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EWheels 84v Fast Charger Review


Marty Backe

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21 minutes ago, Marty Backe said:

the KingSong app can be trusted. The steadiest measurement can be had by laying the wheel on it's side and then turning on the wheel.

Thanks, great advice... once the blasted factory app is available again! But I'm not needing every available W from the battery at this point, so mute for now. Am trying to better understand battery behavior and best charging practice.

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8 hours ago, gonnabiff said:

Ah, so perhaps every 10 charges leave charger connected overnight even though the charger light has turned green?

And I don't really understand "balance." Can the cells be balanced at a voltage less than their design capacity? I.e, if deliberately charged to only 80 or 90% of max voltage, for instance, but current is supplied at that voltage for many hours?

Leave it overnight or just for a few hours extra during the day. Personally I prefer not to leave stuff running overnight for safety reasons.

To be clear I am not a battery guru but to balance cells at a lower voltage would (I think) require a specialist BMS that would shunt power around the charged cells at a lower than normal voltage allowing the undercharged cells to catch up. This normally happens at 4.2v.

If you really want to understand the charging characteristics of your wheel I thoroughly recommend getting a Charge Doctor (you can buy in the US from eWheels.com). It doesn't just cut off charging at premature levels to help with longevity it also allows you to record and graph the charge cycle. This is how I know that the V8 only uses 82% of it's total available cell capacity. It has also allowed me to accurately determine a voltage for cutoff at certain charge levels (% charge of total capacity not the wheel reported capacity). I recorded charge data for both the original charger and the eWheels V8 fast charger to see how charging at higher amps shifts the charging graph and transition from increasing volts/constant current to constant volts/decreasing current. In 6 months I will repeat the process to see how much capacity has been lost through aging. It is a cool device.

Also if you want to understand Li-Ion batteries more be sure to check out batteryuniversity.com

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From the fantastic resource http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries

• 75–>65% SoC (state of charge) offers longest cycle life
• EVs use 85–>25% SoC to prolong battery life
• 100–>25% SoC gives long runtime, makes best use of battery, but reduces battery life.

(Of course) only a full cycle provides the specified energy of a battery. With a modern Energy Cell, this is 250Wh/kg, but the cycle life will be compromised. All being linear, the life-prolonging mid-range of 85-25 percent reduces the energy to 60 percent and this equates to moderating the specific energy density from 250Wh/kg to 150Wh/kg.

Also, worst thing you can do to degrade Li lifetime is store at full charge at high temperature. The article says our laptop and cell phone chargers should have two modes: routine charge to 85%, then a user-selected top-off to 100% prior to anticipated requirement for full capacity. Except we obsolete these devices well before the battery is significantly degraded.

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

This article does not use the term "balancing." Is "saturation" phase the same as balancing? And no mention there of periodic 100% to-end-of-saturation charging prolonging battery longevity.

Good to know that, "Charging lithium-ion batteries is simpler than nickel-based systems." Seems plenty complex to me, optimizing charge time vs. capacity vs. battery longevity vs. safety.

Well, I appreciate that with forum wisdom at least I am making informed choices. And how wonderful that a fast charge to 85% (stopping prior to saturation phase) minimizes charge time while maximizing battery lifetime with cost of relatively small hit on runtime for that charge. One can plan for the max rides that need max capacity.

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Balancing the pack is not about longevity (quite the opposite as you stress the cells quite heavily with a full charge) but what it does is ensure that no one cell becomes the weak link in the chain. If one cell had an imperfection or had aged quicker resulting in a higher resistance it would not charge as fast as the rest. With each partial charge the difference between that cell's voltage and all others would increase. This results in less than optimal capacity and the potential to ruin the pack by having one cell drop so low that the BMS shuts the entire pack down for safety (cells that go too low become dangerous and must not be recharged).

Also note that most of the info on Battery University refers to tests on a single cell rather than many in serial. This is why there is little mention of balancing as this only relevant in multi-cell setups.

