making a battery pack for my gotway tesla 84V (images heavy)

[Shad0z]

so i had a CLONE segway mini pro once. the battery cant really be sold anymore

but i was thinking maybe making a battery pack for my gotway tesla, to get a little boost

eaither make it external or internal

if it has to be internal then i would have to make it long and not wide since there isnt much space

i cant seem to find any information on the batteries what manufacturer made them

but theyre 2000mah and 3,7 V

and it saids: Li-18650

and there is 30 cells in total

so what should i do to make it either internal or external. and working with my tesla?

im especially looking for making it internal and charges from the standard port that alos charges the other batteries

 

 

[wehey]

Watching with interest.

I'm about to make my first battery for my ebike ?

[esaj]

Tesla's 84V wheel (AFAIK), so you need 20 cells in series. I don't think Mini's had more than 15 or 16 cells in series (hard to tell from the picture, but I'd guess it's a 15S2P?) so you could only make a 20S1P from those, and have some leftover cells. Don't even think about using something like these:

They won't hold, likely a cell becomes loose with all the shocks and vibrations of the wheel, and even if they would, the connections between the tabs and the cells wouldn't be too good. They might heat up enough to melt the plastic holders. What you actually need is to spot-weld the cell-series together using nickel strips. Normal spot-welders won't do (the kind you have in metal workshops, with "jaws" below and above), but ones which have smaller welding prongs. Also I've heard that the best way to make the small but good welds for the batteries is using a spot-welder that produces two pulses whose lengths (time-wise) can be adjusted. The first pulse pre-heats the weld and the latter one finishes the job. A good quality machine likely costs about as much as a Tesla-battery.

Then, you need a BMS for 20S battery with balancing and separate charging and discharging rails. Likely about 30-50€? The balancing lines are connected between each two cells, and at the top and bottom of the series. You also need a soldering iron, wires etc. Be careful soldering the cells, you don't want to overheat them. Likely also at least a basic multimeter and some form of adjustable power source/electronic load for testing.

The above is just an example, this wouldn't actually work because it uses the same rails for charging and discharging. The problem is that the charging high voltage protection can kick in when the battery is near full and you brake... the regenerative braking can push the voltage above the threshold and cut all power (guess how I know? )...  If you really want to do this, it can be done (and there are far more thorough guides floating around the 'net), but the equipment you need costs more in total than just getting a ready-made battery pack, so getting the stuff just to make packs for yourself likely won't be cheaper than buying the packs outright, on the other hand, if you want to start a business or do it just for fun (regardless of cost)...

In Europe, a good place to get custom battery packs for wheels done correctly and that don't cost a small fortune is  http://www.1radwerkstatt.de/epages/80603321.sf/en_GB/?ObjectPath=/Shops/80603321/Categories/Category2

[Shad0z]

16 minutes ago, wehey said:

Watching with interest.

I'm about to make my first battery for my ebike ?

i basically have no idea how to do any of this stuff. well i know how to solder

im right now looking at youtube for ways to do it

but as far as i can see i dont think its an easy option to make a battery that supplies power directly to the control board and motor, because i think these cells have insuficient max amp outputs, i cant find out what brand made them, so im just thinking of making these batteries charge the main batteries that then deliver the correct current to the control board and motor, or else i could go cheep and just make a battery pack that would work with the charging port. but i mean i want better solutions 

[esaj]

Also, if you haven't fooled around with the battery packs before, read this:  

 

[Shad0z]

12 minutes ago, esaj said:

Tesla's 84V wheel (AFAIK), so you need 20 cells in series. I don't think Mini's had more than 15 or 16 cells in series (hard to tell from the picture, but I'd guess it's a 15S2P?) so you could only make a 20S1P from those, and have some leftover cells. Don't even think about using something like these:

They won't hold, likely a cell becomes loose with all the shocks and vibrations of the wheel, and even if they would, the connections between the tabs and the cells wouldn't be too good. They might heat up enough to melt the plastic holders. What you actually need is to spot-weld the cell-series together using nickel strips. Normal spot-welders won't do (the kind you have in metal workshops, with "jaws" below and above), but ones which have smaller welding prongs. Also I've heard that the best way to make the small but good welds for the batteries is using a spot-welder that produces two pulses whose lengths (time-wise) can be adjusted. The first pulse pre-heats the weld and the latter one finishes the job. A good quality machine likely costs about as much as a Tesla-battery.

