From: John De Armond Subject: Re: Solar Kit Date: Mon, 29 May 2000 22:27:45 EDT Newsgroups: rec.outdoors.rv-travel Bob Beckwith wrote: > > Thanks for all the advice. I have a TT and plan to use two GC 6 volt > batteries for my power source. If all the 45W solar unit will do for > me is trickle charge these two batteries then maybe I would be better > off not spending the 500.00. Thanks again all. As previously stated > our camping lifestyle is to probably only dry camp for max 5 days and > then be on the road. If I drove for 5 or 6 hours would this in itself > charge my batteries back up or would I have to plug in to a power > source? Maybe my best investment might be a small Honda or Coleman > generator??? Bob, You've received a bunch of (mostly BS) answers from the various fanatics. Now let me suggest how you can figure out what YOUR needs are. There is no substitute for accurate use data. Once you figure out how much power you use, then you can figure out what resources you need. One of the easiest and most accurate ways to determine your power usage is to install a battery gauge of the sort that measures current draw from the battery(s), runs the Perkut equation (to account for the apparent loss of capacity in a battery due to discharge rate.) and displays how many amp-hours you've used and how much battery capacity remains. I have a Cruising Equipment Co E-meter but there are other brands. Don't make the mistake of getting one of several "gas gauges" that are nothing more than voltmeters calibrated to read "capacity". They don'. The E-meter displays amps consumed or charged, amp-hours, percentage of charge remaining and several other parameters. Once you KNOW how much power you use per day or trip or whatnot, THEN and only then can you decide what sources of power you need. Unless you travel in the desert, can take the heat and read by candle light, solar isn't going to do much for you. Example: My Maxxair turbo fan draws 10 amps at full power. That's 120 watts at 12 volts. A 45 watt solar panel would supply only about a third of the power just that one appliance uses. Another example: My vision's not so hot in low light isn't so hot so I use a 55 watt light to read by in bed. Again, this load swamps the solar cells. (yeah, I only read at night but the solar cell only generates in the sunlight so it evens out.) Just driving around will likely do all the charging you need if you do it every so often and you have heavy wire running to the trailer battery. That is one way of charging from the alternator. Another way is to put an el-cheapo square wave inverter in the truck, running 120 volt AC to the trailer through a light gauge wire and feeding a battery charger in the trailer with it. Yes, it's less efficient than running a welding cable back to your trailer but it's sure easier to manage. We've done it that way for years with our catering trailers. If you don't drive enough to charge your batteries, then the generator becomes the next option. There are a couple of brands of engine-driven battery chargers available that directly generate 12 volts to charge your batteries. Probably the niftiest is the Subaru minimite that I wrote about last week. If you choose to go the route of a 120 volt generator and battery charger, make sure the battery charger and generator are compatible. Some aren't because of the high peak current drawn by battery chargers. Only way to know is to test. The other option is to use a combo converter/charger. The better ones have input power factor correction to make them generator friendly. The good part of this setup is that you can fast-charge the batteries either from the generator or shore power. John |