Large battery bank doesn't seem to hold a charge

[spendlove]

Our 12 volt battery bank has about 20 batteries, can't remember the exact number. Now that there is less daylight, I've been charging the bank using our propane generator. One night recently I turned off the generator when the battery voltage was 13.0 and went to bed. All major power consuming devices were turned off, including computer, fridge, etc. Just had on a small fan near the bed to provide some white noise. The whole system shut down around 4AM. This system is about 10 years old, although most of the batteries have been swapped out and date 2016. Why can't a battery bank power a small fan throughout the whole night without shutting down due to the voltage dropping too much?

Please advise.

Thanks!

 

[Supervstech]

I am guessing your batteries have an issue.
Time to open all cells and test voltage.

 

[SCClockDr]

That is indeed a lot of batteries. What do you have to monitor them? Have you verified the charger is charging?
Otherwise I'd suspect a bad cell in one or more of your batteries.

 

[Rider]

Old school, but if you got one of these, you could test each battery without removing it from the chain, see if you have a bad one.
You didn't say, but I was assuming lead acid. Disregard if not...

https://www.amazon.com/OTC-3180-Battery-Load-Tester/dp/B000F5HU6C/ref=asc_df_B000F5HU6C/?tag=hyprod-20&linkCode=df0&hvadid=312158603728&hvpos=1o2&hvnetw=g&hvrand=14613105460093658331&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=1014895&hvtargid=pla-569693209121&psc=1

 

[spendlove]

Old school, but if you got one of these, you could test each battery without removing it from the chain, see if you have a bad one.

Is a load tester like the one you suggested an overall better tester than one like this?

https://www.amazon.com/E-Z-Red-SP101-Battery-Hydrometer/dp/B000JFHMRU/ref=sr_1_3

Thanks!

 

[Rider]

Not better, just different tests. The load meter (non invasive test) will determine if you have batteries that can't supply the rated current under real load. The hydrometer (if you have access to the cells) will show individual weak or bad cells withing the battery. Each have their merits.

 

[Ped]

For one you only charged to 13v. You have to charge to 14.4v-14.8v and hold that until the amps taper to below .1%. And do that every single day. Or your batteries will do what theyre doing now...sulfate.

You cannot just have a bunch of batteries and a random amount of panels. You have to charge them at C/10. So if you got 2000Ah you need 4kw of solar (200 amp @ 8-16hrs a day).

On top of that paralleling 20 batteries is going to cause the end of the string to constantly under-charge just by resistance.

 

[SCClockDr]

If you have access to each cell (a true wet lead acid battery) get a real hydrometer with the three glass float made for battery maintenance. They are rather inexpensive. Then charge them up and let them rest an hour or 2, then record the specific gravity & temp for each cell.
This will reveal any bad batteries & provide insight on the weaker batteries that are still functioning.