solarsam avatar image
solarsam asked

BYD - Multiplus II not charging to float

Hi all.

Have a system with BYD Battery Box LV in a stack of 3 on a Multiplus II and about 3kW of DC coupled PV coming in through a regulator. System was working quite fine until a few months ago when customer noticed a few strange things happening, basically ever since he added some grid connected PV to his house that isn't being seen by the Victron.

The batteries are only charging at a very minimal rate and cap out at 76% SoC with full PV power available. Have spoken with BYD reps and they can't see anything perculiar/fairly unhelpful entirely.

In normal opertaion the charge controller is only putting about 500-600W at best into the batteries even at low SoC, opening up further to cover any loads in the house. This suggests the batteries are only asking for such a reduced charge rate. However, if I turn on a scheduled charge (thinking this would force charge from the grid), the charge controller happily opens up and pushes 1500-2000W into the battery. This still ceases at 76% at which point the batteries begin to idle until needing to discharge to loads.

I have updated firmware on the MultiPlus, charge controller and CCGX, as well as reloaded the ESS assistants into the MultiPlus but none of these seemed to have fixed the issue. Firmware on the BYD is at the latest already.

Any help greatly appreciated

img-6174.jpgScheduled charge disabled: charge current = <10Aimg-6173.jpgScheduled charge enabled: charge current = >10A

img-6173.jpg (2.7 MiB)
img-6174.jpg (2.8 MiB)
2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

1 Answer
snoobler avatar image
snoobler answered ·

At the same time, preferably at low charge or discharge conditions:

  1. Measure battery terminals with voltmeter:
  2. Voltage reported by BMS:
  3. Measure MPPT battery terminals with voltmeter:
  4. Voltage reported by MPPT:

2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.