Amp Hour question

Interstate's website lists them with reserve capacity at 25Amp for 100 minutes = 42 Amp Hours, That's sorta the 2 hr rating, at the more common 20 rate, its probably 50 to 55 AH.

I'd set the controller for 100 AH for the pair.

They're not the best for your application, but with a little bit of care will serve you well for years.

Doug

I am still running on similar batteries, with 300w of solar. I don't have to worry about them overcharging, since it will float at 13.2 volts if they get totally charged up, anyway. I've been looking at some AGM deep cycle batteries, since the 6v golf cart batteries I'm most familiar with won't fit the metal compartment under the step! So, I've seen some AGM's that will fit, and some that might have to go in sideways, in over to fit. I have another remote camp with true deep cycle batteries and there is a big difference in reliability and duration compared to marine batteries. I started solar with used forklift batteries that I could only move with a front end loader.

You'll love having solar, and when you add more, you'll love it more. The people that have already answered have some consistently good advice about batteries and solar. To me, it's fascinating to make the whole rolling residence as self sufficient as possible.

4aSong wrote:
I would guess that these batteries are not a true deep cycle battery is why no Amp Hours are posted but I may be wrong.

Correct. You have Marine batteries, meaning they are a cross between deep cycle and starting.

The battery specs online (a good source of information) say that it's about 45ah, so two of them are 90ah. I've never encountered a controller that asked for that kind of information. 45ah is not very much for a camping battery.

When you get the urge to replace them, get some true deep cycles.

Trojan 24TMX is rated 85 and probably 70 to 80 for Interstate that does not seem to like publishing the A/h rating.

Group 24 battery is typically about 75 amp hours.

If this will be hooked up to the RV and you have more than one battery, then you add up the sum, and set it for that.

They might have suggested 45 amp hours so that it will allow charging at 5 amps or so. Should you have set it for say a 20 amp hour scooter battery size, it might limit charge rate to say 4 amp to keep from overheating the battery.

Really 100 watts is nothing in a RV. Sure it will attempt to charge the battery, but your CO meter, propane detector and refrigerator will combined use about 35 amp hours daily, while the 100 watt solar panel can at best produce about 30 amp hours per day. It is better than nothing, but still after 3 days you will need to crank up a generator - even if using no lights or anything else on 12 VDC.

I have a pair of 120 watt panels, pair of 45 watt panels and a 75W panel. That way I can watch as much TV as I want, and never need to run the generator just to recharge the battery.

SunElec.com THey sell solar panels for about $1 - $2 per rated watt. Controllers are extra, but a low cost 20 amp PWM controller is good for about 300 rated watts, and only run about $20 these days.

Select 12 volt 'nominal' panels, with a 20 - 22 volt 'open circuit' voltage rating. These will quickly charge the battery, no matter how large your battery bank ends up being.

I have 4 golf cart batteries rated at 440 amp hours at 12 volts, and each is 67 pounds! That is to much weight for the typical RV, and a larger solar system can make up for a smaller and lighter weight battery, because you will be generating power all day long, and only need to store 1/2 as much for nighttime use only.

If you can add water to the battery that you have now, I would say keep it until it dies. Deep cycle battery is one that you can add water to it. If it is sealed, then still keep it until it dies, perhaps next spring replace it with something better. It will not last more than 3 years, regardless. I have never had a 12 volt battery last 4 years, but my Trojan 6 volt battery lasted 13 years!

Good luck,

Fred.