solar panel install

[porkslap]

Hi Folks,

So my end-game is to have a roof-installed solar panel on my trailer to assist with battery charging when I am not hooked to shore power.

I have a WFCO WF-8735-P power center. Do we know if it is possible to hook the solar panel to the battery charging part of the power center instead of using a separate charge controller hooked directly to the battery?

If not, is there any issue with having essentially two battery chargers hooked to the battery (one from the power center and one from the solar panel)? Will they "interfere" with each other if they are both charging the battery at the same time?

I appreciate any insights!
-Tom

[porkslap]

Thanks for everyone's input and reconfirming my suspicions. I didn't want to miss a possible cool way of utilizing the power center and, for me, using a separate controller is no big deal.

[Almot]

porkslap wrote:
if it is possible to hook the solar panel to the battery charging part of the power center instead of using a separate charge controller hooked directly to the battery?

If not, is there any issue with having essentially two battery chargers hooked to the battery (one from the power center and one from the solar panel)? Will they "interfere" with each other if they are both charging the battery at the same time?

No, you need a separate charge controller for panel. At least with +50W panel you do.
No, controller won't interfere with WFCO.

What's a big deal with getting a controller? Disposable junk from Ebay will cost from $10. A decent charger for 12V array up to 500W will cost $100-120, and you will spend about twice as much on panel(s), wires and fuses, depends on the system size. Solar parts cost roughly $2 per watt, including panels, controller and everything else.

Controller should be as close to batteries as possible, connected to battery with substantial cable (think starter cables gauge 4 or better).

You may or may not need a thick wire from panels to controller. This depends on the panels wattage and voltage, impossible to tell without these data. Make templates of cardboard with panel size and width, go on the roof and see how many panels of what you can fit there. Though you should first read those links posted by Don and decide how much solar wattage you need, what this system is for (ex. few days or a few weeks with no shore power etc).

[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.

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 Spread Sheet N8GS

For a nice explanation of solar, try this link:

Golden rules of solar

[robatthelake]

Way back when Solar Panels first started being used on RV's it was common practice to hook them up to the 12 Volt connections on the Fridge.

This supposedly worked fine,although there must have been significant line loss.

The best way to get the most out of a Solar Panel is to connect via a charge controller directly to the Battery. Use the largest Wire that is practical and locate the controller as close to the Battery as possible.

[2oldman]

porkslap wrote:
Do we know if it is possible to hook the solar panel to the battery charging part of the power center instead of using a separate charge controller hooked directly to the battery?

If not, is there any issue with having essentially two battery chargers hooked to the battery (one from the power center and one from the solar panel)?

We do, and it is not. No.