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Small doc enhancements

This commit is contained in:
Tony Cabello Miguel 2021-04-16 07:49:25 +02:00
parent 025ee87a7a
commit 518bc1b165
2 changed files with 11 additions and 1 deletions
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10
docs/Battery.md
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@ -175,6 +175,16 @@ amperage_meter_scale = (Imax - Imin) * 100000 / (Tmax + (Tmax * Tmax / 50))
= 205 = 205
amperage_meter_offset = Imin * 100 = 280 amperage_meter_offset = Imin * 100 = 280
``` ```
Measuring Imax requires a battery and an ESC that can both deliver and support max current for the duration of the measurement, so it's prone to big inaccuracies. Alternatively, current can be measured at a much lower throttle position and be taken into account in the calculations.
Following the previous example, if we measured an Ibench current of 6A at 30% of throttle (1255 in the motors tab because (0.3*(max_throttle-1000))+1000))
```
Tbench = Tmax * bench_throttle = 850 * 0.3 = 255
amperage_meter_scale = (Ibench - Imin) * 100000 / (Tbench + (Tbench * Tbench / 50))
= (6 - 2.8) * 100000 / (255 + (255 * 255 / 50))
= 205
amperage_meter_offset = Imin * 100 = 280
```
#### Tuning Using Battery Charger Measurement #### Tuning Using Battery Charger Measurement
If you cannot measure current draw directly, you can approximate it indirectly using your battery charger. If you cannot measure current draw directly, you can approximate it indirectly using your battery charger.
However, note it may be difficult to adjust `amperage_meter_offset` using this method unless you can However, note it may be difficult to adjust `amperage_meter_offset` using this method unless you can

2
src/main/sensors/current.c
View File

@ -191,7 +191,7 @@ void currentMeterVirtualRefresh(int32_t lastUpdateAt, bool armed, bool throttleL
throttleOffset = 0; throttleOffset = 0;
} }
int throttleFactor = throttleOffset + (throttleOffset * throttleOffset / 50); // FIXME magic number 50, 50hz? int throttleFactor = throttleOffset + (throttleOffset * throttleOffset / 50); // FIXME magic number 50. Possibly use thrustLinearization if configured.
currentMeterVirtualState.amperage += throttleFactor * (int32_t)currentSensorVirtualConfig()->scale / 1000; currentMeterVirtualState.amperage += throttleFactor * (int32_t)currentSensorVirtualConfig()->scale / 1000;
} }
updateCurrentmAhDrawnState(&currentMeterVirtualState.mahDrawnState, currentMeterVirtualState.amperage, lastUpdateAt); updateCurrentmAhDrawnState(&currentMeterVirtualState.mahDrawnState, currentMeterVirtualState.amperage, lastUpdateAt);