Using different batteries and solar chargers questions

Thanks for the tips!

gemsworld wrote:
I bought the 120W kit. I used the 100W pics for demonstration purposes since both of them are practically identical.

BTW, the specs on the 120W kit from Solar Blvd incorrectly states the kit weighs 13 lbs. The actual weight is closer to 27 lbs. Solar Blvd is going to correct the mistake.

The kit weighs 13 kilograms. About 29 pounds. The 5 meter wire in the kit is a bit small gauged for 7 amps, and pinches you with maybe 3% and a voltage loss of maybe .2 to .25V from the controller to at your batteries. Since the controller only puts out 14.4V, you are down to about 14.15 to 14.2 at the terminals. While this is great, fine and dandy for plug and play... when you get serious, some good 10 gauge wire, as short as possible from the controller to the battery, will minimize any voltage losses and up your Vbat to a higher state of charge.

Once every 10-12 days of camping, you'll need to get 15V or more into your battery bank, to work on the sulfation on the battery plates from too many 50 to 90% charge cycles. Otherwise, if just weekend camping, top the batteries off once you get home, with a good smart charger that will really get the voltage, just to the batteries, up to 15.7 to 16.0V to equalize and desulfate them.

Brings up a point....a one-axle tow trailer. But that's for another thread and maybe even for another forum :)

I thought the question about the battery, dealt with constant current. With constant voltage the value is known beforehand, with current, it takes an algebraic know-two-values-to-arrive-at-the-third sum. In this case it was a constant current source a solar panel - how many amperes or fractions to maintain a couple of group 24 batteries.

Shore power battery maintainer selection is easier than selecting an uncontrolled solar panel via wattage...

MEXICOWANDERER wrote:
The battery should be disconnected - physically. 500 ma per battery would be fine if days are 12 hours, and there is nary a cloud and the temperature don't rise.

To backup MW's comments above (I'm certainly NOT qualified to contradict him on battery matters :B ) When we left our Dodge Caravan at home for the winter and headed to Mexico to winter in the motorhome I disconnected the battery negative, put my "smart" charger on the battery for a day and we left (late October) We returned late March to find the battery voltage at . . . 12.6V :C Put the ground lead back on, turned the key and away it went.

Now Mex is going to say we should have left the Jeep home and towed the Caravan! :B but it won't tow 4 down.

I bought the 120W kit. I used the 100W pics for demonstration purposes since both of them are practically identical.

BTW, the specs on the 120W kit from Solar Blvd incorrectly states the kit weighs 13 lbs. The actual weight is closer to 27 lbs. Solar Blvd is going to correct the mistake.

gemsworld wrote:
Update:

I took a drive to Solar Blvd and purchased the 120W portable kit for $190. The kit comes assembled and prewired as shown in the pics in the link below. The legs for tilting the panels are rather flimsy, but they should work. My kit did not come with the light bulb accessory shown in the pics, but I'd rather have the extra 20 watts than the light bulb. Due to rain and cloudy skies, I won't be able to test the system until the skies clear. Pictures

Batteries:

My local Interstate Batteries distributor wants $108 plus $18 core charge for the exact battery that came with the TT. :E I can get a Costco battery with the same RC 140 rating for $75 and $9 core charge. Needless to say, I'm getting the Costco battery.

Correct me if I'm wrong; When I connect the batteries together, I connect positive to positive and negative to negative. Right?

Wait a sec, your link is for the 100 watt ebay unit? Which did you buy?

12v batteries are parallel - positive to positive, negative to negative.
6 v batteries are series - you make a 12v battery by connecting trailer negative to battery 1 negative, battery 1 positive to battery 2 negative, battery 2 positive to trailer positive.

Better diagrams can be found here:
http://www.marxrv.com/12volt/12volt.htm

You can usually avoid the core charge by giving them an old battery. It doesn't have to be the same type, but they generally count power sport batteries as half a core.

Update:

I took a drive to Solar Blvd and purchased the 120W portable kit for $190. The kit comes assembled and prewired as shown in the pics in the link below. The legs for tilting the panels are rather flimsy, but they should work. My kit did not come with the light bulb accessory shown in the pics, but I'd rather have the extra 20 watts than the light bulb. Due to rain and cloudy skies, I won't be able to test the system until the skies clear. Pictures

Batteries:

My local Interstate Batteries distributor wants $108 plus $18 core charge for the exact battery that came with the TT. :E I can get a Costco battery with the same RC 140 rating for $75 and $9 core charge. Needless to say, I'm getting the Costco battery.

Correct me if I'm wrong; When I connect the batteries together, I connect positive to positive and negative to negative. Right?

gemsworld wrote:

NinerBikes wrote:

gemsworld wrote:
What do you think about this 100W portable kit?

I think that because you are in southern CA, you should go to Solar Blvd, and buy directly.

120 watt folding panel.

Maybe call them and also ask about their 100 watt or 80 watt panels that are portable too.

Or look at this. with an RJ special 12V 10 amp controller, for like 12 or 13$ on ebay.

20 watt panel.

Thanks for pointing out this kit. I will give Solar Blvd a call.

Like you, about 6 months ago, with a 21 foot travel trailer, I sought the same information. I ended up jumping in with that 120W solar kit, that is folding. I can tell you, that once it's March, if my single 24DC battery is at a 50 to 60% charge, by about 9:30 AM that panel will make almost 7 amps, and if you move /aim the panels 2 or 3 times during the day, here at the 33* N, I'll get that level, if the battery can take it, to 4 or 5 pm. I get more time as the days get longer and approach June 21st. Safe to say that for half the year, you're good for 35-to 50 amps of charging during the strongest portions of sunny days with this unit. 50 amps on a 75 amp hour battery is plenty. It might not be enough if you drain two 75 amp batteries down to 50% daily. You'll come up 25 or more amps short.

But if you put LED lights in, to replace your incandescents, and go a little easy on inverters and TV's, the 120 watt is good enough for one group 24. If you use a lot of TV and a sat dish, consider the 160W or building a system that will get you 2 100 or 120 watt panels for 18 to 25 amps of PWM charging at 12 volts, and a single 30 amp charge controller to handle it.

Run the controller as close to the batteries as possible, without them getting exposed to gases and corrosive sulfuric fumes while charging from the batteries, and run fat, low resistance wires, on a very short run from controller to the batteries, to minimize amperage and voltage drop. Wiring from the panels to the charge controller is a bit more forgiving, you can afford a bit of voltage drop if the run from the portable to the charge controller needs to be a bit long from areas of sunshine to the shady rest you are parked at.

gemsworld wrote:

BFL13 wrote:

gemsworld wrote:
What do you think about this 100W portable kit?

Very expensive! On that same page at the bottom you can see other 100w kits for $170.

I did see the cheaper kits, but this one may be more suitable to take in the TT when boondocking since it is hinged and takes up less space.

Can't say how much room you have. I found the 100w panels were very light and much smaller than my 130w panel, so to me a 100w panel is just a little fellow, easy to hide in the trailer while going down the road, and then easy to manhandle out and in as a portable too.

It might be cheaper to get two panels and hinge them yourself and get your own controller on eBay. Probably not a lot of money difference either way you do it for that small an array, if convenience is worth something. One of those individual situational things.