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[Richard230]

Ever since I got my new "power tank" my bike has stopped charging at an indicated 98% (13 kWh).  If you pull the charging plug out and then plug it back in, the charger will continue to charge for another 10 minutes, or so, until it reaches 100% (13.22 kWh).  The only reason that I can think of for this change before the tank installation, when the bike would charge to 100% before turning off, is that my bike received the latest and greatest Zero firmware at the same time. 

I now believe that this is a deliberate programed change to prevent the regen from cycling on and off when the battery pack is completely topped off during the first few miles of riding.  I noticed this morning that, even in Eco mode, the regen acted normally while coasting down the hill while leaving my home when the charge display was reading 98%.  However, when the pack is showing 100%, the regen cycles on and off (you can see it on the display, as well as feel it), while riding downhill with the throttle closed.  So the update solves that issue (if it ever was an issue).

[protomech]

My suspicion is that you're better off not worrying about that top 2%, and let the bike do what it does.

[Richard230]

My suspicion is that you're better off not worrying about that top 2%, and let the bike do what it does.

I wasn't worrying, I was just curious why the charging program had changed and was trying to think of a reason why the change had occurred.  I just like to know the reason why everything happens.   

[ultrarnr]

Richard,

I am seeing similar things on my SR. Sometimes you check on it expecting it to be fully charged only to find it isn't and still has a long way to go. But unplugging everything and plugging back in kind of resets everything and suddenly you at at 100%.

[protomech]

Richard230: I think that's a reasonable explanation.

[dc5dd]

When I plug the SR in at night, one night it will be 99% and the next it will be 100%.  I don't try to pull the plug to get to 100% maybe I should try that and see what happens.  I hope it is just a miscalculation on the MBB and not something bigger .  Anyway I love the bike so far.  Richard I don't think it is limited to the power tank addition everyone else is getting this problem.

[WindRider]

I have seen this on my FX 5.7 as well.

I don't think it is a problem.

It could have something to do with multiple BMS computers in one bike as well..... if you have a power tank you have a BMS in the powertank and one in the main bike.    In the FX there is a BMS in each power module.

If I am up to 98% I am at peace.   :  )

[GNU]

Could it be that it's still balancing the cells?

I leave my SR on the charger overnight (outdoors) and I've never seen it below 100% in the morning.

[Richard230]

I just never saw this phenomenon when the bike was new and before the power tank was hooked up.  It would top out at 100% ever time.  Now it goes up to 98% and stays there for a day or two, then it goes to 99%, but sometimes it hits 100%.  Kind of random and a little strange, but I don't see any negative effects. 

You can tell when the batteries are being balanced.  The power draw drops to around 4 amps and the light display in the BMS window kind of dances around.  When it stops charging and balancing at 98%, the power draw drops to 4 watts, so I don't think it is balancing then.

[dc5dd]

Could it be that it's still balancing the cells?

I leave my SR on the charger overnight (outdoors) and I've never seen it below 100% in the morning.

I get home at 10pm plug it in and in the morning around 9am it is still at 99%

...  When it stops charging and balancing at 98%, the power draw drops to 4 watts, so I don't think it is balancing then.

Doesn't non-balancing mean a problem?

[Richard230]

I see the BMS balancing right before it stops charging at 98%.  I don't think there is any problem.

Plus, the app shows that the batteries are withing 2 or 3 mv when charging is done, so that is a pretty good job of balancing.  After arriving home from a long ride, the balancing part of the app shows 13 to 14 mv.

[Richard230]

OK, I give up.  I bought a new Kill O Watt (figuring that the old one was malfunctioning) and gave it a try yesterday, after an 80-mile ride where (according to the Zero app) I used 9.5 kWh of power out of my 13.2 kWh pack.  I plugged the charger into the Killer at 2:15 pm and I checked it at 10:45 pm.  By then it had finished bulk charging, the display showed a 99% charge, and it was balancing the pack. (It has these little white lights that blink alternately, one in the center and two at the edges of the BMS inspection window when it is tossing electrons around from cell to cell.)  The KOW showed the power used through the meter was 9.14 kWh, compared with the Zero showing the battery power having had 9.5 kWh replaced. (So we know that something is not kosher between these two devices when measuring power.) Oddly, the previous meter showed 4 watts when the monitoring system was on and the new meter is showing 2 watts, with the charger plugged in and nothing happening.

So I have concluded that the Kill A Watt and the Zero BMS system calculate power consumption in different ways.  And that sometimes you are better off not having too much information.  The more dials and indicators that you look at the more confused you become.   I think I just won't think about it any more.  No doubt I can find something else to think about soon.   

[protomech]

ZF14.2 is rated at 12.5 kWh nominal capacity. Is the Zero app stating capacity at 13.2 kWh?

The Kill-o-Watt measures AC power and energy at the wall plug.

I would expect the Zero BMS to report energy consumed/charged into the battery via coloumb counting. It's possible that instead it's measuring and reporting kWh in expected AC energy consumption, and if so then it's apparently pessimistic.

[Pprior]

Watts flowing through the kill o watt are not 100% converted into battery power. There are losses...

[Richard230]

When fully charged to 100%, my Zero battery app shows either 13.22 or 13.33 kWh.  When charged to 98% it shows 12.99 kWh.   

Since I only paid $20 for the Chinese-manufactured KAW, I assume that its accuracy is probably not up to laboratory standards.   

I am pretty sure that my battery charger is not more than 100% efficient.  And I am willing to point the finger at the Kill A Watt, rather than the Zero BMS - which no doubt was designed and built to a higher standard.