1 Battery Has Lower Voltage

[surfergirl]

Hi all~ I have 4 x 12v lead acid agm sealed batteries in series to run a 48v system. The battery connected to the positive lead has lower voltage (10.1v) every 2-3 weeks but charges up to full after running my generator or by sunshine. The other 3 batteries are fine. Any ideas?

 

[sunshine_eggo]

Will adding more solar panels charge my batteries to full?

Hi all, Needing some advice. I currently run 6x405watt panels (approx 2.4kw) with 4x12v 270ah AGM batteries and 5kva inverter. I get 6 hours of full sun in the non summer months but even during summer, my battery volts never go above 54.8v. As soon as the full sun disappears from my panels, I'm...

diysolarforum.com

Been a few months. Ever get a battery monitor?

Again, what are your 12V batteries reading when at absorption voltage?

I'm guessing you never got your charging sorted and murdered your batteries since you abandoned that thread. Can we expect the same here?

 

[surfergirl]

Hi there- answers are below

Will adding more solar panels charge my batteries to full?

Hi all, Needing some advice. I currently run 6x405watt panels (approx 2.4kw) with 4x12v 270ah AGM batteries and 5kva inverter. I get 6 hours of full sun in the non summer months but even during summer, my battery volts never go above 54.8v. As soon as the full sun disappears from my panels, I'm...

diysolarforum.com

Been a few months.Yes I have had great winter generation, hardly running my generator. All was tickety boo until recently.

Ever get a battery monitor? Sorry I haven't but is on the list to buy. They are very expensive here

Again, what are your 12V batteries reading when at absorption voltage? It's 2pm here and they're reading 13.1v each. Pretty good since it's been raining all morning.

I'm guessing you never got your charging sorted and murdered your batteries since you abandoned that thread. Can we expect the same here? Yes, batteries don't die, they're murdered- agreed. But mine are holding their charge very well for their age (overnight) apart from the one as mentioned. It's actually the battery hooked up to the negative lead, have edited my original post saying so. Thanks

 

[sunshine_eggo]

Again, as I requested in the other thread, please hit enter after my text, before you reply, so yours drops below it. I can't quote anything in your message because it will filter it out since it thinks it was posted by me.

I didn't ask what they were now. I asked what they are when you're at absorption voltage. If you're not getting to absorption voltage nearly daily, your batteries are being murdered.

 

[surfergirl]

Again, as I requested in the other thread, please hit enter after my text, before you reply, so yours drops below it. I can't quote anything in your message because it will filter it out since it thinks it was posted by me.

I didn't ask what they were now. I asked what they are when you're at absorption voltage. If you're not getting to absorption voltage nearly daily, your batteries are being murdered.

Hope this is correct. I pressed enter and now typing....let me know. Okay so 13.7v per battery is around the max I get. If it was a charging issue, wouldn't all of my batteries be failing at the same time? This morning the left one was 10.8v and before I could even connect the generator, the sun came up and within 15 minutes the batteries were all reading 12.6v. Any ideas?

 

[sunshine_eggo]

Hope this is correct. I pressed enter and now typing....let me know. Okay so 13.7v per battery is around the max I get.

You are murdering your batteries by using too much energy for what your PV can replace. Get more PV or use less energy... or both.

If it was a charging issue, wouldn't all of my batteries be failing at the same time?

No. Your logic is like expecting all Toyota Corollas driven in a given environment will all experience the same failures at the same time.

Each battery responds individually to its operating conditions as no two batteries are exactly alike. Additionally, batteries behaving differently have different consequences.

Not only is each battery different, but each cell is different. You have 24 2V cells, and those will all respond differently from each other... even within the same battery.

This morning the left one was 10.8v and before I could even connect the generator, the sun came up and within 15 minutes the batteries were all reading 12.6v. Any ideas?

What were the others reading when it read 10.8V?

 

[surfergirl]

You are murdering your batteries by using too much energy for what your PV can replace. Get more PV or use less energy... or both.



No. Your logic is like expecting all Toyota Corollas driven in a given environment will all experience the same failures at the same time.