Then, you need a BMS for 20S battery with balancing and separate charging and discharging rails. Likely about 30-50€? The balancing lines are connected between each two cells, and at the top and bottom of the series. You also need a soldering iron, wires etc. Be careful soldering the cells, you don't want to overheat them. Likely also at least a basic multimeter and some form of adjustable power source/electronic load for testing.

The above is just an example, this wouldn't actually work because it uses the same rails for charging and discharging. The problem is that the charging high voltage protection can kick in when the battery is near full and you brake... the regenerative braking can push the voltage above the threshold and cut all power (guess how I know? )...  If you really want to do this, it can be done (and there are far more thorough guides floating around the 'net), but the equipment you need costs more in total than just getting a ready-made battery pack, so getting the stuff just to make packs for yourself likely won't be cheaper than buying the packs outright, on the other hand, if you want to start a business or do it just for fun (regardless of cost)...

In Europe, a good place to get custom battery packs for wheels done correctly and that don't cost a small fortune is  http://www.1radwerkstatt.de/epages/80603321.sf/en_GB/?ObjectPath=/Shops/80603321/Categories/Category2

i wasnt even going to begin with those plastic things, if its the things you see in the corner of the photo? its just the platic holder for the batteries after i took them out of the battery pack. there are 30 cells. and i think they are connected 4 in paralel

but from what i can see it would be best to just try and make an external one then.

 

[esaj]

4 minutes ago, Shad0z said:

i wasnt even going to begin with those plastic things, if its the things you see in the corner of the photo? its just the platic holder for the batteries after i took them out of the battery pack. there are 30 cells. and i think they are connected 4 together?

Two cells are always in parallel, connected to the opposite polarity ("minus to plus") of the next 2 cells in parallel:

There's 15 of these pairs in series in the pack you have. The reason it seems four are connected together is because they're arranged like this (note the polarities):

With BMS-balancing wires going between the pairs.

 

4 minutes ago, Shad0z said:

but from what i can see it would be best to just try and make an external one then.

You'd still need a BMS, at least for balancing. If one or more of the cells goes out of balance (drops to lower/higher voltage than the others), you either kill the cell sooner or later through overdischarge (if it drops voltage faster than others), or worse, cause a fire when it overcharges because the charger only "sees" the total voltage of the series, so if others are at 4V (19 * 4V = 76V) and one has already reached 4.2V (for a total of 80.2V), the charger will continue charging, pushing that one cell to overvoltage, and sooner or later it's going to overheat and either catch fire or explode. These cells/batteries can be really dangerous if "mistreated"...

[Shad0z]

15 minutes ago, esaj said:

 

You'd still need a BMS, at least for balancing. If one or more of the cells goes out of balance (drops to lower/higher voltage than the others), you either kill the cell sooner or later through overdischarge (if it drops voltage faster than others), or worse, cause a fire when it overcharges because the charger only "sees" the total voltage of the series, so if others are at 4V (19 * 4V = 76V) and one has already reached 4.2V (for a total of 80.2V), the charger will continue charging, pushing that one cell to overvoltage, and sooner or later it's going to overheat and either catch fire or explode. These cells/batteries can be really dangerous if "mistreated"...

yeah i know the importance of a bms. and i know these cells are like tnt. needs to be handled properly otherwise. very dangerous as you said.

but now im starting to think if its even a viable option. definetly not an option for me to make it internal. but would it be possible to make a battery pack external that i just plug in the charging port to charge my wheel, but when driving basically?

and if so how? and also i need it to charge it with sufficient amps so i dont have to wait for it to charge my batteries again. but it does it fast enough that i dont have low battery but still high battery in the external pack

[Scatcat]

23 minutes ago, esaj said:

Two cells are always in parallel, connected to the opposite polarity ("minus to plus") of the next 2 cells in parallel:

There's 15 of these pairs in series in the pack you have. The reason it seems four are connected together is because they're arranged like this (note the polarities):

With BMS-balancing wires going between the pairs.

