Battery charging. .                                                     Hi tks for all the good info I would like some advice. I have 12 vision , 200 ah batteries connected for a 48 v system with two mercer 5 kw invertets for 10 kw what would be a max charge current we are off grid and a good cut of voltage

tks 

Hi Neville

You have 3 strings of 4 battery's , 200Ah per string so a total of 600Ah. For normal Lead Acids we would then recommend charging at 10% of the total bank size, 60 Amp. 

What is interesting though, the spec sheet shows max charging current as 60A (In a single string application), so I guess you can safely go higher than that. 

From what I read here you should be able to go to 180 Amps. I must admit, this is the highest charging current I have seen on a battery and personally I wont go to 180 Amps.   

14 hours ago, Neville h said:

what would be a max charge current

Just remember that the maximum charge current settings add (they are per inverter). So for example, you could have a maximum charge current setting on one set to 30 A, and the other to 40 A, for a total maximum charge current of 70 A.

A 5 kW Mecer probably has a maximum charge current of 80 A per inverter (depending on the exact model), and the 5 kW of panels could provide about 100 A each (at 50 V battery voltage), more than the inverters can use. So it seems a shame to charge at only 30 A per inverter. Since your batteries seem to be able to take more current than average, and the usual maximum charge rate for lead acid is 0.15 C (15% of the Ah capacity), that would come to 0.15 x 600 = 90 A. So that would be 40 A on one and 50 A on the other, or you could go for 50 on both.

I agree with @Jaco de Jongh that 180 A is probably too much, as three strings of batteries won't share perfectly, so one string would be getting more current than the manufacturer's limit. At a wild guess, I'd say no more than 120 A maximum, but that's just a gut feel.