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I have had my MiniPro for 6 months now and have just over 1000 km on it. Today it decided to stop charging past 41%. Is this indicative of a battery cell failure?

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Not seen a problem, like that, you are best calling Segway.  If you have equipment you can measure the charger voltage and the battery voltage to see if everything is in order there.  I take it the charger light never goes green, or the charger light goes green and the App and/or display still says 40% only.  You need to provide more information.

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2 hours ago, FreeRide said:

Not seen a problem, like that, you are best calling Segway.  If you have equipment you can measure the charger voltage and the battery voltage to see if everything is in order there.  I take it the charger light never goes green, or the charger light goes green and the App and/or display still says 40% only.  You need to provide more information.

The charger light goes green but when I turn on the Segway it says it only shows two bars and the app says that it's only at ~40%.

I contacted Segway and they told me to disconnect the battery and try charging it. Didn't help. When the LED on the battery itself turned solid green I reconnected it but it still was only at 40%. I don't think it's a charger problem because I've tried using another charger and it doesn't make a difference.

This of course happened 190 days after purchase, 10 days past the Segway warranty on the battery.

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Posted (edited)
37 minutes ago, Seastan said:

The charger light goes green but when I turn on the Segway it says it only shows two bars and the app says that it's only at ~40%.

I contacted Segway and they told me to disconnect the battery and try charging it. Didn't help. When the LED on the battery itself turned solid green I reconnected it but it still was only at 40%. I don't think it's a charger problem because I've tried using another charger and it doesn't make a difference.

This of course happened 190 days after purchase, 10 days past the Segway warranty on the battery.

It sounds to me like it might actually charging correctly.  If the light on the battery turned green generally everything is fine.  Have you tried riding it and see if it lasts more like 100% or 40%?  I guess the only other way to know is to install a different battery and see what it says.  Do you know anyone else with one that you can swap the battery on?

One more thing, in the App, does the mac rating still say 5700 mAh and the current capacity says 40% of that on mAh?

Just to clarify; the light on the battery turned green, while it was still connected to the charger?

 

Edited by FreeRide

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4 minutes ago, FreeRide said:

It sounds to me like it might actually charging correctly.  If the light on the battery turned green generally everything is fine.  Have you tried riding it and see if it lasts more like 100% or 40%?  I guess the only other way to know is to install a different battery and see what it says.  Do you know anyone else with one that you can swap the battery on?

One more thing, in the App, does the mac rating still say 5700 mAh and the current capacity says 40% of that on mAh?

 

I haven't ridden it all the way to 0, but after riding it for 10 minutes it drops to 1 bar and imposes a reduced maximum speed so it is pretty frustrating.

In the app it still gives the 5700 mAh rating but says it's only charged 1912 mAh. So I guess it's using the 4800 mAh max that the stock charger goes up to to compute the percentage.

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One weird thing that happened was yesterday I charged it up until it stopped charging (40%) then took it down a long hill. By the time I got to the bottom it was showing 3 bars and the app was showing 54% charged. So I guess the regenerative braking is capable of charging the battery past 40%, but not the actual charger.

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18 minutes ago, Seastan said:

One weird thing that happened was yesterday I charged it up until it stopped charging (40%) then took it down a long hill. By the time I got to the bottom it was showing 3 bars and the app was showing 54% charged. So I guess the regenerative braking is capable of charging the battery past 40%, but not the actual charger.

This is very confusing. That would indicate the fault is in the battery, but somewhere between the battery and the charging connector, if the regenerative charging can push it higher using the internal contacts.  Seems like swapping the battery might still fix it since you've tried a different charger already.  

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5 hours ago, FreeRide said:

This is very confusing. That would indicate the fault is in the battery, but somewhere between the battery and the charging connector, if the regenerative charging can push it higher using the internal contacts.  Seems like swapping the battery might still fix it since you've tried a different charger already.  

Unfortunately I don't know anyone nearby with a miniPRO that I could swap batteries with. Looks like I just need to get a replacement.

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16 hours ago, FreeRide said:

Just to clarify; the light on the battery turned green, while it was still connected to the charger?

Yes

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I have the same issue, will only charge to 40%. I have 2 and maintained both exactly the same with no issues with the other one. I suspect a bad cell or two may be the issue internally. Planning on troubleshooting soon 

While riding I would get huge swings in mileage left in the app. Dropping to 3 miles then back up to 12 miles ect... The remaining power mAh would fluctuate .

I used a 63v power brick that appeared to take it to 100% but after riding for a few minutes it quickly dropped. Went from 15mi range down to 12 then 6 pretty quickly.

