Question for pouch cell battery pack (im a full on idiot)

[wturber]

One more question, if i kind of cheap out and buy some INR 21700-40p cells for their 10c discharge and their small size so i can make a huge battery, would i notice the performance impact from not buying name brand/tested cells? since these claim 500 charge cycles and are cheaper, but i do not know if i should buy them?

Well, EVE is a name brand. They just don't have the same reputation of Panasonic, LG, Samsung, etc. But it isn't like they have a bad reputation. From what I've seen, they are a well thought of Chinese brand. And given that they sell batteries to EV car makers, they are not a fly-by-night company and almost certainly they value their reputation. That said, I understand that they will sell batteries on consumer channels as "B Grade". These are batteries that don't pass certain rigorous standards as specified for car use. But this has more to do with how well they maintain nearly perfect balance. Even so, such batteries are probably fine for many consumer applications.

Whether you should buy them or not is, IMO, only something you can decide. I would expect genuine EVE cells to perform pretty much as rated. So it all depends on your priorities, size of pocketbook, etc. I'd also check the reputation of the seller as an aid to ensure that you don't end up buying used cells sold as new or counterfeit cells.

 

[docw009]

if i kind of cheap out and buy some INR 21700-40p cells for their 10c discharge and their small size so i can make a huge battery, would i notice the performance impact from not buying name brand/tested cells? since these claim 500 charge cycles and are cheaper, but i do not know if i should buy them?

Depends who makes these "INR 21700-40p" cells and where you buy them. Google says Eve markets a 4AH 21700 cell and Eve is a well known company. However, if you buy them on alibaba at $2USD/cell, you're probably getting counterfeits.

In Europe, you have sellers like nkon.nl, where the above Eve's cost € 2.85 for a quantity of 200.

I think the impact is battery capacity, which will depend on the Ah rating of the cells yo use and the current you run thru teach cell. The higher capacity 21700 cells are around 5Ah, but if you want to get close to those numbers, you want to average 1-2A per cell in current. If you run that Eve 4AH at 10A, I suppose you would see maybe 2.5AH out of it. A good 5Ah cell might do a little more than 3AH. Just a guess.

 

[BlueSwordM]

One more question, if i kind of cheap out and buy some INR 21700-40p cells for their 10c discharge and their small size so i can make a huge battery, would i notice the performance impact from not buying name brand/tested cells? since these claim 500 charge cycles and are cheaper, but i do not know if i should buy them?

You're not getting anywhere near 10C sustained out of these cells if you want them to live the longest time possible or get the most capacity:

https://www.evebatteryusa.com/_files/ugd/abe55e_8087b092dec842768070af51a1fb80a2.pdf

I wouldn't worry too much though as even at 30A discharge, you still get around 3.75Ah; you're not going to get the full 14.4Wh because of the much lower average voltage, but it's decent overall.

 

[jonescg]

As others have said, pouch cells are no better or worse than cylindrical or prismatics for longevity, however the one ace in the hole (copyright Zap Brannigan) they do have is the potential to discharge batchit crazy amps. This is because it's possible to have a meaty connection between all of the electrodes and the tabs outside of the cell. 30 C is not unheard of from pouch cells.

The downsides are plenty, especially in the DIY world. They're as fragile as an unpeeled banana, they need compression, they are very susceptible to corrosion even from humid air.

That said, I found a number of ways to terminate them and package them, but these were hobby LiPo pouch cells which I never expected to have a long life. Have a read of my battery thread, linked in my signature.

Chris.

 

[TheoneKnocker]

As others have said, pouch cells are no better or worse than cylindrical or prismatics for longevity, however the one ace in the hole (copyright Zap Brannigan) they do have is the potential to discharge batchit crazy amps. This is because it's possible to have a meaty connection between all of the electrodes and the tabs outside of the cell. 30 C is not unheard of from pouch cells.

The downsides are plenty, especially in the DIY world. They're as fragile as an unpeeled banana, they need compression, they are very susceptible to corrosion even from humid air.

That said, I found a number of ways to terminate them and package them, but these were hobby LiPo pouch cells which I never expected to have a long life. Have a read of my battery thread, linked in my signature.

Chris.

