Solar Panel meets dual battery issues

[roverpat]

I have done some searching on the forum before posting this asking for a little help. I think I know what the problem is but want to ask if anyone has had this issue as well. Here are the build specs

2009 Land Rover LR3
OEM Land Rover starting battery
Group 34 Yellow top
National Luna dual battery kit
Mohoo CMG-2420 Solar charge controller
HQST 100 watt 12 Volt Polycrystalline Solar Panel

My issue is that the panel will charge the second battery at 14.5-15volts then kick up to 18volts due to the NL kit allowing simultaneous charging. In turn the charge controller reads the linked batteries as a 24V system. 18v going to a 12v battery is not good. Does anyone or has anyone had this same issue and what did you do to alleviate. I may have to switch the dual charge kit as I think there is not an easy way but maybe I am wrong. Thanks

 

[Scoutn79]

18V isn't enough to charge a 24v battery. Are you sure the solar charger isn't acting up? Solar panels run 18+ volts OC voltage. Maybe something wired backward is my first guess?

Darrell

 

[roverpat]

18V isn't enough to charge a 24v battery. Are you sure the solar charger isn't acting up? Solar panels run 18+ volts OC voltage. Maybe something wired backward is my first guess?

Darrell

My system is not 24v it is 12v. I have dual batteries connected by the national luna controller. It may be the solar controller. I have to monitor how long before the charge voltage goes above 15. If it is 5 minutes then I has to be the battery controller as thats how long the timer on the NL operates on single battery mode.

 

[john61ct]

The NL dual kit should just be opening/closing the connection, passively sensing charge voltage.

 

[dwh]

My issue is that the panel will charge the second battery at 14.5-15volts then kick up to 18volts due to the NL kit allowing simultaneous charging. In turn the charge controller reads the linked batteries as a 24V system.

Um...well, this interpretation of why the problem occurs cannot be correct.

The charge controller cannot read the batteries as 24v unless 24v is present - but if the batteries are wired in parallel (and they must be), then 24v cannot be present.


So let's shelve that diagnosis and start over...

The NL must be tying the batteries at some voltage far below 14.5v-15v. So if the charge voltage actually is jumping from 14.5v-15v up to 18v, then it is not happenening due to the NL tying the batteries.

I may have to switch the dual charge kit as I think there is not an easy way but maybe I am wrong. Thanks

Hold off on that. First determine:

A) If there actually is a problem,
B) What is the cause,
and then,
C) What to do about it.


At this point, nothing you've said has me convinced that a problem actually exists.

So, exactly where and how are you getting these readings? Specifically, where are you measuring 18v?

 

[dwh]

Guys, c'mon...

OEM Land Rover starting battery
Group 34 Yellow top
National Luna dual battery kit

Two 12v batteries, tied in parallel by an ACR.


Bog standard kit.

 

[dwh]

Looked up that Mohoo. Looks like a decent PWM controller.

I'm betting you are seeing that jump from 14.5v up to 18v on the Mohoo's display panel. I'm further betting this will turn out to be a misinterpretation of the readings (operator error), and both the NL and the Mohoo are working correctly.

 

[Scoutn79]

My system is not 24v it is 12v. I have dual batteries connected by the national luna controller. It may be the solar controller. I have to monitor how long before the charge voltage goes above 15. If it is 5 minutes then I has to be the battery controller as thats how long the timer on the NL operates on single battery mode.

Didn't say your system is 24V. The only way I can think that the controller is reading 24V is if something is wired wrong....

Darrell

 

[dwh]

Just let me know when you're ready for The Full Monty, Pat.

 

[roverpat]

Looked up that Mohoo. Looks like a decent PWM controller.

I'm betting you are seeing that jump from 14.5v up to 18v on the Mohoo's display panel. I'm further betting this will turn out to be a misinterpretation of the readings (operator error), and both the NL and the Mohoo are working correctly.

Yes that is correct. I am seeing the 18v reading on the mohoo display. I then checked the voltage at the batteries and was getting 17.9 on the both of them. A 12v battery getting 17.9 volts is no bueno. I have panel unplugged but later toady I will plug it in and time when the voltage jumps up. If it jumps up at the 5 minute mark then it most likely has something to do with battery controller as that is when the built in timer allows both batteries to charge.

 

[Martyn]

You do have a problem and it needs to be fixed to prevent further damage to you electrical system.

First disconnect the solar system or pull the fuse from it. This will isolate the dual battery system from the solar system. Check to make sure the dual battery system is wired per the instructions. Check the voltage with the batteries isolated from each other, then check the voltage with the batteries connected using the manual override. If you get something in the 12 - 14 volt region the system is wired correctly. If you get something in the 24 volt region you have the batteries wired incorrectly. Make sure the positives and negatives from both batteries are going to the correct terminals. You do not want a situation where a positive goes to a negative as 24 volts will be produced on linking. If the system checks out correctly move on to the solar.

A solar panel will put out voltage in the 18 volt region. The voltage is regulated by the controller to around 14 volts. You can test the voltage coming out of the solar panel, and the voltage coming out of the controller using a volt meter. To do so disconnect the solar wires from the battery and check the voltage. If you get a reading of say 18 from the solar panel, and 14 from the controller the controller is working as designed.

Some controllers will only work when connected to a battery. They can be a little harder to test but it can be done. First disconnect the solar from the battery allow the battery to sit for 10 mins. Then take a voltage reading on the battery, should be 12-13 volt region. Connect the solar to the battery and observe the voltage, the voltage should increase to 13-14 volts. If it jumps to 18 volts your controller is not working.

There is a strong possibility that you have already damaged the dual battery system and the controller by running high voltage through them, hopefully not.

 

[dwh]

If it jumps up at the 5 minute mark then it most likely has something to do with battery controller as that is when the built in timer allows both batteries to charge.

Again, that would only be possible if you have the batteries wired in series (24v) instead of parallel (12v).

If the batteries are wired in parallel as they should be, then tying in the second battery via ACR will not change the voltage that the charge controller sees from 12v range to 24v range. The charge controller will still see voltage in the 12v range, and that will not affect the behavior of the charge controller and cause it to run wide open.


I believe your observed results. But if you measured 18v at the battery, and the batteries are wired in parallel, then it's not ACR related.

Either you've got something else wired wrong, or the charge controller is junk.

Or operator error.

 

[dwh]

Check the voltage with the batteries isolated from each other, then check the voltage with the batteries connected using the manual override. If you get something in the 12 - 14 volt region the system is wired correctly. If you get something in the 24 volt region you have the batteries wired incorrectly.

That depends on where he takes the readings. Even if he's got the batteries rigged in series, he's not going to read 24v by putting the meter across the terminals of one battery then the other. Each battery will still only show him a 12v reading.

 

[roverpat]

The dual battery controller has been installed for almost 9 months. I have had zero issues with it until I installed the solar panel and solar controller. I triple checked all connections and they are tight and correct and no corrosion. I check yesterday multiple times and did not see the high volt number on the solar controller. I am leaning towards a bad controller for the solar.

 

[Martyn]

The dual battery controller has been installed for almost 9 months. I have had zero issues with it until I installed the solar panel and solar controller. I triple checked all connections and they are tight and correct and no corrosion. I check yesterday multiple times and did not see the high volt number on the solar controller. I am leaning towards a bad controller for the solar.

That's an important piece of information. So go ahead and check your solar system as I previously described to find out if the 18 volts is coming from the solar controller. Disconnect the solar first to take a reading to confirm that the battery system is in the normal 13-14 volt range. Depending on the controller you may be able to get a voltage reading from the controller, if not you will need to reconnect the solar output to the batteries and look for the voltage increase.