I have a 24 V system 4P 2S with 8x12V life 200A=800A batteries
I charge the system with 100A max. The max mid point deviation
never exited .1% up to about a monthago. The last month
for some reason just before absorption
when the charging voltage reaches 28.+ volts
(absorption is set to 28.40 V) the mid point deviation
jumps to 3.5% as you can see from the graph
please note that i also have a 24V non Victron Balancer
and that the last month we have high weather temp close to 40 C
smart shunt reports batteries temp just 1 decree higher.
Why this happens now with no obvious reason and
what can i do correct it
How did you realise your cabeling for the parallel connected batteries?
Is it (like always recommended for parallel batteries) acroos/diagonal connection for the terminals?
You find very good details how to handle this in the Victron Wiring Unlimited documentation.
Hob big are the charge / discharge currents?
Nevertheless, these 3,5% deviation for a short moment (maybe while there is a charge/discharge) seems absolutely uncritical to me.
wiring is as commented and it has nothing to do with load
charging with less Amp is lowering the spike but not as low as it was before a month that never pass 1% my worry is why now ??
I assume you did not change anything? Configuration of the system, and new or other laods or firmware…? Did you move the system, - is it mobile (RV) ?
Did you check all the connection? Maybe something went loose…
Next point could be age of the batteries… are these lead acid, or LiFePO ? Maybe the temperature has bigger impact then expected. Did you check the datasheet? 40°C is quite hot already, maybe the chemistry is running ouf of spec bit by bit the more hotter it gets…
I am also running 12V batteries in Series / Parallel sets and using a balancer. I too noticed that when the solar output is much higher than the demand, and it approaches 28V, the mid-point deviation starts ramping up to 6%. I set up Node-Red to ramp down the maximum available current on the MPPT’s to ensure less than 100W is going to the batteries, and that now keeps the Mid-Point % under 1.5% during the Absorption phase.
No i did not change anything the batteries are life po and yes the temperature is what i am afraid that may be one of the bms is cutting off that is why i am asking for the opinion of people who may know. by the way the system is in my home in doors
@ Brett Styles
thanks for the answer i too noticed that reducing the charging current helps but to me it happen only last month my system works for about a year
Finally i did not find the reason for the sudden increase of the Mid-point % but by setting in DVCC maximum charging voltage to 24.4 solve the problem
Mid voltage% never goes over 0.8 % what ever charging Amp limit i set
Hope this helps and others with the same problem
Note : This is not the solution as to why after 1 year of the system working with the midpoint % never going over 1% and with no apparent reason jumping high to 3+% it is a temporary solution to stop it going high and protect the batteries at present.
The problem is still there. I suspect one or more of the 8 life po4 batteries is the problem but i can not switch off the system to check them now as i am off grid.
If i find the solution i will post here if it is still open or to a new thread
It looks like the problem was the high temperature 40C now that the weather temp drop down to 28 C
everything is back to normal max mid point deviation 5 to 7%
Thanks to all
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