JBD error "FET Software Locked"

[hwse]

I am getting the following error error on my 200A JBD BMS

FET Software Locked

It showed up after I turned off discharging just after my battery got to LVP cutoff at 2.5v on one cell. I wanted to take one of my two batteries off line which I continued the test on the other which was at a slightly higher SOC.

Does anyone know what this error means and how to get it to go away?

 

[Samsonite801]

Check this thread and see if it helps (2nd post):

MOSFET software locked · Issue #134 · smagicld/xiaoxiangBMS

I got an alarm saying mosfet software locked now my e-bike won’t charge but there is current going through the charger and the battery can someone tell me how to fix this issue

github.com

 

[hwse]

Thanks, that worked. I switched off both the charge and discharge and then turned them back on and the warning went away. Hopefully that will solve the other problem that I encountered after my capacity test.
When I charged them after the full discharge both batteries seemed to be taking charge but the one with the FET locked, indicated that it was filling far faster than possible. I.e., taking in 200Ah in an hour from a 100A charger that was connected in parallel to another fully discharged battery of equal size. Yah, right! This morning they were both in float but the FET lock showed 13.35v while the other showed the correct float voltage of 13.6v.
Now that I have the error reset, I am re-bulking them both at 14.0v and they are both at the same voltage with the one that had been locked taking about 80% of the current so it is obviously trying to catch up from the lower voltage state that I saw.

 

[Samsonite801]

Thanks, that worked. I switched off both the charge and discharge and then turned them back on and the warning went away. Hopefully that will solve the other problem that I encountered after my capacity test.
When I charged them after the full discharge both batteries seemed to be taking charge but the one with the FET locked, indicated that it was filling far faster than possible. I.e., taking in 200Ah in an hour from a 100A charger that was connected in parallel to another fully discharged battery of equal size. Yah, right! This morning they were both in float but the FET lock showed 13.35v while the other showed the correct float voltage of 13.6v.
Now that I have the error reset, I am re-bulking them both at 14.0v and they are both at the same voltage with the one that had been locked taking about 80% of the current so it is obviously trying to catch up from the lower voltage state that I saw.

Also make sure your cabling is good (like 'diagonal' or 'halfway' wiring topology for example), and lengths / gauges are matched on all the parallel leads so they have the best chance at 'seeing' the same voltage from the chargers, and drawing down equally on the loads.

Victron Unlimited Wiring PDF has a good diagram to show the 4 cabling topologies when wiring together parallel batteries, you can search that PDF on Google...

Oh here it is anyways:

https://www.victronenergy.com/upload/documents/Wiring-Unlimited-EN.pdf

 

[hwse]

Also make sure your cabling is good (like 'diagonal' or 'halfway' wiring topology for example), and lengths / gauges are matched on all the parallel leads so they have the best chance at 'seeing' the same voltage from the chargers, and drawing down equally on the loads.

Got that covered. My bank is just two 460Ah packs and I use a diagonal connection with 4-0 paralleling wires.

I was unable to tighten the ring terminal tightly against the batteries terminal because it is flush to the top of the case and did not provide any space for the insulation. I resolved that by making 1/4" 100% copper washers by cutting the ring off of some 4-0 ring terminals which allowed for a good installation. I have a set of grub screws on order so that I can get full depth engagement into the copper terminals in the battery.

 

[imbuere]

I found this thread after searching for the same problem. Cycling the “batt on” and “batt off” did nothing but show a message that said “Port change failed”. Disconnecting the BMS also did nothing.

After thinking I had a bad BMS for days, I started to fiddle with settings preparing to call Currentconnected for a return. The final solution was to flip this switch in the iPhone app. I don’t know how this might have been disabled or what it does, but it seems to have corrected my problem.

Just commenting here in case someone has the same issue.

 

[hwse]

I found this thread after searching for the same problem. Cycling the “batt on” and “batt off” did nothing but show a message that said “Port change failed”. Disconnecting the BMS also did nothing.

After thinking I had a bad BMS for days, I started to fiddle with settings preparing to call Currentconnected for a return. The final solution was to flip this switch in the iPhone app. I don’t know how this might have been disabled or what it does, but it seems to have corrected my problem.

Just commenting here in case someone has the same issue.

It sounds to me like you did the same thing that worked for me based on the info I got from post #2. I get that message any time I turn off the FETs for charge or discharge and they stay there until I manually switch it back on. I have needed to do that a lot, so it is second nature now. One of my packs was about 300mv out of balance when I received it which reduced the capacity by 15Ah below the rated capacity. I have been balancing it by charging it until one cell gets close to 3.65v and then turning off both charge and discharge FETs and letting it static balance for a day. I am now down to about 70mv of delta which is a huge gain.

 

[gord12]

I too have same issue using Overkill app on android.[fet software ;locked] also noticed new purchased jbd bms has manufacturing

date of 1999 any help welcome . will try xiaong..... from apple store

 

[Seabhac]

Using the Xiaoxiang app I turned the charge and discharge function of the BMS off and on. This cleared the error in the Overkill solar app. I couldn't switch them off in the Overkill app prior to this.

 

[KevinSolarNovice1]

I found this thread after searching for the same problem. Cycling the “batt on” and “batt off” did nothing but show a message that said “Port change failed”. Disconnecting the BMS also did nothing.

After thinking I had a bad BMS for days, I started to fiddle with settings preparing to call Currentconnected for a return. The final solution was to flip this switch in the iPhone app. I don’t know how this might have been disabled or what it does, but it seems to have corrected my problem.

Just commenting here in case someone has the same issue.

What app is this? And on what OS? I've tried overkill and the unpaid Xiaoxiang app for Android and I can't find any FET settings

 

[imbuere]

What app is this? And on what OS? I've tried overkill and the unpaid Xiaoxiang app for Android and I can't find any FET settings

XiaoxiangBms on iOS.

 

[KevinSolarNovice1]

XiaoxiangBms on iOS.

Free version or the paid version