Let's talk about batteries!

[LawyerMan]

It's time for me to buy two new group 31 batteries for my 270 SLX. I've done a lot of reading on batteries, and I think I've decided to go with 2x Interstate Marine AGM batteries (http://www.interstatebatteries.com/m/product/agm/marine-agm). First, are these good batteries? For the price, they better be.

So let's talk battery maintenance and best practices...

Questions

1. Should I always run the boat with the switch on dual, or one or the other?
2. When anchored out for long periods of time, what should I do with the switch?
3. If I run the boat on one, and accessories while anchored on the other, when I start back up and cruise should I run it on both again so both get charged?
4. When back at the dock, how often should I hook up the shore power and let the Guest 10/10 charger charge the batteries?
5. Is a solar panel hooked up to the batteries while using them (anchored out) a good or bad idea?

 

[Ike]

Interstate is a good choice. I use Interstate and they have served well in my boat, car, motorhome. Most batteries on the market are all third party labeled. They are made by either Johnson Controls or a company in China, the two largest battery makers in the world. Interstate AGM batteries come rom Optima which are made by Johnson Controls. So at least they're made in the USA.

However far more important is how they are charged. AGM Batteries are voltage and temperature sensitive, meaning, two high a voltage will dry out the glass mat and ruin them, too high a temperature will do the same. So you need a charging system that is designed for AGM. Many battery chargers made today have an AGM setting. But if you are relying on your engine alternator to charge them then you need to know what voltage the alternator is putting out and whether it is in the range required by these batteries. Otherwise you will cook them and they won't last very long.

 

[paulswagelock]

If you have the factory battery charger, it does not handle AGM charging well. As mentioned, your alternator might not either.

When anchored alternate between 1 and 2 each time out. Never run a battery below 50% capacity, it will shorten its life. Start on the opposite battery at the end of the day. The alternator will not fully charge the battery on your trip back unless it is a few hours, so no need to switch it once started.
Plug into shore power every time you return. A 10 amp charger will take 2 days or so to recharge your battery. Solar charger would take weeks, so save your money on that item.

For your boat, I would recommend group 31 lead acid wet cell batteries from interstate or deka. Well suited for your application, lower cost, will work with all your charging equipment, and you would get 5-6 years out of them at minimum if treated properly.

 

[bbwhitejr]

If you have the factory battery charger, it does not handle AGM charging well. As mentioned, your alternator might not either.

When anchored alternate between 1 and 2 each time out. Never run a battery below 50% capacity, it will shorten its life. Start on the opposite battery at the end of the day. The alternator will not fully charge the battery on your trip back unless it is a few hours, so no need to switch it once started.
Plug into shore power every time you return. A 10 amp charger will take 2 days or so to recharge your battery. Solar charger would take weeks, so save your money on that item.

For your boat, I would recommend group 31 lead acid wet cell batteries from interstate or deka. Well suited for your application, lower cost, will work with all your charging equipment, and you would get 5-6 years out of them at minimum if treated properly.

To paulswgock's point-I installed 2-Grp 31 Duracells(Dekas) from Sam's($94/ea) and so far they are performing perfectly. We have run all 12v equipment for a 2 day weekend-TV, stereo, fridge, water pump, head, etc and have yet to pull below 80% and never ran the gen to run the battery charger.

Bennett

 

[LawyerMan]

I wish I saw these posts before I went out to the boat. I installed two Interstate AGM group 31 batteries yesterday, to the tune of $878 for both.