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Posted (edited)

OK, here's what I got and kind of fixed it? I compounded the problem of charging only to 40% by letting the battery discharge to the point it shutdown and wouldn't take a charge. So, I cracked open the battery case and measured voltages at each cell. Sure enough 3 of the cells were considered dead at 2.25v~2.74v all other cell voltages varied from 3.11v to 3.65v which is a huge difference and well below nominal charge. That put the variance at .37v with a 1.4v difference between lowest and highest cell. I think anything beyond .05 variance is considered bad.

 I nursed the 3 "dead" cells up to 3.7v followed by all the other cells. I then balance charged to within a .02 variance with the lowest cell at 4.08v and highest at 4.10v

 In the app the battery showed 100%, 5,704 mAh, 60.66v. I went for a ride and everything seemed fine. However, capacity and range are reduced. The app showed I had 18 mi range. After 9.4 miles, I noticed I was limited to 9.9 mph. At ~10.5 miles (kind of lost track) the limit was 8.7 mph. I finished the ride at 11.5 mi with 3.5 mi showing for remaining. I estimate maybe another mile left at best, with an excruciatingly slow speed restriction.

Initial charge with stock power brick 'appears' normal showing 16 miles left, 100%, 4986 mAh, 58.83v. I'll have to see how it actually performs later.

Some of the cells are weak and probably should be considered bad. I think the MiniPRO's BMS can't handle balance charging cells with different charge rates and throws things all out of wack. I'm hoping that I can at least get a few 'regular' charges before having to go through this pain again.

 

Edited by Syber7

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Posted (edited)

Nice investigation.  When you charge your MiniPro, do you typically wait until the battery-level lights on the miniPro blink? Or were you typically charging it just until the green light on the charger was on?  If you don't wait until the blinking on the MiniPro you're not giving the BMS a chance to balance.  After a while not allowing for balance could cause some imbalance in the cells and the more they are used in that state the more they will get damaged.

Sound like as you say you may have some cells now that have less capacity in the pack, enough to affect the range.  These cells could cause cut-outs also under high current situations.

Edited by FreeRide

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 With the most recent firmware v1.4.0 the power brick LED turns green and the battery status LEDs turn off. Same behavior for both MiniPros that I have. I don't think it to be related but the "only charging to 40% problem" occurred after the firmware update. Probably coincidental. Prior to the firmware update, I would wait for the power brick LED to turn green and the battery status LEDs would be on solid (not flashing).

 At least we know these battery problems are recoverable. I had called tech support and they said the battery is bad and needs replaced. No surprise there. I can't justify paying the outrageous cost of a new battery pack while I believe there is an inherent quality issues with the internal batteries. I'm not saying inherent quality issues across the board for all MiniPros, just the one I'm having problems with along with others like OP Seastan . Maybe it was made on a Monday or Friday.

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Posted (edited)

Thanks for the feedback. I think i'm running the newer firmware and still get blinking, not off. That might be a sign that it knows something is not right with the battery.

It is important at least on the firmware i have to wait for the blinking after the charger goes green and all the lights are solid on the minipro. This can take a while, as balancing is very slow. Once blinking balancing is complete. Segway appears to not have discussed or explained the charging process completely in all documentation. 

For longest battery life the balancing is important every so often depending how often one is running the pack quite low and the matching of the cells. 

Edited by FreeRide

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From my experience, status led turns off after the charging if BMS stops charging process abnormally. Normally it should "blink" forever until power disconnection.

My story:
Once I managed to discharge the bot to the moment when it refuses to allow me to ride it. But, there was a long descent in front, so I decided to ignore low battery and ride the bot. Very slow in the beginning, but then recuperation did the trick, and bot went faster and faster. At the end of slope, the battery indicator even returns one bar.
BUT,
When I charged the bot after that "torture", the battery indicator just turned off right at the end of charging (no blinking stage, green led on PSU). That's never happened before.
Next rides (between charges) were not so extreme. Discharged to 20-30% remaining power.
Second charge - was starting blinking, but after about a half hour the battery indicator turned off again.
Third charge - a couple hours were passed until the shutdown of battery indicator.
Next charge - it took more then 5 hours to get this off again.
And only on fifth charge the battery indicator started to blink forever as it was before the incident.

I think, the battery was unbalanced when it was charged by recuperation. And BMS was not capable to rebalance battery during just a single charge.
I'm not sure if it's help, but I left bot connected to the charger overnight every time. Even if indicator turned off and PSU led was green.

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