Bafang BBS02: Assist Power Levels

Although Gee’s Terry Symmetry is sized for female bodies, I managed to ride it up and down the driveway while watching the power display:

Voltage52.5
Rated Current24
Max current18
PowerPower
PASAssistAmpCalcObservedRatio
00%0.000~
14%0.7382669%
26%1.1575292%
39%1.6857892%
413%2.312310485%
520%3.618918296%
630%5.428425891%
750%9.047345396%
885%15.380367584%
9100%18.094590095%
Bafang BBS02 on Terry Symmetry – actual voltage

The variations in the last column suggest my data-taking is … wobbly, at best.

I think the displayed power does not come from actual current and voltage measurements, because recalculating the power using the nominal 48 V battery value produces an unnatural agreement:

Voltage48
Rated Current24
Max current18
PowerPower
PASAssistAmpCalcObservedRatio
00%0.000~
14%0.7352675%
26%1.15252100%
39%1.67878100%
413%2.311210493%
520%3.6173182105%
630%5.4259258100%
750%9.0432453105%
885%15.373467592%
9100%18.0864900104%
Bafang BBS02 on Terry Symmetry – nominal voltage

The motor controller may measure the actual winding currents while generating the BLDC waveforms, but the values may not be available to the display at the end of the cable. If Bafang documented the commands & responses, we’d know for sure, but they don’t.

Those assist values come from Mary’s Tour Easy, a much heavier bike than the Symmetry, but the first few levels work well in my limited tests. The highest levels may be too peppy for Gee’s normal routes, but having some serious boost in reserve can defang (hah) the worst hills.

Terry Symmetry - Tour Easy
Terry Symmetry – Tour Easy

IMO, the bike would burn rubber at the motor’s full 24 A current …

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