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84.2v Rapid Charger Issues/Question

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Lithium-ion batteries gradually lose capacity over time. After 50-100 battery cycles a remaining capacity of 96% is not so unusual at all.

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24 minutes ago, Mono said:

Lithium-ion batteries gradually lose capacity over time. After 50-100 battery cycles a remaining capacity of 96% is not so unusual at all.

I have roughly 500 miles on my MCM5 and I've owned it since May. I'm not sure if I hit 50 battery cycles but I guess it's possible.

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Posted (edited)

My Battery is exactly at 83,98 Volt after full charge and 5 hours resting time. 

That the 80% and 90% charge doesn't work properly is definitely not due to the other problem that you can't reach 100% anymore. This problem is definitely due to the charger itself.

That you don't reach 100% is probably due to the battery itself. Either all cells have decreased a bit, or one or more cells are bad.

1400 km since April 2019

Edited by buell47

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47 minutes ago, nickysneids said:

I have roughly 500 miles on my MCM5 and I've owned it since May. I'm not sure if I hit 50 battery cycles but I guess it's possible.

Either way, the other factor is the voltage of the charger. In my experience it is very common that chargers do not deliver the specified voltage. Can you measure the voltage output of your charger?

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On my mcm5s original board that was replaced at 370 miles I would get 83.4v using the stock charger and the rapid charger. This was from day one. 

My replacement board that gas 1800 miles on it only charges to 82.3 volts max no matter what. Strangely this figure has not changed in 1800 miles. 

The wierd part is that my range has stayed the same, only difference is on the current board I do not have low battery beeps when wherl log is showing 0%. I can still cruise at 15mph when I'm at 0% (under load of course). 

My conclusion is the current board is reporting the voltage wrong, but I have no confirmed the battery voltage on a volt meter as most of my useful things are in storage at the moment. 

The batteries have 2100 miles on them, charged to 80% (90% on the rapid charger switch) most of the time and full charging about once a week for a longer ride. 

My range at 190lb rider weight is:

Ride like your being chased for 15 miles

Or, ride how ever you like for 20 miles

Or, baby it staying at 18mph and under without accelerating hard squeezing out 30 miles. 

I dont think I will ever know exactly why the reported voltage is different between the boards but my range has stayed the same. If it has lost any capacity the difference isnt noticable. Nor is it showing up in the reported voltage number.

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i have the 84V and 67V ewheels fast chargers, have for a couple years now and used them on many eucs.. the battery level is never exact but has always worked to within 3% and 100%  goes just slightly over 84.2 and 67.2.. i believe this is a common "issue" and there is a small potentiometer inside the charger that you can adjust until it gets to the correct voltage... keep in mind different wheels have different battery voltage allowances and some chargers even cap the max voltage to lower than 4.2.. for example the KS18XL will allow you to drain the batteries to 3.0V.. 84V/20 = 4.2 which means 4.2V per for a full charge.. 3.0V x 20 = 60V which is empty.. the difference between 84 and 60 is 24.. 24 x .9 = 21.6.. so you add 60 (empty) to 21.6 (90% of the difference between empty and full) which gives you 81.6 which should be ~90% battery life...  if for example i take a gotway wheel which only allows me to drain the batteries to 3.3V for empty this 90% charge level voltage now goes from 81.6 on the kingsong 18XL to 82.2 on my gotway wheel.. so you can see how if my charger stops at 81.6V because it is assuming 3.0V = empty that now my gotway wheel would only show an ~86% charge.. now depending on the specific fast charger whether its labeled for gotway or for kingsong, the specific unicycles batteries, firmware, and how the BMS operates this can confuse it and cause the voltage to differ between the "battery level" depending on which wheel youre talking about... even one wheel can be different to the next from the same manufacturer in how these things are set up so you would need a specific charger unfortunately... alternatively you could increase this max voltage on the charger by opening it up and tuning it so when you set it to the 90% mark it actually gives you a 90% reading in the app.. this would be a bit of a guessing game and not recommended if you dont know what youre doing, or you use the charger on multiple wheels...

Edited by Rywokast

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On 8/22/2019 at 3:40 AM, nickysneids said:

So I tested charging my wheel up with the original charger last night and found that even with the original charger I was only able to charge up 82.80v, 96%.

Does this mean that my battery packs have essentially degraded to not being able to hold 100%/84v charge?

