Hello, I installed 1600W peak panels connected to a Victron MPPT 150/35. Output goes to two 24V LiFePo Batteries with 100Ah each and a Soyosource Inverter with 600W.
My question is:
The solar input today is 64.3V and 16.5A giving 1060W. My battery charger's output is only 24.8V and 27.3A giving 675 W. Can someone explain where the difference comes from?
If the inverter is supplying loads, it will consume DC power. That would come from the MPPT in your situation.
If you have any DC loads in your system, these also would reduce the battery charging power.
BTW Victron's technical data sheet indicates a peak efficency of 98%
The Victron 150/35 MPPT output is limited to 1000W, even with more PV power available.
If the MPPT it self would take 10% then you stil would expect at least 900W to come out.
In this case 900-675=225W / about 9A of current is missing, or could flow towards a load.
Did you check the temperature of the MPPT? Efficiency reduces with higher temperatures.
Do you have both the MPPT and a separate charger? They could both be providing charging power to the battery: ~1000 watts from the MPPT and 675 watts from the charger.
If the "charger" measurement you provided is from a battery monitor, make sure the only thing connected to the battery side of the shunt is the battery and nothing is connected to the battery negative except the shunt. This includes any chassis connection. All loads and chargers should be connected to the load/system side of the shunt.
I'm using only this battery charger: https://www.victronenergy.de/solar-charge-controllers/bluesolar-mppt-150-35 (only one box). I don't have a shunt.
The measure comes from a Raspi with the official Victron Venus OS connected via Ve.Direct interface. This is in principle the same as Victron's Cerbo GX.
Without a shunt, Venus OS reports only the power in/out of the inverter's DC connection. The charge contribution from the MPPT is NOT included. Also, the SOC calculation will be way off since it's not accounting for the MPPT charge current or any DC loads you have in the system.
So this accounts for the power differences you are seeing.
You really should add a smart shunt in the negative lead of the battery so it can account for the MPPT charge current/power.
I had this mind anyway in favor of a better battery control. I'm gonna order it right away now. Thank you for that info.
There is an old and a new version of it. Do you know the differences, if any?
I'm not sure it is "old" and "new". AFAIK both versions will continue to be available.
One is IP65 rated for damp locations.
I found the reason for the difference: I had limited the current for the battery to 20A. When I set it to 35A which is the charger's maximum I'm getting a comparable power for input and output.
Interestingly I had not limited the current in Venus OS. Only changing the limit in Victron's bluetooth app did the job.
Still one mystery remains. Where did the difference in power of almost 400W go? If the battery charger would have consumed it, it should have been quite hot, while it was only handwarm.
