eWheels Fast Charger issues?

[Ben Kim]

25 minutes ago, esaj said:

Sounds like the fast charger output voltage is too low. I adjusted a friends' fast charger (bought from Wheelgo, Jason McNeil's UK-company before he moved to US) a couple of years back because the output voltage had dropped to too low, it was around 66V or even a little bit below, don't remember exactly anymore.

It's normal for the battery voltage to drop a bit after removing the charger, to get "full" 67.2V after removing the charger, you have to wait until the charging current drops to near zero (which can take hours after the charger light already turns green) and all the cells have charged to full. Even the relatively small current required to run the electronics and keep the wheel upright at standstill (when it's own) can drop the voltage somewhat.

With KS's and other wheels having reverse protection for the batteries, you can't measure the battery voltage directly from the charge port (and Charge Doctor won't turn on when plugged to the wheel without the charger plugged to power outlet), what you see during the charging in CD or similar, or in the charger itself, if it has voltage display, is the charger output voltage, which is higher than the actual battery voltage as long as current is flowing (once they reach the same voltage, the current has dropped to 0).

my eWheels charger hovers around 67.2-67.3, which leads to a 66.7-66.8V when it’s fully charged. 

 

The “dumb” charger shows 67.5-67.6 via multimeter and settles at 67.1.

I actually prefer it settling below 67V simply because then there is no risk of my brakes cutting if i have to brake hard with a full charge.

[esaj]

25 minutes ago, Ben Kim said:

my eWheels charger hovers around 67.2-67.3, which leads to a 66.7-66.8V when it’s fully charged. 

Do you leave it charging (sometimes) until the current has dropped to zero? Did you measure the output voltage with a multimeter or just by the display on the charger? The displays look like the cheapo chinese voltage/current meters that aren't exactly precise, or at least drift over time.

Quote

The “dumb” charger shows 67.5-67.6 via multimeter and settles at 67.1.

I actually prefer it settling below 67V simply because then there is no risk of my brakes cutting if i have to brake hard with a full charge.

I have Firewheel charger that outputs around 67.6V, I initially assumed it was to overcome a reverse protection diode in the BMS, but later on learned that probably the reverse protection is done with mosfets ("ideal diode"), and it's just off... nevertheless, I've used it at times to fully charge the battery (current dropping to near zero) to make sure the cells get balanced. Never had issues with overcharging even with slightly too high voltage, probably the balancing circuits in the BMSs can handle the slight overvoltage.

If you leave the "dumb charger" on until the current drops to zero, do you reach full 67.2V (or thereabouts)? If looking just at the wheel app (requiring the wheel to be turned on), it might show 67.1V just because of the current required to run the MCU & other things on the mainboard, and keep the wheel balanced on its own. Checking that the voltage is correct with a multimeter and then allowing the charge to run until (near) zero current should allow the batteries to charge all the way to full voltage.

I start my rides with less than 100m of going straight and then a more steep downhill for a couple of hundred of meters, followed by more gradual decline for maybe about half a kilometer. Never had the wheels warn me of overcharge there, although it might push the voltage somewhat above 67.2V. I've done this for years, never had to do any really hard braking though.

Charging the batteries all the way every now and then (say, every 10-20 charges for example?) is a good practice to make sure that the cells get balanced. For longevity, charging to less than full (most of the time) is good, also if you need to store the wheels for a longer time (I do, for about 6-7 months every year over the winter), discharge them down to something like 30-40%. If stored for longer while at full charge, the batteries lose maximum capacity much faster. If stored "empty" for a longer while and the voltage drops too much, internal short circuits will ruin the cells.

Last winter, the wheels (at that time, I still had both the KS16S & KS16B) were both run down to 3 leds before putting them to "sleep", I didn't even bother checking the wheels or voltages over the winter. The voltage drop over about 7 months wasn't enough to drop a single led from the side panels (both KS16's set to show the battery state with the side leds when not moving)

Ninebot Z-series is different, the vampire drain requires the wheels to be charged monthly or so.

Edited July 13, 2019 by esaj

[Rywokast]

29 minutes ago, Ben Kim said:

my eWheels charger hovers around 67.2-67.3, which leads to a 66.7-66.8V when it’s fully charged. 

 

The “dumb” charger shows 67.5-67.6 via multimeter and settles at 67.1.

I actually prefer it settling below 67V simply because then there is no risk of my brakes cutting if i have to brake hard with a full charge.

hard braking there is no risk.. on smaller wheels i charge them to 100% every time and have no fear of a cut out, you just dont want to start your ride at the top of a big hill with 100% charge.. to get the recharge effect you have to be going down a steep enough hill in order for gravity to be pulling you down fast enough, whilst you maintain a slow enough speed that would essentially be gravity pulling you down the hill... if i accelerate down a hill i dont get any regen.. and braking on its own doesnt do this, you dont regain battery after every time you brake or the thousands of people who leave their wheels charging overnight would faceplant almost every time they went out xD i always recharge beyond 100% every couple weeks to allow the bms to balance the cells its important for longevity and can also be important for safety ive seen a few accounts of people who had one or more cells out of whack which could cause many problems some have gone so far as to actually take apart the pack and recharge the individual cell to get it back up in line because it was so far out that it didnt even let him ride.. think it was a ninebot one E+ that i last saw someone do that to

Edited July 13, 2019 by Rywokast

[Ben Kim]

1 hour ago, esaj said:

Do you leave it charging (sometimes) until the current has dropped to zero? Did you measure the output voltage with a multimeter or just by the display on the charger? The displays look like the cheapo chinese voltage/current meters that aren't exactly precise, or at least drift over time.

