Tuesday, May 29, 2012

Too much voltage, a new motor, and self discharge.

Sorry for the long delay in updates. I ran into just a couple months after starting to drive again (this was more than a year ago now). The ADC just couldn't handle the extra voltage and fried. The armature had a nice black burn on it. I debated getting it repaired but figured this motor was never intended for this much voltage. I purchased the gen 2 Warp9 which is suppose to handle a lot more voltage. It was also suppose to be a direct bolt in compared to the ADC 9. Some of this is true as the transmission mounted up perfectly. Unfortunately the motor itself is slightly longer and wider. I had to redo my motor mounts and the battery rack above the motor to get it to fit. The AC, of course, then also did not mount back up and I still haven't finished redoing it.

While driving though I did figure out the cutting out issue I'd been seeing. It was not the motor but the controller itself. It was switching frequencies and making a terrible jerking affect. My friend has now modifed the controller to remove this feature.

The car was done for quite awhile and then not driven at all the last year which led to another interesting discovery. Remember that I dropped all balancing boards to experiment to see the real need for this. Every 3 months or so I'd go out and plug the car back in to charge. Now, after a year I was getting ready to take it on a long drive and notice one cell was very low 3.1v resting. I charged the pack but only to replace about 20Ah in the pack. I then charged the one cell to find it took an additional 60Ah! My first thought was this cell is bad but it turns out most of pack was VERY unbalanced just from the self discharge. Each cell was different taking another 20-60Ah compared, I guess, to some of the better cells that didn't self discharge so bad. I'm in the process of replacing the balancers and getting the pack balanced again. I then plan to do another capacity test on this pack and see what shape it's in. I'm hoping to start driving it to work again when weather permits.


Anonymous said...

Welcome back... about this regard... you should look at some videos on www.evtv.me
They make a lot of sense...

Brian said...

I have seen many of Jack's shows. He has done many episodes which I find quite informative. The recent show on brush efficiency was really amazing. I even ran out and check which brushes I have, luckly the red tops :)

I can't say I agree with every theory Jack has, especially when it comes to BMS. His bottom balancing techniques are clever, but only work on an ideal pack where IR and self discharges are equal across all cells for the life of the cells. If they are not, balancing is required. I'm a bit surprised he doesn't at least use a BMS just for high voltage cut off on the charger. This would have saved a few of his batteries :) However they are a pain and you can tell the guy isn't broke. If he can afford to waste a few cells, then keeping it simple works too.