2 Battery setup

Had this Pontoon boat a few years. Yamaha 40 2 cycle. No trolling motor --yet. Stereo/CD player/fish finder/GPS. Came with 2 batteries. I unhook the GPS system after using. The FF is built in
No way to switch between batteries. Big black cables connect positive to positive and negative to negative. Second battery in line has a yellow wire with a black box on it connected to the positive. Second battery has a yellow wire connected to the negative.
I went to charge the batteries up for the season. The first battery inline(closest to the motor) took one hour to charge. The second battery in line took 10 minutes. Why is this? How do you find out if something is running the batteries down? They were low in charge before I disconnected them for the winter. The stereo used to come on when it sat for awhile, so I took the face plate off after each use. Could it still be running? How can I find out if the alternator is charging right with a 2 battery system.
Another question is what are the benefits of having a 2 battery set up like this one? Do I really need 2 batteries? If not, how would I or somebody wire it back one and what AMP would I need? I think the 2 combined are around 1200 amp. ,Matching cranking batteries bought at the same time a year ago. The boat was used just about every weekend during the season. Sat for 7 months during the off season

Thanks in advance!

DC

Re: 2 Battery setup

DayCruiser said:

Another question is what are the benefits of having a 2 battery set up like this one? Do I really need 2 batteries?

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no benefit in my opinion. I would remove one battery, and keep the connections as basic and simple as possible. Simple wiring=reliable starting.
Pick up a nice booster pack and carry that on board in case of emergency.

Re: 2 Battery setup

Yea, I could see it if I had a switch so I could run a trolling motor just on the second battery and use the first battery for starting. But as is, I don't see the benefit either. So I just move both yellow wires to the first battery?
Thanks for the help!

Re: 2 Battery setup

yes, just make sure anything currently connected to + stays on the + terminal, and anything connected to - stays on the -

In boating circles there are a lot of fans of installing 2 battery switching systems, but I think a lot of that thinking was from an era before booster packs became affordable, powerful and safe. In my experience, any additional cabling just creates additional resistance and problems.

Here's my booster pack stored next to my one battery- for less $ than a battery switch and 2nd battery, it has a worklight, backup navigation lights, can inflate a trailer tire, boost a stranded boater, has two 120V AC outlets, a USB charging port and in the off season it is handy around the garage/house. We take it camping on shore too.

Re: 2 Battery setup

Ok about the wiring setup. Looks like the booster setup is what I need. Thanks for letting me know about it

Re: 2 Battery setup

One battery charging in 10 minutes says one of two things: 1) That battery is bad, or 2) it is a good battery and didn't discharge much during the off season. A lesson here is that you charge the batteries BEFORE you store them -- not leaving them in a discharged state for long periods hoping they come back to life in the spring. I too feel paralleling two batteries is a waste unless a dual battery switch is installed and in most cases people wire them and use them in ways that do not take full advantage of the system. So use one large capacity battery and enjoy the boat. Have both of your batteries load tested at any auto store (fully charge them first). That will tell you if they are good or bad. The stereo system on your boat likely has an internal clock as well a station memory feature. Both of those draw current whether the unit is turned on or off. Granted, they don't draw much but over several weeks or longer it can draw down a battery to where it won't start the engine. If your boat is docked and shore power is available, by all means install a single output on-board charger and plug into shore power when docked. The battery will always be topped off and ready to go.

Re: 2 Battery setup

Since you already have two batteries, why not add a Battery Switch and a few battery cables.
Then just use one battery one day and the other battery the next time out. Stay away from the both setting.
Then you have the best of both worlds. Plus it might help a bit when you sell.

Re: 2 Battery setup

Thanks for the info Silvertip and Don!

Re: 2 Battery setup

That is a good idea too Don, since both batteries are practically new

Re: 2 Battery setup

definitely avoid the "both" setting if going to a Perko switch. The charging system of a 40 Yamaha may struggle if both batts were discharged and it was asked to charge both.

Re: 2 Battery setup

Ok Howard, thanks for the tip!

Re: 2 Battery setup

On the second battery. The positive terminal has a red wire then a black box(looks like it can be pulled apart) then the line turns yellow. What is this black box and what does it do? The negative ground just has a yellow line connected to it. Of course, other than the connections to the first battery.
Thanks!

Re: 2 Battery setup

DayCruiser said:

On the second battery. The positive terminal has a red wire then a black box(looks like it can be pulled apart) then the line turns yellow. What is this black box and what does it do? The negative ground just has a yellow line connected to it. Of course, other than the connections to the first battery.
Thanks!

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Post some pictures.