 

You'd still need a BMS, at least for balancing. If one or more of the cells goes out of balance (drops to lower/higher voltage than the others), you either kill the cell sooner or later through overdischarge (if it drops voltage faster than others), or worse, cause a fire when it overcharges because the charger only "sees" the total voltage of the series, so if others are at 4V (19 * 4V = 76V) and one has already reached 4.2V (for a total of 80.2V), the charger will continue charging, pushing that one cell to overvoltage, and sooner or later it's going to overheat and either catch fire or explode. These cells/batteries can be really dangerous if "mistreated"...

Cannot be overstated. One is enough to cause all sorts of grief if it goes into a temperature loop. If you have a ton of batteries side by side that go off in unison, you will have a EUC that looks like melted cheese before you can say "oh shit, hand me the extinguisher!"...

[esaj]

7 minutes ago, Shad0z said:

yeah i know the importance of a bms. and i know these cells are like tnt. needs to be handled properly otherwise. very dangerous as you said.

but now im starting to think if its even a viable option. definetly not an option for me to make it internal. but would it be possible to make a battery pack external that i just plug in the charging port to charge my wheel, but when driving basically?

and if so how? and also i need it to charge it with sufficient amps so i dont have to wait for it to charge my batteries again. but it does it fast enough that i dont have low battery but still high battery in the external pack

Simplest way I can think of off the top of my head would be to use a "suitable" step-up converter with current limitation (adjusted to 84V and whatever amperage the batteries / the step-up converter can safely output continuously, likely a few amps) to step the 15S pack voltage to 84V for charging. Likely it still won't charge as fast as you're using the battery while riding, and some of the battery power is wasted as heat (the converter can never be 100% efficient).

[Shad0z]

14 minutes ago, esaj said:

Simplest way I can think of off the top of my head would be to use a "suitable" step-up converter with current limitation (adjusted to 84V and whatever amperage the batteries / the step-up converter can safely output continuously, likely a few amps) to step the 15S pack voltage to 84V for charging. Likely it still won't charge as fast as you're using the battery while riding, and some of the battery power is wasted as heat (the converter can never be 100% efficient).

i mean it will start charger my wheel as soon as its under 100 percent. so it would be like slowing down the battery decrease. and hopefully be fast enough to use all its capacity before my euc is at 0%

but i rarely drive from 100% to 0 in one go and never at full speed so about 3 hours is the fastest i can discharge my battery. so im sure if i make it external and do the right kinds of things i think it should be able to work as intended. 

[esaj]

2 minutes ago, Shad0z said:

i mean it will start charger my wheel as soon as its under 100 percent. so it would be like slowing down the battery decrease. and hopefully be fast enough to use all its capacity before my euc is at 0%

but i rarely drive from 100% to 0 in one go and never at full speed so about 3 hours is the fastest i can discharge my battery. so im sure if i make it external and do the right kinds of things i think it should be able to work as intended. 

That's the idea of stepping the voltage up to 84V, the voltage of a full 20S -pack. If the voltage from the external voltage source, in this case a step-up (boost) converter, is less than the battery voltage, no charging will occur. If there'd be no reverse voltage protection in the Tesla packs (I'd assume there is though), it would actually work the other way around if the converter outputted a smaller voltage (the current would flow in reverse, possibly damaging the converter and/or the smaller battery pack).

