Solar: I have a converter, need a charge controller too?

[SlowBro]

I have a converter, do I also need a battery charge controller for solar? My trailer comes with a WFCO 8945, which is three stage, and I can't find a definitive answer on this question anywhere. Seems like a dedicated charge controller would be redundant.

Spec sheet
Brochure
Manual

Edit: I had a brain fart about how converters work. They only accept 120VAC. Nevermind :B

[SlowBro]

smkettner wrote:
If your solar panels puts out 120vac

I've never seen any that do... plenty that put out higher voltages but only DC.

My question was a brain fart.

[time2roll]

If your solar panels puts out 120vac the converter will plug right in.

Otherwise you need a controller if you have more than ~8 watts per battery.

> Forum Members Solar Installations With Pics

[SlowBro]

Good stuff. I almost put a grid-tied PV array on my roof a couple years ago but I can see RVers have a slightly different way of tackling the same issues, as well as unique needs.

If you haven't figured it out yet, my question in the OP was a brain fart :B Ahh well, they say the only dumb question is the one un-asked. Maybe someone else will wonder the same thing.

[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 by N8GS

For a nice explanation of solar, try this link:

Golden rules of solar

[SlowBro]

So you're using a combo to get the best of both worlds. Sounds like a winner, RoyB.

[RoyB]

This is what we would do using solar panels to support our battery system charging capabilities.

For camping off the power grid what you want to do is beef up your trailer battery system to run all of the 120VAC appliance you want to run from an INVERTER and all of the 12VDC items you want to run in a one day/night run off the batteries. This of course will not run your air conditioner or other high wattage appliances.

Then when your batteries drop to their 50% charge state (around 12.0VDC) you will want to recharge them. You need to plan out your battery system setup to make this occur at 8AM the next so that you can run your generator at those camp sites that have generator run time restrictions in place.

We use our 2KW generator each morning at 8AM each morning to run our trailer so the on-board smart mode converter/charger will re-charge our batteries in a quick three hour generator run time. I suspect your WFCO 8945 setup is not going to do this for you as it is a very poor three stage smart mode setup. I had to change mine out for a PD9260C converter/charger unit.

Once your batteries are charged back up to their 90% charge state then you are good to go again for the next day/night run off the batteries.

Where the solar panels come into play is after you have run the generator for about one hour after the high current demand has dropped from some 50AMP DC CURRENT to around 8AMP DC current then you shut down down the generator and allow the high sun to continue charging your battery bank until the high sun goes away. Keep in mind a 120WATT solar panel will only produce around 5 amps DC current. For two or three batteries in your setup you will need enough solar panels to produce around 20AMP DC current for the remaining solar high sun day. The solar panel controller will mimic the on-board converter/charger DC outputs and do a great smart mode charging technique for your batteries...

This is what I would use solar panels for at any rate. It would take a lot of solar panels to just live off of them alone. You have to use the solar panels to re-charge your high current capacity battery banks and the use the BATTERIES to run your 120VAC/12VDC appliances etc..

Have been doing this method since 2009 camping off the power grid all over the VA/WVA areas up and down the Blue Ridge Parkway, as far south as the Gulf Coast and as far west as Okla/Texas. We do just about all the same things we do at camp sites with hookups.

Just my thoughts
Roy Ken

[enblethen]

Yes, you need a separate controller for the solar.
Some kits come complete with a control and other accessories to make the install.
go power solar kits

[SlowBro]

You're right, I forgot that converters don't work that way. I had it backwards in my head.

No wonder I couldn't find an answer on it :B

[2oldman]

Your converter has nothing to do with solar. Yes, you need a charge controller.

The only way your converter would work is if you managed to invert the panels DC output to 120vac, then plugged the converter into that. And that's just crazy.

Sounds like you need Solar 101.