Acid batteries

[Phil T]

I have taken a house in Spain which has solar panels and from what I can see they work perfectly when the sun is beating down on them. My issue is I have a bank of 12 2v batteries which create 24v all going through an outback flexmax 80. 2 of my batteries constantly have fizzing water in them when in charging stage and settle down when not charging. These 2 batteries get a reading of 27v where the others show 24v. Have these batteries had it or is there a way to reduce the voltage to bring them online with the others. At the moment they cause an FX error and the power goes off in the evening.
sorry for the essay bit I'm a newbie to all this.
many thanks

[Xplode]

Welcome Phil!

A little fizzling is normal for Flooded Lead Acid Batteries when they are charging. Can you provide a pic or make/model of the batteries?

I'm not sure how you're measuring the voltage and getting 27v vs 24v. If the batteries are all in series, you should only be able to read one voltage across them all.
Check the voltage of the battery bank while it is charging/fizzling, and let us know what that number is.

I'm assuming these are flooded style batteries, and if they are, have you opened the caps to check the water levels?
There are several VERY GOOD sticky'd topics in this forum and the "Lead Acid" sub-forum. Give those a read a couple times and see if any of it makes sense.
I'm newish to battery/solar and they have been immensely helpful.

[Phil T]

Thank you for the info. The batteries were tested by a so called solar engineer while they were charging and 10 of the batteries were reading 24v on his meter he attached to them whilst the other 2 read 27v.
I will send a picture when they are charging again as at the moment they're floating.
I will also have a read the post on batteries as I have started to.

[Ampster]

I have the same question that Xplode has. How do you get 27 volts out of two 2 volt batteries. I can understand how 10 batteries would read 24 volts.

[Phil T]

When the solar guy put his meter probes onto the first 10 batteries they read 24v. The last 2 batteries they read 27v on his display. These are the 2 in question that are fizzing more than the others when charging.
the water levels are topped up in all the batteries to their acquired levels.
I have 12 fulman 2v. 1200 AH/100h batteries

[Phil T]

Forgive the way I have pit this across as all this is very new to me. All I know is the house runs off a 24v system going through a outback flexmax 80.
thank you to anyone who gives info and help with this dilemma

[Ampster]

Okay I think I understand. All 12 measure 27 volts. The first 10 measure 24 volts or 2.4 v per cell. The last two (27-24=3) measure 3 volts or 1.5v per cell. Those two are a problem

[Phil T]

That is correct.
The panels have had sun beating down on them all day and even though it's dusk here now the power has gone off caused by an FX error. (Low power)
I have had to out the generator on to give it a boost.
very frustrating

[inetdog]

We still do not know the wiring arrangement of your batteries. They can be set up as pairs in series to get nominal 24 volts, then all of those 24V pairs in parallel to get more current. Or they can be set up as half in parallel to get 12V high current and then the two halves in series to get 24V. If batteries are "boiling", actually electrolyzing water into hydrogen and oxygen gas, they are gettig too much voltage applied. The Flexmax cannot deliver more than a single uniform voltage to the battery bank, so the measurements do not seem to make sense to me. Unless he was disconnecting the whole bank and then connecting two batteries at a time to measure the voltage. You can get boiling in five of the six cells of a 12V battery if one cell is short circuited internally, leaving extra (excess) voltage per cell on the remaining five.
What happens if you simply disconnect the two odd batteries? Does the remaining bank work properly but at reduced capacity?
It sounds like your solar guy is not very good at diagnostics!

[Phil T]

I agree about the solar guy. Happens a lot out here when people like myself don't understand something.
anyways the batteries are laid out in 2 rows of 6.
I haven't disconnected any batteries as if yet. I will try and get a picture of the set up during daylight as I've tried to upload one but saying file too large.
the solar guy said we couldn't disconnect the 2 offending batteries as the house runs off 24v so therefore there would t be enough power to run the house. Is this correct?
thank you

[Xplode]

Your inverter will have a low voltage cutout, probably in the 21-22V range, so with 2 basically dead cells, even if the others are fully charged, you're only going to get a little bit of power out of them before the voltage drops too low

[Ampster]

We still do not know the wiring arrangement of your batteries. .......
It sounds like your solar guy is not very good at diagnostics!

It sounds like he has 12 two volt cells in series. Two of those are bad.

[Phil T]

That seems to be what is happening explode and the set up is as you said Ampster.
so basically those 2 batteries have had it or is there a way to get them sorted?
thanks again for all the advice

[Phil T]

I disconnected the 2 bad batteries wbich causes the remaining batteries to bubble vigorously which worried me a bit so I have connected them back up to how they were as I don't want to damage the remaining batteries. Unless the 2 bad batteries can be rectified it looks like I will have to purchase 2 new ones.
I forgot to mention that there is also a air x wind turbine attached to the system and unsure if this works although it is a 24v one and not a 12v one as the solar guy pointed out. I think he gives false information as he earns money every time he comes out to us.

[Xplode]

Well a wind turbine would need to be 24v to work with your system, so that is ok.

As for adding batteries to the existing bank, that's generally regarded as a bad idea. I would see if you can find out how old the batteries are and if there is any warranty. It's possible the batteries are already several years old and due to be replaced.

And definitely don't run 10 battery only, you will definitely damage the rest of them