Charging Multiple Batteries

[Mr_Shamrock]

I think I know the answer to this, but I wanted to get everyone's opinion. I currently have 3 batteries installed in my boat (2 - house & 1 starting). I have a Guest brand 2 bank charger which I purchased when I was only running 2 batteries. Currently I am running the charger to just the 2 house batteries and I have a seperate Battery Tender running to the starting battery. Call me lazy but it is a pain to have to climb up there each time we return to connect the pigtail from the battery tender. I have the Guest charger hard wires to a very convenient spot where I can plug it in from the outside the boat. On to my question - since the 2 house batteries are ran in parallel can I charge them as one battery from one of the leads and then connect the starting battery to the other lead. I assume it will take twice as long to charge the house bank which isn't a huge deal. We only go out once a week so a full week should be plenty of time to charge the house bank at 2.5 amps each. Would it be beneficial to connect the positive to one battery and the negative to the other one?

 

[captain zac]

Re: Charging Multiple Batteries

I had a guest charger and it allowed me to charge two parallel bats
the manual showed me the wiring yours should too
I had no problems with this system
If you lost your manual maybe give Guest a call but as I recall
I had to wire the pos too the first bat and the neg to the second bat
but check with Guest

Harry

 

[Mr_Shamrock]

Re: Charging Multiple Batteries

I had a guest charger and it allowed me to charge two parallel bats
the manual showed me the wiring yours should too
I had no problems with this system
If you lost your manual maybe give Guest a call but as I recall
I had to wire the pos too the first bat and the neg to the second bat
but check with Guest

Harry

I am getting mixed reviews on whether it matters or not to connect the positive to one battery and the negative of the other. Logically, it doesn't seem like it would matter as they are connected in parallel and the charger should just "see" it as one large battery. The way my batteries are positioned it would be more difficult to connect the pos. of one and neg. of the other so I am going to just connect it to one batter and moniter the other periodically with a meter. If anyone has a definite answer to whether it matters or not I would highly appreciate it. Thanks!

 

[Mr_Shamrock]

Re: Charging Multiple Batteries

OK I just got off the phone with a Guest service rep. He said it doesn't matter if the neg/pos are connected to different batteries or not. However he also said to pay close attention to the amp hour rating (when run in parallel the amp hour is now added among the 2 batteries). If the amp hour is too high, and the batteries are brought to a low level the charger may stay in the charging mode (either red or red/green light stage) for longer than 8 hours and it could boil/harm the batteries.