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V8 88V 21S overvolt mod (balance charged to 86V~90%~10k+ cycles)


alcatraz
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Hi everyone

I'm tempted to run my V8 with a 21s 88V battery. (63 cells internal). BMS is connected to 20 of these grouops. Battery will be charged with balance chargers using an ATX connector to 4.1V ~ 86.1V. I'd then like to try unlocking 31,32,33,34km/h in slow increments, doing at least a few hundred km before going up one more step. Checking for instability.

Has it been tried before? Are there any issues with the motherboard?

Thanks /a

Edited by alcatraz
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O.e

ERROR

I would uh.... NOT try this. If the motherboard wasn't specifically designed to handle that voltage, you'll probably fry it. Even if most of the components on the motherboard can handle it, if the buffer capacitors can't they will literally explode on you. And even if everything in the circuitry is fine and can deal with the 100 volts, the firmware almost certainly won't know what to make of the increased voltage and will most likely give you some odd behavior as it tries to react (or overreacts) to things happening too quickly when it sends a given amount of power to the motor and the motor spins up way faster than it expected it to.

In any case, I wouldn't try this unless you REALLY don't care if you ever get to try riding your V8 again...

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I don't recommend to change stock BMS to something else, because in this case you will get situation when controller will never turn off.

The BMS has data connection with controller, and they exchanging some data between BMS and controller. Thus, any other BMS will make the controller to work not properly.

The first bug that you will get - low battery tiltback, you will not been able to return it to normal position without disassembling V8, you will need to disconnect power cable (XT60) to resolve low battery tiltback. Also it is just not safe for you that the controller will be turn on everytime. 

In Russia we have guy who assembled many 60 cell batteries for V8 (20S3P) with 740-780 Wh capacity, many people use it and all of them really satisfated with it.

I put 80 cells and assembled 20S4P 1050Wh battery for my V8. Now I have about 70 km on one charge.

Regarding cycles.. I used to charge stock battery twice a day (at home and at work), but with new battery I charging it only once in 2 days. So the problem with cycles is not so big as before.

Edited by palachzzz
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19 minutes ago, palachzzz said:

I don't recommend to change stock BMS to something else, because in this case you will get situation when controller will never turn off.

The BMS has data connection with controller, and they exchanging some data between BMS and controller. Thus, any other BMS will make the controller to work not properly.

The first bug that you will get - low battery tiltback, you will not been able to return it to normal position without disassembling V8, you will need to disconnect power cable (XT60) to resolve low battery tiltback. Also it is just not safe for you that the controller will be turn on everytime. 

In Russia we have guy who assembled many 60 cell batteries for V8 (20S3P) with 740-780 Wh capacity, many people use it and all of them really satisfated with it.

I put 80 cells and assembled 20S4P 1050Wh battery for my V8. Now I have about 70 km on one charge.

Regarding cycles.. I used to charge stock battery twice a day (at home and at work), but with new battery I charging it only once in 2 days. So the problem with cycles is not so big as before.

Hey man! Good idea with 80pcs.

How many cells were you able to fit inside the wheel and how many are external?

Aren't you tempted to get 4.10-4.15V reliable charging every time? No matter how old your battery is? It will just start to kill itself after a while.

What if I connect the bms to the 20 groups but have another group left over that it doesn't see. (but the control board and motor does).

I would like to get a safe unlock of 33-35km/h on this wheel which could maybe be helped by supplying 2-3V higher voltage under load to everything. Getting better response.

Futhermore it is possible to squeeze in 63 cells inside the machine.

I realise this is all very experimental. I'm trying to discuss it before trying anything. 

/a

Edited by alcatraz
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37 minutes ago, alcatraz said:

What are the capacitors and mosfets rated for in the V8?

Unfortunately I can only speculate, but I would assume, based on what I know of how electronics manufacturers tend to do things, that you will find them rated for 100V. This would give the components a safety margin over the approx. 84v that a full battery could possibly feed them. But I would never, NEVER try to feed a big honking cap the voltage that's printed on it (or any other electronic component for that matter...). You want to give those suckers a WIIIIDE margin of error, because if they go, you go.

All that said, the DIY spirit rages within me, and it is cheering your idea on and even giving me ideas for the future. Another part of me, however, knows what's coming and is waiting with baited breath. It's waiting for you to go out to test the system and give it that tiny little bit of acceleration that  bumps the voltage just a smidgen too high and either blows one or more MOSFETs or sets off one of the caps like an M80 and sends you hurtling to the ground, neither of which would be good in any way.