I don't think saturation is the same as balancing. I understand saturation is the period where the cell has attained max voltage but still has available room for more charge. This is the period where the voltage is kept at a constant 4.2v/cell but the supplied current is decreased allowing that last bit of available capacity to absorb the power (saturate) without overvolting the cell (bad).

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1 hour ago, gonnabiff said:

Also, worst thing you can do to degrade Li lifetime is store at full charge at high temperature. The article says our laptop and cell phone chargers should have two modes: routine charge to 85%, then a user-selected top-off to 100% prior to anticipated requirement for full capacity. Except we obsolete these devices well before the battery is significantly degraded.

My wife had a Sony Vaio laptop which is the only one I have ever seen that offered a battery saver option that only charged the battery to 50%. You could, when desired, turn it off for a full charge when travelling. 50% was plenty for sofa surfing at night. During the day she worked on it at a desk plugged in. The battery lasted a very long time so it certainly worked and this was a laptop where you could replace the battery easily by just pulling it out. We both now have Microsoft Surface devices (Pro 4 and Book). Replacing the battery on them is very difficult and risks cracking the screen yet they don't offer any battery saver option. Highly annoying!

Anyway. I fear we have derailed this thread. Perhaps any further conversation should be in its own post.

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1 minute ago, Jason McNeil said:

To improve safety, I've been on Gotway's case about putting in a reverse diode on the charging input, as all the other mainstream manufacturers have. Their argument against doing this is that it introducing a small amount of resistance; on the 67.2v system, it's 1.2v, which is why the measured voltage on a King Song will not exceed 66v on a fully charged battery.  

What a sad state of affairs.

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  • 4 weeks later...
5 hours ago, esaj said:

A friend of mine has a 67.2V fast charger without a voltage/current display that he bought along with a KS16 from Jason a couple years back (from the UK-store back then), it gave out something like 65.x V (probably closer to 66V, don't remember exactly) when I measured it. In that case, the charger had trimpots (trimmer potentiometers) inside for adjusting the maximum voltage, maximum current, the red/green led switch-point and fourth one for something... don't remember what, I think I figured it out back then when I was fooling around with it, could have been adjustment for when the fan turns on. Not sure if it came like that from the factory or if the pots had wandered off a bit over time, although I doubt they would turned over half a turn on their own (usually the trimpots have at least 10 turns from end-to-end). I adjusted it actually ever-so-sligthly above 67.2V (something like 67.25V if memory serves) when it was set 100% charge. So technically slight overcharge, but it's only 67.25V / 16 cells = 4.203125V per cell, I just wanted to make sure the balancing kicks in. Don't know if it has never hit the actual balancing over the lifetime of the wheel (over 1 year at that point), I doubt even KS's have active balancing and just rely on shunting the current past a fully charged cell.

From Marty's video, I didn't notice any trimpots inside the charger, so don't know if those are adjustable or if they just rely on component tolerances not to wonder off too far and the output is completely reliant on non-adjustable components. Could be that they were just out of view in the video, on the other end of the board, as the NTC is placed at the AC-side. In general, the entire board of that charger seems much simpler than the 67.2V charger my friend had.

The one thing that this charger has in common with your friends is that it under-charges. I haven't bothered to measure the voltage but I can only get a ~97% charge on any of my wheels. I don't always use this charger (certainly not for the last couple of months) so they get their periodic 100% charge with the supplied wheel charger. I don't recall if their are any potentiometers on the board. Maybe I'll take a look later.

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  • 2 months later...
On 11/26/2017 at 7:04 AM, esaj said:

t), I doubt even KS's have active balancing and just rely on shunting the current past a fully charged cell.

according to the ks-18 manual

”after charging,  the protection circuit will perform flow equilibrium” 

i was thinking that was balancing.

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6 minutes ago, novazeus said:

according to the ks-18 manual

”after charging,  the protection circuit will perform flow equilibrium” 

i was thinking that was balancing.

Yes, it is...

Esaj is just talking about different balancing techniques....