Each battery responds individually to its operating conditions as no two batteries are exactly alike. Additionally, batteries behaving differently have different consequences.

Not only is each battery different, but each cell is different. You have 24 2V cells, and those will all respond differently from each other... even within the same battery.



What were the others reading when it read 10.8V?

Okay, makes sense. The other 3 batteries were reading 12.6v and the sunlight charged up the one with the 10.8v reading to 12.6v
I checked the reading every 1/2 hour today and it got up to 58.4v so am thinking it does this on a daily but I'm not at home during the peak sun hours

 

[sunshine_eggo]

okay... that's good news... now back to my original question...

What do the 4 12V read at absorption voltage?

 

[surfergirl]

okay... that's good news... now back to my original question...

What do the 4 12V read at absorption voltage?

Approximately what time of day would this voltage reading be? At 12:30 the reading was 13.7v each for a total of 54.8v

 

[sunshine_eggo]

Approximately what time of day would this voltage reading be? At 12:30 the reading was 13.7v each for a total of 54.8v

How would I know? I have no idea how you use your system. You could hit absorption by 7 am or never.

You just told me you saw it at 58.4V today. That's an average of 14.6V.

Let's call that absorption.

When the batteries were at 58.4V, what was the actual voltage of each 12V?

 

[surfergirl]

How would I know? I have no idea how you use your system. You could hit absorption by 7 am or never.

Haha- fair enough

You just told me you saw it at 58.4V today. That's an average of 14.6V.

Understood.

Let's call that absorption.

When the batteries were at 58.4V, what was the actual voltage of each 12V?

Each battery was 14.6v but it did go down, back up again etc. Normal as there was a load

 

[sunshine_eggo]

Haha- fair enough

Understood.

Each battery was 14.6v but it did go down, back up again etc. Normal as there was a load

If that's the case, I would conclude that the battery that reads 10.8V while the others read 12.6V has a failed cell. The 12V must be replaced.

 

[SamDeleted]

If that's the case, I would conclude that the battery that reads 10.8V while the others read 12.6V has a failed cell. The 12V must be replaced.

Yep sound like a dead battery

 

[surfergirl]

If that's the case, I would conclude that the battery that reads 10.8V while the others read 12.6V has a failed cell. The 12V must be replaced.

Yes, that's what I'm thinking also. I measured the individual batteries this afternoon and the 'faulty one' actually read 13.8v while the other 3 were at 13.5v. Thoughts?

 

[surfergirl]

Yep sound like a dead battery

Thanks

 

[sunshine_eggo]

Yes, that's what I'm thinking also. I measured the individual batteries this afternoon and the 'faulty one' actually read 13.8v while the other 3 were at 13.5v. Thoughts?

When a cell fails, it's not uncommon to:

Exhibit higher voltage during a charge.
Exhibit lower voltage during a discharge.
Exhibit lower voltage when left sitting due to loss of charge.

 

[surfergirl]

When a cell fails, it's not uncommon to:

Exhibit higher voltage during a charge.
Exhibit lower voltage during a discharge.
Exhibit lower voltage when left sitting due to loss of charge.

Much appreciated. I'm keen to increase my knowledge and thanks for all the help!

 

[sunshine_eggo]

Much appreciated. I'm keen to increase my knowledge and thanks for all the help!

https://rollsbattery.com/wp-content/uploads/2018/01/Rolls_Battery_Manual.pdf

 

[surfergirl]

Hi all, happy to report the battery has been behaving. I adjusted the Float (from 54.8 to 55.2v) and Bulk/Absorb (from 58.4 to 57.6v) I am reaching higher volt readings on my battery bank during the day and even had 54.9v at 5pm last night (usually it's 50.8v) Also, wondering if this battery monitor do the job? One per battery or one for the bank of 4 x 12v? https://www.aliexpress.com/item/100...ea!NZ!3747161663!S&curPageLogUid=aa8TlYE6iXij

 

[sunshine_eggo]

You still need to keep an eye on that battery. Simply upping the float voltage doesn't compensate for the pretty drastic voltage difference with one at 10.8V and the others at 12.6V.