Those are the best built batteries ive ever seen, i doubt myself that i would even come close to doing an alright job if i don't short them somehow and catch them on fire, i will start learning on battery design and connections before i make my first battery pack so i don't do any easily avoidable mistake that could lead to a whole battery pack igniting. Thank you very much for his information on the pouch cells and how you connected them since on youtube i could barely find any information on how people connect them.

 

[TheoneKnocker]

Depends who makes these "INR 21700-40p" cells and where you buy them. Google says Eve markets a 4AH 21700 cell and Eve is a well known company. However, if you buy them on alibaba at $2USD/cell, you're probably getting counterfeits.

In Europe, you have sellers like nkon.nl, where the above Eve's cost € 2.85 for a quantity of 200.

I think the impact is battery capacity, which will depend on the Ah rating of the cells yo use and the current you run thru teach cell. The higher capacity 21700 cells are around 5Ah, but if you want to get close to those numbers, you want to average 1-2A per cell in current. If you run that Eve 4AH at 10A, I suppose you would see maybe 2.5AH out of it. A good 5Ah cell might do a little more than 3AH. Just a guess.

You are 100% correct on me getting fake cells since these cells look off but the seller on alibaba is verified if that means anything, so i wouldn't say that anything on the specifications of the cells are true. Also thanks for the info about the lifetime of the battery. Another seller is selling me some LR2170LA-4.0Ah lishen cells for $2,52usd/cell and im unsure of if they are legit, the INR 21700 40p cells are being sold at $2,20USD/cell while the lishen are a little more expensive.

 

[TheoneKnocker]

You're not getting anywhere near 10C sustained out of these cells if you want them to live the longest time possible or get the most capacity:

https://www.evebatteryusa.com/_files/ugd/abe55e_8087b092dec842768070af51a1fb80a2.pdf

I wouldn't worry too much though as even at 30A discharge, you still get around 3.75Ah; you're not going to get the full 14.4Wh because of the much lower average voltage, but it's decent overall.

Thank you very much for linking the website about the cells, i was thinking on how the cells would perform on different discharges and this has answered a lot of my questions.

 

[TheoneKnocker]

As others have said, pouch cells are no better or worse than cylindrical or prismatics for longevity, however the one ace in the hole (copyright Zap Brannigan) they do have is the potential to discharge batchit crazy amps. This is because it's possible to have a meaty connection between all of the electrodes and the tabs outside of the cell. 30 C is not unheard of from pouch cells.

The downsides are plenty, especially in the DIY world. They're as fragile as an unpeeled banana, they need compression, they are very susceptible to corrosion even from humid air.

That said, I found a number of ways to terminate them and package them, but these were hobby LiPo pouch cells which I never expected to have a long life. Have a read of my battery thread, linked in my signature.

Chris.

Also would love to ask how could i start with making a pouch cell battery pack? How can i connect 2 in parallel and how would i get the pcbs, how to properly seal them from corrosion, thats the hard part about these batteries that i cant find anywhere, your batteries are super great in every build but i cant understand how you plan them out, make the pcb, connect them together, i would love to know how that process goes on.

 

[jonescg]

Buy the cells first, then design the PCB and build the enclosure. The cells vary from one batch to the next, so while they might claim to be 8 mm thick, they could be 8.2 mm. By the time you've stacked 24 of them cheek by jowl, you're looking at 5 mm bigger than you expected. Build a jig that keeps them dead straight, and allows you to press them fairly firmly as you terminate them. Then tape and strap them as required.
The PCB needs to have slots and holes at exactly the right spacing, and make sure the nut on the underside clears the foil of the pouch cell. If it touches, it can discharge a cell all the way to zero. Add a bit of Kapton tape if you're uncertain. Make sure your screws are stainless steel, and no longer than absolutely necessary - you might screw it right down into the top of the cell!
Make sure the enclosure is non-conductive, or at least has some non-conductive surface between it and the cells. Maybe even include a grease nipple near the bottom so you can pump sone inexpensive dielectric grease in there. I glued the cells to the walls of the enclosure. This was a good move in general as it stopped them from rubbing or fretting, but the grease idea might work in a similar way, and contribute to their waterproofness.
If you want to keep them cool, passing air across the busbars is a robust way to do this, as the busbars are directly connected to the hottest part of the cells. However, this is not a waterproof, or short-proof way of doing it. You can glue the bases to a chill-plate like I did for the Prelude modules using a thermally conductive, electrically insulating material, but it's probably not worth it for small packs.
I think that's a pretty good start.

