Understanding Solar

Whh3 · 01-08-2023, 02:20 PM

Hi All:

Hoping that someone out there can give me some pointers on a typical solar set up. We bought an Atlas 3172 5th wheel a couple months ago that came with a solar panel on the roof (front right side of the roof) and a DOMETIC GP-PWM-30-SQ 30amp PWM Solar Controller. The inverter is a Xantrex Freedom X 2000. We have two AGM 12 volt batteries, each with a cut-off switch. My questions are:

1. How do I know if my both my batteries are charged by the solar. The solar display shows battery 1 full but not sure if there is a way to switch to a battery 2 (I’m not seeing anything in their manual)

2. If the cut-offs are both off, does the solar still keep the battery topped off? The solar display still shows full its both cut-offs are in the off position. I’m assuming that the cut-off just keeps power from going to the camper and the solar portion is alway on. Sound right?

3. I assume one battery is connected to the solar and the inverter to supply power to the Fridge and select outlets. The other battery supplies power to the other outlets, lights, etc. That sound right? Maybe one of them also supplies power for slides and levelers.

Thanks in advance for any insight.

Whh3

dsol · 01-08-2023, 04:49 PM

I have no knowledge of your system but having said that I would be surprised if both batteries weren’t tied together and read as one battery, the same way that in almost all RV’s with more than one battery they are interconnected so your 12v system has greater capacity and when you check your battery level you get the combined charge.

Typically, the only way to determine the actual charge level of a single battery is to disconnect it and put test probes on each terminal. If you do not disconnect a battery and put test probes directly on the terminals you will still get the combined charge of all batteries in your system (in your case two batteries) as they are connected in parallel.

persistent · 01-08-2023, 06:14 PM

Hoping that someone out there can give me some pointers on a typical solar set up. We bought an Atlas 3172 5th wheel a couple months ago that came with a solar panel on the roof (front right side of the roof) and a DOMETIC GP-PWM-30-SQ 30amp PWM Solar Controller. The inverter is a Xantrex Freedom X 2000. We have two AGM 12 volt batteries, each with a cut-off switch. My questions are:

1. How do I know if my both my batteries are charged by the solar. The solar display shows battery 1 full but not sure if there is a way to switch to a battery 2 (I’m not seeing anything in their manual)

Typically both batteries are tied together. 12 volt batteries would be in parallel.
Look for a connecting cable between the two negative terminals. If the two cut-off switches are next to the batteries, then the connecting cable for the positive terminals may be after the cut-off switches.

If the cut-off switches are near the entry door, they are probably not true cut-off switches. Some things are probably still connected (parasitic draw).

Solar is usually connected directly to the battery bank and would charge both. If the cut-off switches are next to the batteries, solar may be connected to the switches.

Inverters are also usually connected directly to the battery bank. There is usually a large fuse or circuit breaker in the inverter positive cable

2. If the cut-offs are both off, does the solar still keep the battery topped off? The solar display still shows full its both cut-offs are in the off position. I’m assuming that the cut-off just keeps power from going to the camper and the solar portion is alway on. Sound right?

Inverters and solar panels are typically connected directly to the battery bank. Measure battery terminal for charging voltage to know.
Fully charge battery bank of 14 hours
Measure battery terminal voltage. Charging voltage should be 13.6 volts or higher. Sometime it is 13.2 volts. Sometimes it is 14.4 volts.
Disconnect shore power
Shut down generator
Turn inverters off
Turn off all 12 volt appliances
If in bright sunlight, voltage will stay up if getting solar charge.
If not, voltage will drop to 13.0 volts or less after a few hours.

3. I assume one battery is connected to the solar and the inverter to supply power to the Fridge and select outlets. The other battery supplies power to the other outlets, lights, etc. That sound right? Maybe one of them also supplies power for slides and levelers.

This is not likely. Both batteries are probably wired in parallel to each other.

