Multiplus + Dyness Buddy + 1xDL5.0C + 2xA48100: DL5.0C reaches 1% SOC

DIY
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1

Hello,

I have a Victron ESS system with:

Victron MultiPlus 48/5000
Cerbo GX
Fronius Primo 5.0-1
SmartSolar MPPT 150/60
Dyness Buddy
2 × Dyness A48100 on the Buddy 48 V CAN port
1 × Dyness DL5.0C on the Buddy 51.2 V CAN port
Buddy INV port connected to Cerbo GX BMS-CAN

Victron detects one managed battery: DYNESS-L Battery. Communication works, DVCC is enabled, charge current is limited to 50 A, inverter power is limited to 2000 W, and ESS works normally from the Victron side.

The issue is the discharge behavior. The Buddy seems to discharge the DL5.0C first. When the DL5.0C voltage drops to around 49–49.5 V, discharge then moves to the A48100 bank. This matches what Dyness Spain told me: the Buddy apparently transfers/balances based on voltage.

However, after installing the WiFi module on the DL5.0C, I can see its internal SOC. At the moment when the Buddy transfers discharge to the A48100 bank, the DL5.0C reports:

DL5.0C SOC: 0–1 %
DL5.0C voltage: approx. 49–49.5 V
Current: near 0 A or already reduced
Temperature: normal
No visible BMS alarm

This now happens daily. The system is stable and there are no BMS alarms, but my concern is battery lifespan: could taking the DL5.0C down to 0–1 % SOC every day degrade the battery, even if voltage remains around 49–49.5 V?

I also noticed that the global SOC reported to Victron/VRM by the Buddy does not seem to be weighted correctly for the real installed capacity. The system has 2 × A48100 + 1 × DL5.0C, but the Buddy appears to treat the two branches as equivalent. This makes ESS minimum SOC difficult to configure, because Victron only sees the Buddy’s aggregated SOC, not the real SOC of each battery branch.

Current relevant settings:

DVCC charge current limit: 50 A
ESS inverter power limit: 2000 W
Peak shaving: disabled
Dynamic cut-off: 46 V
MultiPlus low shutdown: 46 V
Low restart: 49 V
Low pre-alarm: 47 V

My main questions are:

  1. From a battery/BMS point of view, should I worry about the DL5.0C reaching 0–1 % SOC daily if the voltage is still around 49–49.5 V and there are no alarms?
  2. Is the DL5.0C SOC shown in the Dyness app likely to be a real SOC value, or could it be inaccurate in this Buddy mixed-bank setup?
  3. Is there anything on the Victron ESS/DVCC side that can protect the DL5.0C minimum SOC when the Buddy only presents one aggregated battery to Victron?
  4. Has anyone used Dyness Buddy with mixed A48100 + DL5.0C batteries and monitored the internal SOC of the DL5.0C separately?

Dyness has not identified a product defect so far and has advised continuing to monitor while their R&D reviews the case. My main concern is whether this daily low SOC could accelerate DL5.0C degradation.

Thanks in advance.

2
  1. Don’t think that this will be an issue.
  2. Yes.
  3. No, Don’t think so.
    Does your A48100 battery have the same voltage range as the DL5.0? It seems that as one is nominal 48V and the other is Nominal 51V, it seems that the lower voltage bank may be turned off while the voltage is above ~50V, and the 51V bank is turned off when the voltage drops below 49V.