 

[TheoneKnocker]

Buy the cells first, then design the PCB and build the enclosure. The cells vary from one batch to the next, so while they might claim to be 8 mm thick, they could be 8.2 mm. By the time you've stacked 24 of them cheek by jowl, you're looking at 5 mm bigger than you expected. Build a jig that keeps them dead straight, and allows you to press them fairly firmly as you terminate them. Then tape and strap them as required.
The PCB needs to have slots and holes at exactly the right spacing, and make sure the nut on the underside clears the foil of the pouch cell. If it touches, it can discharge a cell all the way to zero. Add a bit of Kapton tape if you're uncertain. Make sure your screws are stainless steel, and no longer than absolutely necessary - you might screw it right down into the top of the cell!
Make sure the enclosure is non-conductive, or at least has some non-conductive surface between it and the cells. Maybe even include a grease nipple near the bottom so you can pump sone inexpensive dielectric grease in there. I glued the cells to the walls of the enclosure. This was a good move in general as it stopped them from rubbing or fretting, but the grease idea might work in a similar way, and contribute to their waterproofness.
If you want to keep them cool, passing air across the busbars is a robust way to do this, as the busbars are directly connected to the hottest part of the cells. However, this is not a waterproof, or short-proof way of doing it. You can glue the bases to a chill-plate like I did for the Prelude modules using a thermally conductive, electrically insulating material, but it's probably not worth it for small packs.
I think that's a pretty good start.

This is a very good guide but my own lack of knowledge kind of prevents me from this, i can find a software to design a PCB but the main problem is that i do not know any designs on how it would look like to connect 2 cells together, ill have to do this step by step starting with the design and how it should look like so the tabs get connected, the rest i can probably figure it out somehow but the first part is what is stopping me. Also how would one terminate the cells and screw them to eachother? Id like to have a good connecting that isn't going to give way anytime, but I do not know how to start designing or connecting them at all. Thank you very much for the detailed guide

 

[jonescg]

I had a big thread in the 'for sale' section but it was nuked in a clean out. You might find some more progress on these builds in other threads, but sadly the most detailed one is gone. I started here 15 years ago you know!

 

[TheoneKnocker]

I had a big thread in the 'for sale' section but it was nuked in a clean out. You might find some more progress on these builds in other threads, but sadly the most detailed one is gone. I started here 15 years ago you know!

You are a legend, I've heard of you through a dirt bike build with a zero motor, they said you made their pouch cell battery pack, i will try to learn as much as possible on these pouch cells, but i might go with the li ion cells since they are easier, ill still give it a giant try on learning these cells since they are very new to me, i just need some help if you could explain these small pouch batteries, how you connect the terminals and how would i connect 2 packs in parallel so i can get 50Ah 126V with a 30s2p configuration? Also forgot to ask how did you machine the copper bus bars so you can connect multiple batteries without the need of solder or anything? Did you contact someone that has a machine for cutting copper? I am starting to understand your design

 

[TheoneKnocker]

You are a legend,ive heard of you through a dirt bike build with a zero motor, they said you made their pouch cell battery pack, i will try to learn as much as possible on these pouch cells, but i might go with the li ion cells since they are easier, ill still give it a giant try on learning these cells since they are very new to me

Ive though about it and might switch to the smaller cells and not these bigger cells since i think it would be easier to connect them in parallel after making the battery packs, 25Ah with a continuous of 25c and instant of 50c discharge

 

[TheoneKnocker]

I had a big thread in the 'for sale' section but it was nuked in a clean out. You might find some more progress on these builds in other threads, but sadly the most detailed one is gone. I started here 15 years ago you know!

I've just seen and analyzed the battery you made for Sketch Coleman's super moto and I might just copy the design for the battery's on the left and right which aren't connected together, ill make the same ones and just connect the positive and negative leads in a Y configuration either via high gauge wire or by a copper bus bar specifically cut to match the negative and positive ports so I can achieve a parallel configuration, I do not know how else I would do it otherwise. Using that logic couldn't I just make 2 battery packs and connect the positive and negative leads with a giant copper bus bar so I could make a 30s2p pack? or is it more than that and I am trying to use my normal logic on batteries which doesn't work in this situation?

