What happens when a dual battery carks it

Hi,

Probably not safe. If one cell shorts in one, the other will try and dump into the other. Can involve very high current, heat and general destruction.
Much better way to have to 6V in series to get higher aH capacity.

Cheers

If one of you batterys carks it it will hog most of the charge putting your good battery at peril. There is still something to be said for the old style cole hersy switch which you can individually test the starting power of each battery and issolate a dud one

So many things to worry about .... but it hasn't happened yet! If it does happen you'll have problems and you will have to disconnect and then replace the dead battery - but don't worry about it now!! Carry a third battery if it will put your mind at ease. But what happens if your starting battery fails? oh no but then you could also get 2 punctures .... or you could find coolant loss etc, etc ... DON'T WORRY and have a good holiday!

This could be an issue with some of the cheaper electronic battery isolators that only stop the flow of current in one direction when the engine is switched off. If you are using a smart relay (like the redarc or Arrid) this is not something that is going to leave you stranded anywhere.

If for example one of my batteries drops a cell, I'm going to get an alarm in the cab telling me that the system's voltage has dropped bellow 11.5V. Then I can turn the vehicle off and switch between the batteries to see which one has the problem, dissable it and run off one battery.

If my starter dies while I'm parked up and my vehicle won't start, I can check the voltage with a metre, say WTF disable it and rig my second battery to start the vehicle, run on one battery.

If my aux fails while I'm parked up I'm going to get an alarm saying my battery is going flat, I'll start the car and the voltage won't be increasing correctly, so I'll know something is not right, find the faulty battery and disable it.

So personally I can't see why it would be a major problem.

with 2 in parallel, if one drops a cell, it will pull the charge put of the 2nd batt, easy enough to disconnect one at a time and load test them if you are worried. but if you find the dud one early enough on its way out then you can just disconnect and continue on one.

Glenn,

We are talking about two "deep cycle batteries in paralel (12V) setup in the truck.
I was wondering what typically happens when one of them cark it?"

As both DC batteries are wired in parallel and disconected from the crank battery by an isolator till the vehicle starts and then the two good batteries will be scavenged by the dud battery.

Bradley stated,
"with 2 in parallel, if one drops a cell, it will pull the charge put of the 2nd batt, easy enough to disconnect one at a time and load test them if you are worried. but if you find the dud one early enough on its way out then you can just disconnect and continue on one" .......I could not have said it any better, so won't try.