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Video on 80% charging, "Good or Bad?"


mrelwood
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6 hours ago, mrelwood said:

I finally got this video made. I hope that the crucially important information spreads better this way.

 

 

Hey Mr Elwood!

That is a great video and easy to understand.

The ninebot Z6/8/10 has a smart BMS where You can always check the voltage of all the cells in parallel. Does a smart BMS always charge "smart" so that the the cells are actively balanced in the charging process or should I also charge to 100%? I do not like charging to 100% because I have to go down a steep hill after exiting my house.

My Nikola by 1Radwerkstatt has a smart BMS by Xiaoxiang. The voltage difference is at 0,013V after interrupting the charging process at 80%. But it is the same after leaving it plugged in for 60 minutes at 100%. Is that because of the BMS or because of the good health of the battery?

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1 hour ago, Boris Lämpel said:

Does a smart BMS always charge "smart" so that the the cells are actively balanced in the charging process 

Smart is a marketing term telling one absolutely nothing about the BMS capabilities.

I have not heard of any EUC BMS doing active balancing. Just one description of an Onewheel sounded like it does active balancing.

1 hour ago, Boris Lämpel said:

or should I also charge to 100%?

Yes. Ninebot definitely has no active balancing. Their "smart" means they show cell voltages and do joule counting.

1 hour ago, Boris Lämpel said:

I do not like charging to 100% because I have to go down a steep hill after exiting my house.

Or as long as your cells are balanced with less charges it's ok, too!

Balancing of balanced cells is useless! ... And the BMS will not start balancing anyhow if cells are equal...

Otherwise do full charges and ride some short distance uphill or ride some minutes around the house.

1 hour ago, Boris Lämpel said:

My Nikola by 1Radwerkstatt has a smart BMS by Xiaoxiang. The voltage difference is at 0,013V after interrupting the charging process at 80%

That's great! So such xx% charging is absolutely ok if one can ensure equal cell voltages! Once they differ one should charge full and by this balance the battery again.

1 hour ago, Boris Lämpel said:

Is that because of the BMS

The BMS (most likely) does more or less the same passive balancing and other protection measures as every other BMS. It just has the additional very important cell voltage measurement and reporting!

But if you are interested in details ask 1radwerkstatt - they'll know. ;)

Btw - if you like you can once write a small review about this bms. It was just once announced that 1radwerkstatt offers them but since that nothing was heard of it again....

1 hour ago, Boris Lämpel said:

or because of the good health of the battery?

That's the good health of the cells!

Imho well matched high quality cells are the most important point.

There is no study how much balancing helps/can help. It seems from experience that not balancing can prematurely destroy batteries, while balancing keeps the pack healthy.

How much/long balancing can keep not so well matched not so high quality cells alive is not really known.

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Great video! It makes a good case with the description of risks involved.
Some feedback: it might be more correct to describe that the BMS today monitor "each cell group" instead of "each cell".

I hope that the BMS monitoring each cell will become a thing however, and it will become even more feasible with fat cells.

Then a 24s6p battery would have a different topology, more like 4x 24s1p packs in parallel.
That way, a single bad cell would not be able to destroy a whole group, and a dead cell could only downgrade a 6p battery into a 5p battery.

I guess that today we have 2x 24s2p for 24s4p wheels, 3x 24s2p for 24s6p wheels.
It's already better than the single packs as found on electric scooters.

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3 hours ago, Boris Lämpel said:

My Nikola by 1Radwerkstatt has a smart BMS by Xiaoxiang. The voltage difference is at 0,013V after interrupting the charging process at 80%. But it is the same after leaving it plugged in for 60 minutes at 100%. Is that because of the BMS or because of the good health of the battery?

This BMS is very configurable.

If I remember correctly, you can choose at which voltage balancing starts to occur which means you could have your packs balancing sufficiently for 80% charges.
Going even further, you can enable balancing even when not charging so your pack will remain balanced no matter what - at the expense of some battery drain.

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My 16s does not show a loss of range yet with 4200 miles on it. It doesn't sit empty, and is charged up full prior to riding. 

My MCM5 has been used the same way and it has about 4k miles on it, also no noticable loss of range. This wheel reports low on the voltage by about 1.5 volts, however the pack reading on meter is 83.8 so within the tolerance of error. It's stayed like this since new.

I'm using my RS the same way, not having it sit full, and a full charge prior to riding. 

I'm happy I saw some of this info about 80% charging a long time ago when my 16s only had about 250 miles on it. I bought a rapid charger for it when new specifically to preserve the battery. Once I saw what could happen from not balancing I stopped charging to 80% for my commute.

Great video!

 

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5 hours ago, meepmeepmayer said:

:thumbup:

Rename the title to "Electric Unicycle: 80% Charging, Good or Bad?" so new people who look for electric unicycle stuff find it more easily. "EUC" is too obtuse unless you already know what it means.

Good idea! Done.

15 minutes ago, Richardo said:

@mrelwood how did you make the animations in this video? im impressed.

