Battery Dilemma

[Dern]

I just spent the weekend upgrading my solar set up. I installed two 140 watt panels. I'm torn as to what route I should take in regards to batteries. Price and longevity wise, I'd just assume go with two 6volt wet cell golf cart batts. and wire them in series .( I'm powering a Waco/Dometic 12v fridge) My concern is the off gassing. I don't think being in a camper full of battery gasses would be good. Is this an issue? I have an off grid set up down in Baja and the batteries there do vent/offgas.
The other route is the AGM battery. However, the price is double what a 6volt is and I'd need two as well. $300 vs $600. Decisions, decisions.

Darren

 

[pods8]

Yes it is an issue, you should put them in a sealed box that is vented to the outside if you put them in the camper.

 

[fish more]

GO WITH AGM, NO VENTING NEEDED. BUY GOOD AGM BATTERIES WITH HIGH RESERVE CAPACITY. YOU WON'T GO WRONG WITH AGMS. I HAVE TWO GROUP 24 MOUNTED ON THEIR ENDS IN THE AREA THAT MOST PEOPLE HAVE ONE BATTERY.

 

[JHanson]

Darren,

Wow - you went even more overboard than we did on PV input. We get by with a piddling 200 watts.

We live completely off the grid at home and use ten six-volt batteries there as our storage. But our camper has two Exide AGMs. They're really much more suitable for a mobile application.

 

[Dern]

I'll be the one glowing in the campground. I got a group 31 105ah AGM. I'll start with one and see how it holds up with the fridge. I have to do a little disassembling to get the thing into its rightful cubby though. Thanks for everybodys input.

Darren

 

[leadsled9]

I have two group 31 AGMs for my 12v fridge. Remember that the shallower the discharge....the longer the battery life.

 

[Dern]

I have two group 31 AGMs for my 12v fridge. Remember that the shallower the discharge....the longer the battery life.

cycle life.JPG

I understand the basic discharge/cycle life of batteries theory. The basic rule of thumb that I was taught was to have more panel and less battery.So with your panels you're able to get both batteries fully charged during the day while the fridge is drawing from the batt as well? Also, on the chart you supplied, as well as other chart/graphs I've seen, what's considered say 50% discharge capacity? 10volts? 11 volts?
I'm not opposed to adding another battery to my array. I just don't wont to spend another $300 bucks if it's not necessary.

 

[leadsled9]

Here is a "State of Charge" chart.

Everyone's usage and habits are different. Just monitor your battery during your normal camping conditions and see if your battery is being drained deeper than you would like. If need be you can add another battery.

You should use identical batteries and they should be the same age.

 

[Dern]

Basicly the only things that will use power in the camper is the fridge, water pump and a light in the evening. I'll be putting the battery to the test this weekend. I'm waiting for a charge controller in the mail. I'll get the battery fully charged and let the fridge run all night. In the AM I'll put the volt meter on it and see what it says. Thanks for the %chart.

Darren

 

[camelracer]

It should be noted that the battery voltage should be checked with no load on the battery. Any load will drop the voltage below the true static charge.

 

[ntsqd]

In addition, some of the reading that I've done says that the battery should be "rested" (no loads, no charging) for a period of time before making any measurements. How long seems to vary. Some say an hour, others a day.