Background: Purchased a used coach, came with a solar panel/controller setup that's connected to Two 6-volt house batteries. I got no paperwork for any of it but scouring the interwebs I at least found out what kind of controller is in place (a Chinese brand w/little info in the online manual). Literature describes it as a 12/24v unit.I'm FAR from an electrical expert but it seems like the batteries are getting heavily charged during the day (boiling or near boiling the fluid... can audibly hear them peculating louder than what I'd expect. Seems like something's not right with the system but again, I'm not an electrical guy & never had any solar home or RV equipment before now. Question: Can using a 12/24v solar controller lashed up to a solar panel send too much voltage to 6v batteries effectively killing them prematurely? Pretty sure I need to replace these 2 house batteries but I don't know if I should go back to the OEM setup of Group-24 12v types or stay with 2 6v types.Thanks much for any assistance you guys can offer!

Your solar is working and two 6s has some advantages over two 12s as the house battery bank.The 6v in there now may be older and bubble "early", so it is not the solar's fault. (older batts with their reduced capacity from being old means they get to their fulls quite soon) The batteries are bubbling because they are "full" and need to have the voltage dropped to 13.x vs the 14.x they need to get to full. It is a matter of timing how long it takes to get to full and how much sunlight you get in any day for how long you want that 14.x to last.Try it with your new 6s and see how that goes before changing the solar.

RICH807 wrote:I at least found out what kind of controller is in place (a Chinese brand w/little info in the online manual). Literature describes it as a 12/24v unit.can you share that info? What voltage at battery = boiling?

RICH807 wrote:Question: Can using a 12/24v solar controller lashed up to a solar panel send too much voltage to 6v batteries effectively killing them prematurely?If it's a cheap one and doesn't know when to back off, yes. The 6v batteries don't have anything to do with it...unless somebody hooked them up in parallel.A voltmeter will tell you a lot.

'LMS Series Controller' - https://www.amazon.com/dp/B018N01GWO/ref=cm_sw_r_em_api_i_c_9pwsDbFSZC9GYHighest I've seen in the last few days is mid 13's when tested as they're connected now (in series).

RICH807 wrote:Highest I've seen in the last few days is mid 13's when tested as they're connected now (in series).How do they test after sitting uncharged for an hour?

12/24v Solar Controller --> 6v Batteries | Good Sam Community

BFL13
Explorer II
Aug 06, 2019
Your solar is working and two 6s has some advantages over two 12s as the house battery bank.

The 6v in there now may be older and bubble "early", so it is not the solar's fault. (older batts with their reduced capacity from being old means they get to their fulls quite soon)

The batteries are bubbling because they are "full" and need to have the voltage dropped to 13.x vs the 14.x they need to get to full. It is a matter of timing how long it takes to get to full and how much sunlight you get in any day for how long you want that 14.x to last.

Try it with your new 6s and see how that goes before changing the solar.
red31
Explorer
Aug 06, 2019
RICH807 wrote:
I at least found out what kind of controller is in place (a Chinese brand w/little info in the online manual). Literature describes it as a 12/24v unit.

can you share that info? What voltage at battery = boiling?
2oldman
Explorer II
Aug 06, 2019
RICH807 wrote:
Question: Can using a 12/24v solar controller lashed up to a solar panel send too much voltage to 6v batteries effectively killing them prematurely?
If it's a cheap one and doesn't know when to back off, yes. The 6v batteries don't have anything to do with it...unless somebody hooked them up in parallel.

A voltmeter will tell you a lot.
RICH807
Explorer
Aug 06, 2019
'LMS Series Controller' - https://www.amazon.com/dp/B018N01GWO/ref=cm_sw_r_em_api_i_c_9pwsDbFSZC9GY

Highest I've seen in the last few days is mid 13's when tested as they're connected now (in series).
2oldman
Explorer II
Aug 06, 2019
RICH807 wrote:
Highest I've seen in the last few days is mid 13's when tested as they're connected now (in series).
How do they test after sitting uncharged for an hour?
RICH807
Explorer
Aug 06, 2019
2oldman wrote:
How do they test after sitting uncharged for an hour?

Last night I checked them a bit after dark & got a little over 12v across them.
2oldman
Explorer II
Aug 06, 2019
RICH807 wrote:
Last night I checked them a bit after dark & got a little over 12v across them.
Healthy charged batteries should be 12.7 or so.
BFL13
Explorer II
Aug 06, 2019
That is a decent controller, similar to my Solar30, which is an older version of that one. It has an adjustable voltage feature. No reason not to use it with a pair of 6s. ( I did)

Note that this PWM controller is for 12v panels on 12v battery banks or 24 on 24. You cannot use it with 24v panels and 12v battery bank. (You need MPPT for that.

https://www.amazon.com/dp/B018N01GWO/ref=cm_sw_r_em_api_i_c_9pwsDbFSZC9GY

Bubbling 6s at 13.x voltage as reported, does sound like the batteries are about shot. Confirm with an hydrometer if they are in the red or green.
RICH807
Explorer
Aug 06, 2019
BFL13 wrote:
That is a decent controller, similar to my Solar30, which is an older version of that one. It has an adjustable voltage feature. No reason not to use it with a pair of 6s. ( I did)

BFL13 wrote:
Note that this PWM controller is for 12v panels on 12v battery banks or 24 on 24. You cannot use it with 24v panels and 12v battery bank. (You need MPPT for that.

I have no idea what type of panel is on my roof, would I have to take it off the coach to figure that out?

https://www.amazon.com/dp/B018N01GWO/ref=cm_sw_r_em_api_i_c_9pwsDbFSZC9GY

BFL13 wrote:
Bubbling 6s at 13.x voltage as reported, does sound like the batteries are about shot. Confirm with an hydrometer if they are in the red or green.

Copy that, this stuff is a huge help to me.
RICH807
Explorer
Aug 06, 2019
Any issue with putting a disconnect switch of some sort between the solar panel & batteries? If so, would that go before or after the controller?

Thanks again everyone, I REALLY appreciate the assistance/education.

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