DIY 280AH battery JK BMS JK-PB2A16S20P Canbus to SMA 5048

[kommando]

Update, boring, nothing has happened, batteries are balanced, they charge and discharge with no alarms on the BMS or the SI's. The Gels are for the scrapman I think but their shortfalls are a dim and distant memory.

 

[1201]

Update, boring, nothing has happened, batteries are balanced, they charge and discharge with no alarms on the BMS or the SI's. The Gels are for the scrapman I think but their shortfalls are a dim and distant memory.

Nice. I ordered one. Hoping it gets here this week.

 

[christianrodher]

Update, boring, nothing has happened, batteries are balanced, they charge and discharge with no alarms on the BMS or the SI's. The Gels are for the scrapman I think but their shortfalls are a dim and distant memory.

Hi seems you done a lot of testing on this BMS. Im trying to make it work with WOW protocol... but it just reboots as soon as I plug the rs485 cable. Is RS485 working at all for inverter comunication?

video of the problem, Also using your same case!

 

[kommando]

Hi seems you done a lot of testing on this BMS. Im trying to make it work with WOW protocol... but it just reboots as soon as I plug the rs485 cable. Is RS485 working at all for inverter comunication?

video of the problem, Also using your same case!

I have not tried RS485 to an inverter only a PC, with a PC the JK app acts differently with the Dip switch setting. Set to 0 then the PC app allows you to change all the settings and see the battery data but no parallel battery info, set to 1 then no access to settings only parallel info. So try changing you dip to 0 or 1.

 

[Consumerbot3418]

Found the ref to the 1V error

Enhancement: SMA Sunny Island · Issue #85 · stuartpittaway/diyBMSv4ESP32

Ahoy, Stuart. Thanks a lot for sharing this BMS and giving us DIYers a nice option to care for our batteries. I couldnt find any issue about "SMA" or "Sunny Island". It is also a very popular off-g...

github.com

Final comment in the thread is


So it is a problem even in the later models.

I'm in the process of trying to integrate a Victron SmartShunt, ESP32, and Pylontech protocol using ESPHome. When I first got comms working, I noticed the missing 1V, and thought there must be some bug in my canbus code.

I wonder if SI is intentionally targeting a volt lower to account for big loads switching off when close to 100% SoC, to give itself some breathing room?

Edit: it's almost certainly what I mused about above. The "missing" volt comes back as soon as SI connect to the grid, and doesn't have to worry about sinking a bunch of AC-coupled power into a fully-charged battery.

 

[Hedges]

Set on the Jk BMS +1V as the SI takes 1V off so JK is set to 56.2V and the SI takes that as 55.2V.

See post 40

I'm in the process of trying to integrate a Victron SmartShunt, ESP32, and Pylontech protocol using ESPHome. When I first got comms working, I noticed the missing 1V, and thought there must be some bug in my canbus code.

I wonder if SI is intentionally targeting a volt lower to account for big loads switching off when close to 100% SoC, to give itself some breathing room?

Edit: it's almost certainly what I mused about above. The "missing" volt comes back as soon as SI connect to the grid, and doesn't have to worry about sinking a bunch of AC-coupled power into a fully-charged battery.

I'm thinking it is for that reason.
If SI periodically goes on-grid, can charge to higher voltage and get balanced up there. If load-dump occurs, SB's output just gets shoved into grid.
Then when running off-grid at lower voltage, load-dump gets shoved into battery for a few seconds and battery remains balanced because it doesn't exceed balancing voltage.

If system happened to drop off grid at the moment battery got charged to highest voltage, only saving grace is that SB is usually knocked offline for 5 minutes. Any loads, at least idle consumption, would draw battery down a bit.

Other issue would be if always off-grid. Or with generator, don't know yet if this -1V adjustment occurs with generator or not. There is a reverse power watts and time setting.

Kommando - can you try digital input saying generator is connected? But I think you have to configure system for that, grid + generator. No harm, if generator never actually used? Or would SI then behave different, requesting generator at some SoC and hours?

If always off-grid, battery gets bulk voltage to the -1V level, then can float later. If charging at bulk and load-dump occurs, could have a runner cell and high voltage disconnect. If it has not recently (or ever) been balanced at a higher voltage, BMS might disconnect and shut system down.

 

[kommando]

After seeing the SI in off-grid operation in full midday sun PV input and house loads low you can see the Frequency shift has a lag and the Target volts of 55.2V SI (but 56.2V on BMS) is exceeded until the Frequency shift gets the PV curtailed. I have seen 55.8V before it started to drop.

So my guess is the 1V drop is a safety feature put in by SMA in off grid mode so the Target voltage is not exceeded. With on grid the reaction time to over production would be faster as the grid takes it.

So what you set the BMS to is down to the balance between on grid and off grid running you do. If you are mainly off grid then the 1V drop means you run the risk of not enough cell balancing. A regular on grid operation would be enough to trigger the balancing.

As it is I monitor the Frequency and turn on loads to suit, so the risk of over voltage is a lot lower for this type of setup.

Have lost RS485 comms to my SI a couple of hours ago so can't do any testing, got to wait until the sun is low so I can have a look inside. May have to put a replacement piggyback board in. It can't be the Webbox as SDC will not connect either.

 

[kommando]

Kommando - can you try digital input saying generator is connected? But I think you have to configure system for that, grid + generator. No harm, if generator never actually used? Or would SI then behave different, requesting generator at some SoC and hours?

Will not take the change from ExtSrc from PV only to Grid/Gen even with auth code, I would have to do a QCG.