 

[jonescg]

I've just seen and analyzed the battery you made for Sketch Coleman's super moto and I might just copy the design for the battery's on the left and right which aren't connected together, ill make the same ones and just connect the positive and negative leads in a Y configuration either via high gauge wire or by a copper bus bar specifically cut to match the negative and positive ports so I can achieve a parallel configuration, I do not know how else I would do it otherwise. Using that logic couldn't I just make 2 battery packs and connect the positive and negative leads with a giant copper bus bar so I could make a 30s2p pack? or is it more than that and I am trying to use my normal logic on batteries which doesn't work in this situation?

You can, but the risk is the cells will wander out of balance, unless you have two BMSs. Generally we try to manage one string of cells of larger capacity than two separate strings in parallel.

 

[jonescg]

You are a legend, I've heard of you through a dirt bike build with a zero motor, they said you made their pouch cell battery pack, i will try to learn as much as possible on these pouch cells, but i might go with the li ion cells since they are easier, ill still give it a giant try on learning these cells since they are very new to me, i just need some help if you could explain these small pouch batteries, how you connect the terminals and how would i connect 2 packs in parallel so i can get 50Ah 126V with a 30s2p configuration? Also forgot to ask how did you machine the copper bus bars so you can connect multiple batteries without the need of solder or anything? Did you contact someone that has a machine for cutting copper? I am starting to understand your design

CNC Water jet cutting. Only way to cut 2 mm copper without a fibre optic laser.

 

[TheoneKnocker]

You can, but the risk is the cells will wander out of balance, unless you have two BMSs. Generally we try to manage one string of cells of larger capacity than two separate strings in parallel.

So it would be smarter to just make 2 seperate batteries with bms's but not connect them like how i mentioned due to the wandering out of balance. How could i connect 2 packs in parallel or is it way smarter to just have 2 packs seperate with a bms?

 

[jonescg]

If you must split the battery into two half packs, use one BMS, but you will need to run balance/sense wires to each cell and centralise the BMS somewhere. So if it's 30s2p, build two 15s2p batteries with a harness of wiring for each cell tap.

 

[TheoneKnocker]

If you must split the battery into two half packs, use one BMS, but you will need to run balance/sense wires to each cell and centralise the BMS somewhere. So if it's 30s2p, build two 15s2p batteries with a harness of wiring for each cell tap.

I don't need to split the battery, I just don't know how to connect them together or make a big battery using 60 cells in a 2p configuration, I was confusing myself trying to use your design to make it into parallel, I might use 2 bms's and 2 separate packs then connect them both with bus bar to their positive and negative leads and just use it like that, and charge the packs separately once depleted

 

[jonescg]

I don't need to split the battery, I just don't know how to connect them together or make a big battery using 60 cells in a 2p configuration, I was confusing myself trying to use your design to make it into parallel, I might use 2 bms's and 2 separate packs then connect them both with bus bar to their positive and negative leads and just use it like that, and charge the packs separately once depleted

The screw termination system works best with 2 or more cells in parallel

 

[TheoneKnocker]

The screw termination system works best with 2 or more cells in parallel

The only design that keeps getting in my head is just getting the 2 rows of batterys then punching holes through their negatives and positives then folding one tab over the other flat and screwing it into a pcb and doing that with all of them and alternating so i can get the series connecting, and then for the parallel i just connect their positive and negatives together, would this in theory work? Or would i need to think of a different design?

 

[jonescg]

The only design that keeps getting in my head is just getting the 2 rows of batterys then punching holes through their negatives and positives then folding one tab over the other flat and screwing it into a pcb and doing that with all of them and alternating so i can get the series connecting, and then for the parallel i just connect their positive and negatives together, would this in theory work? Or would i need to think of a different design?

Thats basically it, yes.

 

[TheoneKnocker]

Thats basically it, yes.

So basically like this video,

, but instead of soldering them i just punch a holes through their positive and negatives and just connect them with screws (currently building the pcb for the pouch cells, managed to find a seller that sells 39Ah cells with 15c continuous and 25c peak discharge)

 

[jonescg]

If you have two in parallel, the gap between then is sufficient for a soldered nut on the underside. Holepunch the tabs and fold them over the hole. Repeat for the next pair of cells, and screw a copper bus link down, spanning both.
If you go 1p, the gap between cells is too small for a single screw and buslink.

 

[jonescg]

This is what I mean by 2p being a minimum: