Batteries

[Porcupine]

Hi - my batteries will be 12.5 in the evening and then jump up to 12.7 even though there is nothing charging them. 
 

Is this a symptom of dieing batteries because they do seem to be struggling to hold their charge like they used to?  
 

Thinking it might be time to get a new set of leisure batteries. 
 

Thanks, 

Matt. 

[Tony Brooks]

Is that 12.5 supplying power and the 12.7 when not supplying power? If so the on load voltage will always be lower than the off load voltage but 0.2V seems a tad high unless it is a heavy load. It might be indicative of a higher resistance in the circuit. I would clean all the battery terminals and clamps and put both master switch leads on one terminal in case the contacts are dirty.

 

There is a faint chance that if it does it on load that and internal battery cell interlink may be restive, but it is exceptionally rare.

 

If there is no significant load when it is at 12.5V, I don't have much idea.

 

If the batteries are discharging faster than they used to under similar use, then they may well be sulphated, but if so they probably reach fully charged faster. If a cell is shorting, then they would tend to discharge when left off charge with no load for many hours - say overnight.

[Porcupine]

Thanks Tony. I will try and clean up the batteries and see what happens.

 

 

[MtB]

Sounds to me as though you might have a solar panel.

 

 

[magnetman]

8 hours ago, MtB said:

Sounds to me as though you might have a solar panel.

 

 

One that works in the dark? 

 

OP "my batteries will be 12.5 in the evening and then jump up to 12.7 even though there is nothing charging them."

Edited February 24, 2023 by magnetman

[Tony Brooks]

8 hours ago, MtB said:

Sounds to me as though you might have a solar panel.

 

 

 

Except he said "in the evening", but I suppose he could have a combi-unit that starts to charge when he turns it on but who knows. There was not really enough info to be sure.

 

No confirmation about any loads applied, so it may just be a load pulling the voltage down.

Edited February 24, 2023 by Tony Brooks

[magnetman]

To be fair the jump to 12.7 could be in the morning in which case the MtB suggestion may well be correct. 

 

More detail needed I think. 

[Rob-M]

If our fridge is running and we have had the TV on for a couple of hours the battery monitor will show 12.6v or 12.5v as we go to bed but will be showing 12.7v in the morning before the solar has kicked in.

[Lily Rose]

Doesn't the amount of pull down on load depend partly on the size of the battery bank?

 

At some point each evening my batteries (el cheapos installed August 2020) will have settled down to a steady 12.7v with no load. Each time the fridge starts up the voltage drops to 12.5 or even 12.4. Once the fridge goes off it takes only minutes to go back to 12.7. 

 

I put this down to battery bank size (no space to add more). My battery bank consists of only two 110 a/h cheap Midland Chandlers Albion batteries. The last pair lasted 3.5 years and could probably have gone a while longer but I didn't want to risk overnight fridge cut-out.

 

I don't think the OP mention battery bank size but I suspect it is the fridge coming on and off periodically that lies behind those voltage readings.

Edited February 24, 2023 by Lily Rose

[Tony Brooks]

43 minutes ago, Lily Rose said:

Doesn't the amount of pull down on load depend partly on the size of the battery bank?

 

At some point each evening my batteries (el cheapos installed August 2020) will have settled down to a steady 12.7v with no load. Each time the fridge starts up the voltage drops to 12.5 or even 12.4. Once the fridge goes off it takes only minutes to go back to 12.7. 

 

I put this down to battery bank size (no space to add more). My battery bank consists of only two 110 a/h cheap Midland Chandlers Albion batteries. The last pair lasted 3.5 years and could probably have gone a while longer but I didn't want to risk overnight fridge cut-out.

 

I don't think the OP mention battery bank size but I suspect it is the fridge coming on and off periodically that lies behind those voltage readings.

 

I think that you may well be correct but until we get some idea of the load at 12.5V and I suppose the cable thickness all the way from battery to meter connection anything will only be an informed guess. LA batteries certainly seem to recover a bit of voltage when rested for a while.

[Onewheeler]

The temporary drop in terminal voltage with current drawn is very non-linear. My batteries drop 0.2 V with quite a small load (say, the fridge running or the lights and radio) but a much bigger load doesn't take them down much more. I did find a report on it somewhere but I'd struggle to find it...