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Underutilization

DaHawg

New Member
Joined
Jan 9, 2023
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21
Location
Youngstown, Ohio
Hello,

I am new to the forum, but have been learning from Will for a few years.

I put together a little system with 8 100 ah AGM batteries with 1.2 kw in panels. I have a SmartSolar MPPT 100/50 Charge controller, the 712 shunt and the Victron 8 amp AC charger.

More hardware:

My 800 Ah AGM battery bank:

4 batteries are two years old but were 80% charged when I put them back into my system. I also purchased 4 new of the same type AGM batteries from Amazon. Specifications: Voltage: 12V Amperage: 100 Ah Chemistry: SLA, AGM

I have them in a series/parallel config for 24 volts.

My issue: I ran a 2 Amp load for 7 hours and my Victron battery monitor shows my systemat a 98% state of charge, but my voltage was down to 24.66 vdc. This is the under load voltage and I have read thai should mean around a 65% SOC.

I should have 400 Ah's to use and stay at 50%, but I'm almost there after only 30 Ah's.

I really don't know what to ask, but this math does not add up for me.

I am planning on breaking my two sets of batteries apart, new vs old, and test again.

I want to see if there is any performance difference between the two sets.

Thanks for reading...
 

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Just a guess based on the fact 4 of your batteries were 2 years old. One or more is going bad. You might need to do a good equalization charge for each battery and than load test them.
 
I'm guessing try putting the 2yr old batteries in parallel with the newer ones.

Also i suggest getting a 24v balancer, i have 2 ha01 units and they seem to work well.
 
Just a guess based on the fact 4 of your batteries were 2 years old. One or more is going bad. You might need to do a good equalization charge for each battery and than load test them.

I'm guessing try putting the 2yr old batteries in parallel with the newer ones.

Also i suggest getting a 24v balancer, i have 2 ha01 units and they seem to work well.
Thanks for the reply. I have them all in two battery sets in series and then all series sets in parallel. I am not familiar with a balancer, I will do some googling.
 
I will upload a pic later after I get home, thanks.

Here is a drawing, but my setup has 8 batteries in the same config.
 

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I guess this is the relevant quote from that item:
Certainly. Do you know any AGM manufacturer that does not recommend to equalize it? You made the statement to not do so after I recommended it. I would have accepted if you had simply said to check with the battery maker concerning equalization.
 
Do you know any AGM manufacturer that does not recommend to equalize it?
It's not recommended for mine (Enersys SBF) but then in that context I was referring to SLA, not AGM specifically.

Trojan does not recommend equalising their AGM batteries, only their flooded batteries. Others however do suggest it can be done.

I guess it depends on the internal construction of the battery, plate gaps, plate dimensions etc. It causes gassing and results in a reduction of electrolyte so one needs to be careful they follow manufacturers advice.

You made the statement to not do so after I recommended it. I would have accepted if you had simply said to check with the battery maker concerning equalization.
Yes, you are correct, that's what I should have said.
 
High voltage - equalization charge of 15V +/-, burns off sulfates on lead plates in FLA's.
An AGM may not respond well to very high charge voltages for extended periods. An equalization charge could be an hour or more with some chargers, some are ten minutes or so. Same for GEL.

For ANY lead acid batteries, they should only be connected in parallel when they are equal in charge state, age, and type. Mix and match will cause a weak one to ruin a good one - basically the good one just gets overcharged while the system tries to charge the weaker one(s).

One time I saw a parallel setup of starting batteries in a motor yacht that had literally cooked all the water out of a newer battery in a bank.
 
This is a “new” install, so my battery monitor has not seen even one battery cycle down to 50% until now. I have read that they “learn” and will get better at estimating. Is that expected?
 
I am just starting out and my cables will all be rebuilt before being used in attended.
 

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If absorption is 80%, then I had 80 Ah left to full. Looks like 50 more to go till full?
 

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