Charging mode mismatch across multiple MPPTs with DVCC enabled

Q&A and troubleshooting
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1

Hi All,

We replaced our 14 kWh Pylontech US3000C bank (failed in two and half years, what a horrible product and support) with a 16S EVE LF280K DIY pack + JK 150A active balancer BMS.

System:

  • 3× MPPT 150/45
  • 1× MPPT 100/20
  • 1x SmartShunt 500A ( Connected to main battery negative)
  • Cerbo-GX
  • 2× Meanwell TS3000 inverters ( only for AC loads. not charging the batteries)
  • ~7 kW solar, fully off-grid
  • Also has DC system that directly powered from 48v bus

Settings:

  • MPPT: Absorption 55.2 V, Float 54 V, Absorption 2h, Tail current off
  • Shunt: 280 Ah, Charged 55.0 V, Floor 10%, Tail 2%, Eff. 99%
  • CerboGX: DVCC on, SCS on, SVS on , others default, Battery Monitor: Smart Shunt

Now we don’t have BMS communication with Cerbo-GX anymore. (yet to purchase the kits for communication) and we have few problems with our system

  1. MPPTs often switch to float when SOC is only 70–85%. Is this due to low charge voltage
  2. One controller (always the same 150/45) shows a different charge stage than the others. e.g., in bulk while others are in absorption, or in absorption while others are in float.
  3. With long absorption on sunny days, it charge fast but BMS cuts charging (guess due to high voltage). On cloudy days, it only charge to 70-80%
  4. I thought DVCC will dynamically manage everything. but it seems MPPTs not really listening to DVCC

But other than these issues, New battery bank working fine.

What’s missing in my setup? I’d appreciate any help.

2

When not using ESS and not using an intelligent battery the system devices default to internal algorithms, see this table.

probably, check your voltages on the terminals and charge settings

check the voltage on the terminals, power loss from the wires being too thin can cause a voltage drop

3

BMS cutting charging or discharging should be last resort /safety feature.

Sounds like BMS and or charging parameters need adjustment.

Best solution is get jkbms talking to victron and set BMS to control charging.

See Introduction | dbus-serialbattery

4

Thanks for the reply.

I’ve already ordered the parts for BMS communication, but due to shipping delays it will take a few months before they arrive at this site. In the meantime, could you suggest good MPPT and shunt settings for my setup that I can use until I enable comms with the BMS and Cerbo?

Do you think the baseline values I set are okay? And what would happen if I increased the voltage a bit, say to 55.60?

5

What settings has the BMS ?

Sounds like the BMS is going into over voltage shutdown, due to receiving too high voltage.

Either drop charging voltage or increase BMS shut down voltage, dependent on Max allowable voltage of the batteries.

6

I would also check that it’s not a voltage drop between MPPT battery connections, or that the one of the MPPT voltage references is off (rare, but it happens).

Use a multimeter to measure MPPT battery connection and compare it to its value as displayed on the Cerbo (ie: is MPPT accurate).

Then measure each MPPT against the others (cabling).