Xiaoxiang BMS app capacity launched to full capacity without single watt going in

Draconius

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So my BMS did something weird last night. It is NOT plugged into any charging source and only drawing about 4amps at max when my truckfridge turns on. Opened app this morning and the capacity launched to full and also zero current draw after around 11pm. Bummed because I wanted to try and drain this pack down to 10v. The voltages/pack voltage all appear to be accurate (gotta compare to DMM).

BMS: lithiumbatterypcb.com model
App: Xiaoxiang 3.1.1026
Battery: 4s 120ah LiFePo4
 

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Hedges

I See Electromagnetic Fields!
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Semi-wild @$$ guess:
BMS resets to full capacity at some sensed voltage.
When load was removed, voltage bounced up and triggered the reset.
Check actual battery voltage and specs/settings of BMS to see when reset is supposed to occur.

Inductance can cause voltage spikes. Bad connections are likely in a system, not sure what that would do to cause such a bounce.
I assume 11 pm means no charge source.
 

Draconius

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Naw...I've been off charge source since Monday when I tested my 100w solar panel. Checked voltages, all good, checked connections, all good. This morning everything is working normally, just capacity and absolutely no logging of data. Here is my other page that shows before charge/discharge after charge/discharge, faults, protections, etc.

Any idea what setting I might be looking for in the app? I only changed capacity and temperature cutoff.
 

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Draconius

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Here are my capacity percentage settings in the app
 

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Hedges

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"Single full voltage 3.4V"

Do you know what exactly that means?

It has several voltages vs. SoC which seems odd, since voltage is a poor way to determine SoC for lithium except near full and near empty.
It needs to reset to full or empty at extreme limits of voltage range, then count amp hours in/out to track SoC in between.

There ought to be some high voltage at which it resets to 100% SoC, then goes by current in/out.
See if there are additional parameters. Find out what "single full voltage" means, what BMS does there.
What voltage does battery have now?
 

Draconius

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Here are my current voltages. The settings for single full voltage/etc I didn't adjust. Everything I've read online says only change capacity, charge temperature to 2°C and maybe temp sensor readings if off.

Absent the capacity and chart behavior, everything else is spot on.

I emailed James @ lithiumbatterypcb.com but he can be VERY slow to respond.
 

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WingNut

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Use FUNCTION SETTING -> RESET CAPACITY to bring it back inline with your 20/40/60/80% voltage set point choices.

With Single cut-off voltage set to 3V you can discharge down to 12V (3V*4 cells in series = 12V).
 

Draconius

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Use FUNCTION SETTING -> RESET CAPACITY to bring it back inline with your 20/40/60/80% voltage set point choices.

With Single cut-off voltage set to 3V you can discharge down to 12V (3V*4 cells in series = 12V).
That just put me back to 120ah....
 

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WingNut

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Post screen captures of other settings. Maybe there will be a clue there as to what's causing this.
Also, try re-entering your 20/40/60/80% voltage set points. I've used RESET CAPACITY several times and it always brings SOC it back inline with my tested 20/40/60/80% voltage settings.
 

Draconius

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Here it is. I'm thinking it might also be xiaoxiang v3.1.1026. This version also doesn't have the lock symbol anymore, so if you have a protection lock you have to install down to 3.1.1015 in order to get the lock symbol...
 

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Bob B

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The other thing that normally resets the SOC to a guestimate is writing a parameter change.

If you do that, and it doesn't default back to using those voltage parameters .... maybe there is a problem with some versions?

There is another thread going where a similar problem is being reported.
 

p.f.w.

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may be that the bms is a newer(?) one not fully supported by the android (and iOS) apps? Newer bms(since last year(?)) have separate settings for 10%,30%,50%,70%,90% and 100%, that can not be set via android app or other apps are not adapted, only with newest(?) JBD Tools

i think, that all %-settings must be changed, not only for 20,40,60,80, but i'm not sure and i don't know,what the different is between setting for "Single full voltage" and "100%", these are different points in settings of bms

and i'm also not sure, that it will really help

please take a look at https://gitlab.com/bms-tools/bms-tools/-/issues/30 (latest entry there and a screenshot posted before by other one(MauroXnt))
 
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