Solar installation project

[keithgregg]

Well I'm finally getting started on my solar install. I have
-1 250watt panel from Grape Solar
-1 320watt mppt charge controller from Grape Solar on the way
-3 35ah solar batteries (temporary use for testing)
- Origional Univolt 4 still works
- 20 led lights on the way

I'm looking for more of a boondocking setup with all or most 12v use and no shore power. At most I'm looking a powering the trailer lights, vent fan, a small fridge or 12v cooler, a radio, and maybe a tv with a digital antenna.

I was contemplating installing the controller and batteries in the closet next to the bathroom and lighting up the circuit breaker that's in the closet.
Any suggestions?

[lewster]

If you look at the specifications for your 250 watt panel, it is designed for stationary use in a residential or commercial solar array (per Grape Solar web site). Panels of that size do not do well in a mobile environment due to flexing of the large frame. This is why the largest panel we have for RV use is a 160 watt unit.

Next, it is a 60 cell panel, which means that the nominal voltage will be in the 30+VDC range or based on a 24VDC battery bank. If you plan to use a 12VDC battery bank (which you definitely should as everything in your trailer runs on 12VDC....NOT 24VDC), then you will need a solar charge controller capable of a 24VDC nominal input with a 12VDC output.....one like this: Solar Boost 3024iL MPPT | Charge Controllers

Further, If you will be getting new batteries, I strongly suggest that you dump the Univolt.....working or not. It will cook any battery in short order. Better to replace it with a modern converter with automatic 3-stage charging.

A bit more research into what will work and what will not in your proposed system is in order too.

[idroba]

If your "small fridge or 12 volt cooler" is one of the non compressor thermoelectric diode ones, you will find the power draw of it to be very high. They take 3 to 4 amps virtually all of the time, and will kill your batteries rapidly when you have no sunshine.

I don't understand your three 35 amp hour solar batteries. They are way too small to be useful, especially with a 250 watt panel. What does "temporary use for testing" mean?

I hope your maximum voltage from your single large panel does not exceed the maximum voltage input for your MPPT charge controller. Be sure to check that the controller will not take an over voltage situation.

The original Univolt single stage converter/charger is due for replacement with a more modern 3 stage converter/charger such as one from Progressive Dynamics. Whatever batteries you have will thank you for it.

The trailer lights should be all changed to LED ones, not the original incandescent one which were in the 1970 trailer.

[lewster]

Two great minds at EXACTLY 8:53 !!!!

[keithgregg]

I appreciate the input guys but this ain't my first solar rodeo.
The panel and batteries are left overs from a variety of solar systems I have had.

The panel is not going to be mounted on the trailer but placed in the sun while I am parked in the shade. If I was going to mount panels on the roof they would be 100w flexible panels which I may do when I can afford to buy more panels. But I intend on being parked most of the time so mounting panels on the roof isnt going to be of as much use to me.

The charge controller is Grape Solar GS-MPPT-320W and is rated for 15v-37v input 12v output. It will charge a 12v system and handle the higher voltage of their panel.

The univolt doesn't need to be replaced with a newer charger/converter because it won't be in use. Unless it cooks batteries when it's not plugged in. I don't intend on spending money I don't have on something I won't use.

I have already ordered the led lights to replace the incandescents as stated.

Temporary use for testing means the trailer didn't have a battery when I bought it, I currently have 3 35ah batteries laying around and I don't need more battery while my airstream sits in the driveway being worked on. When I get ready to hit the road I will upgrade. Probably 2 or 3 100ah.

As for refrigerators go, I haven't done my research yet. My 2way Ac/propane fridge works but does not get very cold at all. I'm looking for a dc replacement with a very low amp draw. I don't care about ac or propane as I won't use it. Actually the refrigerator is going to be the primary draw on my solar system. I was thinking of going to Grape Solar again as they have a fridge that matches my system but it's a bit more than I can really afford. About $750. Any recommendations? I'm looking for low amp draw but I'm not looking at spending alot.

So back to my original question, is there any reason I can't hook my batteries up directly to the 12v circuit in the closet next to the bathroom?
Thanks for the help.

[idroba]

I have looked at what I could find about the Grape Solar 12 volt DC refrigerator and it looks like it could be a candidate for what you want, but there really were no useful specs as to current draw and time of operation available. So, hard to comment on it's suitability, and the $750 cost to experiment is hard to take. I have seen no reports on it at all.

In general, there are two compressor types which are very efficient used in 12 volt DC refrigerators. A very popular one is the Danfoss 12 volt compressor which is good and used in a number of applications by various manufacturers. They are not cheap though.

The second type is the "swing motor" compressor which is used in the Norcold ice chest style refrigerators as well as the Engel brand of chest style refrigerators. Norcold used to make a regular looking refrigerator using that compressor, but apparently they do not make it any more. The compressor is very good, but quite uncommon and impossible to find a source of replacement for. Like the Danfoss units, they are all expensive.

I don't know enough about your specific trailer to give you any comments on the location of your proposed equipment, so sorry I cannot help on that.

[keithgregg]

Most reviewers on amazon say that you can run the grape solar fridge all summer on 200-300w of solar panel and 200ah of battery.

[keithgregg]

Ok so I guess I figured it out for myself.
The 110v shore power comes into the closet next to the bathroom and attaches to breaker #1. This when turned on supplies power to circuit #2 and by jumper wire circuits #3 & #4. Circuit #3 supplies 110v power to the univolt which then supplies power to the 12v fuse panel.
So no I can't put my charge controller and batteries in the closet unless I run a 12v power supply to a new fuse block where the univolt is now.

Or just unhook breaker #3 from the 110v and supply 12v to the univolt fuse panel via a couple of jumper wires. Hehehe!