Battery

[Igor]

What is the most proper way to calculate battery discharge ratio?

 

I am trying to add this here:

Load: 0.10, 0.50, 0.38 - Memory: 974Mb - Battery discharging: 30%

AXP209 gives me:

http://linux-sunxi.org/AXP209

 

- voltage

- charge / discharge current

 

Battery capacity should be the only parameter I want to set.

 

Is there any advanced calculation script or simply, but not so accurate, direct connection between voltage and percentage?

[Patcher]

Hi Igor, i´am not much of a coder, hardware is my thing.

 

I just wanted to point out as i geuss the perfectionist u are, that there are simple hardware add-ons, i am using to measure my solar panel charge/discharge in real time.

The sensor i am using comes with a 3 pin 2,54 inch connector and communicates very straight forward in mV to a/d channel.

U could pop it into the strip connector of the board, if we can find a 5volt + /- and an a/d channel besides another. (did'nt check yet)

 

I could elaborate more, if this is interesting for the community.

 

This is the 1 i´am talking about and costs about 2-3 euro's and is very accurate.

[Marv21]

Hi Igor, i´am not much of a coder, hardware is my thing.

 

I just wanted to point out as i geuss the perfectionist u are, that there are simple hardware add-ons, i am using to measure my solar panel charge/discharge in real time.

The sensor i am using comes with a 3 pin 2,54 inch connector and communicates very straight forward in mV to a/d channel.

U could pop it into the strip connector of the board, if we can find a 5volt + /- and an a/d channel besides another. (did'nt check yet)

 

I could elaborate more, if this is interesting for the community.

 

This is the 1 i´am talking about and costs about 2-3 euro's and is very accurate.

I think he wants to implement this for everybody.

(cat /sys/class/power_supply/battery/capacity) there i get the % from my battery.?

[KF5YFD]

This may be of use to you

 

http://en.wikipedia.org/wiki/Peukert%27s_law

[KF5YFD]

This script was originaly for using acpi to get the values but should give you an idea on how to calculate what you need. Requires calc to be installed

#!/bin/bash
math() { calc -d "$@"|tr -d ~; }
cd /proc/acpi/battery/BAT0;
max=$(grep 'design capacity:' info|awk '{print $3}')
current=$(grep 'remaining capacity:' state|awk '{print $3}')
percent=$(math "($current / $max) * 100");
echo $(echo $percent|cut -d. -f1)%

[Igor]

I came out with this: 

######################################################################################
#
# Battery info
#


i2cset -y -f 0 0x34 0x82 0xC3
# read power OPERATING MODE register @01h
POWER_OP_MODE=$(i2cget -y -f 0 0x34 0x01)
BAT_EXIST=$(($(($POWER_OP_MODE&0x20))/32))  # divide by 32 is like shifting rigth 5 times
CHARG_IND=$(($(($POWER_OP_MODE&0x40))/64))  # divide by 64 is like shifting rigth 6 times

########################################################################################
#read battery voltage   79h, 78h        0 mV -> 000h,   1.1 mV/bit      FFFh -> 4.5045 V
BAT_VOLT_LSB=$(i2cget -y -f 0 0x34 0x79)
BAT_VOLT_MSB=$(i2cget -y -f 0 0x34 0x78)

BAT_BIN=$(( $(($BAT_VOLT_MSB << 4)) | $(($(($BAT_VOLT_LSB & 0xF0)) >> 4)) ))
BAT_VOLT=$(echo "($BAT_BIN*1.1)"|bc)

# store maximum battery voltage to compare to
if [ -f "/etc/default/battery" ]; then
        source "/etc/default/battery"
else
        echo "MAX=$BAT_VOLT" > /etc/default/battery
	echo "MIN=3484" >> /etc/default/battery
fi

# integer is enough, cut down the decimals
MAX=${MAX%.*}
BAT_VOLT=${BAT_VOLT%.*}

# mainline kernel shows battery existence even if not exists. this is walkaround 
if [ "$BAT_VOLT" -ge "3200" ]; then


# if we have new max value, alter defaults
if [ "$BAT_VOLT" -gt "$MAX" ]; then 
MAX=$BAT_VOLT
sed -e 's/MAX=.*/MAX='$BAT_VOLT'/g' -i /etc/default/battery
fi

# if we have new min value, alter defaults
if [ "$BAT_VOLT" -lt "$MIN" ]; then
MIN=$BAT_VOLT
#sed -e 's/MIN=.*/MIN='$BAT_VOLT'/g' -i /etc/default/battery
fi

# calculate percentage
percent=$(echo "($BAT_VOLT-$MIN)*100/($MAX-$MIN)"|bc)

# colorize output under certain percentage
if [ $percent -le 15 ]
then
  color="31"
fi

if [ "$BAT_EXIST" == "1" ]; then
BATT=" - Batt: "
# dispay charging / percentage
if [ "$CHARG_IND" == "1" ]; then
BATT=$BATT"charging $percent%"
else
BATT=$BATT"\e["$color"m$percent%\x1B[0m"
fi
fi
fi
OUT="${OUT}${BATT}"


echo ""
echo -e ${OUT}
echo ""

Load: 1.64, 1.14, 1.00 - Board: 36.2°C - Ambient: 27.0°C - Drive: 43°C / 2.5Tb - Memory: 934Mb - Batt: 7%

 

Working on both kernels.

Edited June 16, 2015 by Igor
update

[micropad]

Hi, 

 

how i can use that script to monitoring battery ?

 

is it  a shell script? 

[Igor]

Yes, it's a bash shell script.

 

It needs some extra adjustments to gain more accuracy but generally it's usable.

[micropad]

thanks

[Igor]

You need to install one extra package which is by default in my install.

apt-get install bc

[AurelianRQ]

Any chance to have the sys/class part for the battery info ? 

 

Before i used to have all the details about the battery here when running lubuntu but now no more details about the controller. 

 

Thanks 

[shea]

I think that @Patcher has the right idea in that the only way to get an accurate measure of the battery charge is to integrate current in/out (+/-) of the battery over time (as confirmed by @KF5YFD's wikipedia link).  Fortunately the AXP209 includes a coulomb counter which should do the trick. I'm just getting started with Armbian on an Olimex Lime A20 myself, but Igor's script is a great starting point and example of communicating with the AXP209 via I2C. At some point when I have some time I might try to sort out a technique that uses the coulomb counter to track battery charge. If I do I'll be sure to post here. In any case I think the coulomb counter is the way to go.