The newer technology AGM batteries are very nice also. They can lay on their sides without leaking & work fine, be taken to a 20% charge state & bounce back and deal with more abuse than a FLA battery. They never need water or maintenance and can deal with more drains and be good as new for years, but they don't like heat. They can charge back up about five times faster than a flooded battery.
I bought a cheap Renogy 100 watt solar system for my trailer & it's been working very well. The worst thing I did to the the group 27 Trojan AGM battery was make a pot of coffee recently. How bad can that be, really, one pot of coffee? The Trojan is rated at 95 amp-hours. The coffee pot is rated as drawing 900 watts at 110 volts. With the 1,000 watt inverter making 110 volts, this means the coffee pot is drawing about 80 amps at 12 volts, a huge load for a battery. It took 15-20 minutes to make the coffee & everything worked as planned, but also took about 27 amps to do it. In other words, it used up about 30% of the battery charge in a very short amount of time. I would only do this again in an emergency!
As I said, the system is working well enough, but I've been looking at the volt meter and it spikes to 14.4 volts at times (briefly) when the sun is shining during the charge cycle. This charge is good for a flooded battery, but an AGM battery shouldn't charge at over 14.1 volts, ideally. Fortunately, it's been winter since things are up and running, so there are no problems with heating at this point. An AGM battery should never be charged when temperatures are about 120 degrees, that's the weak point in this type of battery. It's also the reason I've decided to not use a charge-while-towing system in the summer, since it's just too warm in the desert from May until September.
I went on line & found a Morning Star 10 amp charge controller & just hooked it up yesterday after work. It has a couple of features I was wanting & at $43, the price was right for my small system. It is far superior to the Renogy unit, which came with the original kit. The new one allows for both FLA charging or an AGM battery. The normal configuration is for the AGM battery & tops off at 14.1 volts, no cooking of the battery now. The other feature I like is that a heat sensor regulates the charge cycle. As temperatures increase, the module changes it's output to take care of the battery and keep it from cooking. The Renogy module, while it's great for a FLA battery, just doesn't have this ability. I've installed it above the battery box at the bulkhead, so it will read the battery temperature as closely as possible. No worries now!
I though I'd share this with people who are doing a solar setup & might want to avoid the pitfalls of charging & making a long life battery last as long as possible. Here's the new charging module, still need to attach the wire cover, but it's up & working now.
