BMS V2 with mixed v1/v2 batteries - Solution to persistent BMS alarms.
Posted: Tue Dec 20, 2022 10:25 pm
If you don’t want the context nor a description of the issue (which may be helpful to some to diagnose the issue) then please skip and scroll to the solution below.
Context
There will be many who have invested in the Fox system over the past 2 years and the numbers continue to accelerate as time goes on.
Within the past 6 months, the news broke that chip shortages across the globe have resulted in a need for a new version of the HV2600 batteries (V2) which have now been released with a new chip to cope with the continued demand.
This has posed a somewhat significant compatibility issue with many choosing to add additional battery modules (the whole point of a modular system!) and ending up with a mixture of version 1 (V1) and version 2 (V2) batteries.
The consequence of this; the need for a new version (V2) of the Battery Management System (BMS) which would be reverse compatible with the V1 batteries that many people will already own.
Problem
There are initial signs that the so called ‘reverse compatibility’ has not gone smoothly. The mixture of V1 and V2 batteries along with the V2 BMS has resulted in a number of unwanted BMS & Battery Voltage alarms which interrupt the force charging of the batteries. Mainly the “BMS Hardware Protect” (211) and “Bat Voltage Low” (198) errors.
These seem to happen more commonly when the battery enters a “force charge” period (usually overnight for most with off-peak tariffs) and there seems to be a varying degree of results in terms of the alarms that occur and when.
I suffered with this for a couple of weeks and my issues varied from an alarm at the beginning of a charge period and never recovering (zero charge!), to a seemingly random alternating alarm every 5/10 mins but still managed to charge to roughly 60%(less annoying, but still annoying!) – examples of problematic charging profiles and the fixed one below.
Examples of problematic charging profiles.
How the charging profile should look (aside from a random point.. who knows what that was).
Solution
I can’t take credit for this as someone else did the hard work in getting the info out of Fox UK and Fox China but the solution involved taking a spare ethernet cable and modifying it slightly – you will likely have a spare after taking delivery of the v2 BMS as you already have one for the v1 BMS.
See the image below for how this should look when finished.
Before beginning, shut down the system by firstly throwing the breaker on the BMS and turning the AC/EPS isolators to off. Lastly, turn the DC isolator off on the inverter itself. The screen will go blank and the lights on the BMS will all be off.
Step 1:
Peel/cut away about an inch of the sheathing of the spare ethernet cable – DO NOT CUT THE WIRES.
Step 2:
Of the 8 strands of wire inside the ethernet cable, identify 2 out of the 8 wires to cut - the solid green wire and white/brown striped wire.
It's not clear what these wires (number 6 & 7) do, or why they cause an issue - I'm sure this will become known in time but for now - it just works!
Step 3:
Isolate those wires and cut them carefully so as not to damage the others – you should have 6 wires inside the ethernet cable intact.
It would be best practice at this point to wrap a length of insulating tape around the exposed wires or any other fancy technique you may have up your sleeve!
Step 4:
Connect this modified ethernet cable to the RS485 port of the V2 BMS and to the RS485-1 port on the first battery in the series.
It has also been reported that connecting the modified cable between the COM port on the BMS and the BMS port on inverter also works - so take your pick!
It should be said though that, in my opinion, it is probably easier to connect the BMS to the first battery as this doesn't involve trying to fumble about under the inverter!
Please note: It’s not clear if this is important but it’s probably best that the V2 battery(ies) are first in the series.
Step 5:
When done, start up the inverter in the reverse order to that at the beginning of these steps.
The end result will look like this:
If successful, and it certainly has been for me and two others on this forum that I know of so far, you should no longer experience any of the alarms described here and you can breathe a sigh of relief!
It’s not clear how this will evolve with Fox support – no doubt people experiencing this issue will be inundating Fox with requests for help. Anecdotally, it seems that they will probably be following this fix by either providing their own instructions or supplying modified ethernet cables.
