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Tesla owners, squeezing in a 21700 battery pack, possible?


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15 hours ago, alcatraz said:

What do you mean by "load balancing"?

I suspect the board pictured isn't the whole bms. There doesn't seem to be enough space for the balancing circuits. Maybe this board acts as a junction and connects the two packs together as one pack, but that there is another board internal somewhere.

The FETs on the board pictured look to be for switching in and out of charge mode. The smaller red lines look to be charge rails. Doesn't look to be anything actively regulating the charge rails. The board pictured is too simple for that. They could possibly have put another PCB in the packs that uses a passive balancing approach. Such an approach would bleed off excessive charge with a weak cell through a resistor. Would have to open one of the battery packs to know. Measuring the voltage and current of the charge rails would confirm a few things about the design.

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And here it is. An original tesla v2 with 1480Wh from the factory. ~20kg

I have received my new gotway tesla v2 1480wh! Bare with me as I am a newbie and had to learn how to ride it first before i can do some proper testing! Day 5 and I am feeling pretty comfortable on it.

Hello guys, found this thread interesting... so I asked that store you got these pictures from, a few questions about it. here are some info i got from them. hope this helps... for the curious...

Posted Images

4 minutes ago, LaserEdge said:

The FETs on the board pictured look to be for switching in and out of charge mode. The smaller red lines look to be charge rails. Doesn't look to be anything actively regulating the charge rails. The board pictured is too simple for that. They could possibly have put another PCB in the packs that uses a passive balancing approach. Such an approach would bleed off excessive charge with a weak cell through a resistor. Would have to open one of the battery packs to know. Measuring the voltage and current of the charge rails would confirm a few things about the design.

You need to change your profile pic to the Energizer Bunny.

Edited by ND4SPD
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12 hours ago, Marty Backe said:

You can tell all that from a couple of pictures :confused1: Impressive

Ask me in a few years how my Tesla V2 is doing and if it burned up in a fire :)

500 or so charge cycles would definitely prove the design.

Doubtful it will cause a fire for just you. If the battery packs aren't getting very hot during charging or frequent heavy breaking whatever design they have is good enough.

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37 minutes ago, Marty Backe said:

I know people who have over 8000-miles on a particular wheel which is nearing end of life. About 175 charge cycles.

In my estimation, most people don't ever accumulate near 200-cycles let alone 500.

Personally, I've never come close to 50 on any of my wheels.

People spend way to much mental energy worrying about or contemplating EUC batteries.

Good point. If a wheel is only going to get 200 or less charge cycles for the lifetime the design, the BMS isn't as important as other parts of the system. Really just need something to charge the batteries without them getting very hot. The other main aspect of BMS focuses on increasing the life span of the batteries by balancing the charge and drain. As you point out not really a concern for the typical usage of a wheel. A highly stressed li-ion battery by a poor BMS will likely yield around 300 charge cycles. An average BMS will yield around 500+ charge cycles. A great one over 1000+ charge cycles.

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5 minutes ago, LaserEdge said:

Good point. If a wheel is only going to get 200 or less charge cycles for the lifetime the design, the BMS isn't as important as other parts of the system. Really just need something to charge the batteries without them getting very hot. The other main aspect of BMS focuses on increasing the life span of the batteries by balancing the charge and drain. As you point out not really a concern for the typical usage of a wheel. A highly stressed li-ion battery by a poor BMS will likely yield around 300 charge cycles. An average BMS will yield around 500+ charge cycles. A great one over 1000+ charge cycles.

its important for the guy you sell it to haha.. people dont just toss their eucs in a river when they want to upgrade.. ive sold multiple wheels with 150+ charge cycles, i have had a lot of smaller wheels that i would charge and ride every day.... however if youre talking FULL charge cycles, then thats going to take a long time to get to...... but all wheels unless they come to a horrific end will get there eventually lol

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24 minutes ago, Rywokast said:

its important for the guy you sell it to haha.. people dont just toss their eucs in a river when they want to upgrade.. ive sold multiple wheels with 150+ charge cycles, i have had a lot of smaller wheels that i would charge and ride every day.... however if youre talking FULL charge cycles, then thats going to take a long time to get to...... but all wheels unless they come to a horrific end will get there eventually lol

My concern (if I was concerned :)) is with the wheels I own. Once they're out of my hands it becomes an absolute "I don't care".

Yes, I was referring to full charge cycles.

But I still think wheels eventually collect dust and end up in the landfill. The guy that puts 10,000-miles on an EUC has used it up and if it has much more life it'll probably be for training purposes by a newbie. Wheels get old and out of date. Someone getting into EUC's isn't going to want to ride a 3 to 5 year old wheel for very long.

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6 minutes ago, Marty Backe said:

My concern (if I was concerned :)) is with the wheels I own. Once they're out of my hands it becomes an absolute "I don't care".

Yes, I was referring to full charge cycles.

