Testing potential solar harvest?

keep the controller in bulk mode with a load or multiple loads.

1/2 a day is enough cuz the 2nd half of day mimics the first half.

You live off batteries so the # of them and the size will determine what your drain rate capabilities are(how fast your panels replenish the battery bank). A moderately sized system should include 4 6V deep cycle batteries for maximum capture of charge during the day. Very generalized but fairly applicable for the frequent boondocker.

I pretty much know what to expect with charging my battery bank using the on-board Converter/Charger setup.

In my case I want to get charged up to point that I can use my batteries again right away so I follow the 50% to 90% charging rules so I can get safe use of the batteries in as short of charging time as I can pull off...

Again in my case I know how many DC Amps I can pull from my battery bank so that I can stay with-in the 50% charge state. When I see 12.0VDC on my battery monitor I know I am approximately at the 50% charge state so I will stop using my batteries until I get them charged back up to the 90% charge state as soon as possible... If I can supply 17-20Amp per 12VDC battery in my battery bank I know they can be charged from the 50% charge rate to the 90% charge rate in approximately a three hour charge period. When camping OFF-GRID I will run my 2KW Honda Generator with the Popup Trailer shore power cable connected to do this. Most often the camp sites allows the use of generator starting at 8AM each morning so this is the perfect time for me to do this...

I also know from experience my battery bank will accept around 53 AMPS DC Current when first hit with 14.4VDC charge from my smart mode charger setup when the battery bank is at its 50% charge state. This will last for around 20 minutes and then starts tapering back. After around one hour of charging with 14.4VDC from my smart mode charger it will then drop back to 13.6VDC.

At this point I would like to shut down my generator and hook up enough solar panels to continue my charge mode the rest of the afternoon in high sun. I can get my battery bank up to its 90% charge state by running the generator for an additional two hours after it drops down to 13.6VDC. Hopefully in the several hours of high sun left I can do this setup using only the solar panels.


I would most likely want to have at least 20AMPS of DC Power being generated by the solar panels to feed my three 12VDC batteries... A single 120WATT Solar panel will only generate around 6AMPS DC current to give you an idea how many panels you will need...

These are my thinking of using solar panels to charge my battery bank for me when we are camping OFF-GRID...

We may be using more power then most do when camping off grid because of my Ham Radio use and wife's use of watching HDTV … I regularly see 20-25AMPS of Dc Current being drawn from my battery back between the 6PM to 11PM time frame each evening to give you and idea of how much we pulling from the battery bank each evening...

It all kinda depends on each camper's need for power I guess...

I know I can do it by running my 2KW Generator for three hours each day to get my battery bank from its 50% charge state to its 90% charge state. Would like to reduce the generator run down to around one hour aday and let the high SUN get my batteries back up to their 90% charge state so I can do all of this all over again each evening...

My 12VDC battery bank story haha... I'm sure other do it differently...

Roy Ken

Hi,

If you have an inverter load it up and that will soon have the solar pumping out watts.

Careful unhooking all your batteries without disabling the solar panels first...blanket, darkness etc.

"With batteries disconnected obviously. "

You may see smoke come out of the controller. I use a trimetric but victron and others are also available

azrving wrote:
"With batteries disconnected obviously. "

You may see smoke come out of the controller. I use a trimetric but victron and others are also available

I understand that you should not run the controller without batteries, but I was suggesting some other type of load in place of batteries. Perhaps using a pair of disconnects to switch between loads. A Trimetric would not do what I was hoping for.

pianotuna wrote:
Hi,

If you have an inverter load it up and that will soon have the solar pumping out watts.

Now that makes sense. I'm not really planning on an inverter, at least not at the moment. Maybe a small one at some point to run entertainment. We've become very comfortable camping without AC power, and I don't want to haul more than 2 GC batteries just to support an inverter. I think you are right though, that would be a way to test the system. I thought of just turning on every 12v device in the entire coach, but that still would not tax the 40a charge controller, or even the 30a that the solar array might be capable of on its best day. A good sized inverter would, then try to find enough AC gizmos to run for a while.

I was hoping someone had devised a simpler method. Haven't seen it done as of yet. Maybe something similar to a battery load tester?

I know it is kind of a silly curiosity of mine. And is due to the fact that I haven't been able to take it out camping yet. It won't matter once I have a little experience with the system.

If you are at the bulk or float voltage you are good to go.
If voltage is still rising (bulk) at 2pm your system is weak or something is wrong.

time2roll wrote:
If you are at the bulk or float voltage you are good to go.
If voltage is still rising (bulk) at 2pm your system is weak or something is wrong.

It is doing a fine job of that. But sitting in my driveway with full summer sun, so not very meaningful.

if you can't figure out how to apply a load, yo can measure the panel's current directly with a ammeter with the panel disconnected from the controller.