I simply can't recommend changing the voltage that you feed into the board. On the other hand, making additional battery packs and strapping them to your wheel in parallel? Go for it! Go for it as fast as you can!

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8 hours ago, alcatraz said:

Hey man! Good idea with 80pcs.

How many cells were you able to fit inside the wheel and how many are external?

Aren't you tempted to get 4.10-4.15V reliable charging every time? No matter how old your battery is? It will just start to kill itself after a while.

What if I connect the bms to the 20 groups but have another group left over that it doesn't see. (but the control board and motor does).

I would like to get a safe unlock of 33-35km/h on this wheel which could maybe be helped by supplying 2-3V higher voltage under load to everything. Getting better response.

Futhermore it is possible to squeeze in 63 cells inside the machine.

I realise this is all very experimental. I'm trying to discuss it before trying anything. 

/a

Everything inside, just posted photos in right topic: 

 

If you want to charge battery to 4.10-4.15, just open charger and adjust output voltage to 82V, and you battery will be never charged to 84 (4.2v per cell) 
You will not get 33-35 km/h using 21S battery.. Simple calculation: 35 km/h / 30 km/h = 1,166. To get safe 35 km/h you need 84V * 1.166 = 98V.
Just one additional cell will give not so much.. 

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7 minutes ago, WARPed1701D said:

will mean the BMS will never balance the cells

Probably I'll surprise you, but the BMS in V8 does not have the balancing function. So it is never balance the cells at 84V, just cut-off at ~4.215V on the highest cell. Also if one (or more) cell go down to 2.8V - V8 will say "please repair" and will turn on red triangle near battery indicator. You can just charge bad cells and use it.

But the good idea - to control from time to time your cells, and balance it if needed. 

Edited by palachzzz
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24 minutes ago, palachzzz said:

Probably I'll surprise you, but the BMS in V8 does not have the balancing function. So it is never balance the cells at 84V, just cut-off at ~4.215V on the highest cell. Also if one (or more) cell go down to 2.8V - V8 will say "please repair" and will turn on red triangle near battery indicator. You can just charge bad cells and use it.

But the good idea - to control from time to time your cells, and balance it if needed. 

WHAT! You most certainly did surprise me!

@Bobwheel can you confirm this? 

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Are you sure the lower cells don't continue to receive charge after the highest cell is at 4.215V? That would work as a balancer too if it were the case.

I really like my V8. Boosted to 33km/h cruising and more range it's a perfect wheel. Being able to go 50km/h is nice for short moments but to be honest it's a pain to lug that extra 5kg around for the few seconds of joy. Not to even go into the risk of creeping the average speed higher and higher. For this reason I'm at peace with maybe topping out at 30km/h if the unlock isn't reliable. Call it a bizarre life insurance.

The wheel isn't that comfy for crazy long rides so I'm good with 60-80 cells. My feet would probably become the limit trying to deplete a 1000wh pack.

21S pack balance charged externally is sounding better and better. I got a source for new LG MJ1 cells for 2usd and _low_ resistance used LG MH1 (like 100mAh less, original v8 batteries) for 1usd.

Edited by alcatraz
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I'm desperately hoping that folks decide to try to mod their V8 to increase the battery capacity because it's something I've wanted to do ever since I bought it, but don't have the technical knowledge to be the first to attempt it.

I agree with @alcatraz  about the V8 being a nearly perfect city wheel.  I just want the extra 250wh to decrease charging frequency and increase battery longevity.  My dream would be that I could simply buy additional batteries and rig them into the current system without too much hassle.  I'm sure it won't be that easy, but that's the hope.  

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On 7/19/2018 at 2:31 AM, alcatraz said:

I'm tempted to run my V8 with a 21s 88V battery. (63 cells internal).

Someone in Korea built a 60 cells V8, he seems to have fit everything in without sacrificing the internal handle. 

10 hours ago, alcatraz said:

I got a source for new LG MJ1 cells for 2usd and _low_ resistance used LG MH1 (like 100mAh less, original v8 batteries) for 1usd.

Are these new cells? I would extremely suspect of these, the current market price for the MJ1 is $3.5, & $2.7 for the MH1 when ordered in qtys of 10,000pcs.

