10% Battery Drop within First 1 Km

[r_713]

Hello.

I now have approximately 1800km on the VS (Xmas Eve batch).

Starting about a month or so ago (~1400km), I'm finding that my battery now drops around 10% within the first kilometer (0.6 mile). Every time I start at 100% (around 100.# volts) and every time the battery precipitously drops immediately. This is not voltage sag. I'm taking the battery level reading while stopped. Typically it's around 89% while riding, and then around 91% when stopped.

However, after this initial 10% drop, the battery proceeds to deplete as normally expected. It's a minimum of another 15/20km before the battery has depleted another 10%.

I'm curious if anyone else is experiencing this effect. Should I be expecting this kind of fatigue after only 1800km? (or am I being battery naïve?) Before the VS, I had an 18XL. After 1800km on it, I never saw the battery behave in this manner.

[RetroThruster]

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Edited May 7, 2021 by RetroThruster

[null]

Maybe try to look at the display voltage reading, very long press on OK will make it show the voltage.

[r_713]

20 minutes ago, null said:

Maybe try to look at the display voltage reading, very long press on OK will make it show the voltage.

Actually, I did take a photo of the display right after I took the screenshot of EUC World. It's a bit hard to see due to the plastic cover but it reads 98.4 V. I started at 100.1 V (it never gets to 100.4) less than a mile before that.

[null]

That’s maybe close to what mine does: a drop of 0.4-0.5V after end of charge (apparently normal according to battery specs) Then the next 0.5V going fairly quickly after being powered on, ran a little. Add your Km and we should be at the same.

First O.5V should be normal, I wonder if it also is that the next 0.5V is “weak”..

[Tawpie]

I have seen reference to a characteristic called 'surface charge' and I don't know what it is or means, but the context in which the term was used implied that post charge, the voltage will drop rapidly upon initial load. I see this on my 16X, where it starts out at 83.8V (there is measurement error in my control board) but immediately drops to 83V when loaded and 'unloaded' (it never gets back above 83V). I don't think this drop should be 10% and would be mildly worried myself, but again, I have no personal knowledge of this term and there are others here that can provide better info.

Also, check EUCW to make sure you're not using the 'custom battery level' setting for battery %... there is voodoo involved and it may be clouding the issue.

Here's a reference to 'surface charge' being something different than 'state of charge' "First, we estimate the average-electrode, or single-particle, solid-electrolyte surface concentration, called critical surface charge in addition to the more traditional bulk concentration called state of charge." from https://asmedigitalcollection.asme.org/dynamicsystems/article-abstract/132/6/061302/470149/Lithium-Ion-Battery-State-of-Charge-and-Critical?redirectedFrom=fulltext

Edited May 7, 2021 by Tawpie

[gon2fast]

I lose the first bar within a half block of my house on the Sherman. My older IMs do/did the same.

[Chriull]

9 hours ago, RetroThruster said:

Mine is still pretty much new from the January batch and per EUC World, mine states 95% charge when it is fully charged, I went round and round with eWheels and was left with the answer that the Sherman doesn't communicate well with EUC World.  I measured 100.0 volts at each pack at full charge.  

This is a well known mesurement weakness of about all wheels, including sherman and is _not_ caused by any app like EUC World, wheellog or Darknessbot. (Beside maybe optimized/non standard charge % computation is enabled, as @Tawpie already mentioned)

The Voltage measurement by the motherboard is just not too accurate. So with 95% the motherboard measures and reports to the apps some ~99.5V instead of the real 100V. One gets this measured and reported voltage by

9 hours ago, null said:

Maybe try to look at the display voltage reading, very long press on OK will make it show the voltage.

if one wants to compare it with a more accurate real battery voltage.

To prevent this "not charging to 100%" issue most manufacturers (but leaperkim) cheat a bit by showing 100% for some already lower voltages like from 99V up to full 100.8V! 

This 100% range would also hide such percentage drop in the beginning of a ride.

@r_713- how long do you let your wheel rest between charging (disconnecting wheel from the charger) and riding? Imho@null got the "main point" - the battery voltage settling is normal after charging and not consumption.

The surface charge, as @Tawpielinked, needs to "settle".

This should be about the same reason why one has to stop and let the wheel rest a bit for sensefull charge measurement, as you already noticed.

Afaik Sherman shows 100% for 4.2*24=100,8V and 0% for 3.15*24=75,6V? So 100.1V are 97% and 98.4V are 90% - so "just" 7% - in combination with "an after charge voltage drop" everthing seems fine?!

 

4 hours ago, gon2fast said:

I lose the first bar within a half block of my house on the Sherman.

Afair Sherman has a "very strange way" to map charge % to bars display. Or is this already straightened out with newer version?

Quote

My older IMs do/did the same.

As written above IM have a "broad" 100% range and by this such a drop should be "hidden". As you mentioned "older" this could be a first sign of imbalance - battery not really charging full, but still showing (near) 100%?

Edited May 7, 2021 by Chriull

[Dominic Winsor]

Voltage ≠ mileage

My Sherman drops like this too. But then it sits around 70-80% for miles and miles and miles… Three things to consider.

• Voltage measurement accuracy adds a lot of variance as others have stated.
• The Lithium Ion voltage discharge curve is not linear. It is normal for it to drop faster, then level out, then drop faster again.
• Voltage varies a lot depending on load.

What's interesting to me is that creating a link between voltage and range/capacity is as much a game of psychology as it is physics.

I worked on the design of the Onewheel Community Edition and had many conversations that probe the link between voltage and range for people with extended range batteries, and there were some really interesting and sometimes strange/superstitious ideas around the topic. 

