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Dual Battery System dying over night HELP?


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As you can tell by the tittle i have a dual battery system with the batteries just wired together. And for some reason i have to jump start my truck everytime i need to drive it in the morning and sometimes right after shutting it off..

I DID have the main battery tested and was told it had a bad core but i don't think that could be true because the battery was only a year old but my second battery should still be able to keep most of the charge over night.

when i shut off the engine my batteries read most of the time near 10v and after sitting over night my volt meter reads 6v or 7v and i cant start the engine. 

I have a stock alternator and stock wiring and i know i need to upgrade but i cant afford too but i don't see a reason for both batteries dying over night when nothing is turned on.. no lights.. nothing.. Please help any would be appreciated as i can NOT afford to get a new battery/wiring etc.. Thanks 

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It's possible you purchased old cells under the impression that they were new. It's also possible that your alternator isn't charging enough for the demand or not charging at all. It's also possible that something could be constantly on that you don't know about, like a bulb or your amps. A digital multimeter will assist you in finding out your issue. You can grab one from your local hardware store for under $20. YouTube... How to test for parasitic draw, how to test if alternator is charging, etc. Honestly, if my battery guy was testing it, I'd be over his shoulder and asking questions

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13 minutes ago, 8ten8 said:

It's possible you purchased old cells under the impression that they were new. It's also possible that your alternator isn't charging enough for the demand or not charging at all. It's also possible that something could be constantly on that you don't know about, like a bulb or your amps. A digital multimeter will assist you in finding out your issue. You can grab one from your local hardware store for under $20. YouTube... How to test for parasitic draw, how to test if alternator is charging, etc. Honestly, if my battery guy was testing it, I'd be over his shoulder and asking questions

true and thanks i will probably just keep saving up for a new battery and i will search around on youtube i bought a cheapo multimeter and i have no clue how to read it (cause im an idiot) but ill just keep searching around for more clues to whats wrong

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1 minute ago, Skullz said:

That old main battery is killing your second battery, a bad battery will pull all other batteries down, and not the other way around where it raises your bad one up.

i figured as much.. problem is the other battery does not have enough cranking amps if it did i would be using it

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Battery's sound toast. Doesn't take long for a dead battery to kill a good battery and then both are dead. Its happened to me. I think it would be in your best interest to learn how to use a multi meter and here's why...

Basically to save you $ and everyone wants to save $. Lets say you replace the battery's but alt dont charge or you still have a drain somewhere. 2 new battery's now dead with the cost of having to replace them again or have weak battery's. Youtube has tons of vids to help you thru it and in the end you will have trouble shot and fixed the issue. Priceless if you ask me.

Good luck and keep us post to what the issue was...

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