I have my starting battery and my deep cycle battery

[Seadeals]

I use dual deep cycles as our engines require much lower cranking amps than other boats. No issues; but my new amp seems to have a dormant draw. I left the battery on when connected to my battery minder and it still drew down. I have the off/1/2/1+2 switch and also isolate during use. Sometimes when both (identical batts) were fully charged I will combine on the battery minder.

 

[subysti]

You need to add a charging relay to isolate the batteries the relay will combine them when charging from the engine but isolate them on e the engine is off. That way you never kill your starting battery. Starting batteries have a lot of thin plates inside for giving high amp fast discharge for starting and engine. Deep cell have fewer thicker plates for long slow discharge, like running stereos, trolling motors etc.. If you discharge a starting battery too low it damages it and you will kill it quicker. Same as connecting the batteries together the voltage will try to equalize and the low battery will suck the voltage out of the higher battery. That's why the newer boats DVSR will fully charge the starting battery first before switching to charge the house battery.

 

[Tiger J]

What he said ^^^^^^

In all seriousness get a 2 bank charger and minimum a perko battery switch and keep on rocking..

Ok. So I have 2 switches now. One for my starting battery and one for my deep cycle battieries(2 connected parallel). And I have a 2 bank charger charging all.

I feel a little better now. At least now I dont think I am harming any batteries.