26
Aug

Let the fun begin

Written by admin. Posted in Build Diary

OK, now that the BMS (battery management sys) is installed and working, I can finally go full throttle with a sense of confidence in the cell control. We learned early how quickly cells can be destroyed with such high currents involved. These cells are very robust when properly monitored/controlled, however.

So, let the serious fun begin:

Heads up about the noise level in the first video. Because of the auto gain mic input on the camera, it cranks up the gain from the lack of noise when nearby to the volume level that would match a four stroke, for example, in your audio playback.

 

 Here are a couple pics from the dyno session

We will post the curve data when we get the gas bike dyno data to overlay directly. Dyno session with CRF250X and CRF250R is planned for Thursday Aug 6.

We were able to monitor the cell voltages with precision while full on the throttle

Sorry for the blurry display..

The charging is automatic now, just plug the cable into the… what else…the filler neck. When the charge is done, the LED (next to the plug) turns from red to green. With the relatively weak charger we have now, it takes more than 45 minutes to charge after playing hard for about 15 minutes. We will be cranking up the current to the point the charge will take 20 minutes for a full capacity (2kW/4kW charger 120V/ 240V).

These cells have the ability to charge in under 10 minutes, you just need a charger that can deliver it.

Although charging is automatic, here we are monitoring the charging details (gray, flat comm cable) just to be sure all is OK.

Here are the three battery boxes which have their own BMS boards attached. The center box has them installed internally with only their communication pins protruding.

These BMS boards were designed for the BMW but also work fine here as a development platform. So far, so good: After approx 16 charge/ride cycles, no faults or communication errors, even under full power. 

Here is the waveform of the current drawn from the pack during a couple throttle blips:

The scale in this case is 1mV/Amp showing a peak of 570 Amps. We limit the current to 300 Amps per motor so this got very close to the 600 Amp total from a blip while on the bike stand, where we applied some rear brake for load, thus the flat segments in the waveform.  The brake disc gets very hot very fast doing this.

Sneak peek at another bike conversion that has been going on in the background – the EVDrive e-MotoGSXR – if the interest is there we will sell both the completed bike and complete conversion kits to select powersports custom bike/service/dealers …

This AC motor drive conversion has a unique twist to it… stay tuned …

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