Simple Solar RV expertise needed

[aviat]

I want to purchase a simple solar panel to keep my 4 golf cart 6v batteries up to charge when in storage.  Any idea of what I would need?  My RV sits most of the time and it's not near a plug to keep the batteries up to charge and I don't want them degrading.  It also takes forever to charge them back up as it's a lot of storage. What about mounting it on my roof?  A little concerned about problems with rain leakage.  Would a simple $99 single panel 100w system work (that I saw at camping world)?  1997 Rexhall Airbus RX2900L (30').   Suggestions?  jeff

[ewarnerusa]

A solar charge controller should be a smart charger with at least 3 stages: bulk, absorption, and float.  Same as a plug-in smart charger or converter.  You get what you pay for to an extent, the higher quality ones will have selectable or even fully programmable charge settings for differently battery chemistry.  So in theory, your fully charged batteries in storage would transition to float pretty quickly on a daily basis and you wouldn't lose much water since most of the time it would be in float charge.  But it depends on how the charge controller does its absorption phase, if it does absorption based on time rather than a measurement then it may be in absorption for too much time each day and you'll lose more water.  One 100-watt panel isn't a whole lot when matched with 4x6V batteries, but without a charge controller to monitor things I think it would be enough to boil them out and wreck them.

My PWM solar charge controller is fully programmable and I change the program for storage to lower voltage settings.  I leave the solar charging system in operation year round.

[CarnationSailor]

I have a 5th-wheel with 4 6-volt golf cart batteries. I use a Renogy 30-watt solar panel with an appropriate charge controller. It's about 18 x 24 inches - very portable. It keeps the batteries topped up during the off season, and the charge controller prevents over-charging.

[1995brave]

Check out the Renogy website. They can help you select a system for use on your RV.  I think their two panel roof mount system with controller would be good for you. You can even purchase them through Amazon. 

[StirCrazy]

it might work, but my take on it is if your going to go through the trouble to mount a panel on the roof, go with as big of a panel or two even and use solar while your camping also.  I have four 6V GC batteries on my 5th wheel  with three older panels giving me 480 watts of solar and I never worry about power if I am not using a bunch of 120V apliances.  I am going to upgrade them though as I want to be aboe to run my bar fridge in the outdoor kitchen.  

I would say if you can get two good panels with a MPPT controler you'll be laughing, but for just keeping the batteries topped up a 100 will probably work.

as for leaks, I drilled pilot holes into my studs, put sealant into the holes and on the bottoms of the brackets and then screws the mounts down, then I put self leveling over the tops of the brackets, if any moisture gets through that somthing is wrong..  it then just becomes part of your yearly roof check and fix the self leveling if it needs it.  

[aviat]

 Thanks for the info, Since my RV sits most of the time, will the batteries get overcharged and cooked out? or will the PWM stop delivering juice in sensing that the batteries are full?

[StirCrazy]

I leave mine conected all year, make sure the solar controle has different options for different types of batteries and it should do the corect charge.  I would still check on them and top up watter a couple times while in storage.  I check on mine at the begining and middle of camping season and the same with storage.. so when it goes into storage and about 1/2 way through the storage season.

I find its easier to check a little to often than not enough, this also gives you a chance to see how your solar set up is doing, the first couple months I would probably chek once a week just to get an idea if it is working like you expect and keeping the battery up.  since your talking about stoage another thing to be aware of is if it is a snowy area your in, if so you should go down after each storm and sweep the panels off.