jbd / overkill bms - state of charge

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Since I only charge to 3.41 volts the current accounting never resets.
It drifts lower by ~1.5ah per charge cycle.
Not a problem because I have an hall effect sensor based battery monitor which is accurate enough for my application.
 
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squowse

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Since I only charge to 3.41 volts the current accounting never resets.
It drifts lower by ~1.5ah per charge cycle.
Not a problem because I have an hall effect sensor based battery monitor which is accurate enough for my application.
Id be happy enough if it reset at the top or bottom. It's just resetting itself in the middle. I'm going to leave it alone and see what it does. When the parameters are changed it resets and uses voltage estimation.
 
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Id be happy enough if it reset at the top or bottom. It's just resetting itself in the middle. I'm going to leave it alone and see what it does. When the parameters are changed it resets and uses voltage estimation.
Have you manually reset it at the top?
 

MrM1

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Yeah I like some of the features of the IOS version. Like you can calibrate the cell voltages to a meter, you can not do this with the Android app, but not sure if can do the reset of the amp hour / % of charge or not. Im going to take mine home here in a few and check it out
 

curiouscarbon

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anecdotally, the JBD 120A 4S BMS i use only seems to report 0.0A or 0.5A but rarely anything in between.

this quantization error surely causes some amount of the drift in coulomb counting mode.
 

MrM1

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Unless the "reset" button in the middle of the page does it, it looks like you'll need the pro version of the ios app
 

MrM1

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Just got them pro version. I am definitely not as good impressed with the ios version
 

MrM1

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The android version has this setting that resets the battery percent used to what ever the amp hour used is based on your capacity.

It's handy to sync the capacity when the amp hours are full.

Capture+_2021-10-27-22-04-15.png

Capture+_2021-10-27-22-04-39.png

Capture+_2021-10-27-22-04-54.png
 

Isaac-1

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This all leads to the question of what is the proper way to do a charge cycle on these batteries to get them to switch to method 2?
 

squowse

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This all leads to the question of what is the proper way to do a charge cycle on these batteries to get them to switch to method 2?
Did you read the pdf? It seems to be saying that a complete charge, complete discharge followed by a complete charge should do it.
I still struggling 🤣
 

drbytes

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So what was it in the end? I'm facing similar problems, I cannot rely on the SOC.
Perhaps it's because the battery pack is still new, it only has had 4 cycles and from what I read it will start ie at 310ah but eventually settled to what's on the tin, in my case this is 304ah.
I've set it to 310 in the beginning and after the fourth cycle I've set it to 304. Immediatly the SOC shot up from 8% to 14%. So I set a lower capacity and then the bms decides it now has an extra 6% soc? Baffling.
 

Bob B

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So what was it in the end? I'm facing similar problems, I cannot rely on the SOC.
Perhaps it's because the battery pack is still new, it only has had 4 cycles and from what I read it will start ie at 310ah but eventually settled to what's on the tin, in my case this is 304ah.
I've set it to 310 in the beginning and after the fourth cycle I've set it to 304. Immediatly the SOC shot up from 8% to 14%. So I set a lower capacity and then the bms decides it now has an extra 6% soc? Baffling.
Anytime you change a parameter the BMS reverts to a guestimate for SOC based on voltage ..... Once you go thru a full charge cycle after that it will start tracking based on current in and current out again.
 

squowse

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So what was it in the end? I'm facing similar problems, I cannot rely on the SOC.
Perhaps it's because the battery pack is still new, it only has had 4 cycles and from what I read it will start ie at 310ah but eventually settled to what's on the tin, in my case this is 304ah.
I've set it to 310 in the beginning and after the fourth cycle I've set it to 304. Immediatly the SOC shot up from 8% to 14%. So I set a lower capacity and then the bms decides it now has an extra 6% soc? Baffling.
Anytime you change a parameter the BMS reverts to a guestimate for SOC based on voltage ..... Once you go thru a full charge cycle after that it will start tracking based on current in and current out again.
Yes I haven't had a problem for a while. I made sure not to touch any parameters. As best as i can tell from the slightly broken English of the manual it needs to be discharged from 100% to 0% then all the way back up to 100% to initialise. I think the charging might need to be uninterrupted as well.
 

squowse

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So what was it in the end? I'm facing similar problems, I cannot rely on the SOC.
Perhaps it's because the battery pack is still new, it only has had 4 cycles and from what I read it will start ie at 310ah but eventually settled to what's on the tin, in my case this is 304ah.
I've set it to 310 in the beginning and after the fourth cycle I've set it to 304. Immediatly the SOC shot up from 8% to 14%. So I set a lower capacity and then the bms decides it now has an extra 6% soc? Baffling.
I had much bigger jumps than that
 

drbytes

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Thx for the info, I'm in the midst of cycling it now, hope it'll rectify itself as I have quite a bit of Nodered logic tied to the SOC to switch output source to battery/utility and initiate charging etc
 

Bob B

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Thx for the info, I'm in the midst of cycling it now, hope it'll rectify itself as I have quite a bit of Nodered logic tied to the SOC to switch output source to battery/utility and initiate charging etc
In my experience, the SOC would reset if I reached 100% ..... it didn't require a full charge and discharge cycle .... there are several different version of this BMS, so your mileage may vary.
 
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