X8 down on power

[Speedie]

Hi,

i have an Airwheel X8 that I have been using for a little over 18 months. I use it to commute to the train station and back which is approximately a 5km round trip. The trip out is uphill and there are a few sections with quite steep inclines for short distances. Initially when I first got the X8 riding up these inclines was no problem. Now the X8 really struggles on these inclines. It is as though the battery is no longer able to deliver  what the motor is trying to draw. The X8 is also no longer as zippy (good at accelerating) as when new. I can't imagine it would be the engine, as these are reasonably bulletproof.

The battery still charges and holds the charge according to the indicator lights. Does anyone have any ideas on what the issue could be? Dead or non charging cells in the battery? Is there anyway to "reset" the battery?

Thanks.

 

[steve454]

18 months is a long time for a battery.  Buy a new battery

[Pingouin]

Hi,

18 months is not too bad but the battery should still hold. How many miles/km have you ridden on your x8 ? Are you a heavy person ? Did you use it toughly ?

Did you leave your battery fully charged for storage ? Did you often completely discharged your battery ?

[Speedie]

All up I would have ridden about 1300km. I'm 83 odd kilos. It's always ridden on concrete paths. I always charge it after each ride. The charge rarely if ever would get below 2 of the 4 indicator lights, so it has never been completely discharged and has always be stored with a full charge.

I am no battery expert but I wonder if it is the repeated heavy draw every day for the few short steep segments of the ride that has shortened the life of the battery.

[steve454]

You could use a multimeter at the charge port and see how many volts you have fully charged.  If fully charged is, say 60 volts in the owner manual and yours only charges to 57 volts then you might have a bad cell.  But be careful touching the pins.  @esaj melted one of the probes doing something like that.

[esaj]

1 hour ago, Speedie said:

All up I would have ridden about 1300km. I'm 83 odd kilos. It's always ridden on concrete paths. I always charge it after each ride. The charge rarely if ever would get below 2 of the 4 indicator lights, so it has never been completely discharged and has always be stored with a full charge.

I am no battery expert but I wonder if it is the repeated heavy draw every day for the few short steep segments of the ride that has shortened the life of the battery.

Keeping the battery sitting long times at full charge will age it much faster, as well as storing it in high temperature and always discharging it all the way:

Table 2 compares the number of discharge/charge cycles Li-ion can deliver at various DoD levels before the battery capacity drops to 70 percent. All other variables such as charge voltage, temperature and load currents are set to average default settings.
 

Depth of discharge	Discharge cycles	Table 2: Cycle life as a function of depth of discharge. A partial discharge reduces stress and prolongs battery life. Elevated temperature and high currents also affect cycle life.
100% DoD 50% DoD 25% DoD 10% DoD	300–500 1,200–1,500 2,000–2,500 3,750–4,700

Lithium-ion suffers from stress when exposed to heat, so does keeping a cell at a high charge voltage. A battery dwelling above 30°C (86°F) is considered elevated temperature and for most Li-ion a voltage above 4.10V/cell is deemed as high voltage. Exposing the battery to high temperature and dwelling in a full state-of-charge for an extended time can be more stressful than cycling. Table 3 demonstrates capacity loss as a function of temperature and SoC.
 

Temperature	40% charge	100% charge	Table 3: Estimated recoverable capacity when storing Li-ion for one year at various temperatures.Elevated temperature hastens permanent capacity loss. Not all Li-ion systems behave the same.
0°C 25°C 40°C 60°C	98% 96% 85% 75%	94% 80% 65% 60% (after 3 months)

Most Li-ions charge to 4.20V/cell, and every reduction in peak charge voltage of 0.10V/cell is said to double the cycle life. For example, a lithium-ion cell charged to 4.20V/cell typically delivers 300–500 cycles. If charged to only 4.10V/cell, the life can be prolonged to 600–1,000 cycles; 4.0V/cell should deliver 1,200–2,000 and 3.90V/cell should provide 2,400–4,000 cycles.

http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries

 

3 minutes ago, steve454 said:

You could use a multimeter at the charge port and see how many volts you have fully charged.  If fully charged is, say 60 volts in the owner manual and yours only charges to 57 volts then you might have a bad cell.  But be careful touching the pins.  @esaj melted one of the probes doing something like that.

16S -pack should charge to around 67.2V when totally full (4.2V per cell * 16 cells = 67.2V). Certain chemistries (NMC?) can go even higher, up to 4.35V per cell (69.6V), but from what I know, the highest voltage drops off very fast, so no use to trying to "fill it to the brim". Just enough to make sure the balancing has done its job every now and then (say, every 10 recharges or so?), otherwise you can charge it lower to get more cycles out of it (if you have a charger with voltage control, pull the plug or have a Charge Doctor to stop the charging before full).

And yes, be careful when measuring the battery. My mistake was that I had forgotten that I had used my multimeter for measuring currents before, and left the probes into current-measurement holes (minimum resistance). The pack can push out a good 100+A in short circuit...

 

[steve454]

I u could use a multimeter at the charge port and see how many volts you have fully charged.  If fully charged is, say 60 volts in the owner manual and yours only charges to 57 volts then you might have a bad cell.  But be careful touching the pins.  @esaj melted one of the probes doing something like that.

 

@Speedie just thought of something.  You have a lot of kilometers on the X8, the performance is going down, instead of a new battery why not get a new, different wheel?  If  I had the money, I would like to have several different wheels.  So far have had three, TGT3 learned on,(barely) Osdrich T5 got 20 miles on according to Endomodo app, and now the Ninebotone E+ that I have 57 miles on.  Money spent, about 240 dollars for the first, 300 dollars for the Osdrich off craigslist, and 950 dollars for the NB1 E+ from a local Segway dealer.

[Speedie]

Thanks, I will give the voltmeter a go. Should have thought of that really. (The Internet can make me lazy at times)

Much appreciated for all the responses.