Solar Panel for charging Coach Batteries

[Grandpa_Joe]

Does anyone have a good low cost model they have purchased to charge the coach batteries when away from shore power? Amazon had a 100 watt Renogy folding unit which I saw on my last trip, owner has happy with it, went to amazon and it was $187.00 or so , week later, went up to $279.00?

[mlts22]

If you are not travelling on a day to day basis, one thing you might consider is getting a portable solar kit, and perhaps a dedicated charge controller (MPPT preferably.) This way, you can have your rig in the shade if it is hot, but still be able to get decent solar charging.

[tpi]

https://www.solarblvd.com/product_info.php?cPath=1_269&products_id=2666

https://www.solarblvd.com/product_info.php?cPath=1_269&products_id=2668

You'll need a controller with this.

Chalk me up as saying one 100W panel is valuable in any case the RV is not stored with power hooked up. It will recharge (eventually) and maintain the battery. Very frequently RV batteries are not maintained at all.

Two or three panels would be a good starting point if you're trying to recharge batteries when dry camping. Swapping to LED lights and other low draw systems (electronics) can be as rewarding as piling on the panels. Of course the actual panel capacity needed is totally related to how you camp. See below:

I'd highly recommend reading the solar discussions in the tech issues portion of this forum.

[pianotuna]

Here is a simple flow chart.

Budget-->Energy Audit-->Battery bank size-->number of watts-->PWM or MPPT. What ever type of controller is chosen, make sure it has adjustable set points and a temperature probe that is on the battery.

If you use solar as a battery charger, one rule of thumb is between 60 and 150 watts of panels per 100 amp-hours of storage. The smaller the battery bank the higher the wattage needed (per 100 amp-hours). Here is a link to the rather special spreadsheet which includes an energy audit, that N8GS has created to help size solar battery charging systems!
solar spreadsheet by N8GS

If you full time or use an inverter lots, then populate the entire unshaded area of the roof with panels. I'm considering replacing my awning with solar panels.

For a nice explanation of solar, try this link:
Golden rules of solar

[Grandpa_Joe]

Thanks Guys

[coolmom42]

There is tons of info in this thread:

Solar experiences


You need to start with the calculator to determine your electrical needs.

Then size your batteries for your needs.

Then size your solar panels and controller to have ample capacity to charge your batteries to 100% in a reasonable amount of time.

There are also lots of recommendations on panels and controllers in this thread and the links from it.

[RoyB]

Solar panels are a two-edged sword. Everyone thinks "Hey I can just add a 100WATT SOLAR PANEL and it will solve my battery charging problem when camping off the power grid."

A typical 120WATT SOLAR PANELS will only provide 5-6AMPS DC CHARGE when in high SUN. If your 12VDC items draw much more than the 5-6AMPS then it won't be a whole lot of help keeping your battery charged.

I am doing my camping off the power grid in baby steps. I immediately upgraded my off-road camper with smart mode charging capabilities and added more batteries and larger battery cables etc. I also converted my OFF-ROAD trailer with LED lighting to really cut back on battery usage...

We beefed up the batteries to run all of the things we wanted to run when camping off the power grid and then used our 2KW Generator each morning at 8AM to power up the off-road trailer so that the on-board smart mode converter/charger would re-charge our battery bank in a three hour generator run time. Where we camp we always run into the problem of the campground seems to always have generator run time restrictions so we have to run it during those times.

Now that we have established how we want to camp off the power grid and can re-charge our batteries in a quick three hour time frame each it is now time to add some solar panels to cut back on my generator run time requirement. There is always times when you don't have good HIGH SUN too so having the generator is really a must have thing to have as primary for battery charging.

We will run down our battery bank to its 50% charge state by 8AM each morning so we now have to recharge them back up to the 90% charge state before we use them again the next evening/night time frame. If the batteries are not at their 90% charge state they will not hold the almost full performance through the night.

When I first hit my battery bank with 14.4VDC smart mode charging they immediately draw 52-53 AMPS DC from the on-board converter/charger unit. This current draw will eventually drop back to around 8AMPs in 30 minutes or so and remain around that level throughout the remaining three hour charge period. I will have to run the generator during this initial high current drain period but then can turn it off after lets say one hours time and then let the SOLAR PANELS finish my remaining charge for the rest of the high sun day. This is the only way I can see to "FOR SURE" get my batteries to their needed 90% charge state before the high sun goes down.

As you can see there is more to charging your battery then just adding a 100WATT solar panel.

Now if you only use a couple of LED lights over night then you could probably pull it off. We like to use almost everything we have available to use with the exception of the Air Conditioner and high wattage Microwave. My other hobby is HAM RADIO... Everything else gets used just like we do when we are camping at regular electric campgrounds.

Just my thoughts and experiences here - It does take some planning on what you are going to do when camping off the power grid.

I am just now thinking about adding solar panel and I really like the folding panel idea to start seeing what I can do with solar panels. For my OFF-ROAD POPUP I am probably only going to room on the roof for two 120WATT panels on either side of my fantastic fan installed on one end and maybe a larger 240WATT Panel on the other end between the roof air conditioner and the end of the roof. I will also have the extra weight added for the panels to be considered. Might have to raise my POPUP roof first then do a quick snap-in quick mount of the solar panels. My 12VDC motor may not raise my roof with the added weight?...

It might be a four sided edge sword for me haha...

Roy Ken