The cell capacities are rated in milliamphours, 2000mAh = 2Ah, that is, if charging at a constant current of 2A, it should take one hour from empty to full (or discharging at 2A, one hour from full to empty), although this is not exactly true for charging (the current will start to drop when the battery is closing full, as the internal resistance of the batteries will start to limit it). The "speed" of the charging depends on the amperage. More amperes, the faster the battery will charge. But there are limiting factors, like wire gauges (thicknesses) and if the new Gotways still use GX-16-3 connectors for charge ports, it's not rated for above 5A (the connector can overheat and melt, same for the wires). The converter itself will also have limiting factors, like how well it's cooled. Finding a suitable converter for 45...63V -> 84V and with current limitation might also be a slight issue, as the voltages are much higher than "usual", although probably such exist (maybe something like adjustable up to 100V, with suitable input range). Also monitoring the external battery voltage would be wise, so that the converter doesn't overdischarge it (although the BMS would likely cut power at some point).

 

[Shad0z]

23 minutes ago, esaj said:

That's the idea of stepping the voltage up to 84V, the voltage of a full 20S -pack. If the voltage from the external voltage source, in this case a step-up (boost) converter, is less than the battery voltage, no charging will occur. If there'd be no reverse voltage protection in the Tesla packs (I'd assume there is though), it would actually work the other way around if the converter outputted a smaller voltage (the current would flow in reverse, possibly damaging the converter and/or the smaller battery pack).

The cell capacities are rated in milliamphours, 2000mAh = 2Ah, that is, if charging at a constant current of 2A, it should take one hour from empty to full (or discharging at 2A, one hour from full to empty), although this is not exactly true for charging (the current will start to drop when the battery is closing full, as the internal resistance of the batteries will start to limit it). The "speed" of the charging depends on the amperage. More amperes, the faster the battery will charge. But there are limiting factors, like wire gauges (thicknesses) and if the new Gotways still use GX-16-3 connectors for charge ports, it's not rated for above 5A (the connector can overheat and melt, same for the wires). The converter itself will also have limiting factors, like how well it's cooled. Finding a suitable converter for 45...63V -> 84V and with current limitation might also be a slight issue, as the voltages are much higher than "usual", although probably such exist (maybe something like adjustable up to 100V, with suitable input range). Also monitoring the external battery voltage would be wise, so that the converter doesn't overdischarge it (although the BMS would likely cut power at some point).

 

i think all this battery stuff is too complicated  

[esaj]

12 minutes ago, Shad0z said:

i think all this battery stuff is too complicated  

Well, yeah, it's not that easy... I think some people in the forums have made external packs before, so it's doable, but it does take a lot of research and some understanding of electronics/electricity and the batteries. Also I'd be wary of riding with a charging wire running from my backpack to the charge port, imagine what happens if you fall, the wire might break or tear your charge port off. If there's room inside the shell, you could ask 1RadWerkstatt for the price of an extra (internal) pack(s) made properly. Don't know if they make external packs though.

[Shad0z]

1 hour ago, esaj said:

Well, yeah, it's not that easy... I think some people in the forums have made external packs before, so it's doable, but it does take a lot of research and some understanding of electronics/electricity and the batteries. Also I'd be wary of riding with a charging wire running from my backpack to the charge port, imagine what happens if you fall, the wire might break or tear your charge port off. If there's room inside the shell, you could ask 1RadWerkstatt for the price of an extra (internal) pack(s) made properly. Don't know if they make external packs though.

there is very minimal space inside. but i think if i cut away a few of the plastic barriers that hold the battery in place i could probably add about a 2 batteries height and 2 batteries width and then all the way from the bottom to the top (not sure how many in total)

but a battery pack that is internal there wouldnt  be enough space for a standard square battery pack with my cells. 

but there would definetly be space for a smaller square one in a bottom corner. but the cells would have to be pretty high density to make a big difference. but i think a a little internal pack with 3500mah cells would still give enough to make a difference

[winter]

 

[Hunka Hunka Burning Love]

@Battling had some good info in this thread: