MPII 48/5000/70 only charging at ~35 amps

Q&A and troubleshooting
, , ,
1

IMG_2843
IMG_28434032×3024 2.63 MB

As per the pic. The charge rate starts at low 60’s and rapidly falls to mid 30’s

Batts are 500ah and charge from DC at 200A just fine without going over 54v
Cabling is 0/2
Voltage all read low 52/53 ish against 55.5 target
No DC current limit
AC current limit 20A
No BMS integration
Weak AC disabled. UPS disabled.
Batt profile - Lithium
Ambient temps about 10C-15C
System has VE.Bus to Cerbo and BMV712

Why does it not sustain a decent charge rate?

Does your 48/5000/70 maintain a good charge rate.

2

As is so often the case, the problem will probably be determining the SOC of the multis or BMVs . The 88% Soc will only be a very rough estimate. Your batteries do not have their own BMS ? what can you see ?

Maybe Charger is limited at 35Amps ? at Ve Configure … “Charger”

3

88% is from BMV712 via Cerbo / VE.Bus and is accurate / top calibrated every few days.
Aligns closely with REC BMS

MP is not using SOC charge limits, only voltage.

Same charge rate at 25%

DC charge limit set to 70A

Same results with second seperate MPII

4

What kind of batteries?

4×12 in series or 2x48 parallel

Do the batteries have bt ? If yes, what are they saying ?

Weak ac set in mp ?

We need more input !

5

2 x Winston 16S, 500AH total.
2 x REC BMS with CAN not connected. Standalone
I have tried with every combination disabled. Weak AC, PowerAssist, Dynamic Current Limiter.
Charge Current is set to max 70A
AC In to 20A as per pic

Pack reliably charges at 200A DC from Solar & high power alternator

6

Well, then it should possibly be thin wiring or bad contacts between batteries and mp

7

Check the image. That should refute that comment.

Further we regularly load to peaks and voltage drop is minimal.
2/0 rated for >300A at 2m.

8

Try setting ac in to max.

And check if you have the newest firmware 552 installed

2/0 is 70sqmm, good for 147a

9

I would wire up the remote voltage sensing for the inverter - which is frequently overlooked. also to check the voltage charging parameters.

10

Confirmed 552
No AC limit still rolls back from lows 60’s to mid 30’s over 5 minutes

1.6% drop at 300A. Where do you get 147A?

11

What is the ventilator doing ?

12

Hard to tell. Ambient is 10C and unit is cool to touch / near silent.

Do you have a 48/5000? Can you get 70A?

13

No, i have a 12/3000-120, should deliver 120a, never seen more then 100.

The victron numbers are overly optimistic.

But in your case i think something else is wrong.

Did you check the voltage at the mp terminals and battery terminals ?

Do you have a thermographic camera to check the whole system for hotspots ?