Configuring C.H.U.C.K. for 18650 Li-ion cell voltage

[djoris]

The voltage drop is significant with Li-ion cells, how do you configure the Disco to handle that? And does low voltage hurt performance much?

[djoris]

Some relevant data:
The values will be in /etc/parameters.conf, with lines like BATTERY_PERCENTAGE_TABLE_VOLTAGE

• https://www.rcgroups.com/forums/showpost.php?p=39338949&postcount=1830
• https://www.rcgroups.com/forums/showpost.php?p=39344365&postcount=1844
• https://www.rcgroups.com/forums/showpost.php?p=39344807&postcount=1845
  and further on

idea: create a script that will switch the battery tables from and to "Li Ion"/"LiPo" with button presses? Might be very risky

[djoris]

Frame on Slack: https://uavpal.slack.com/messages/C6TCG655E/convo/C6TCG655E-1530986888.000005/Titan Li-ion 3500mah S3P1 battery pack (NCR18650GA cells)
"• from 10% to 1% it went quite fast - ie voltage dropped fast in the end. So when reaching down to 15% (ie 10 volts) - start thinking about landing…"
Using this configuration:
BATTERY_PERCENTAGE_TABLE_VOLTAGE = 9.05, 9.45, 9.86, 10.09, 10.36, 10.83, 11.14, 11.78, 11.92, 12.01, 12.05, 12.11, 12.15, 12.22, 12.38
BATTERY_PERCENTAGE_TABLE_PERCENTAGE = 0, 5, 10, 15, 25, 45, 55, 79, 84, 88, 91, 94, 96, 98, 100

[djoris]

the reference configuration in above mentioned 1830 post, seem to have a really steep drop at the bottom 5->0%. Frame's numbers seem more plausible; thus, I've used those in https://github.com/uavpal/disco-docs/wiki/batteries#Reference_configuration_parameters

[djoris]

One question I have: is the voltage measured when under load? Probably yes, perhaps only under cruise speed load (6A?). What voltages can be expected under those conditions? And: is heat an important factor in the measured voltage?

[djoris]

using the black box data, we could compile more info on real-life usage/voltage. Using spec sheets and external tests, we can see battery voltage tables..

[djoris]

cturn:

6Ah usable out of this 3s2p INR18650-36G
310.6g including connectors
Under 3.2v per cell, the voltage commonly drops sharply.

[djoris]

received these from 'jc fa' for his 18650GA pack:
12,5 100
12,26 98
12,22 96
12,17 94
12,16 91
12,12 88
12,06 84
11,97 79
11,47 55
11,22 45
9,97 25
9,72 15
9,60 10
9,45 5
9,20 0