I have Firewheel charger that outputs around 67.6V, I initially assumed it was to overcome a reverse protection diode in the BMS, but later on learned that probably the reverse protection is done with mosfets ("ideal diode"), and it's just off... nevertheless, I've used it at times to fully charge the battery (current dropping to near zero) to make sure the cells get balanced. Never had issues with overcharging even with slightly too high voltage, probably the balancing circuits in the BMSs can handle the slight overvoltage.

If you leave the "dumb charger" on until the current drops to zero, do you reach full 67.2V (or thereabouts)? If looking just at the wheel app (requiring the wheel to be turned on), it might show 67.1V just because of the current required to run the MCU & other things on the mainboard, and keep the wheel balanced on its own. Checking that the voltage is correct with a multimeter and then allowing the charge to run until (near) zero current should allow the batteries to charge all the way to full voltage.

I start my rides with less than 100m of going straight and then a more steep downhill for a couple of hundred of meters, followed by more gradual decline for maybe about half a kilometer. Never had the wheels warn me of overcharge there, although it might push the voltage somewhat above 67.2V. I've done this for years, never had to do any really hard braking though.

Charging the batteries all the way every now and then (say, every 10-20 charges for example?) is a good practice to make sure that the cells get balanced. For longevity, charging to less than full (most of the time) is good, also if you need to store the wheels for a longer time (I do, for about 6-7 months every year over the winter), discharge them down to something like 30-40%. If stored for longer while at full charge, the batteries lose maximum capacity much faster. If stored "empty" for a longer while and the voltage drops too much, internal short circuits will ruin the cells.

Last winter, the wheels (at that time, I still had both the KS16S & KS16B) were both run down to 3 leds before putting them to "sleep", I didn't even bother checking the wheels or voltages over the winter. The voltage drop over about 7 months wasn't enough to drop a single led from the side panels (both KS16's set to show the battery state with the side leds when not moving)

Ninebot Z-series is different, the vampire drain requires the wheels to be charged monthly or so.

I'm personally not a fan of charging to the full 4.2 per series unless it is for balancing purposes, but I also don't believe in charging only to 80%. Capacity will degrade over time regardless of use.  90-95% is fine (65.5-66.5 on a 16S), as the packs will degrade over time regardless.  Crappy Chinesium batteries (e.g. Sincpower and other counterfeit branded 18650s) are rampant in the scooter world, but in the EUC world, it appears manufacturers stick to Sanyo GA or LG MJ1 cells on the higher end, which means a far lower frequency of poor cycle life and defects.  I would love to see a wheel utilize Samsung 30Q's for even higher discharge rates at the expense of some capacity, it would also somewhat mitigate the potential for cutouts if beeps are ignored.  

 

[esaj]

15 minutes ago, Ben Kim said:

I'm personally not a fan of charging to the full 4.2 per series unless it is for balancing purposes, but I also don't believe in charging only to 80%. Capacity will degrade over time regardless of use.  90-95% is fine (65.5-66.5 on a 16S), as the packs will degrade over time regardless.

If the wheel's being used all the time, likely it won't sit at high charge for a long while, so mostly the degradation likely comes just from the general cycling of the battery. The degradation in storage seems to mostly occur over longer time, depending on temperature (who'd really keep their wheel at 40C or 60C = 100-140F?  ) and varies with state of charge:

Temperature	Lead acid at full charge	Nickel-based at any charge	Lithium-ion (Li-cobalt)
			40% charge	100% charge
0°C 25°C 40°C 60°C	97% 90% 62% 38% (after 6 months)	99% 97% 95% 70%	98% 96% 85% 75%	94% 80% 65% 60% (after 3 months)

Table 2: Estimated recoverable capacity when storing a battery for one year. Elevated temperature hastens permanent capacity loss. Depending on battery type, lithium-ion is also sensitive to charge levels.

( https://batteryuniversity.com/learn/article/how_to_store_batteries )

 

 

Quote

 Crappy Chinesium batteries (e.g. Sincpower and other counterfeit branded 18650s) are rampant in the scooter world, but in the EUC world, it appears manufacturers stick to Sanyo GA or LG MJ1 cells on the higher end, which means a far lower frequency of poor cycle life and defects.  I would love to see a wheel utilize Samsung 30Q's for even higher discharge rates at the expense of some capacity, it would also somewhat mitigate the potential for cutouts if beeps are ignored.  

Apart from the early "generics" (14" Airwheel X3-copies that were rampant back in 2015) and a few less known manufacturers that disappeared from the markets years ago (F-wheels used to have LiPo-packs?), I don't think any wheels used anything but big brand-name cells.

Smaller capacity, but higher discharge chemistries have been used in some Gotways, I think. In the end, the voltage's going to cause a faceplant if you go fast enough (the motor back-EMF raises to the battery level => no current, no torque).

Edited July 13, 2019 by esaj