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Hi all, I have a 230V MultiPlus-II 12/3000/120 connected to 650Ah of lithium. I have the charger set to 120A but I can only get the charger to pump out 85A for some reason. I notice that at 85A charge current the input voltage is down to 219V. Could the reduced charge current be due to voltage drop measured at the input voltage?
A big thank you to all that offered advise, I have found the problem and it was because I’m an idiot!!! I was trying to fix 2 issues as I had the reduced charge current but also an alarm on 1 of the BMS’s saying over voltage on 1 set of cells. I had 4 profiles saved with different absorption voltages that I was swapping between and for some reason (me being an idiot) I had inadvertently left the weak AC box checked in the 1 profile that I ended up using. Again thank you all for helping me.
Per the datasheet:
https://www.victronenergy.com/upload/documents/Datasheet-MultiPlus-II-inverter-charger-EN.pdf
It can accept down to 187V; however, it might need to be configured to go that low. My 120V Quattro needs a special setting to allow input down to 101V.
I doubt that's your issue.
What is your battery voltage? If the charger is in absorption mode, it is voltage limited and will not run at max current.
It’s right through the bulk stage. I ran the batteries right down to 20% so the bulk stage was going for at least 4 hours.
Weak AC input enabled will reduce the output by about 20%. Is that enabled?
Are you using loads while charging? Charging can only be done with surplus AC.
Is your charger configured to charge at 120A
Is your AC input current limited?
Just to eliminate it as a possibility, you indicated "BULK" - is that you know you're in bulk because of the depth of the prior discharge, or you noted that the charger reported it was in BULK mode for 4 hours?
If you have wiring losses or connection issues, the voltage at the charger is at absorption when the battery is lower, and it's reduced the peak current to hold it. LFP charge curve is flat, so the current would taper much slower than it does with lead acid.
Worth checking voltage at the battery terminals and voltage at the MP terminals with a meter when moving the 85A.
That answers that.
Hopefully the temperature sender doesn't have any influence as temperature compensation should be disabled for LFP.
I don't know the exact relationship, but the internal temperature of the MP will affect it's performance. Hotter MP will throttle back on performance to protect itself.
Can you share details on your battery - to be a bit more specific: especially the type and configuration of the BMS. Are you sure, that the charging rate isn‘t limited by the BMS?
@The Doon Although it does seem a bit low 120/85A = 70% of rated output, I think your 'low' input voltage may not help. It's already dropped to 219V with 85A so would probably drop much lower if it would get to full output. The rest maybe poor DC cables / connections.
I've noticed if I set our generator: @ 50Hz = 220v then I get 200/165A = 82.5%
@ 52.2Hz = 234v then I get 200/180A = 90%
I've just set it to 53.4Hz = 240v but I need to run the batteries down to see what I can put in before the sun shines tomorrow.
My Suspicion and hope is that the Quattro will have full output at 240v.
This is rough and unscientific averages I've seen at the start of bulk, my genset is massively oversize (57kVa) and 3 phase 380v so 220v @50Hz for each single phase output, but increasing the frequency (RPM) gets a higher voltage for gensets.
Are you able to test with a 'stiffer' input voltage, assuming the cables and connectors are good?