Hope this helped. Any questions please post here or on the Facebook forum.
Context
There will be many who have invested in the Fox system over the past 2 years and the numbers continue to accelerate as time goes on.
Within the past 6 months, the news broke that chip shortages across the globe have resulted in a need for a new version of the HV2600 batteries (V2) which have now been released with a new chip to cope with the continued demand.
This has posed a somewhat significant compatibility issue with many choosing to add additional battery modules (the whole point of a modular system!) and ending up with a mixture of version 1 (V1) and version 2 (V2) batteries.
The consequence of this; the need for a new version (V2) of the Battery Management System (BMS) which would be reverse compatible with the V1 batteries that many people will already own.
Problem
There are initial signs that the so called ‘reverse compatibility’ has not gone smoothly. The mixture of V1 and V2 batteries along with the V2 BMS has resulted in a number of unwanted BMS & Battery Voltage alarms which interrupt the force charging of the batteries. Mainly the “BMS Hardware Protect” (211) and “Bat Voltage Low” (198) errors.
These seem to happen more commonly when the battery enters a “force charge” period (usually overnight for most with off-peak tariffs) and there seems to be a varying degree of results in terms of the alarms that occur and when.
I suffered with this for a couple of weeks and my issues varied from an alarm at the beginning of a charge period and never recovering (zero charge!), to a seemingly random alternating alarm every 5/10 mins but still managed to charge to roughly 60%(less annoying, but still annoying!) – examples of problematic charging profiles and the fixed one below.
Examples of problematic charging profiles.
How the charging profile should look (aside from a random point.. who knows what that was).
Solution
I can’t take credit for this as someone else did the hard work in getting the info out of Fox UK and Fox China but the solution involved taking a spare ethernet cable and modifying it slightly – you will likely have a spare after taking delivery of the v2 BMS as you already have one for the v1 BMS.
See the image below for how this should look when finished.
Before beginning, shut down the system by firstly throwing the breaker on the BMS and turning the AC/EPS isolators to off. Lastly, turn the DC isolator off on the inverter itself. The screen will go blank and the lights on the BMS will all be off.
Step 1:
Peel/cut away about an inch of the sheathing of the spare ethernet cable – DO NOT CUT THE WIRES.
Step 2:
Of the 8 strands of wire inside the ethernet cable, identify 2 out of the 8 wires to cut - the solid green wire and white/brown striped wire.
It's not clear what these wires (number 6 & 7) do, or why they cause an issue - I'm sure this will become known in time but for now - it just works!
Step 3:
Isolate those wires and cut them carefully so as not to damage the others – you should have 6 wires inside the ethernet cable intact.
It would be best practice at this point to wrap a length of insulating tape around the exposed wires or any other fancy technique you may have up your sleeve!
Step 4:
Connect this modified ethernet cable to the RS485 port of the V2 BMS and to the RS485-1 port on the first battery in the series.
It has also been reported that connecting the modified cable between the COM port on the BMS and the BMS port on inverter also works - so take your pick!
It should be said though that, in my opinion, it is probably easier to connect the BMS to the first battery as this doesn't involve trying to fumble about under the inverter!
Please note: It’s not clear if this is important but it’s probably best that the V2 battery(ies) are first in the series.
Step 5:
When done, start up the inverter in the reverse order to that at the beginning of these steps.
The end result will look like this:
If successful, and it certainly has been for me and two others on this forum that I know of so far, you should no longer experience any of the alarms described here and you can breathe a sigh of relief!
It’s not clear how this will evolve with Fox support – no doubt people experiencing this issue will be inundating Fox with requests for help. Anecdotally, it seems that they will probably be following this fix by either providing their own instructions or supplying modified ethernet cables.
Hope this helped. Any questions please post here or on the Facebook forum.
now getting nice bit of sun and battery’s charging up nicely at 85% and added 10.5 kWh from 29% so hopefully with a bit of balancing it should be ok 
love hearing success stories. Glad it helped you!!