SBMS120 and SBMS0 help

[Tim D.]

Dacian,

I hooked up my SBMS120 today and all seemed to work fine at first, but when I disconnected the balance leads to store the parameters I noticed that the CFET and DFET would not activate, I don't know if I did something wrong, I left the Battery Positive cable attached with nothing on the Load or PV inputs , when I disconnected the balance leads to store my parameters, like it says to do in the manual,  but whatever I did, the CFET and DFET will not turn on

So then I figured I would try the SBMS0 that I have, I was going to use this for a different project, but figured I may as well use it since the SBMS120 isn't working, but the SBMS0 seems to have a screen error, when I connect the SBMS0 to the battery sometime the screen will turn on with no backlight, sometimes it will turn on with a backlight but very dim, sometimes it will turn on only the backlight and no image, and sometimes the screen glitches

I've attached pictures to show you what I mean with the SBMS0

Can I send the SBMS120 and SBMS0 back to you for repair, and if so what will the cost be to fix them?

[Plamen]

Tim, I'm not an expert on that but rather it's related to high temperature and moisture at your location. Have you tried (for SBMS120) to touch together with fingers Batt.+ and Load? Many times it do the magic.

[Tim D.]

I'm not sure what happened but the C/FET and D/FET are working again,  I wouldn't have thought temp or humidity would be an issue as I'm just testing this out on my desk in my bedroom,  air-conditioned,  with a room temp of 72F.

I an seeing a strange voltage difference on the cells with the BMS monitoring screen, this voltage difference is not actually present at the cell when I test with my multimeter 

On the SBMS120 the voltage jumps wildly by 120 mV up and down on 2 of the cells 

[Tim D.]

As an update I tried turning off the balancing feature to see if this was causing the voltage differences i was seeing on the BMS monitor screen,  this requires a reset, so I disconnected the  charger wire and then pulled the balancing wire plug, then I restart by plugging the balance leads back into the BMS, and now  C/FET and D/FET will not activate again 

I tired the finger thing between batt+ and Load+, no joy, they won't turn on again 

Temp of the internal temp probe is 83F, and no humidity in my bedroom 

Any suggestions would be appreciated 

[Plamen]

Those 120mv. up and down are with load(inverter) connected or some grid charger?

It's a dumb question but i can't think of anything else. Did you try to turn on charging/loads from the menu?

[Tim D.]

This is a link to s video of the voltage swing I was seeing https://photos.app.goo.gl/xQ9ATdLWqmr1HmyH7 

The C/FET and D/FET turned back on after a while (again), and when I set the BMS to not balance the battery bank I did not see these voltage swings at the cell level as shown in the video link above

So I think that the Voltage swing up and down must be result of the BMS trying to balance my battery bank, because it's not present when I turn the Balance feature of the BMS off. 

The Voltage Delta on my bank is only 12mV to 13 mV when under a 35 amp charge, and closer to 3mV once not under charge, so I think what was happening is the BMS was set to balance at a delta of 11mA, the very thin wires of the balance leads can't take any type of current, so it must be affecting the voltage that the BMS sees when it's trying to balance the battery bank.

I've put an active balancer on the battery pack to maintain balance and with it on I'm not seeing any voltage swings like I see when I try and use the SBMS120's internal balancer

Still no idea why the C/FET and D/FET turn off for a set period of time after a BMS reset, but they have remained on for the rest of my testing, it seems that as long as I don't reset the BMS to store any new parameters that the C/FET and D/FET work just fine. I got the battery pack charged and am currently running a load test to verify the pack's A/hr rating

[Plamen]

Tim,  I have same SBMS 120. Running since January onn default settings without any problems. That voltage swing you see is because cell 2 is being balanced (the < next to the voltage). 

And that's why the balancing is on a few sec. and then off a few so SBMS could make correct voltage reading.

You don't need an external balancer as that's one of the functions of SBMS. Depending on imbalance it may take some time, just let it do it's job.

[Tim D.]

Thanks for the reply,

 

Good to know that the voltage variations I was seeing on my SBMS120 isn't abnormal