Suggested Marine Battery Size

kieranmullen · 07-28-2017, 12:21 PM

Other than to fit the size of your box... any other suggestions ? Cranking amps or reserve? I suppose those don't matter too much since we aren't cranking anything. Thank you!

**Kidkraz** · 07-28-2017, 12:28 PM

Well, how do you camp? At places with full connections or do you do mostly dry camping or some mix of both? I do about 85% of dry camping without power, so I installed two group 27 batteries. My TM came with one group 24 and that didn't work. I was up in the air on going to two batteries, but as a friend said, you can't really go wrong with having too much battery power.
I bought thru a local Interstate distro center, and got a better price. They even gave me a military discount.

kieranmullen · 07-28-2017, 12:44 PM

Usually only for the weekend and I have a solar panel for recharging it. Not sure why the old 30 AMP connector corroded. So I ordered a new one from trail manor since they said theirs has #8 wire instead of #12 wire like most the stores sell. If it is only to prevent backfeeding, I am not sure why the wire size matters.

Padgett · 07-28-2017, 01:06 PM

I'd call that light use but if I only had one it would be a grp 31 Duracell AGM from Sam's Club.

Mine is sized for a week or 10 days dry camping so have a bit more.

BrucePerens · 07-28-2017, 01:54 PM

Do not buy a marine battery. Marine batteries are mixed starting and running batteries and are generally not sold with the thickness of plates that real house batteries come with.

Your best buy will be two GC-2 batteries with a cable between them and the proper sized box to hold them. This will fit on the A frame.

You are also advised to buy a battery protector that will cut off if something brings the batteries below 12V. Every RV owner kills a set of batteries once in a while, unless they have a protector.

Padgett · 07-28-2017, 03:39 PM

Was talking about this. Have had a couple. If goint to have just one battery, this is it.

OTOH I agree. 2 GC2s would be better.

tentcamper · 07-28-2017, 09:52 PM

For a few more dollars I would get the biggest one, a G-31. It has about 75% more stored energy than a g-24 and maybe is $20 more. In the sumer we get about 7 day off a G-31

The thing you want with a marine battery is the highest RC number. I think the G-31 will be around 225 amps. CCA - Cold cranking amps means nothen for a camper, but is great to start a boat engine.

Padgett · 07-29-2017, 06:34 AM

What I look for is a spec like this: Minutes at 5 amps:1265 (21 hours at 5A - Grp 31). A Pair of GC2s is about double that.

**Bill** · 07-30-2017, 09:30 AM

Quote:

Originally Posted by BrucePerens

Do not buy a marine battery. Marine batteries are mixed starting and running batteries ...

I'm definitely with Bruce on this one. Do not buy a marine battery. Why not?

Standard lead-acid batteries come in two very different types, depending on their internal construction. They are Motor-starting batteries, and Deep Cycle batteries.

In order to start the engine of your car, a Motor-starting battery must deliver a huge current for a short time - this is called cranking amps, since it is used to crank the engine of your car. The amount of available current depends on how much surface area of lead is in contact with the acid, so motor-starting batteries have many thin plates crammed close together. Thin plates are fragile, and they tend to warp and short out unless they are recharged immediately.

By contrast, deep-cycle batteries need to deliver much smaller current, but for a much longer time. To do so, they are constructed with thick plates. Thick plates are strong, and resist warping.

Marine batteries claim to do both jobs. In reality, they are kind of the worst of both worlds.

Buy a true deep-cycle battery. Even WalMart has them if you look. Avoid batteries that say "Marine" or "Deep Cycle / Marine".

Bill

tentcamper · 07-30-2017, 11:22 AM

I'm with Padgett with the G-31 batteries. You only need one and can add as many as you need.

Most deep cycle batteries are GC batteries optimized to the amps to push a golf cart, with a load of about 500-600 lbs around for 4 - 5 miles, running a large apm sucking motor. They are designed to maximize the number of time that it can be deeply discharged (below 50% and recharged (deep Cycle). One round of Golf. Its the life of a golf cart, charge them and deeply discharge them on the next 18 holes with maybe 150-250 times you turn on the electric motor to discharge in a round of golf.

My camper almost never sees a 10+ amp draw, which is far below a golf cart draw. Only when the furnace is running, water pump is, on and some lights do I go a little above 10 amps. Maybe when I forget to turn off the 12V fridge. I almost never see the south side of 50% charge, it been a few years. So I'm not using the true deep cycle characteristics (high number of deeply discharge and charge cycles).

I have been using G-31 batteries since the late 80's. Normally getting 7+ years from a battery. The camper I just sold the battery, I had moved the battery from my previous camper and it was almost 7 years old,. It was testing at 95% of new. Maybe if I became a full timer and was going to be discharging my battery a lot below 50%, I would think about GC.

Plus my empirical experience tell me that the lead mixture of a battery defines the charging voltage. I believe most campers the converters are designed to charge to the lead mixture and charging voltages of Marine batteries. I think the peek charging voltages are different os something like 14.4 compared to 13.6.