 

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20 hours ago, WARPed1701D said:

WHAT! You most certainly did surprise me!

Ninebote one e plus also does not have a balancing System on the BMS.....so not that surprising…..

Maybe also one of the reason why some cutouts happen on older batterys….cells which are very low on voltage drop a lot on a draw and might trigger the cutout…..

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21 hours ago, palachzzz said:

If you want to charge battery to 4.10-4.15, just open charger and adjust output voltage to 82V, and you battery will be never charged to 84 (4.2v per cell) 
You will not get 33-35 km/h using 21S battery.. Simple calculation: 35 km/h / 30 km/h = 1,166. To get safe 35 km/h you need 84V * 1.166 = 98V.
Just one additional cell will give not so much.. 

Just one Question...wasnt Darkness Bot or wheellog able to "unlock" the V8 to 35kmh at all? At least at some FW versions?

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On 7/19/2018 at 8:31 AM, alcatraz said:

Hi everyone

I'm tempted to run my V8 with a 21s 88V battery. (63 cells internal). BMS is connected to 20 of these grouops. Battery will be charged with balance chargers using an ATX connector to 4.1V ~ 86.1V. I'd then like to try unlocking 31,32,33,34km/h in slow increments, doing at least a few hundred km before going up one more step. Checking for instability.

Has it been tried before? Are there any issues with the motherboard?

Thanks /a

Just a sidenote, if anyone's ever looking the for the "ATX"-connectors for any reason, the actual model series names are:

MOLEX 5556/5557/5558/5559   -  The kind used in motherboard 20- or 24-pin connectors and the 4- or 6-pin extra power feeds for bigger graphics cards and such

MOLEX 8981 - The 4-pin "peripheral" (or "disk drive") connector used to power CD/DVD-drives, older hard disks ("IDE") and disk drives

Just putting it out here, I spent quite a few tedious hours looking for this information a year or two ago  :P

 

 

22 hours ago, palachzzz said:

Probably I'll surprise you, but the BMS in V8 does not have the balancing function. So it is never balance the cells at 84V, just cut-off at ~4.215V on the highest cell. Also if one (or more) cell go down to 2.8V - V8 will say "please repair" and will turn on red triangle near battery indicator. You can just charge bad cells and use it.

But the good idea - to control from time to time your cells, and balance it if needed. 

 

11 hours ago, alcatraz said:

Are you sure the lower cells don't continue to receive charge after the highest cell is at 4.215V? That would work as a balancer too if it were the case.

Exactly, to my knowledge most BMSs used in the wheels seem to "balance" just by shunting (bypassing) the fully loaded cell(s) and allowing to rest to continue charging, but don't know if V8 does something differently (ie. cuts the charging current completely if one goes over or something). What palachzzz means is probably the "real" balancing systems which can do the balancing more intelligently, keeping the cells at same voltage throughout the charging.

As for overvolting, I have no idea how the wheel might react. Some KS's had issues with measuring the battery voltage through a voltage divider, and could detect fully charged battery as "overvolted", so at least there trying to use higher voltage batteries would already be impossible, as the mainboard wouldn't let you. I'm not sure, but EUC Extreme might have at some point overvolted some of his older Gotways, don't remember if it worked out...

 

Edited by esaj
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15 minutes ago, esaj said:

Exactly, to my knowledge most BMSs used in the wheels seem to "balance" just by shunting (bypassing) the fully loaded cell(s) and allowing to rest to continue charging, but don't know if V8 does something differently (ie. cuts the charging current completely if one goes over or something). What palachzzz means is probably the "real" balancing systems which can do the balancing more intelligently, keeping the cells at same voltage throughout the charging.

I hope you are right although this is not how his text reads.

I never expected 'active' balancing in any wheel but considered 'passive' balancing (shunting) to be the bear minimum for a multi-cell pack. If the V8 did not have passive balancing I would be extremely concerned. 

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59 minutes ago, US69 said:

Just one Question...wasnt Darkness Bot or wheellog able to "unlock" the V8 to 35kmh at all? At least at some FW versions?

I think the key word to note there is 'safe' 35kph. Yes wheellog unlocks the V8 to 35kph but I've no desire to use that 5kph on a 2P 800W wheel. Little safety margin left at that speed. 

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8 minutes ago, WARPed1701D said:

I hope you are right although this is not how his text reads.