This doesn't really solve my original problem of not being able to utilize the 80% or 90% charge function on the rapid charge but it does make me wonder about the integrity of my battery packs.

could be a few things, battery degradation, cell imbalance, improper readings (unlikely)... i would recommend you allow the charger (factory) to sit on the green light for at least 12 hours to allow it to trickle charge and for the BMS to balance the cells... this is something everybody should be doing on every wheel once in a while as an imbalance can only lead to bad things if left unchecked... check back at the reading after that and if it hasnt moved at all then nothing you can do at least not without taking it apart.. but if it has moved even less than 1% just continue to let it sit until it goes past 84V.. my opinion is you would have to have been doing some pretty bad battery charging/maintenance practices for it to degrade that much after just 500 miles.. after many thousands of km on many wheels none have shown any noticeable battery degradation for me.. the worst thing you can do to lithium batteries is expose them to high temps (even 25 celcius can be enough to degrade the battery 5-20% over the period of a year depending on the sitting charge level), and to fully drain them.. letting them sit over 4.1V for extended periods is also unhealthy (a reading of above 82V) but less so than the aforementioned unless for a very long time 

Edited by Rywokast

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31 minutes ago, Rywokast said:

i would recommend you allow the charger (factory) to sit on the green light for at least 12 hours to allow it to trickle charge and for the BMS to balance the cells...

@nickysneids 

Maybe even a couple of time with some (small) discharge inbetween.

33 minutes ago, Rywokast said:

my opinion is you would have to have been doing some pretty bad battery charging/maintenance practices for it to degrade that much after just 500 miles.. after many thousands of km on many wheels none have shown any noticeable battery degradation for me..

Could also be just bad luck - if one gets a pack whith not well enough matched cells, etc ...

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1 hour ago, Chriull said:

@nickysneids 

Maybe even a couple of time with some (small) discharge inbetween.

Could also be just bad luck - if one gets a pack whith not well enough matched cells, etc ...

oh yea never rule out bad luck.. especially with any electronics made in china lmao

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On 9/11/2019 at 3:00 AM, Rywokast said:

could be a few things, battery degradation, cell imbalance, improper readings (unlikely)... i would recommend you allow the charger (factory) to sit on the green light for at least 12 hours to allow it to trickle charge and for the BMS to balance the cells... 

 

On 9/11/2019 at 3:35 AM, Chriull said:

@nickysneids 

Maybe even a couple of time with some (small) discharge inbetween.

Could also be just bad luck - if one gets a pack whith not well enough matched cells, etc ...

So I tried this for a solid 12 hours and I got the voltage to 83.04, trying again for another 20 hours or so to try and get it to a full 84v but I doubt it’ll get there considering it hasn’t moved past 83 in 12 hours.

I’m sending back the rapid charger after having spoken with Jason at eWheels, he’s going to send me a new one so cheers to that.

Thanks for all of the advice!

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Alright so after a long bout of charging, the farthest I got my wheel to was 83.09 of a charge and soon after it dropped back down to 83.00v. This makes me think that my wheel is relatively balanced but I just got unlucky with the cells being matched?

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On 8/22/2019 at 12:40 PM, nickysneids said:

So I tested charging my wheel up with the original charger last night and found that even with the original charger I was only able to charge up 82.80v, 96%.

Does this mean that my battery packs have essentially degraded to not being able to hold 100%/84v charge?

This doesn't really solve my original problem of not being able to utilize the 80% or 90% charge function on the rapid charge but it does make me wonder about the integrity of my battery packs.

 

11 minutes ago, nickysneids said:

Alright so after a long bout of charging, the farthest I got my wheel to was 83.09 of a charge and soon after it dropped back down to 83.00v. This makes me think that my wheel is relatively balanced but I just got unlucky with the cells being matched?

I'd assume this both posts relate? Original Charger and MCM5.

Not too long ago you still had 100% (and unkown voltage)?:

On 8/17/2019 at 9:59 PM, nickysneids said:

I haven’t measured the voltage of a full charge to 100%, that’s just the voltage for the rapid charger.

The stock charger charges to 100% no problem 

So either your original charger maximum output voltage slowly "drifts" to lower values or yes, the cells are bit mismatched.

If you discharge the batteries a bit (to something like ~80V) and put it on a full charge again, rinse and repeat this a couple of times you'll see if the max voltage increases...

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I don't know if this info below means anything or not.

My mcm5 only gets to 82.30 on wheelog when my rapid charger reads 84. This is also true with the stock charger no matter how long I leave hooked up. This gives me a 93% reading on wheelog. 

This is my 2nd board, my 1st board went to 97% on wheelog with the same chargers, and if I went down hill right away it would tilt back due to over voltage.

Last night I went down a pretty steep hill and watched wheelog. I went from 82.20 (my normal full charge) and while on the hill the reading went up to 83.40. I never had it beep n tilt due to over voltage.  

Now I'm wondering if the readout is off on my rapid charger and wheelog is correct. 

I know I should just open it up and check the battery voltage. I'm a little worried that both the stock charger and the rapid charger wont balance the cells. 

This change happened when I changed the board very early early in the mcm5s life (370 miles) so it wasnt a slow change like the batteries degrading. I had just assumed the board is reporting improper voltage to wheelog as my 16s reports 67.1 when full. 

I'd like to test my rapid charger but I dont know how to tell which holes to stick the prongs from the volt meter into and definitely dont want to mess that up. How do I know where to put the prongs? 

 

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