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Battery Bank Health


Bobby Kaucic
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Hi all,
I have a simple system with a 48V (54.4V) Battery Bank (Gel Batteries) and a Victron Multiplus II 5000VA Inverter.
Batteries are already two years old. Previous loadshedding period that we had last year, I was able to go through the 4 hours cycle with no problems, but now I am able to run only for an hour before inverter goes into shutdown due to low battery.
I checked the battery bank voltages shortly before it shuts down, and they are anywhere between 38V-41V
Once inverter is shut down, after 10-20minutes, the voltage comes back up on its own to 48V. As soon as I put on a bit of load (around 200w), comes down to the 41V in minutes. When fully charged, battery bank voltage is around 54.3-54.4V

Does this mean that my batteries are dead?

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2 hours ago, Bobby Kaucic said:As soon as I put on a bit of load (around 200w), comes down to the 41V in minutes. When fully charged, battery bank voltage is around 54.3-54.4V

Does this mean that my batteries are dead?

My brother has the same type of gel batteries and the same short runtime. And he kept his DOD to just 90%.
if a 12v acid battery falls to just under 10v it is dead and cannot recover. 
Your inverter can cope with charging lithium batteries. There are good prices on Pylontech now. 
If you reduce your load you may be able to extend their life. 
Don’t waste money on battery balancers. 
I bought Pylontech batteries a short time after his installation and my setup is still 100%. My 4 x Pylontech 2000 batteries have lasted 4 days at a time when the power was out. They also recharge to 100% far quicker than a gel battery. 
Personally my opinion is that gel batteries were a wasted R25k. 

Edited by Johandup
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My bank also went from an easy 4H30 Load Shedding session when new to a just barely making it with very careful load management after two years - but it still made the 4H30 sessions. I did have balancers which kept the batteries in better shape than would otherwise be. My initial choice was to go the cheaper LA, but still $$$, option until such time that LiFePO4 prices came down a bit and now is a good time for that. I upgraded to LiFePO4 two months ago and very happy.

In short, I fear your batteries have had it if it can't deliver on your 4H requirement. Have them checked and tested just for your own peace of mind.

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