I never expected 'active' balancing in any wheel but considered 'passive' balancing (shunting) to be the bear minimum for a multi-cell pack. If the V8 did not have passive balancing I would be extremely concerned. 

Yeah, I've never analyzed the actual BMSs, so I don't know for certain. On a quick glance, the common passive balancing mechanism are further divided to non-dissipative and dissipative-topologies, the dissipative (discharging the cell that's at the limit through a parallel resistor) might even be more common than shunting schemes.

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It is not possible to use shunting of any cell for balancing, because they connected by nickel strip, and if you try to shunt one cell you will make short circuit of this cell, and also you will brake main rule of charging Li-ion batteries: do not charge Li-ion batteries using more then 4.2V per cell (for example, if you shunt one cell, you will start to charge 19 cells using 84V, something about 4.42 volt per cell). 

I'd think (could be wrong though) that you could shunt the cell through the BMS, assuming that the current itself runs through the BMS and not "directly" to the cell string, in principle something along the lines of:

SGdvlo3.png

Of course probably normal zener-diodes couldn't be used here, but something more complex, a mosfet acting as load dropping ~4.2V over it? And the switches themselves would likely have to be mosfets too, with a somewhat complex scheme to keep the gate voltages in check. Couldn't be used with high currents and might need switching on and off to keep power dissipation in check, but in principle, I'd believe this to be possible? Complex and somewhat costly, yes, but possible...

From checking the "dissipative balancing" circuits, they indeed seem to just burn off "excess" charge through resistors in parallel:

Passive-cell-balancing-fill-300x296.jpg

Makes me think, why not use the "flying capacitor" active-balancing, it shouldn't be much more costly or complex? Haven't checked the prices on the control chips though, the difference might be there... needs high resolution ADCs?

 

Edited by esaj
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18 minutes ago, esaj said:

Couldn't be used with high currents and might need switching on and off to keep power dissipation in check, but in principle, I'd believe this to be possible? Complex and somewhat costly, yes, but possible...

Yes, it may work, but Zener (or anything else instead) need to dissipate a lot of energy. Do you want that your EUC became an electric kettle when you stay it charging for a night (when for example 19 of 20 cells will shunted, to charge one last cell)? I think it is main reason to not to add balancing into Inmotion - safety reasons.

Edited by palachzzz
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I measured the voltages in my current pack and even at around 3.66v and 4.14v levels (40/90%?) the 20 cell group voltages deviated by 0.01v at most.

I'm very impressed by the quality of the original pack. Now I'm waiting for some soldering supplies and after I can finish my new charger (with adjustable voltage 80-86V). It's also twice as high charging current as the original charger, 3A so the cells will be charged at 0.5C instead of the 0.25C with the original charger. With the new pack finished it will charge at 0.33C.

I will order 30 cells even though I only need 20. After testing them I'll choose the 20 most matching ones in the middle. Then I'll have some strong/weak spares I can use to balance the pack with in 1-2 years.

At 4.04 cell voltages I already had 5/5 lines showing. And the dreaded (throttled) 2/5 lines was already at 3.66v. It means there is no way I will ever go under 10% charge because the wheel is too damn slow after 2/5 lines which appears to be close to 30-40%.

If this wheel doesn't balance the cells then my cells must be absolutely amazingly matched because I have almost no voltage deviation and I've put 3000km on the wheel riding in -17 to 35 degrees celsius. I've charged the battery probably 300-400 times and never cared about stopping the charge prematurely.

Edited by alcatraz
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22 hours ago, alcatraz said:

At 4.04 cell voltages I already had 5/5 lines showing. And the dreaded (throttled) 2/5 lines was already at 3.66v. It means there is no way I will ever go under 10% charge because the wheel is too damn slow after 2/5 lines which appears to be close to 30-40%.

When you will increase battery power, your wheel won't be such slow at <40%, it will be much better.

5/5 lines at >3.98V per cell
4/5 lines at 3.84-3.98V per cell
3/5 lines at 3.69-3.84V per cell
2/5 lines at 3.55-3.69V per cell
1/5 lines at 3.47-3.55V per cell
blinking 1/5 lines at 3.40-3.47V per cell.

22 hours ago, alcatraz said:

I measured the voltages in my current pack and even at around 3.66v and 4.14v levels (40/90%?) the 20 cell group voltages deviated by 0.01v at most.

In my original battery after 1200 km and ~70 charging cycles was about 0.02V deviation, so yes original pack is pretty good. 

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