power loss on startup

[LiFeCycle]

Hey

Got a curly one, I've been zipping around at 4-5kw for a while now on my raptor /sabvoton 72v150a / hyena 10k motor.
Going pretty well.

I switched to a half twist throttle recently. I like the ergonomics of it so far. Since I've been using it i notice a bit of a problem with takeoff sometimes - seems to be under high throttle at about 5kmh, pushing 4kw, it will occasionally just cut out for 1/2 - 1 second, then just come back on again and be fine.

Thing is, it has no problem with this power level for sustained periods at higher speeds. Once i get over the initial stutter, it roars to life.

In the CA3 settings, i can see the throttle response is consistent, until it spikes a bit in the last mm of twist, which i've eliminated by fiddling with the Throttle Vin.

I dialled back throttle out to 3.15v max from 3.8 to try and tame the beast a bit. Max A = 99, Max W= 6000. Throttle ramp up 2v/s, ramp down 30v/s, fast 2v/s, threshold 3a.

Thanks!

 

[wesnewell]

What kind of battery pack. Sounds like controller or CA is hitting LVC under load. Voltage sag is considerable with most lifepo4 and 18650 battery packs. Especially with a max 99A controller.

 

[teklektik]

Check the Limit Flags on the CA Diagnostic Screen to see what is limiting. The parameters that affect each limit flag are laid out in a table in section "4.7 Test Throttle and Limit Settings (Interpreting Limit Flags)" of the Guide.

Also - bikes with high power to weight ratios can sometime trip up the speed PID controller under high acceleration. Unfortunately, there presently is no flag for that limit, but the matter is discussed in section "4.9.2 Speed Gain (PSGain, IntSGain, DSGain)". It describes a means to disable that limit which is quick and easy to try. Basically, hard acceleration makes the CA think you are going to speed, even though you haven't actually done so, and so it does a 'Whoa Nelly!'.... The same WOT throttle has no effect later when you are at speed because there is no resulting hard acceleration.

 

[LiFeCycle]

Woohoo! Thanks teklektik. I disabled the speed control logic as suggested, and haven't been able to reproduce the issue.

I had ruled out LVC issues already. The battery is 20AH of multistar 10c lipo - so in theory, good for up to 200A. I know I can easily draw 80A with around 2-3v of sag. I can run this current even at 3.6v/cell. So the intermittent cutouts at <50A, regardless of the state of charge, pointed to something different i thought.

Thanks again for your suggestion teklektik. I do love the power control mode on the CA when this speed setting is taken out of the picture. Pass through felt like you only got the first 25% of throttle extension before power hit 100%, whereas with power mode it extends the useful range of the throttle to the whole range.