AGM Battery bank or hybrid inverter problem?

[Alan B]

After 2 years use ,I recently notice my bank will not charge above 49.6 volts , the system is an EPEVER hybrid 5KW with 8kw of hoppecke AGM batteries.
I have checked my user and default engineer settings for AGM with EPEVER customer care and all is good .
As far as im aware the batteries have been charging and discharging ok. {until I changed to "utility priority" output a week ago}
when i use a multimeter across the main terminals of inverter that lead to the bank it reads 49.8 v ,this is when the LED display is showing "equalize".
the equalize voltage should be 58.4 v, { "equalize" has been on display constantly for a week} .could this be because....
Im measuring at wrong place or because the bank is connected while testing.
the inverter is faulty
the batteries have bit the dust .
EPEVER have said the need me to return the inverter for testing ,which would be inconvienient .[especially if it turns out to be batteries at fault ]
Im not a sparky but can do basic testing ,any ideas where to go from here please,

 

[binky]

so it was working fine until you changed something - unchange it and see if works properly again.

Equalize sounds like differences between the batteries, if it's been on for a week, that doesn't sound right. Out of interest are any of the batteries on a cold floor?

 

[Alan B]

Hi, firstly,no this problem has been for weeks and settings were the same as they had been for 1 year , i changed the settings to stop the batteries getting discharged while i work out the problem
the batteries are outside under my shed ,but inside a plybox that has 4 inch insulation board all round [and floor].
there is a temperature probe that should make allowances for outside temps.
from my understanding the "equalize" mode should be sending 58.4 volts to the bank ,but when i measure from
the bottom of the inverter where the fat leads connect to batteries it only reads 49.8 volts .{equalise mode should only be 180 mins not 2 weeks}
what im wondering is should i disconnect the bank to get a proper reading or am i doing it correctly
could it be that the bank has had it and wont accept more than 49.6 v [obviously its a 48 volt bank]
any other tests i could do before having to send the inverter for a bench test. Much thanks for answering Binky

 

[binky]

2 weeks is certainly excessive, which may indicate one knackered battery in the set. It might be worth disconnecting the entire set, and checking the batteries individually, perhaps recharge them individually before replacing as a stack. I've had problems with Lithium batteries taking days to charge because they fell below 10%, which puts them into a trickle charge rate. That happened mid winter in similar conditions to what we are having now in sunny Devon. I'm not sure what the min level should be for AGM, but suspect it's around 20%. Does your system have a BMS?

 

[Chrisbee]

Alan B you say there's a temperature probe that should make allowances for outside temps. Maybe that is exactly what it's doing? i.e. Reducing charge completion voltage slightly because the batteries are cold.

 

[Alan B]

HI ,system does not have BMS I thought it was only lithium that used them ,should I have one?
49.6 v still seems very low ,even for the chilly conditions we are having .
Perhaps i will dismantle the bank and charge seperately as Binky suggests.
thanks for your replys.