270w solar world panels

I plug the trailers shore cord into the big inverter. Two of our big panels keep the 8-D I use as a inverter bank charged up. A third panel keeps the trailers battery up unless we are running big loads, then it too is switched to the inverter bank. Those panels allow the bank to run much more than it can alone. Unfortunately I can not run big loads like that at night when I'm asleep. Luckily the TV/sat is about the only thing that is used late.

Also keep in mind, you do not want to run your batteries down over 4 or 5 days. Sulfation will increase considerably. So, best to charge daily or every other day. And deeper discharges greatly decrease battery life. Also, continually doing less than a 100% full charge, over a week or two will cause increased sulfation. This is where solar really earns its keep. Many folks will charge with the genset in the am, and then let the solar do all the absorption and top charging to full, throughout the rest of the day and evening. But ultimately your daily useage will dictate your charging regimen.

Brian, the problem with a smaller bank is it cannot handle heavy loads, such as a microwave, etc. The peukert effect especially effects 6 volters; although they do bounce back well, but it can set off the low voltage alarm on your inverter.

I will let someone else deal with your wiring set-up, as I built my own camper, and do not have distribution panels and such.

As for how long it takes to charge a pair of 6's. That depends on several things... Ah capacity, charger size, depth of discharge, voltage setting, etc. Roughly speaking, you can do a 50-90%, at 14.8v and a C/4 rate, in about 2 hours. Most people like to keep the rate (and voltage) lower, but there is no evidence I know of that suggests faster charging will hurt your batteries. And even if it does take a year or two off your batts, it saves so much in genertor run time and fuel, it's well worth it. Of course, going solar, you'll need the gennie much less. So you have to consider your needs, camping habits, budget, etc.

Just keep in mind, converters can be very slow at charging, because many drop down to 13.6v during the constant voltage / absorption stage. So just as the battery's acceptance is dropping, the converter's ability to "push" amps into the bank is significantly reduced at the lower voltage. 2-3 hours can turn into 6-9 hrs... not good when running the gennie.

I noticed you said 2-6's wired in parallel. No. You wire two in series for 12v. Two such "strings" can then be wired in parallel to double Ah's.

http://www.trojanbattery.com/Tech-Support/TechologyLibrary/ConnectionsDiagram.aspx

jrnymn7 wrote:
I'm all for the OP going with a 540w mppt system, if he plans to increase his boondocking, considerably. But then I'd also suggest a larger bank.

Now, I think if I went with four batterys I could stay out longer.
I want to run all the appliances for (limited time)seperatly except
the a/c unit.
I just need to find the space, and wire them in
(parallel 2-6v together) I want to know how you wire your appliances
to run off a inverter. does the inverter feed the panel while on solar
and then a transfer switch while on shore power?
Does someone have a schematic for something like this?
I will make sure size wise the panels will fit on the roof.
Sorry for all the questions, just getting started with solar.
Brian

I'm all for the OP going with a 540w mppt system, if he plans to increase his boondocking, considerably. But then I'd also suggest a larger bank.

$150 is a fine price, I would prefer polys but then again my 245s are mono's.

Recharge in one or two days? Just running the trailer even with lots of furnace use, we simply could not use the power from our 230w panel. Our grp 27 would be in float around 9 am and the panel would cover everything we did till night fall. Being in float all day left the battery well charged to handle another night of LED lights and running the furnace in freezing temps.

Now if you use a lot of power over night and take the battery down to 50%, you are going to need to replace the ah as well as what you use during the day. One panel would do it especially in a two day window. Two panels would have the power to push the bank around and get the voltage up faster when the sun is out. This is a thought if you need that kind of charging on shorter winter days when the sun is lower.

The panels you have listed on a cold day where I camp would push 20a each. My twin 245w panels each peak at 17a and playing with them has been a blast. We don't conserve, we look for ways to use the excess power. Making coffee, cooking, heating water all cut down on propane use. Add a third panel and we can run a small AC on the rare occasion we need it. We could stay out all summer without the generator but food and water limits us to two or three weeks.

sportzfann wrote:

I believe I can get the panels for about $150 ea.
I would like to be able to recharge my batterys in 1-2 days?
It looks like I will need to get the mppt controller.
How many watts/Amps/time is required to charge a pair of 6v batts?

Thanks, Brian :)

That's a good price if they are poly. Check Solar Blvd for a comparison. They've had 250W for $160. Just recharging the batteries you don't need this size panel. Otherwise you need to determine your power consumption. Or buy what fits on the roof.

JiminDenver wrote:
So how good of a price is a good price?

I believe I can get the panels for about $150 ea.
I would like to be able to recharge my batterys in 1-2 days?
It looks like I will need to get the mppt controller.
How many watts/Amps/time is required to charge a pair of 6v batts?

Thanks, Brian :)

I felt the same way when I found my big panels cheap. Well that was until I mated one with the Eco-worthy and found that just one of them flat easily covered our needs. Increasing panel just allows us to have more home like comforts.

Solar sizing calculator
My suggestion would be to put as much module on the roof as you can afford, you'll find a use for any unused power and the large capacity will mean a quick recharge to the batteries.
Don't let the large module and MPPT haters deter you from using that choice. The larger modules have greater power density/area and the MPPT controllers not only harvest more power but have more functionality.