Help with Basic Solar Set Up

[BurbMan]

After years of storing the TT at home we are thinking of moving to a smaller home and putting the TT in a storage lot. One of the luxuries of parking at home is being able to stay plugged in year round and keep the batteries charged up. So I am looking for a small solar set up that will give me enough of a trickle charge to keep the batteries topped up.

Currently have 2 6v batteries that are 8 years old and will likely get replaced this season at some point. I have been looking at Solar for a few years but moving to a storage lot would be the impetus I needed to pull the trigger.

What's a recommended solar set up to keep the batteries charged? Assuming there might be 3 or 4 cloudy days running on batteries, the solar would need to "catch up" and bring the batteries back when the sun comes out. Usage would be minimal...propane detector, idle radio (clock display), about it, and whatever other small draws.

From what I gather I would need a solar panel and a charge controller, any recommendations for size or brands for this application? Is scaling up to add wattage simply a function of more panels?

[Almot]

BurbMan wrote:
Storage is the primary reason, but since I am installing solar, why not add a little more capacity? I am not looking for portable panels, The idea would be to mount something on the roof and wire it in with a charge controller.

This is a slippery slope, you've been warned :)...

What Doug said - to use a solar for something more than a storage is a whole different thing. With a flat roof-mounted panel, unless your location is so dark and rainy that even a 300W solar solar on most days could only do a trickle-charge in storage - it makes a lot of sense getting more than 140W. And a proper controller.

[NinerBikes]

You still need to keep the bird poop and dirt and dust off a solar panel, by cleaning it regularly. They aren't exactly maintenance free if you want peak performance out of them.

[BurbMan]

Storage is the primary reason, but since I am installing solar, why not add a little more capacity? I am not looking for portable panels, The idea would be to mount something on the roof and wire it in with a charge controller. As soon as I leave the CG the solar kicks in and charges the batteries while I'm going down the road. I am not looking to cover all of my boondocking use with solar, but any capacity that helps reduce generator run time is a bonus.

Right now I leave the TT plugged in 24/7 at home and it keeps the batteries on trickle charge so they don't freeze in the winter. Ideally would like to do the same with solar, provide enough energy to keep the batteries onboard through the winter. We don't get much snow down here (except for this winter LOL)so worst case the panel would be offline for a day or two until the snow melts.

[Almot]

doughere wrote:
If all you are trying to do is keep batteries charged, disconnect power from trailer, and get a 15 to 25 watt panel and a cheap e-bay PWM controller.

Yes. 15W, or a little more if batteries are old and the location is not too sunny. 40W would be plenty. He won't be able to equalize with this, but then, equalizing them in storage is not critical.

[doughere]

If all you are trying to do is keep batteries charged, disconnect power from trailer, and get a 15 to 25 watt panel and a cheap e-bay PWM controller.

Bottom end, disconnect batteries, get a 10 to 15 watt panel and tie directly to batteries without a controller.

Scaling up from that is a whole different ball game. Involves a thorough study of loads, how often you will use system, how long at a time, are you going to use a gen, etc???

Many discussion in this forum of various ideas.

Regards,
Doug

[BurbMan]

BfL if I understand you the charge controllers at the charging sources, either converter or solar, will figure out what the batteries can take and adjust accordingly. That's good info and part of what I didn't understand.

Ninerbikes, the 75% was just for example. All lights inside and out are LEDs and yes have two phones plugged in and charging overnight. Sometimes a laptop and or tablet too...

So sounds like 140w would cover some usage in addition to storage charge and possibly cut down gen time.

[NinerBikes]

If you have the eu2000i and the PD4655, and 232 ah battery, and you are at 75% at bed time... call it 240 amps for ease of math... You used 60 amps... and while asleep, is the heater with a fan running? or not? Makes a big difference. You'll use another 10 amps parasitic, just over night. now you're at 70 amps. Plus lights, what kind of lights are you running? Laptop being recharged too? or cell phone, over night? Let's for arguements sake, call it 80 amps... you're at 66% come morning. Maybe more, maybe less.

With a good short run of wiring and your charge controller at 14.4 volts, with the force mode on the charge wizard, you should be close to 85 or 90% charged in 90 minutes, is my guess. You still need to add 24 amps. No problem with a 120 portable Watt panel in 5 to 6 hours of sun, at 6.5 to 7 amp hours in spring, summer and fall. Not so much winter. You might get 5 to 6 hours of charging in winter time, with the sun low on the horizon, unless you've got some snow cover.