[Planemo]

Look at any li-ion discharge curve and you will see that 4.2v to 4v drops like a stone. If it wasn't for balancing purposes, it's almost not even worth fully charging to 4.2v. An option is to use EUCW and set 100% as 4.0v or maybe even 3.9v. This will give a more linear reading. From 3.9v to around 3.3v, li-ions are pretty linear.

Test of Sanyo NCR18650GA 3500mAh (Red) (lygte-info.dk)

[r_713]

I've had my VS for five months now. The first four months I'd watch the battery go 99%->98%->97%->96%->etc. Now in the fifth month I suddenly see it go 99%->89% within 1km. (I'm not quick enough to see any inbetweens.)

This entire time I've been recharging my batteries to 100% after every ride. I hear talk that one should only charge to 80% to preserve the batteries. Has my "method" caused my batteries to hit a threshold and suddenly deteriorate?

[xiiijojjo]

49 minutes ago, r_713 said:

I've had my VS for five months now. The first four months I'd watch the battery go 99%->98%->97%->96%->etc. Now in the fifth month I suddenly see it go 99%->89% within 1km. (I'm not quick enough to see any inbetweens.)

This entire time I've been recharging my batteries to 100% after every ride. I hear talk that one should only charge to 80% to preserve the batteries. Has my "method" caused my batteries to hit a threshold and suddenly deteriorate?

Unless you are going to preserve those batteries for a decade there is no need to charge to 80% instead of 100%. 

The deterioration you can expect from charging it to full every day is negligible and will only impact you in a noticeable fashion if you intend on keeping your batteries alive for a very long time. 

The biggest "danger" about charging to 100% is when you leave it for months or years without discharging the batteries. For storage purposes you should discharge to 60-70% and even then discharging and recharging it back up to 100% only to discharge it back to 60-70% is a healthy practice. 

I understand that it is scary to some seeing the 100.8V at 100% go down to 99.1V at 100% and thinking it is due to deterioration of the batteries. But with all wheels regardless of if you charge them to 100% or 80% there will be rapid voltage deterioration in the first few months/1000's of kilometers and it is normal and will more or less halt at around minus 1-2.5V from the original voltage be it 67.2V, 84.4V or 100.8V REGARLESS of if you charge to 80% or 100% 

From my experience of trying both methods for years. 

Edited May 8, 2021 by xiiijojjo

[Chriull]

6 hours ago, r_713 said:

I've had my VS for five months now. The first four months I'd watch the battery go 99%->98%->97%->96%->etc. Now in the fifth month I suddenly see it go 99%->89% within 1km. (I'm not quick enough to see any inbetweens.)

You could try looking at your battery voltages a bit, maybe it reveals something?

Once when the charger led turns green. 

Then immedeately after disconnecting the charger.

5 minutes later.

30 minutes later.

Next day.

This could gives a jint for elevated self discharge, or maybe cell imbalance.

6 hours ago, r_713 said:

This entire time I've been recharging my batteries to 100% after every ride. I hear talk that one should only charge to 80% to preserve the batteries.

No! Don't do that - this prevents the bms balancing circuitry to work and will so definitely render the battery useless!

6 hours ago, r_713 said:

Has my "method" caused my batteries to hit a threshold and suddenly deteriorate?

No. Just, as @xiiijojjowrote storing at 100%, especially at higher temperatures wears the batteries.

5 hours ago, xiiijojjo said:

it is normal and will more or less halt at around minus 1-2.5V from the original voltage be it 67.2V, 84.4V or 100.8V REGARLESS of if you charge to 80% or 100% 

From my experience of trying both methods for years. 

If not the chargers is misadjusted (give this 1-2.5V less voltage) that's a sign of cell imbalance!

Or you mean the battery settles some time after charging to this 1-2.5V less?

[xiiijojjo]

On 5/8/2021 at 9:08 AM, Chriull said:

If not the chargers is misadjusted (give this 1-2.5V less voltage) that's a sign of cell imbalance!

Or you mean the battery settles some time after charging to this 1-2.5V less?

I mean once charging is done at 100% the eucw app will read out for instance 98.8V = 2V less than 100.8V.

For instance i've ridden my RS for only 850km but after charging to 100% eucw app says it has 99.9V i know nothing is wrong with the batteries as this rapid voltage deterioration has always happened with my gotway wheels: In a matter of a few 1000km it drops voltage quite fast and then more or less settles 1-2.5V under factory setting. It still goes down in voltage after that but only 0.1-0.2V every 1500km or so. 

A few years ago i saw my Tesla's voltage had dropped from 84.4V to 82.2V or something like that, i took the batteries to a friend who has worked with lithium ion for years and he tested the individual cells and although he could detect wear on all of them none were fried, nor did they need replacement in his opinion.

But honestly if anyone is in doubt as to the health of their batteries don't listen to some guy online. Go to an expert - you don't want them going up in flames. 

Edited May 9, 2021 by xiiijojjo

[Tawpie]

On 5/7/2021 at 6:40 PM, r_713 said:

This entire time I've been recharging my batteries to 100% after every ride

I believe this is the correct thing to do with 1 minor modification. Charge to 100% plus an hour or so BEFORE each ride, not after. Reasoning is that Li Ion suffers chemical degradation when it’s at or near fully charged, so you want to spend as little time there as you can. BUT you do want to charge to full+hour or so to balance the individual cells in the pack, and do this regularly (every time!). Failure to balance will accelerate the death of weak cells (there is always a weakest link).

By charging to full+balance before you ride, you get the benefit of balancing while minimizing the time spent at full charge allowing you to minimize the chemical degradation.

As to the current state of your battery, I highly doubt your charging program has anything to do with it and I’d consult with your reseller. Batteries usually only have a 6 month warranty from the time they leave the factory, so you’re probably well beyond that, but your drop off seems larger than I’d expect.

Edited May 10, 2021 by Tawpie