But I still think wheels eventually collect dust and end up in the landfill. The guy that puts 10,000-miles on an EUC has used it up and if it has much more life it'll probably be for training purposes by a newbie. Wheels get old and out of date. Someone getting into EUC's isn't going to want to ride a 3 to 5 year old wheel for very long.

i guess by that point pretty much everything on the wheel will start going anyways haha... thats just another good reason to always go with the biggest battery version, because really small eucs its so easy to just fully drain them every day like the V5F or lower spec KS14D... i think on those you would see serious battery degradation way before any other components started to show signs of wear

Edited by Rywokast
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20 minutes ago, Rywokast said:

i guess by that point pretty much everything on the wheel will start going anyways haha... thats just another good reason to always go with the biggest battery version, because really small eucs its so easy to just fully drain them every day like the V5F or lower spec KS14D... i think on those you would see serious battery degradation way before any other components started to show signs of wear

Agreed. I wonder how many full cycles I'll ever get on the Sherman?

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8 minutes ago, Marty Backe said:

Agreed. I wonder how many full cycles I'll ever get on the Sherman?

check back in four years haha, that thing better last a loooooooong time

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One way of determining the quality of the BMS would be to get the modded Tesla V2 to low charge (under 20%) and measuring the top speed as charge decreases. Create a graph from the data. Repeat the experiment with an unmodded Tesla V2 and compare the data. Such a test could make for an interesting video.

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3 hours ago, LaserEdge said:

Had a long back an forth with Pingouin today over PM. He opened one of the battery packs to his 1480Wh Tesla V2.  I will summarize our findings.

  • The 1480Wh Tesla V2 is using a passive battery management system.
  • We confirmed that the 1480Wh Tesla V2 only has one BMS for both battery packs. The passive charge balancing is done on the on the PCB already pictured in this thread.
  • The configuration of passive balancing is 20s4p meaning there are 20 sets of 4 Li-ion cells connected in parallel which are connected in series. For each BMS in a 1020Wh Tesla V2 it uses a configuration of 20s2p meaning 20 sets of 2 cells in parallel wired in series.

So what does this mean? Having a BMS per battery pack has one significant advantage, it will increase the peak charge voltage achieved with each full charge overtime versus the design with just one BMS. The 1480Wh Tesla V2 will reduce its peak charge voltage with each successive charge cycle faster than a 1020Wh Tesla V2. Another advantage the two BMS design has is that the 1020Wh Tesla V2 will charge and discharge balance faster since the number of cells in parallel is smaller. Passive BMS designs don't load balance across the cells wired in series, only those cell which are in parallel. An advantage that the 1480Wh Tesla V2 configuration has is better ability to handle dead cells since it has more cells wired in parallel. Considering this point the 1480Wh Tesla V2 batteries should give more total charge cycles.

I am curious if anyone has tried a faster charger with the 1480Wh Tesla V2. One potential issue is that the higher number of cells in parallel could potentially indicate charging is finished when in fact the cells need time to load balance. To confirm use the faster charger and let the wheel charge to the point the charger says it is full. Unplug the fast charger. Check the charge level with an app. Wait for an hour. Check the charge level again. If the charge level went down it means the cells were not 100% full charged due to charge balancing issues.

Driving differences:  Besides the peak charge voltage I don't think anyone is going to notice much difference. I don't see any fire hazards with this single BMS design.

Well that is a summary of what we discovered. I will leave it to Pingouin if he wants to share the pictures. They are his pictures after all.

If you watch Marty's range test of his Tesla V2 , he said he has used his fast charger  on the Tesla V2 3 times already.

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32 minutes ago, newbie101 said:

If you watch Marty's range test of his Tesla V2 , he said he has used his fast charger  on the Tesla V2 3 times already.

this would be like over hundreds of charges though, not a few

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Hey guys, it has been some time since I've been on this thread.

I have a 1480Wh V2 Tesla that I bought from Wheel riders store on Aliexpress. I asked them if they have a photograph of the BMS and they kindly sent a photo straight away.

I have no real knowledge of this stuff so thought I would post on here to help some of you get some answers.

Their answer when I asked them how many BMS's are in the wheel:

"There's only one BMS including 1020wh." 

Not sure I quite understand, maybe broken English??

H197016954f8d468d95105d6cc986adb0f.png

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1 hour ago, RyanEUC said:

Their answer when I asked them how many BMS's are in the wheel:

"There's only one BMS including 1020wh." 

Not sure I quite understand, maybe broken English??

H197016954f8d468d95105d6cc986adb0f.png

The big PCB is just for connecting/"mounting" the li ion cells. The small board is the BMS connected to the bigger pcb.

12 hours ago, LaserEdge said:

We confirmed that the 1480Wh Tesla V2 only has one BMS for both battery packs. The passive charge balancing is done on the on the PCB already pictured in this thread.

Only one BMS for two such battery pcb's would mean that each 2p cell pair is paralleled to the corresponding 2p cell pair on the other battery pcb.

Such a design (if this is true) is absolutely inappropriate and dangerous!

At least once these cells age there will be much tio high equalizing currents flowing through the thin pcb traces and balancing wires.

Each such battery pcb needs its own small BMS pcb. And both need a communication wire like gw, ks, ... uses.

Ps.: Sorry - did not read the rest of the topic - why is @LaserEdge stating a 1480Wh 20s4p and why wheel riders store states one BMS per 1020Wh?