[Almot]

BurbMan wrote:
Really just looking for something to keep the batteries charged while the TT is in storage and maybe offset some light use during boondocking.

140W kit will do just fine. Or 120W. For storage-only, you don't need more than 40W.

BurbMan wrote:
When I roll out of bed and fire up the Honda, the PD4655 will start putting out 14.4v to the batteries. Does the solar controller stay online so its amperage will contribute to charge the batteries faster?

I'm guessing here since don't use a generator - I think with generator the solar will keep on contributing, but those few solar amps won't matter.

EDIT - PS:
Perhaps it was confusing when I said earlier that you can do equalization when on shore power, and then said that converter won't do this. Yes, it won't. To equalize while on shore power, you need a proper 120V charger with manual equalization function. But 140W panel should be capable to do equalization on a sunny day and with full batteries - they MUST be full before doing equalization.

[BFL13]

BurbMan wrote:
I upgraded the converter to a PD 4655 and also upgraded the charging wire to the batteries to #2 (#4 in parallel with factory #6) so it's pretty efficient now. Really just looking for something to keep the batteries charged while the TT is in storage and maybe offset some light use during boondocking. I have a Honda 2000 that I use for battery charging while boondocking so I don't need the solar to carry all of the usage.

Let's say I watch the late show and the batteries are at 75% when I turn off the TV. The sun comes out and the solar controller is sending 14.4v to the batteries. When I roll out of bed and fire up the Honda, the PD4655 will start putting out 14.4v to the batteries. Does the solar controller stay online so its amperage will contribute to charge the batteries faster?

Multiple chargers will either add their amps or share the amps the batteries will accept, and the proportion of the amps each charger does depends on the charger's voltage wrt battery voltage and the other chargers' voltages.

If you have two equal voltage chargers that can do 40 amps each and the battery will accept 90 amps then you will get 80 amps. If the battery will only accept 40 amps, each charger will do 20a.

If one charger is higher voltage, there will be a time when say the battery will take 50a and it is doing 30a while the other is doing 20.

It keeps changing as battery voltage rises so that eventually when the battery voltage reaches the voltage of the lower voltage charger, it quits doing any amps and the other charger is left doing it all, however much that might be by then.

You can just leave the solar on when running the converter on shore power and let the electrons sort it out amongst themselves who does what to whom. No harm done.

[BurbMan]

I upgraded the converter to a PD 4655 and also upgraded the charging wire to the batteries to #2 (#4 in parallel with factory #6) so it's pretty efficient now. Really just looking for something to keep the batteries charged while the TT is in storage and maybe offset some light use during boondocking. I have a Honda 2000 that I use for battery charging while boondocking so I don't need the solar to carry all of the usage.

Let's say I watch the late show and the batteries are at 75% when I turn off the TV. The sun comes out and the solar controller is sending 14.4v to the batteries. When I roll out of bed and fire up the Honda, the PD4655 will start putting out 14.4v to the batteries. Does the solar controller stay online so its amperage will contribute to charge the batteries faster?

[Almot]

I wouldn't rely on converter to do anything but floating. They often have many feet of thin wire to the battery and are barely able to get into boost mode, not to mention equalization. Besides, as mentioned, equalization has to be done with everything else disconnected.

No, controller won't necessarily turn the solar off when converter comes online. Solar will try and augment the voltage if needed.

[red31]

160 watt kit, plug and play portable

Reported back order of their 100 and 140 w kits.
http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/27646486.cfm

[BurbMan]

Ok thanks....Still have a lot to learn here. Comments on this 140W kit?

So solar connects directly to the batteries independently of any existing wiring...I guess the charge controller turns off solar charging when shore power brings the converter online?

[BFL13]

BurbMan wrote:
Good point....according the info I have the PD4655 converter goes into "equalization mode" automatically for 15 mins every 21 hrs to equalize the batteries.

Nope! That is an incorrect use of the term. What that does is jack the voltage to the 14.4 bosst voltage every so often in an attempt to prevent stratification while on the 13.2v Float.

"Equalization" means the voltage goes to mid 15s or 16v and really gets things going. Special procedure with batteries disconnected from rig to not ruin the fridge's control board etc.