I have a horse trailer w/ living quarters, trailer has 2 deep cycle batteries would a third battery help longevity of the charge? I can go about 4 days with out charging then I get to listen to the annoying alarm. Would like to get 6 days but may be asking too much. Had hoped that 75 watt solar panel would help but does not seem to be the case. Trying to avoid getting a generator.

 

I had same issue with a 5th wheel. I have (4) 6 volt batteries and a 90 watt solar panel and I'm good for a weeks as long as the sun shines. I also have an 1200watt inverter I use If I need to run the TV or other 110 volt stuff for short periods each day. I would go with at least (4) batteries.

 

"Skinner",what is your electrical load?The draw from your batteries is going to determine how much battery in relation to how long to charge.R/v people who boondock generally like Trojan T-105's(in pairs) with solar panels and charge controllers or,Interstates with the same amp hr.rating.

 

iroc... is right, what are your needs. These can be calculated mathematically and give you an idea of what you will need.

Probably the best route would be to chuck the 12v's and get the 6v's. They are much better at keeping a charge over a long period. A little spendy to buy but a better choice for your situation.

 

You will need to add up what total watts you are using during the (4) days. make a sheet of all the appliances you use (Volts x amps = watts). Next by each item add up the duration you use them . For 120 volt appliances use ((AC watts/12v)x 1.1XHours= Amp hours) For 12v it is just (12v Amps x 1.1 = amp hours). Draining batteries all the way down shortens the life of the battery. I understand you try not to drain your system more than 50% before recharging. The deep cycle batteries I use are 72 amp hour, small trolling motor type. A fully charged battery is somewhere around 12.6 + volts @ 50% capacity 12.06 and less than 30 % it is around 11.75 volts. The batteries should be changed in pairs because as batteries age they charge and discharge differently so they will fight each other when using them or charging. I had it put an inverter ,in my boat, to run a blower for my boat lift. It took 13 amps @ 120 volts for about 6 minutes. I had to put in a second battery because a battery at high discharge rates has less capacity. Some information was research and some information was learning curve.

 

Here is an excellent website for learning about batteries and inverters. Well written and Phred can be very Phuny at times.

http://www.phrannie.org

Go to his poop sheets and look up batteries. Good stuff and easy to read.
Bob

 

I guess I'd also ask what are the stock batteries in your trailer? What are their capacity, and how old are they?

Generally, it is not a good idea to hook batteries of different type, capacity or age in parallel.

Also, unless you are using more power in your trailer than typical, I suspect the batteries you have are performing poorly.

I would think about a pair of Trojan T145's, or T125's. They are 6v and would be hooked in series, and T145's are rated at 260 amp hours. Basically they have way more capacity than the T-105 for not much more money. I don't think they are rated for as many full discharge cycles, but for RV use they will die from old age way before you could use that many cycles.

When one of the cheap RV/Marine batteries that were in my trailer when I got it totally failed, I put in a pair of Trojan T-125's (240 amp hour). It more than doubled the length of time I can drycamp when the other batteries were working.

Here is another excellent source for everything you might need to know about deep cycle battery selection, types, and care and feeding...

http://www.windsun.com/Batteries/Battery_FAQ.htm