# of watts solar system needed to MAINTAIN coach batteries?

Our coach has 4ea 6v deep cycle batteries and we have a 100w solar panel with controller which more than adequately maintains both coach & chassis batteries.

I would also recommend 100 watts of solar and a dual bank controller. That would maintain both the house and chassis batteries quite easily.

calthage wrote:
Class A with 2 12 volt coach batteries. Want to maintain while not in use.

You're talking just a solar float charger, right? Just to keep them fresh during the winter?

From what I read on Amazon this morning, 5-8 watts is working for other people.

100 watts if you don't disconnect, much less if you do.

Hi,

Bare minimum 15 watts per 100 amp-hours of storage assuming no snow cover.

Better 30 watts per 100 amp-hours. This would actually recharge the bank between trips.

60 watts per 100 amp-hours if you wish to be able to equalize the bank.

harold1946 wrote:
I would also recommend 100 watts of solar and a dual bank controller. That would maintain both the house and chassis batteries quite easily.

I also have 100 watts of Solar and 440 hour battery bank.

Battery (and linked Chassis Battery) stays full if I switch off the house battery switch.

If I do not use the disconnect switch, the current draws exceed the solar replacement.

This is due, I think, to my storage area providing sun to the panel for only about 6 hours per day.

If your battery is disconnected with no load then a very small solar panel will do great...

If it is connected to your truck systems or your trailer system than you have to have enough power to overcome the parasitic drains as well as maintaining the battery...

I have a 9WATT solar panel panel laying in the dash area of my truck and it does not do well keeping the truck start battery topped off. I have too much parastic drain for it...

I leave my trailer system batteries plugged inall the time when parked at home during the season and they PD9260C converter/charger keeps them in good shap. During the winter months I just get my batteries charged up good and then completely disconnect them but leave them sitting in the battery box on the trailer tongue.

They do just fine making it through the winter months here. I do occasionally read their charge state and they usually drop down to around 12.3-4VDC by the end of the winter months.

Roy ken

Those 'optional' solar panels on top of many RVs ACs are 8 Watt and I've never heard of them working very well to maintain even small 12V coach or chassis batteries.

I wouldn't get anything less than 50 Watts in the desert areas, and 100 Watts in the northern states.

To make life easy and save any guess work, just buy a 100 watt panel. They're the most commonly available panel.

2 watt is more than enough if batteries are disconnected.

My 5 batteries (2 coach, 1 chassis, 1 SUV and 1 motorcycle) were fully charged (12.7v) after almost 5 months in low-light Boise.

Nature Power Solar Battery Maintainers and Trickle Chargers- 2-watt Catalog Item # 56004 $28
model is weather-resistant for indoor or outdoor use

Dimensions: 16" x 5" x 1 1/2"
Manufacturer: Rdk Products
Mfg Part #: 40019

CW low-cost Solar Battery Charger worked over winter

In Nov, I removed the batteries, connected them in parallel, and used an externally mounted CW solar charger (I believe it was a Nature Power Solar Battery Maintainers and Trickle Chargers- 2-watt Catalog Item # 56004 $28) to keep them topped off. I mounted the panel pointing to the south and at an angle I guessed would be perpendicular to the sun's rays during winter there.

This solar charger has no regulator, so I feared its reverse current draw (during night and low light) might do more harm than good by draining the batteries and ruining them.

However, it worked well. Newer models say they have a built-in blocking diode to prevent reverse flow of electricity

I would LIKE to think manufacturers would state the reverse draw of their products but such is often not the case. The year before the solar battery maintainer I purchased from CW, Sun Force 1.8W, User's Manual says nothing about reverse draw. When I got to my RV storage location and measured it, the draw was of an amount that I guessed it would ruined the batteries. So I had to leave them without charging over the winter. Next year I had to replace both the coach batteries.


Sunforce 50012 is $17 from Home Depot