TC off the grid, and solar question

Hi,

Solar systems may be thought of as a battery charger. I.E. they only fill up the battery, and don't often power anything directly.

The load won't go over 30 amps but that is a moment to moment measurement. What you want to know is the total amp-hours that are used in a 24 hour period.

The load terminal on a solar controller are used to switch on a light at night. The battery terminals are where the charging is regulated. So you can ignore the load terminals for the most part.

The 30 amps is the rated output to the battery terminals.

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

Those two links are great. Study them closely. I would add another to a supplier of solar panel systems. AMSOLAR.COM I installed a 300w system. Their systems are complete, everything is included in the kit. I have had the system installed for two years and it has worked flawlessly. What limits our boondocking now is our freshwater supply instead of our battery capacity.

towpro wrote:

How much current does a TC run for just day to day living (no AC inverter for microwave).
Refreg on propane, hot water on propane, couple LED lights, maybe heater starts, will the load ever go over 30A?
The only High current stuff I might run is a small inverter to run a Satellite receiver.

Don't forget the water pump.

The original question:
Do I wire camper load (and not camper changer) to load terminal? or leave them empty? I expect by using load terminals I can view current amperage usage the RV is using on a display. And If its a 20A controller, that that mean the current between battery and Load is limited to 20A?

If it is a controller with 2 separate battery connections (2 batteries) does it treat each battery different?
example, every 25 days it does a charge to knock sulfation off the plates, but a single 100w panel might not have enough current to run de-sulfation mode on 2 batteries at the same time.

towpro wrote:
The only High current stuff I might run is a small inverter to run a Satellite receiver.

@ about 12a @ 12vdc, that's not high current. High current is a microwave.

Hi,

I have 66 US gallons of fresh water. The pump can drain that in 30 minutes. The pump draws 8 amps, so the total use can be no more than 4 amp-hours. That's about what a single 1156 bulb uses in 2 hours, so it is an insignificant draw.

Hi towpro,

I tried to answer, but you did not understand.

The load terminals would not be used for battery charging. They could, in theory, be used to operate a light from dusk to dawn. I don't know of any RV'er who has bothered to use them.

You do NOT wire the load to anything. You use the battery terminal. In my controller there is just one battery connection.

Your second question would have to be asked about a specific controller--and probably emailing the maker would be your best bet for an answer.

My Blue Sky 3024di does have load output. It can provide up to 2 amps to charge a chassis battery, or to operate a light, or to operate a relay. I chose to do nothing with it. The next iteration is the 3024iL. The load can be up to 20 amps for that. That could, in theory, be used as a diversion load after the main battery bank is fully charged. They want $70 smackers to upgrade my di version, so it is NOT going to happen.

towpro wrote:
The original question:
Do I wire camper load (and not camper changer) to load terminal? or leave them empty? I expect by using load terminals I can view current amperage usage the RV is using on a display. And If its a 20A controller, that that mean the current between battery and Load is limited to 20A?

If it is a controller with 2 separate battery connections (2 batteries) does it treat each battery different?
example, every 25 days it does a charge to knock sulfation off the plates, but a single 100w panel might not have enough current to run de-sulfation mode on 2 batteries at the same time.

towpro wrote:
The original question:
Do I wire camper load (and not camper changer) to load terminal? or leave them empty? I expect by using load terminals I can view current amperage usage the RV is using on a display. And If its a 20A controller, that that mean the current between battery and Load is limited to 20A?

You connect the load side of the solar controller to your batteries with new wiring that you run between the controller and the batteries.

You don't rewire the camper and put all the loads to the solar controller, you just leave those wires as is and run new wire.
Load and the charger already present in your camper are hooked tot he battery - nothing changes there.

As far as what the meter on the solar controller is telling you, it will depend on what brand and model solar controller you are talking about, but generally speaking, it tells you what amount of current the solar is putting out to the batteries, because all it is doing is monitoring solar current. It doesn't monitor the amount of amperage that your camper is using. If you want to monitor what the camper is using, then you need another meter - like a Xantrex LinkLite of LinPro

towpro wrote:
If it is a controller with 2 separate battery connections (2 batteries) does it treat each battery different?
example, every 25 days it does a charge to knock sulfation off the plates, but a single 100w panel might not have enough current to run de-sulfation mode on 2 batteries at the same time.

I haven't seen a controller that had two output isolated from each other - they are parallel to each other, meaning they are "connected" internally (in the controller).

But, what make and model of controller are you referring to? Knowing that details, we can give a proper answer.

No. You connect the battery bank to the battery terminals of the controller.

deltabravo wrote:
You connect the load side of the solar controller to your batteries with new wiring that you run between the controller and the batteries.

Yes. The "feed" for the camper is left on the battery bank.

deltabravo wrote:
You don't rewire the camper and put all the loads to the solar controller, you just leave those wires as is and run new wire.

pianotuna wrote:
Hi towpro,

I tried to answer, but you did not understand.

your right. I did not know what "turn a light on" meant.

as I read the manuals it "sounds" like this "load terminal" is setup to help stop you from cycling your batteries down to far but cutting off the load at a pre set voltage on the batteries. in fact one said something about "if this light flashes, your current on load was over 2X capacity, reboot panel 4 times". (it really said reboot 4x)

I also see there is battery monitors like bogart TM-2030 that use a shunt to show current in ether direction.

I like stuff I can "LOOK AT" to show me its working. Sure solar is cool, but all it really is, is a battery charger and all the solar controller is going to show you is what the charging current is at this point of time (as well as probably voltage).