battery charging problems

hi guys. i installed a brandnew 2 bank battery charger and 2 new batteries about 2 months ago. for a month and a half everything was charging ok. i could fish and use my trolling motor all day with no problems.i took my boat out last week according to the charging lites it was fully charged.about an hour into using my trolling motor(and i use it alot.) my fish finder has a low voltage threshhold set at 10v.it started beeping low volts.it did that for the next three days of my trip after supposedly being fully charged.can u guys help me figure how to troubleshoot this problem? thanks:confused:

Check the output of the charger at the batteries. It should read 13-14 VDC. If not the charger is bad. If voltage is good have the batteries load tested at your local auto parts store.

Check the water in the batteries. I have to add water about once a month if I fish and charge a lot.

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Originally Posted by Fisherman_Wantabe

Check the water in the batteries. I have to add water about once a month if I fish and charge a lot.

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Yeah, My on board charger boiled my batteries almost dry, everything you mentioned is the problem I had today on the lake.

Normally the fishfinder wouldn't be connected to the same battery as the TM. Is yours hooked up that way?

yes the fish finder and trolling motor runs off the deepcycle battery