[86loco]

Instead of possibly giving you misinformation I thought it might be good to add to the great information Earnest Jenkins posted and give it to you straight from the master.

THE BATTERY CHARGING REVOLUTION, May 2007
(Posted on an internet discussion forum by HandyBob, spring 2007, in response to a lot of misinformation posted by the uneducated. Quickly deleted by a moderator who didn’t like the truth.)

How about this revolutionary idea: If you want to know how to charge a battery, try looking at the battery manufacturer’s recommendations instead of believing the charger manufacturers. On Trojan’s web site you will find that they recommend a 14.8 volt daily charge, not 14.4 like everybody else will tell you. They also say to continue charging at that voltage until a specific gravity test shows the battery to be full, not to shut the charge off immediately or even early like most chargers operate. Interstate will tell you similar things. The popular opinions on charging AGM or other sealed batteries are also wrong. Every charger I have seen, as well as every solar charge controller is set too low. I have heard people say that this last .4 volts is insignificant, but they are very wrong. Oh, you can charge at 14.4 volts if you are plugged into shore power for days, but running the generator for a few hours or having your solar controller shut off as soon as it reaches the set point does not work. Then, the “professional” RV manufacturers and solar installers will use too small or too long of wire and guarantee that the battery never sees enough voltage to actually get charged. Plus, the Link meter has a factory default full setting of 13.4 volts, so it tells you your batteries are charged long before they really are. Why things are this way is a mystery to me, but this is why most RV & solar systems do not work very well. You would think that manufacturers in related industries would talk to each other, but it does not appear to be the case. I get blank stares from the RV solar dealers that I have asked about these facts, or they start to argue, so the solution is not to be found with them. One guy (one of the most respected RV solar dealers around) last winter actually told me that a hydrometer was not a good way to check a battery’s charge. What an idiot! He was lying so his installations would look better to the uninformed and he would get fewer complaints. I had bought six controllers from him in the previous few weeks and there he was denying the truth! I’ll take my future business elsewhere.

When I found Trojan’s info was when I started to figure out how to make my solar system work. I now charge my batteries to 14.8 volts & then float them at 13.5 volts, unless my temperature sensor automatically lowers or raises this. I have been full timing (mostly boondocking) for seven years and boondocking exclusively for the past five years, never been plugged in at all and we have NEVER owned a generator. (We also do not own either an inverter charger or a pure sine wave inverter. See November 2008 update below.) Our 345 watts of panels runs everything we want and I do mean everything. Coffee maker, hair dryer, toaster, waffle iron, the electric iron that my wife uses for quilting, power tools like a table saw and big air compressor for powering nailers that I am now using while working on a friend’s off-the-grid cabin site. We have enough power that I can continue to work on cloudy days. It snowed here in Montana two weeks ago and my reaction was to tip the panels so the water would run off as the snow melted when the sun finally came out. My Trojan T105 batteries are over five years old and last winter while I was working on a friend’s solar system I disconnected my system for four hours and ran jumper cables over to his abused batteries to try to get them back in shape (it worked). After four hours of still running the small loads in my rig and putting all of my charging into the friend’s batteries my Link did not show 12.7 volts like everybody will tell you is full. It showed 12.85 volts! THAT is a really charged and really healthy battery.

Those of you with a roof covered with solar panels that cannot keep up with your needs are not getting all of the power your panels could produce into your batteries. Wire that is not way oversized will not efficiently transmit DC power to your batteries. (Look up the history on Edison vs. Westinghouse; there is a reason we don’t use DC power transmission.) Any charger that tapers too early, including the latest “boost” controller is not really charging. They are not boosting; they are shutting the power off. I believe that the solar dealers who know about this will not tell us because the profit motive in selling $700 panels is just too great. I would bet money that 99% of the residential systems are also under wired and adjusted wrong. There is a picture in the old Backwoods Solar catalog of a cabin in the woods with the whole roof covered with panels that I love to use as an example of a system that probably does not work. (They made big improvements in their new catalog & that picture was removed.) I believe that a small home should be able to run on 1000 watts or so of panels if I can run my house on wheels with 345 watts. I have put 250 watts of panels on this cabin that I am now finishing, with four batteries and it is working great because I refused to use the #10 wire supplied by the solar dealer, ran #6 and set the charger up to 15.2 volts (14.8 volts @ the batteries. This is with one of those old technology on-off controllers, so it will not hurt the batteries even during the summer time). Of course you do have to live efficiently, but it’s not that difficult to turn the lights off when you leave the room. One of my friends runs his bus conversion, including a 22 cubic foot residential refrigerator, the light in his kitchen and the TV that never seem to get turned off with 800 watts of panels, and now that I helped him rewire & set it up correctly, he finds that he never runs his generator and really didn’t need that many panels. The solar dealer made a bunch of money off of him. Unless people start to think for themselves and figure out that salesmen lie, this situation will only get worse. (I used to be a sales rep, so I know.)

The majority opinions on batteries & charging are wrong. I am living proof of that and the fact that over 95% of the solar systems I have evaluated do not work well also bear it out. Somebody once attacked me on this forum and said that I should not say things about people that lead a more “robust” life, as if sitting in front of a computer and responding to every query, whether you know what you are talking about or not is more robust that running my power tools on my solar power and actually accomplishing something. So, don’t bother to attack me. I won’t respond. I will continue to live by example and help anybody with an open mind that is willing to listen. Send me your e-mail address and I will respond with a 16 page long rant titled “The RV Battery Charging Puzzle” that will tell you why what you have doesn’t work and what you need to do to make it work. But be patient, I usually only do e-mail on weekends and depending on the access, sometimes not even that often.