Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
On a truck with dual battery’s like a super duty. Would you unhook one battery completely and then unhook the negative cable and put your meter in series?? Or what is the proper procedure. I have the drivers battery completely unhooked then my meter in series on the other I have 25 milliamps. But if I hook the other battery up it goes to 509. Pulled every fuse doesn’t change unhooked alternator
How's the battery condition and state of charge? I'm wondering if the current flow might be between them? Half an amp is enough you should be able to see where it's going with an amp clamp. Or put another DMM inline on the other battery.
It is REALLY important that both batteries feature a very,very similar SOC and SOH, capacity etc. Logic points to current is flowing between both batteries"supposed" the design is a parallel circuits one....
Load testing both batteries would make sense to me. Apart from Matt´s suggestion to draintest the other battery seperately you also could connect/bridge the battery cables from the disconnected battery to the post of the battery with the low drain.
An expert is someone who knows each time more on each time less, until he finally knows absolutely everything about absolutely nothing.
If The "Unhooked" Battery is Bad or low. The good Battery will charge to the bad battery constantly and Drain the Good Battery. (similar to a water level) to do a Draw Test i Leave both Hooked up at first and Test at both with an amp Clamp. Then if Need be, load test both Batteries while disconnected.
Looking at the wiring diagrams it’s a 2013 Silverado 2500 6.0 vin g. There’s only one battery on the factory wiring diagrams. The main battery on the passenger side they have cables running from b+ to b+ and b- to b-. So if I put my meter in series on the main battery I get 25 milliamps. But if I hook up the main battery then go in series on the auxiliary battery negative side I’m getting.875. So is the auxiliary battery draining the primary battery?? It’s new. The auxiliary battery has no other connections going to a fuse box or anything
If the aux bat does not connect to anything else than the main bat and you measure the huge draw only between the two batteries and nowhere else this is indicative of current flow only between the two batteries.
An expert is someone who knows each time more on each time less, until he finally knows absolutely everything about absolutely nothing.
It's not normal and not good. It shows that the two batteries do not match each other.
Another thing to consider in your scenario is the alternator: two batteries instead of one will put an extra load on it, and a second battery is a considerable load! If the alternator was not matched to the demand he will work overtime and chances are he will fail prematurely due to excessive heat.
Do you know why a 2nd battery was put in, are there extra loads?
Not sure on the battery addition. I should just get 2 new batteries and be done with it so they match. I know the truck it’s self doesn’t have a drain only when auxiliary battery hooked up
