truck off, 12.6 volts . just after starting, ( glow plugs still lit ) 11.9-12.4 , 13.6-13.8 idle , no accessories on . 4 year old factory batteries .
 

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Stroked Smoke
Joined
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100 Posts
Discussion Starter #9
After a week of the batteries unhooked they both read 12.78 volts. So I went back and checked for a draw again. Like and idiot when I switched meters the new one defaults to AC amps where the old one defaults to DC. I read 208 mA dc. I have tracked it down to the brake controller and the GEM. The brake controller had 44 mA draw. The GEM is drawing 164 mA. Does anyone know where the best place to get one of these? Are they dealer only? $??
Thanks
 
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