Just wanted to do some quick sanity checks to see how much of a voltage drop we should expect when going with an NiMH battery. The testing was done using a 10S1P pack that has been sitting around unused for about 6-8 months now.
Load Current | Voltage (at DC load) |
|---|---|
0 | 12.5178 |
1 | 12.33 |
2 | 12.18 |
3 | 12.03 |
4 | 11.86 |
5 | 11.67 |
6 | 11.52 |
7 | 11.34 |
8 | 11.13 |
9 | 10.94 |
10 | 10.74 |
Plotting in Desmos to calculate the internal resistance, we see the following: (Note that the voltage was read off of the DC load screen, so we also see the effects of the cables in the internal resistance calculation. This is acceptable since a similar length of cable will be required to connect the AUX battery to the power selection board.
And an internal resistance of roughly 180mOhms. So my initial guess of 200mOhm was in the right ballpark.
With this result, do we need to revisit our undervoltage warning level for the AUX battery? When drawing 4A to energize the contactors, we will see a voltage drop of about 0.8V.