Battery cut-off switches next to the batteries are usually total disconnect.
Entry door switches (salesmen switch) usually disconnect house appliances. Propane detector and other things may still be connected and drawing 12 volt power.

Inverter and solar are usually connected directly to the battery bank.
Some chargers are not connected directly to the battery bank and may be be disconnected when door switch is off. Test for charging voltage to be sure.

Pastot · 01-08-2023, 08:06 PM

I would doubt your battery disconnects impact your solar charger's battery connection, to do so with panels still connected will burn up the solar charge controller. One never wants to pull batteries with the panels still connected to the charge controller.

Next, as stated previously your two batteries are most commonly connected parallel in a 12v configuration. Such connection maintains 12v storage but adds storage capacity; two 12v 100ah batteries in parallel provided 12v but store 200ah of energy (important to note is only 50% of that 200ah is useable with out damaging your battery's recharge life).

Unless your charge controller is designed to charge two separate battery banks (there are a couple available), your charger reports battery state of charge for a single battery bank, and all batteries parallel in that bank are acting as one large 12v battery.

Pastot · 01-08-2023, 08:12 PM

Also battery cut offs installed by a tech or manufacturer will not entirely stop all 12v supply draw.. Your brakes, tongue jack, propane leak detector and stabilizing jacks typically remain useable. What typically lights, control board for furnace, water heater, fridge all are disconnected as well as radio/clock and 12v/is chargers etc (non critical/safety things).

ewarnerusa · 01-08-2023, 11:04 PM

Is this your charge controller?
https://gopowersolar.com/products/gp-pwm-30-sq/
download manual

You've already been given a bunch of info so I won't pile any more on! But I'm following to see if I can help.

Whh3 · 01-09-2023, 02:37 PM

Thank you all for the info. Gonna take a bit to digest it all and go out to look at my configuration...my RV is at the dealer for some warranty work; so depends how long that takes before I can go check things out. Again, Thank You ALL!

P.S. Just re-read everything...a lot of good info!

Whh3 · 01-09-2023, 02:38 PM

Yes, that is the manual. I looked through it trying to make sense of it all. RV is at the dealer for some warranty work, so will try to apply the info from everyone once I get it back and look at the configuration again.

Whh3 · 01-09-2023, 02:44 PM

Got it, so that means that the 13.6v is for both and if one battery got totally drained it should show 50% charge providing the second is full.

ewarnerusa · 01-09-2023, 03:01 PM

Quote:

Originally Posted by Whh3

Got it, so that means that the 13.6v is for both and if one battery got totally drained it should show 50% charge providing the second is full.

Batteries wired in parallel or series don't charge/discharge independently. They act as one and charge/discharge as one. Showing 50% charge means that your battery system is at 50% state of charge (SOC).

It is possible that your 2 batteries are wired up as 2 independent batteries that you can select between, but this isn't common in a 2 battery system.

Whh3 · 01-09-2023, 03:07 PM

Make sense. Thx!

dsol · 01-10-2023, 01:41 AM

Quote:

Originally Posted by Whh3

Got it, so that means that the 13.6v is for both and if one battery got totally drained it should show 50% charge providing the second is full.

Actually, what typically happens when you have one bad battery and one good one is your system will show a full charge but that charge will not last very long. Further, a bad battery will often damage the other “good” battery if they are left interconnected for a while. I would encourage you to disconnect each battery, wait a good hour or so and test them separately. The batteries need to rest for a while before the state of charge will be accurate (they tend to read high initially). State of charge will be one thing but cold cranking amps (CCA) will be more important and you have to check them separately to get an accurate reading.

There is tons of information out there on batteries depending on type, etc., and that will impact how you want to leave them when in storage. However, generally you want lead acid batteries, whether AGM, flooded or sealed to be stored at a full charge and you want to top them off regularly. Other batteries such as LiPo, are better off stored at about 50%.

Good luck.

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