dead battery walking

Well, I took the Mercane single motor off to the "far away shops", got what I thought was not far from home and realised I was wearing my cap not my helmet and went back home for the swap. Then went back to go to the shops. I suggest a quick review of that trip data (and interestingly discharge data discussion) here.

Anyway, I did almost the whole return trip before it caved ... about 2km from home, which was not bad and did a nice predictable draw down consistent with what I'd expect from the discharge curves.

I was watching the battery voltage carefully and can report that at about 42V (running along on a flat smooth road and no head wind) it suddenly (within 2 seconds):

• dove down hard
• powered down the display during that (much like turning it off at the switch)
• powered down the indicator LED's on the "dash"

It then would not power back up, so I walked for a while and clicked on the ignition switch and it briefly powered up and then repeated the above.

So this verifies my understanding of the discharge rates and my concerns about how far I'll get once I start seeing 46V on the flats and buckling down to 44 on the uphills. It also lets me know when the battery management system denies power drain, and its also at a level that's slightly higher than the "low cut off" on the motor controller(s) which is 40V. So this means (assuming correct voltage reporting) that the BMS shuts my battery pack off at about 3.23V per cell.

I've done some calculations on "pack" level voltage from this wonderful data source:

interestingly their "Unknown" battery dies at about where my battery died and follows a very similar discharge curve to what I see. If I'd had genuine LG batteries in there I might just have got home ... maybe.

I checked my trip on google maps and it turns out that my turn around point was just past half way, 4km. So that means that my distance since charging this morning is pretty close to 23Km, which given I did this on "Power" mode is pretty close to what the makers claim for "up to" distances. And I have a number of hills on that trip too.

I got home and stuck it on the charger and it took just under 3 hours to charge (normally I recharge earlier and its under 2).

In my view the battery pack in the Mercane seems "reasonable" for its budget and isn't fantastic nor is it crap.

I hope this data is useful to someone