Edit: just seen it now - each pack seems to be a 10s4p pack and both packs put in series. So one extra BMS is absolutely fine!

Edited by Chriull
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24 minutes ago, RyanEUC said:

Hey guys, it has been some time since I've been on this thread.

I have a 1480Wh V2 Tesla that I bought from Wheel riders store on Aliexpress. I asked them if they have a photograph of the BMS and they kindly sent a photo straight away.

I have no real knowledge of this stuff so thought I would post on here to help some of you get some answers.

Their answer when I asked them how many BMS's are in the wheel:

"There's only one BMS including 1020wh." 

Not sure I quite understand, maybe broken English??

H197016954f8d468d95105d6cc986adb0f.png

Thanks for the pic RyanEUC. Hard to tell from just looking at one side of that PCB. I am guessing the other side has another set of 20 pads to connect to the cells. There should be markings for B11 through B20.

Must be broken English. The 1020Wh Tesla V2 didn't change BMS design. The same Gotway BMS PCB is used for all of the 84V battery packs.

 

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45 minutes ago, Chriull said:

The big PCB is just for connecting/"mounting" the li ion cells. The small board is the BMS connected to the bigger pcb.

Only one BMS for two such battery pcb's would mean that each 2p cell pair is paralleled to the corresponding 2p cell pair on the other battery pcb.

Such a design (if this is true) is absolutely inappropriate and dangerous!

At least once these cells age there will be much tio high equalizing currents flowing through the thin pcb traces and balancing wires.

Each such battery pcb needs its own small BMS pcb. And both need a communication wire like gw, ks, ... uses.

Ps.: Sorry - did not read the rest of the topic - why is @LaserEdge stating a 1480Wh 20s4p and why wheel riders store states one BMS per 1020Wh?

Pingouin from France owns one of the 1480Wh Telsa V2. He opened one of the battery packs and took pictures. He sent the pictures to me via PM. He hasn't posted them in this thread. From his pictures and the information he shared over PM I was able to determine the configuration of the BMS is 20s4p with the 1480Wh design. For the 1480Wh design there is definitely only one PCB for both battery packs. That PCB has both the charging cutoff FETs and the charge balancing resistors.

I agree as the cells age the equalizing currents between the cells increase. Based on the pictures I saw from Pingouin the equalizing currents are not flowing through the PCB. The PCB is only handling 4.2V charge shunting, overvoltage and undervoltage. The equalizing currents is being handle from the way they have wired the cells in the battery packs.

Edited by LaserEdge
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To be clear the PCB RyanEUC has shown is totally different than the one Pingouin showed me. It is likely Pingouin has an earlier design of the 1480Wh Tesla V2.

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15 minutes ago, LaserEdge said:

I agree as the cells age the equalizing currents between the cells increase. Based on the pictures I saw from Pingouin the equalizing currents are not flowing through the PCB. The PCB is only handling 4.2V charge shunting, overvoltage and undervoltage. The equalizing currents is being handle from the way they have wired the cells in the battery packs.

I edited my previous post, as it was hasty and wrong.

The new pictures show 10s4p packs! So there are no equalizing currents in paralleled cells via the BMS and so everything ok!

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7 minutes ago, Chriull said:

I edited my previous post, as it was hasty and wrong.

The new pictures show 10s4p packs! So there are no equalizing currents in paralleled cells via the BMS and so everything ok!

That's what I am thinking. The PCBs Ryan is showing has one central PCB for the BMS, the small one with the ASICs and the FETs. The other PCB is for wiring the cells in 10s4p configuration. Each battery pack will have one of those larger PCBs. Yes, no equalizing currents will flow through the BMS PCB, only the larger PCB shown. I agree such a design should be fine.

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For those who would like to know, rather than worrying about the internals;) I will just give an update on the wheel and my experience so far.

I'm on my 4/5th charge and I am on 400km, it has been great fun so far. This is my first wheel but its defiantly not going to be my last.! I'm Hooked!  I see no better way of getting around the city. The Tesla has awesome speed and handling for what I need and for where I live right now, having that extra battery has defiantly not made me ever worry about range either. I will keep you posted on the battery but I'm not too worried. I keep a good eye on it while charging and if it catches fire while riding, I'm not too worried about. :D  

 

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I only have 225-miles (360-kilometers) on mine. It's been behaving great. It's a keeper :thumbup:

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I've done 100 km so far on my Tesla V2 1480wh from wheel riders store as i'm still learning. 

I fully charged it today and monitored the watts from the outlet and noted the watts the charger consumed without being plugged into the wheel. With my 5a fast charger I got from wheel riders store it seemed to balance charge for a couple of hours (this was after the light on the charger itself turned green) until a steady non-declining watt consumption of about 4 watts. Then I plugged in the standard charger and noticed that it consumed 10 watts of power declining down to 2 watts within an hour or so. Is this an indication that my fast charger doesn't balance as much/all the way and that my stock charger does?

At the end of both charging with my fast and stock charger, my EUC World app read 84.0V from the Tesla.

Edited by Simon Møller Kristensen
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