Thank you! Final Cut Pro X with just a free explosives pack and lots and lots of time keyframing! The black charging table I actually coded on Reaper (audio workstation), since that’s the only software I knew how to make it with! :roflmao:

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5 hours ago, Paul A said:

KS18XL

3 years

14787 km

223 rides

Charged to 100% after each ride

Batteries are fine.

Not one problem ever.

Only one tube replaced.

Still original tyre.

That is one respectable amount of distance!

 It’s interesting though, your detailed data shows it so clearly: ~15k km = 223 rides, meaning you’re probably not even past 150 full li-ion charge cycles yet. 150 cycles should absolutely be no problem at all to li-ion batteries, yet we cheer the batteries for such an achievement.

And 80% charging was supposed to double/triple the cycles from the expected 300-600. So you’re not even halfway there of having normal 100% charging decrease the capacity to 70% from the original.

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So far I have been unable to put more than 3500 miles on a wheel without getting another one. I'm sure once the new crop of wheel are available with out delays and the 1st draft issues are solved I'll be ready to get another one again. By then I'll probably have 3500 to rk miles on the RS which so far has been fine and has 1500 miles on it. I do avoid water like I'm allergic to it but ride on a lot of dry dusty trails. The I'll be happy if I hit 4k miles on the original bearings. 

I don't think even hitting 10k miles on wheel in my future unless they just stop making them and I have keep what I have. A 10% loss of range wouldn't be very noticable since I take rides longer then 30miles most of the time. 

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@Flying W

There's still tread on it, but think will change the tyre anyway at 15k km.

It's a Chao Yang H-5102 tyre if that means anything.

Have always checked pressure before every ride and inflated to 38 psi.

Never used any other tyre so have no idea if it's good or not, seems ok though.

Have had car tyres usually lasting 50k km, so was actually expecting the same for the EUC tyre.

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3 hours ago, ShanesPlanet said:

Why give up range and or safety to increase a number that is by far NOT the biggst concern?

Exactly! Even without the balancing issue, 80% charging would sacrifice more than 20% of the range for the first 30000 miles in order to have 10% more range after 30000 miles. Ridiculozzio!

Whichhowever one puts it, 80% charging Does. Not. Make. Any. Sense!

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1 hour ago, Paul A said:

Have had car tyres usually lasting 50k km, so was actually expecting the same for the EUC tyre.

EUC tires are very much not car tires! A better reference might be half of the life of a bicycle tire.

The H-5102 doesn’t really have any tread pattern anyway, so I wouldn’t be surprised if it was the most long lasting factory install tire on any EUC. Usually an EUC tire is worth replacing at 3000-6000 miles.

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Very informative video! Few questions though:

  • What would be needed by manufacturers to report individual battery voltage? and would that make the internal electronics and wiring vastly more complicated?
  • Would charging to 100% affect available braking?
  • I seem to remember watching a video on Tesla default charging to 80% unless you indicate you're going for a long trip? I don't have a Tesla so can't check but wouldn't they be governed by the same issues.
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59 minutes ago, mrelwood said:

Since the packs are usually built by a different instance than the mainboard, they would have to come up with a standard of communication.

Especially with communication without vampire drain like the ninebots showed - once the wheel is off cell voltahe transmission has to stop, too...

Quote

 Even the BMS having it’s own separate BT connection would be much better than nothing, and it is already available on some (non-EUC) BMS’s.

Afair this is the way @1RadWerkstatt 's BMS work - so they can be used without mainboard support.

I just wonder how the communication betwen the packs work, so that both cut off charging once single cell overvoltage triggers?

 

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@Paul A I get about 2k miles on the 16 for a tire, 1200 miles on the mçm5 and I think I'll maybe eel out 2k miles on the RS. 

I could go longer on the RS but once dirt traction gets noticably lower I need to change it. That wheel is off road about half the time. The mçm5 gets a lot of use at low speed doing spins and practicing 180 to reverse kind of stuff so the tire is getting ground into the pavement a lot. I also think the trade depth on the smaller wheels is less too. 

I'm envious of your mileage haha!

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On 9/24/2021 at 8:08 PM, supercurio said:

This BMS is very configurable.

If I remember correctly, you can choose at which voltage balancing starts to occur which means you could have your packs balancing sufficiently for 80% charges.
Going even further, you can enable balancing even when not charging so your pack will remain balanced no matter what - at the expense of some battery drain.

You are completely right. I just checked it today. The balancing starts at 60% and is also active when I do not charge. - until balanced is completed.

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On 9/24/2021 at 9:46 AM, mrelwood said:

All you need to know about 80% charging:

very nice video ! at first i thought wtf so much effort for that ol saying. I mean its true for devices without BMS sooo u could easily mistake it also for your euc. I´m and electrician and did it the first 10ish cycles. luckily I read that I shouldnt do this because of the BMS. very very interesting to hear :+1: 

would be interested in what happens when the cells are fully outbalanced and the charger is still plugged it? would there be some kind of bypass?

On 9/24/2021 at 9:46 AM, mrelwood said:

 

 

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