Free 7 Day Trial RV GPS App RV Trip Planner RV LIFE Campground Reviews RV Maintenance Free 7 Day Trial ×

Thread Tools Display Modes
Old 06-09-2021, 08:34 AM   #1
Join Date: Apr 2020
Location: Virginia, USA
Posts: 27
Year: 1993
Chassis: GMC Vandura
Engine: GM 3500
Trying to find the weak link in my solar setup

I recently purchased a converted shorty with a solar setup installed and am having trouble diagnosing what needs to be upgraded in order to solve the problem I’m having. .

I have 500W of panels on my roof, and my 2x200ah deep cycle gel batteries are charging up to 12.7v+ most days if my daytime electrical use is moderate to low. However, even trying to keep our electrical consumption low, our battery monitor has been showing that the battery charge is pulled down below 12.1v overnight even running just a couple of small 12v fans and led lights.

Generally speaking, in a situation like this, would you add more panels (and upgrade the charge controller etc etc) so that the batteries are receiving more charge during the day, or add another battery or two to the bank to increase capacity? Or are both absolutely necessary?

Here are the components of my current system:
3x100w panels, 1x 200w panel
50a renogy mppt dc-dc battery charger/charge controller
2x 200ah renogy deep cycle hybrid gel batteries
1x 3000w inverter

Edited to add: I have read the mobile solar power book, and still have this question. So recommending that I read the book won’t help me out of this pickle.
thank you!

littlebunnyhead is offline   Reply With Quote
Old 06-09-2021, 09:19 AM   #2
Bus Crazy
Join Date: Oct 2020
Location: Near Flagstaff AZ
Posts: 1,221

There are a few considerations here...and with what you've provided I'm looking at the batteries...or maybe the inverter draw. It looks like your system is charging, so we need to figure out why your system won't carry you through the night.

First, what's the "phantom" draw from that 3000W inverter? Do you know how much it draws when idle? I'd measure that, and the energy used by the fans and lights, to see if that would account for the battery drain.

If they don't then you might have bad cells in those batteries. I keyed on the Gel part. Gel cell batteries are super sensitive to overcharging and can be damaged, losing capacity, with just one overcharge or a charge done too rapidly.

With AGM or FLA batteries, the electrolyte is a liquid and the gasses produced during a charge...especially an overcharge event...bubble through the liquid. But in a gel battery, the electrolyte gel can be pushed away from the plates by bubble pockets and that separation of the electrolyte gel from the plate can remain...and wherever the electrolyte no longer hugs the plates it no longer works as a battery. So, one single overcharge event can damage the batteries permanently and, for this reason, I am not a fan of gels.
rossvtaylor is online now   Reply With Quote
Old 06-09-2021, 09:51 AM   #3
Bus Nut
Bert06840's Avatar
Join Date: Mar 2021
Location: Connecticut
Posts: 638
Year: 2009
Coachwork: Gillig
Chassis: G27E102
Engine: Cummins ISL 280
Rated Cap: 26,000 lbs
I agree with Ross above. If itís not your inverter, you probably have killed batteries.

Buy one of these off Amazon (DC clamp meters), $29

And trace where the current goes:

Bert06840 is offline   Reply With Quote
Old 06-09-2021, 12:37 PM   #4
Bus Nut
Join Date: Apr 2020
Location: Northern California (Sacramento)
Posts: 634
Year: 1999
Coachwork: El Dorado Fiberglass
Chassis: Ford E450
Engine: V10 Gas
Five hundred watts of solar and a fifty amp charge controller should recharge your batteries easily unless you live in the Arctic Circle.

Does the charge controller show the panels are charging? If you can't tell, you will probably need that amp meter Bert suggests to check if the positive cable from the charger is providing amps to the battery.

Then, as others indicated, check vampire load/leakage. Turn off solar charger, and then turn off all devices being fed by the batteries, and either put an amp meter on the positive cable coming from your battery, or pull the positive cable off your battery and put a voltmeter on it. If any current or voltage is present, that's part of your problem. You can chase that down by systematically removing fuses one by one to see which circuit is leaking.

If there is no leakage, the symptoms you describe are most likely because your batteries have failed. I'm not an expert in batteries (or much of anything else, really) so I can't tell you why yours might have failed however the most common problem other than usage, age or improper charge configuration is too deeply discharging the batteries.

Do you live in a cold climate? That may be another factor for some battery types.
Rucker is offline   Reply With Quote
Old 06-09-2021, 03:08 PM   #5
Bus Crazy
Join Date: Sep 2018
Posts: 2,449
Year: 2007
Coachwork: Thomas Built
Chassis: Minotour
Engine: Chevy Express 3500 6.6l
I think that right now in North America, assuming a flat panel penalty of 25%, you’re parked in full sun, your panels are clean, and assuming your wiring is up to the task, you’re probably making around 1800Wh/day.

How much are you consuming?

Do you have a more accurate way of measuring the voltage on the battery bank? Maybe just around sunset and in the morning?

I have a very similar setup, but I haven’t been monitoring the batteries. I only have the charge controller to indicate percentage and I don’t trust what it says.

But if I did, my 600W/400Ah AGM setup can run a 12v fridge and lights and be around 85% in the morning. If my 1000W inverter sits on standby, it’s like 75%
Danjo is offline   Reply With Quote
Old 06-09-2021, 10:27 PM   #6
Bus Nut
Simplicity's Avatar
Join Date: Aug 2019
Location: Auburn, WA
Posts: 779
Year: 2000
Coachwork: IC / Amtran
Chassis: 3000 / 33' Flat Nose
Engine: IC T444E / Allison MT643
Rated Cap: 72 Kids / 48 Adults
All of the previous reply posters know more about this than I do, yet from one less knowledgeable person to another (the OP), I suggest you do some research on each of the components of your system. The more you understand each of them and how they interact, the easier it will be for you to use and maintain your system.

It's my understanding that (and yes, I fully expect to be educated if what I'm saying is not accurate):

Using similar solar panel is a positive. That said, knowing what type of panels and using consistent wattage may provide more consistent charge.

Using identical batteries that are in the same "health". One bad battery (like one bad apple) can spoil the whole bunch. You didn't clarify, but I'm assuming your batteries are 12v parallel (not 6v in series).

Inverters suck up some energy even if they are not inverting, yet are on, even in standby. Knowing your inverters features is really helpful.

Wires. Having the right size wires to carry the loads efficiently is helpful. Too small a wire can heat up under load, and heat that's not being converted to potential is wasted.

I know in some of your (OP) earlier threads that you bought this bus already converted. I hope some of the issues you were having then are getting resolved.
Simplicity is offline   Reply With Quote

solar, solar kit, solar setup, solar system, troubleshooting

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

» Featured Campgrounds

Reviews provided by

Powered by vBadvanced CMPS v3.2.3

All times are GMT -5. The time now is 11:46 AM.

Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2022, vBulletin Solutions, Inc.