Particle Boron MAX17048 | Battery Capacity Calibration?

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#1

Hello,

Looking for more information as to how one can calibrate the battery fuel gauge IC on the Particle Boron to a different battery capacity number?

I’m using a 10,500 mah 1S3P 18650 battery pack ( 3x LG MJ1 3500mah cells ) significantly greater than the included Li-Po cells that ship with these boards.

Device vitals tell me I’m at 10% currently, however by intuition and knowing the cell’s electrical characteristics ( the battery is reading 3.69v which is basically still above nominal voltage which means the pack still has plenty of juice )

Is there a way to set a capacity value in the device firmware? Or how can I better calibrate this so it reflects the battery State of charge more accurately.


#2

It’s a voltage based capacity chip, there is no current measuring capability so it can not track battery capacity only battery voltage.


#3

Thanks for the reply, this should still mean It can be calibrated differently? Must be working on some kind of discharge curve or something along those lines.


#4

It’s a issue we have been dealing with for along time.

We basically scale the 0-100 SOC scale so when it’s fully charged the SOC reading shows 100% instead of 85-92%.

The problem is that the charging voltage is kept conservative at 4.2v and the Fuel Gauge chip wants to see a higher voltage to consider the battery 100% full. We have not found a way to change this on the chip itself.


#5

Should it not be possible by editing this register?

Says you need to contact maxim for how to set this register value. Is this documented anywhere on this forum?


#6

Probably not, but maybe.

The issue is the battery charge voltage not going up higher which you can adjust on the PMIC but when we have tested that it didn’t really get the results we were hoping for which is the same as your hoping for.


#7

State of charge is working for me in the sense that, at 4.2V and higher I do get 100% state of charge. ( which is perfect, that is what I would expect. )

It’s just the curve that is set in the chip is probably one for a smaller capacity battery than what I’m using. So when the battery is at 3.6v like mine is now, It’s SOC calculation has it much furhter depleted than what It is in reality. Looking at a discharge curve for the battery I have, I have ~50% charge up until 3.35V

( I’d imagine the MAX17048 has curve for a single cell Li-Po battery around 1000-2000mah vs. what I have which is a 3-cell 10500mah battery pack )

Would be nice to be able to change this.


#8

If your desiring that change then you can contact Maxim about programming different battery profiles.