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if it does, might be hope for my ks wheels afterall. i ran them to 70% and no change, still 90 and 93. i’m gonna run them to 60 and try that. i’m only running them that low thinking it will help balance. we’ll see.

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  • 2 months later...
On ‎7‎/‎6‎/‎2017 at 5:58 PM, Marty Backe said:

@Jason McNeil at EWheels.com is supplying an 84v Fast Charger, for free, with all the 84v Gotway wheels that he's selling. As of early July. That may change over time of course.

When I bought my MSuper V3s+ from Jason this charger was included in the box, along with the Gotway supplied charger. Here's my overview:

 

They aren't included free anymore.  I paid $100 extra for mine.  Got the wheel today, just waiting for the fast charger shipment.

Edited by Joe Holliday
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  • 1 year later...
On 11/26/2017 at 12:40 PM, Marty Backe said:

The one thing that this charger has in common with your friends is that it under-charges. I haven't bothered to measure the voltage but I can only get a ~97% charge on any of my wheels. I don't always use this charger (certainly not for the last couple of months) so they get their periodic 100% charge with the supplied wheel charger. I don't recall if their are any potentiometers on the board. Maybe I'll take a look later.

this is my concern as well, i've no idea if it's going into balance mode.

for one of my wheels, once it stops charging, a few hours later

wheellog reports 65.2 (94%)

and darkness bot app reports 65.2 (89%)

all my wheels have been used and everyone of them came with either the 4th or 5th gen ewheels "smart" charger. at first i thought i was lucky, but after going thru some damaged batteries, i think i'd rather have the dumb charger

 

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4 hours ago, someguy152 said:

this is my concern as well, i've no idea if it's going into balance mode.

for one of my wheels, once it stops charging, a few hours later

wheellog reports 65.2 (94%)

and darkness bot app reports 65.2 (89%)

all my wheels have been used and everyone of them came with either the 4th or 5th gen ewheels "smart" charger. at first i thought i was lucky, but after going thru some damaged batteries, i think i'd rather have the dumb charger

 

Since I originally wrote this, over 2-years ago, I use the stock chargers 98% of the time. I only use the fast charger on some periodic group rides where we need to charge midway through a long ride.

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4 hours ago, someguy152 said:

this is my concern as well, i've no idea if it's going into balance mode.

for one of my wheels, once it stops charging, a few hours later

wheellog reports 65.2 (94%)

and darkness bot app reports 65.2 (89%)

all my wheels have been used and everyone of them came with either the 4th or 5th gen ewheels "smart" charger. at first i thought i was lucky, but after going thru some damaged batteries, i think i'd rather have the dumb charger

 

do you not still have the factory charger? I would plug it in with the factory charger and leave it on green all night

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i think im gonna buy this charger. i couldn't find ewheels shenzen fuyuandian charger on aliexpress or ebay nor do i want to spend 3x as much for what should be a $15 to 20 charger with free shipping

https://www.aliexpress.com/item/4000101621951.html?spm=a2g0o.productlist.0.0.7e5a6628KRP54t&algo_pvid=ad206e20-45e9-4987-b050-feeb88269f17&algo_expid=ad206e20-45e9-4987-b050-feeb88269f17-1&btsid=0ab6f82315854997880923366e26d4&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_

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On 3/29/2020 at 1:28 PM, someguy152 said:

i think im gonna buy this charger. i couldn't find ewheels shenzen fuyuandian charger on aliexpress or ebay nor do i want to spend 3x as much for what should be a $15 to 20 charger with free shipping

https://www.aliexpress.com/item/4000101621951.html?spm=a2g0o.productlist.0.0.7e5a6628KRP54t&algo_pvid=ad206e20-45e9-4987-b050-feeb88269f17&algo_expid=ad206e20-45e9-4987-b050-feeb88269f17-1&btsid=0ab6f82315854997880923366e26d4&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_

thatll do just fine.. you should do like i did and get some adapters while youre at it.. if you have more than one 67V machine.. its way more convenient than having ten different chargers

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