BMS that doesnt mess with the coulomb counting?

[squowse]

Well, if that is happening something else isn't working as it should. I've never had that happen in 15+ months of using mine. And surely if that happens then SOC being set to 0 or 100 is appropriate.


Yes, correct.


Really random? I've never had that happen in 15+ months of using mine.

Regardless of your opinion, over and undervoltage can occur other than 0% and 100%. With weaker cells it can happen at higher currents. It then wrecks the capacity calculation which then needs to be redone.
Yes apparently randomly, when it’s without a capacity calculation. Probably make sense to someone who wrote the code, or maybe its just a bug.

Being able to opt out of this “helpful” behaviour is all i want.

 

[squowse]

Ive found from experience that it is necessary to trigger the over and undervoltage to reliably perform the capacity calibration. Thats with JBD.

Actual i tell a lie. The one I’m having this with currently is an LLT. About 2-3 years old. I have observed this behaviour with all BMS from JBD and JK. Maybe they don’t need the cell OVP or UVP triggered but i do it to be sure I’m not wasting my time on the cycle down and up. Sometimes its just not possible. Living off grid sometimes there just isn’t the solar available.

 

[mikefitz]

if a bms firmware had the option to just input the state of charge and let coulomb counting do the rest

You have that option with the JBD, 'reset capacity' sets SOC using the BMS stored values. It's not super accurate but for a resting battery is not far off.

 

[squowse]

You have that option with the JBD, 'reset capacity' sets SOC using the BMS stored values. It's not super accurate but for a resting battery is not far off.

Could you clarify? I’m not aware of this feature

 

[Bob B]

That would be ridiculous, but that is not correct. You only need to trigger "full voltage" and "end voltage" which are typically set much more conservatively than over-voltage and under-voltage protection values.

The JBD has those setting, but I don't think the JK does. I specified the JK BMS in that comment.

 

[mikefitz]

The JBD has set up In the BMS default voltage levels and the generic SOC for that level. When you select 'reset capacity' the BMS makes a best guess based on these stored values and sets battery SOC.

Could you clarify? I’m not aware of this feature

 

[SeaGal]

the BMS makes a best guess based on these stored values and sets battery SOC

And if you use the PC interface, rather than the app, you can set each 10% SOC rather than each 20%...

 

[sunshine_eggo]

And if you use the PC interface, rather than the app, you can set each 10% SOC rather than each 20%...

View attachment 176544

The overkill phone app also gives more SoC to voltage steps.

 

[Bob B]

The overkill phone app also gives more SoC to voltage steps.

Yes it does .... It depends on how old the BMS is, however, whether it can use those additional steps.
My phone app now has more steps, but my BMS won't support them. I was initially concerned that this would cause a problem with uploading and downloading setting, but I have tested and the BMS just seems to ignore them.

Probably the same with the PC software.

 

[squowse]

The JBD has set up In the BMS default voltage levels and the generic SOC for that level. When you select 'reset capacity' the BMS makes a best guess based on these stored values and sets battery SOC.

Thats what i dont want it to do.

 

[Flyzet]

In the newest software version 11.288 one of my friends bms, i found new features like SOC-0% and SOC-100% voltage. On version 11.25 this function not exist. So, should be the way to some how update software version to the newer one by rs485 port and PC, because by the app on IOS at least it’s not possible at the moment.
I tried to contact support by email with this question, still waiting for reply. Any suggestions?

 

[squowse]

This is an example. The SoC has jumped from 16% to 60% apparently randomly. Its done an inaccurate estimate based on voltage during charging.

This morning I had a cell undervoltage I think. It was reset to 0% anyway. I didnt actually notice any interruption, maybe it just decided to reset itself to zero based on a voltage drop under load.

The whole thing is unnecessarily compllicated. Now Im expected to do a full cycle to get the coulomb counting back. Living off grid in winter this is the last thing i need.

 

[SeaGal]

.. Now Im expected to do a full cycle to get the coulomb counting back. Living off grid in winter this is the last thing i need.

Why do you need to do a full cycle? Just update the capacity as @mikefitz and I have detailed and the SOC will reset itself, based on cell voltages.

 

[squowse]

Why do you need to do a full cycle? Just update the capacity as @mikefitz and I have detailed and the SOC will reset itself, based on cell voltages.

It needs to do a full cycle before it will stop randomly estimating SoC based on voltages. I tried to game the system before by manipulating the voltage criteria. What I want is for it to not do that, not automatically/randomly anyway. Once a full cycle is done and it updates the cucle capacity it does stop doing these random SoC estimates. Well mostly anyway.

I seem to have to repeat myself quite a bit on this thread. I tried what you are suggesting years ago. It doesn’t work for any length of time

 

[SeaGal]

It doesn’t work for any length of time

That's odd... I've never had that happen with my Overkill version of the JBD in over 15 month's usage - maybe yours has an intermittent fault and needs replacing?

Maybe having a secondary / back-up battery pack would be a good idea anyway if living off grid?

 

[squowse]

That's odd... I've never had that happen with my Overkill version of the JBD in over 15 month's usage - maybe yours has an intermittent fault and needs replacing?

Maybe having a secondary / back-up battery pack would be a good idea anyway if living off grid?

Ive had several of this BMS and others and they all do the same. Maybe you just haven’t noticed or maybe theres a firmware difference. Thats kind of what i was asking about originally. I do have a newer jbd bms i havent used yet, maybe that one will behave itself.

I’ve got several batteries, thanks for your concern. They all need charging obviously. Charging them is not as easy as plugging them into the grid. They need charging more often than I have access to a plug socket. Why are you trying to turn this around all the time?

 

[SeaGal]

Why are you trying to turn this around all the time?

Oh?... I was genuinely trying to make helpful suggestions ?‍ - sorry if it didn't come across that way. I will stop contributing to this thread.

 

[Bob B]

I haven't tried the hack to reset SOC .... but, from my experience merely doing a setting change will revert the JBD to guesstimating SOC based on voltage.

 

[squowse]

I haven't tried the hack to reset SOC .... but, from my experience merely doing a setting change will revert the JBD to guesstimating SOC based on voltage.

Yes, this is also unnecessary, unwanted and annoying

 

[Bob B]

Yes, this is also unnecessary, unwanted and annoying

Writing a setting change probably wipes out the data necessary for coulomb counting .... but, that behavior also seems like it might keep the hack from working successfully.