Re: Battery Bank Dilema

I have an update to my previous post and to all your replies about the batteries on our Cal 34 sailboat. The previous system was comprised of two 6v's wired in series and then connected to the two other 12's in parallel to create one gigantic bank. BOTH legs of the Guest Pro-2611 charger were connected to these batteries. The Guest charger tech support dept did not like the inclusion of the 6's. All four original batteries have now been recycled and we have three new 12v batteries. One is a 750-CA cranking battery and it's wired as a stand-alone bank. The other bank is made of two 12v, deep cycle batteries wired in parallel. I was told by the PO that the charger was a three phase charger with a "bulk", "trickle" and "conditioning" phase. After installing the new batteries and wiring them, we finally determined our original problem. As it turned out the charger had failed! It was permanently in the conditioning mode and that's what boiled my old batteries over. This new arrangement is simpler and far more common. Now I just have to identify the right battery charger replacement. Practical Sailor likes the Newmar PT-25 and that's probably what I'll buy. Thanks again for your help! Fair winds & calm seas, Dan

On Aug 4, 2008, at 7:59 AM, Dan B. wrote: > > I have an update to my previous post and to all your replies about > the batteries on our Cal 34 sailboat. > The previous system was comprised of two 6v's wired in series and > then connected to the two other 12's in parallel to create one > gigantic bank. BOTH legs of the Guest Pro-2611 charger were > connected to these batteries. The Guest charger tech support dept > did not like the inclusion of the 6's. All four original batteries > have now been recycled and we have three new 12v batteries. > One is a 750-CA cranking battery and it's wired as a stand-alone > bank. The other bank is made of two 12v, deep cycle batteries wired > in parallel. > I was told by the PO that the charger was a three phase charger with > a "bulk", "trickle" and "conditioning" phase. After installing the > new batteries and wiring them, we finally determined our original > problem. As it turned out the charger had failed! It was permanently > in the conditioning mode and that's what boiled my old batteries over. > This new arrangement is simpler and far more common. Now I just have > to identify the right battery charger replacement. Practical Sailor > likes the Newmar PT-25 and that's probably what I'll buy. That's what I bought after a West Marine "smart charger" that wasn't smart enough fried my three batteries. So far so good. Mike Kennedy Conquest Cal 40 # 96 > Thanks again for your help! > > Fair winds & calm seas, > > Dan > > > > >

In the 80s I had a GM diesel station wagon. They used two 12V batteries in parallel to provide the current necessary to turn the 5.7L high compression (for the first 40K miles) engine over. My experience with that arrangement is that you must replace both batteries when one goes bad. In parallel, differences in the two batteries can cause one to suck up all the charging current and the other doesn't get fully charged. Only in theory is the power available from two batteries in parallel equal to twice the power from one. In the real world, any imbalances can cause it to be less. My 1985 Cal-35 came with two deep-cycle batteries and an A-B switch. Either of the batteries can be used to start the engine or run house loads, but only one at a time. The charger has three outputs. I was planning to add a starting battery with a bridging switch. I'll either have to throw the switch or get a battery isolator to charge the house banks from the engine. Afer reading your post and thinking about it, I may just go ahead and get two 6V and wire them in series for the house bank and use the 12V for starting. Unless it's because they were in parallel with the 12V batteries, I don't have a clue why the rep didn't like the two 6 volts in series. IMO, you would be better off with a house bank of two 6V in series and a single starting battery configured as two banks. Since you've already got the 12V's ordered and installed, just plan on replacing both when you have a battery problem.