Hi Everyone,

One of my neighbors has Victron MultiPlus II GX and a Pylontech UP5000 and asked if I could have a look at it and see if I can figure out what the problem is with the battery.

I have managed to connect to the Inverter using VRM.

They have not been used for some time (2 years) and when I turned the inverter and battery on, the UP5000 is totally flat and flashing red.

It comes up with a low voltage alarm when I connect to it from my laptop.

I have tried recharging it using the Victron but cannot get it to wake the battery BMS up (I am not a Victron guru so could be doing it wrong).

Does anyone have any suggestions/experience on how else I can try wake the UP5000 up?

It has been suggested I use a low amperage 48V charger and try wake up the BMS with that.

Thanks

If I measure the voltage over the terminals I get 0V and have tried resetting the BMS by pushing the SW button for 3 seconds but always flashes red.

Is there another way to restart the BMS if I connect to it directly using my laptop perhaps?

3 hours ago, Sc00bs said:

If I measure the voltage over the terminals I get 0V and have tried resetting the BMS by pushing the SW button for 3 seconds but always flashes red.

Is there another way to restart the BMS if I connect to it directly using my laptop perhaps?

What about disconnection any form of charging and using the 5-9V battery like a PP3 used in multimeters as is used to switch on a JK BMS?

Thanks @Scorp007

Hmmm, I don't have a PP3 power supply.

I have a 24V power supply, wondering if that might restart the BMS

Hi Scoobs

Here are a few options for you to consider:

1. External “kickstart” charge

   • A dedicated 48 V lithium charger (or a bench power supply adjustable to 52–53 V DC) with current limited to 2–5 A max is usually the safest way.

   • Connect directly to the battery’s + and – terminals.

   • The goal is to lift the pack voltage above the BMS threshold (usually ~44–46 V).

   • Once the BMS wakes, it will allow the Victron to take over charging.

2. DIP switch “Force Start” mode (on some Pylontech models)

   • Check the DIP switch configuration in the Pylontech manual.

   • Some models have a way to force the battery to accept charge when deeply discharged, but it usually still requires an external voltage source.

3. Chaining with another healthy battery (if available)

   • Sometimes connecting the flat unit in parallel with a healthy UP5000 (only if you or the neighbor has one) will allow it to “piggyback” charge and wake the BMS.

   • ⚠️ Needs care and identical SOC packs, otherwise huge inrush current could flow. Only do this if you’re experienced.

4. Victron + Pylontech CAN comms

   • The Victron MultiPlus can wake the UP5000 only if the BMS is listening, but if the pack is “hard asleep” it won’t talk at all. That’s why the VRM shows low voltage alarms but can’t start charging.

   • So the Victron alone probably won’t bring it back without external help.

Thanks for the suggestions, I decided to take through to Solar Deity and will see what they say before I try any out of warranty solutions :-)

Will let you guys know what they say.