how was the maximum_battery and min batt calculated
SamuelAlinder opened this issue · 6 comments
Hello.. I have a question on these two lines:
define BATTERY_MAXIMUM (1771)
define BATTERY_MINIMUM (1416)
Is it 1771 mVolt? and how did you calculate it?
No, this is the value for each limit where 0-2048 is 0-100% of the
calibration voltage of the ADC. To calculate the value for a particular
voltage input to the voltage divider, you need to use a calculation similar
to this.
value =
(((VoltageIn/VoltageDividerTotalResistance)_VoltageDividerMinimumResistance)/1.25v)_2048
Where:
VoltageIn = the amount of voltage input to the Voltage Divider. that you
want to calculate a value for.
VoltageDividerTotalResistance = 37000 ohm
VoltageDividerMinimumResistance = 10000 ohm
1.27V = The calibration reference of the ADC.
2048 = the maximum value of the ADC at the ADC Voltage Reference
Hope this helps.
I am working on code that will store these limits in Flash memory, so a
full charge/discharge cycle of the LiPo will set these values for you.
Cheers
On Tue, Mar 31, 2015 at 9:54 PM, mayaalinder notifications@github.com
wrote:
Hello.. I have a question on these two lines:
#define BATTERY_MAXIMUM (1771)
#define BATTERY_MINIMUM (1416)
Is it 1771 mVolt? and how did you calculate it?—
Reply to this email directly or view it on GitHub
#3.
John Stevens
"You are how you live, not what you have."
So in your calculation, did you use 4.0V as the VoltageIn for Battery_Maximum? and 1.25v or 1.27 as calibration ref?
I build my system with a 2.2k ad a1.0k resistor in the voltage divider.. the battery says max charge is 4.2V and min 2.75V
I used 3.9V as maximum, & 3.2V as minimum. Reason being that a lipo fully charged to 4.2V will rapidly discharge to around 3.9V, the slowly discharge to around 3.5V, then more rapidly to cut off. I have not yet found a lipo that discharges to the rated 2.75V. My one discharges to 3.2V, which is the rated standard voltage of a lipo, so I used this as an "average" lipo minimum.
Voltage reference is the wixel internal voltage reference, which I don't remember off the top of my head, and am not in front of my computer right now. It is in the wixel doc.
Cheers
John Stevens
M - +61 418526349
On 7 Apr 2015, at 19:40, mayaalinder notifications@github.com wrote:
So in your calculation, did you use 4.0V as the VoltageIn for Battery_Maximum? and 1.25v or 1.27 as calibration ref?
I build my system with a 2.2k ad a1.0k resistor in the voltage divider.. the battery says max charge is 4.2V and min 2.75V—
Reply to this email directly or view it on GitHub.
Internal voltage reference is 1.25V. You can use VDD, but it is less
reliable. I therefore chose to use the internal 1.25V reference, and the
voltage divider I documented.
Cheers
On Tue, Apr 7, 2015 at 7:40 PM, mayaalinder notifications@github.com
wrote:
So in your calculation, did you use 4.0V as the VoltageIn for
Battery_Maximum? and 1.25v or 1.27 as calibration ref?
I build my system with a 2.2k ad a1.0k resistor in the voltage divider..
the battery says max charge is 4.2V and min 2.75V—
Reply to this email directly or view it on GitHub
#3 (comment).
John Stevens
"You are how you live, not what you have."
:-) I calculated backwords from 1771.. 1771/2048_1.25/10_37=3.999
I wish bought a couple of extra batteries.. we have a very nice battery test rig at work..
Great. If you gain a better understanding of how to determine the lipo
battery capacity, let me know. I would like to improve this so that it is
easy for everyone that uses dexbridge2.
I may have mentioned, I am planning to make the bridge code handle a full
battery cycle and set the upper and lower limits in flash. That way it
should be easy for anyone to do a full charge/discharge cycle and have a
relatively accurate capacity indication.
Cheers
On Wed, Apr 8, 2015 at 5:08 PM, mayaalinder notifications@github.com
wrote:
:-) I calculated backwords from 1771.. 1771/2048_1.25/10_37=3.999
I wish bought a couple of extra batteries.. we have a very nice battery
test rig at work..—
Reply to this email directly or view it on GitHub
#3 (comment).
John Stevens
"You are how you live, not what you have."