DIY battery for super soco TS, eve c40 cells

[broskioski]

Hi guys, will I find a helpful soul here to assist me with building my 20s2p battery pack?

I have built 16s8p pack for an ebike before but I had a crash and my memory is not so great.

I am trying to figure how to make connections so i can minimise busbar lenght. Does that look good enough?

 

[broskioski]

Hi guys, will I find a helpful soul here to assist me with building my 20s2p battery pack?

I have built 16s8p pack for an ebike before but I had a crash and my memory is not so great.

I am trying to figure how to make connections so i can minimise busbar lenght. Does that look good enough?

 

[Zambam]

Hi guys, will I find a helpful soul here to assist me with building my 20s2p battery pack?

I have built 16s8p pack for an ebike before but I had a crash and my memory is not so great.

I am trying to figure how to make connections so i can minimise busbar lenght. Does that look good enough?

What's the difference between yellow and red lines? Did you draw the bottom connections? Drawing is incomplete and does not make sense as is.
Should be a nice battery when you're done. How much did those LFP cells cost?

 

[amberwolf]

As Zambam says, it doesn't make sense.

With no further details in the images or post to say, I'm assuming that the black ends are all negative, since all the bare metal ends are marked with a +.

You have red lines indicating some form of connection across entire rows of positive *and* negative connections. I'm guessing the yellow boxes represent futher series connections. I don't see how the pack could operate, but it definitely isn't wired as 20s.

To have 20s 2p, you must wire ten sets of two paralleled cells (40 cells total) in series. So first you must parallel two cells. Then do that ten more times. THen wire all those pairs in series with each other.

How you physically wire it will depend on your specific pack shape to fit inside whatever space you must put it in.

 

[broskioski]

Would this diagram work better?

I paid 7.45euro for 1 cell.

 

[Zambam]

Would this diagram work better?

I paid 7.45euro for 1 cell.

That looks better. + / - terminals are on diagonal corners. Is that ideal? If not, cell arrangement can be reconfigured. With screw studs, building the pack should be much easier than spot welding or soldering (what I did with my 22S2P w. Gotian 32135 LFP cells).

Completely insulate your ratchet with masking tape to prevent blowing it up if you drop the ratchet.

40 of them fit into the Super Soco metal battery box?

 

[broskioski]

That looks better. + / - terminals are on diagonal corners. Is that ideal? If not, cell arrangement can be reconfigured. With screw studs, building the pack should be much easier than spot welding or soldering (what I did with my 22S2P w. Gotian 32135 LFP cells).

Completely insulate your ratchet with masking tape to prevent blowing it up if you drop the ratchet.

40 of them fit into the Super Soco metal battery box?

Sorry whats a ratchet?

It will not fit the original metal box, im gonna have to figure something out for battery case, if you can figure out a better cell arrangment I would appriciate it.

The cells will fit into the frame. Just need to make some mounting for it to sit tightly.

I would be even happy to pay someone to guide me and check through the process on whatsup or other.

 

[Zambam]

Sorry whats a ratchet?

https://www.amazon.com/DURATECH-4-Inch-Stubby-Ratchet-72-Tooth/dp/B099MYL8GZ/ref

It will not fit the original metal box, im gonna have to figure something out for battery case,

The cells will fit into the frame. Just need to make some mounting for it to sit tightly.

Post some photos of how the factory battery fit into the bike so we can give you some ideas.

What happened to the factory battery and what's the spec? How did you come up with 20S2P? The 32135 LFP cells I used fully charged, rests at 3.3V. @ 22S = 72.6V. @ 20S=66V. Have you checked your cell's resting voltage fully charged?

 

[broskioski]

https://www.amazon.com/DURATECH-4-Inch-Stubby-Ratchet-72-Tooth/dp/B099MYL8GZ/ref

Post some photos of how the factory battery fit into the bike so we can give you some ideas.

What happened to the factory battery and what's the spec? How did you come up with 20S2P? The 32135 LFP cells I used fully charged, rests at 3.3V. @ 22S = 72.6V. @ 20S=66V. Have you checked your cell's resting voltage fully charged?

I will do some photos tonight for you guys to see.

Seen a video on youtube that original controller goes into overvolt mode after 74.9v so my battery is within that range.

Original battery is 60v26ah 18650 that is 6 years old now and it simply does not hold its range and I feel that only after the battery drops below 70% I can feel the motor giving more accleration. So I think theres voltage sag that makes battery not working at its full capacity. Just my assumptions.

My goal for now is to just have more range and stay within original components.

In the future I would like to reconfigure this battery for 72v+ and buy a new controller with qsmotor to reach 8-14kw. But thats going to take a whole lot of learning which I am not ready for atm.

You got me quite concerned about resting voltage. I thought I'd be able to achieve 72v and have usable 22v down to 50v before cutoff voltage.

I already bought jkbms thats for 20s max. I have 52 cells so I can extend my series connections. Looks like im getting new bms and have to reconfigure my battery with all connections...

Thanks for your intrest and feedback its really appreciated.

 

[Zambam]

You got me quite concerned about resting voltage.

Charge up a few cells per spec. Measure voltages after overnight rest (wouldn't hurt to put a 1k ohm resistor across the cell to put a tiny load on it). From the reading you can determine how many series cells you want.

 

[broskioski]

Charge up a few cells per spec. Measure voltages after overnight rest (wouldn't hurt to put a 1k ohm resistor across the cell to put a tiny load on it). From the reading you can determine how many series cells you want.

Sorry I was having rough time at work.

I've charged 10 cells as you suggested.
Most of them did not go all the way to 3.65 instead charged only to 3.61-3.63.
After 2 days resting voltage is 3.54 to 3.51.
2 out of those 10 cells went down to 3.43 and 3.46.
So I guess I should put those 2 aside for now?

Not sure if my math is correct but at the moment I have 60v26ah 18650 original battery that gives me roughly 40km of range.
New battery should give me just a bit more if Im correct? It may be more Ah but the working voltage starts from 3.5 instead of 4.2. Any idea what range im looking at with this lifepo4 20s2p pack?

 

[Zambam]

Yours cells have higher resting voltage than my 32135's. At 3.5 rest V, you'd have 70V with 20S.

Did you charge the 10 cells in series or parallel? What kind of charger?
If you did not bottom balance the 10 cells and charged them in series. They would end up not balanced.

 

[broskioski]

Yours cells have higher resting voltage than my 32135's. At 3.5 rest V, you'd have 70V with 20S.

Did you charge the 10 cells in series or parallel? What kind of charger?
If you did not bottom balance the 10 cells and charged them in series. They would end up not balanced.

I just top balanced them in parallel. Is bottom balance neccesery?

I feel like an idiot having issues with space at the moment. May have to do 2x 20s1p packs and keep one in trunk and swap them once one runs out.... Not ideal from my calculations just 30km range on 1 battery. Will post some pictures tonight once I get all side panels and everything out. Its not looking great.

If I dont fit it as 20s2p I may have to squeeze everything I can out of it so was thinking about 2x 22s1p charging up to 3.4v and having 74.8v just before my controller goes to overvolt. What a mess . Not happy at all

 

[Zambam]

I just top balanced them in parallel. Is bottom balance neccesery?

I feel like an idiot having issues with space at the moment. May have to do 2x 20s1p packs and keep one in trunk and swap them once one runs out.... Not ideal from my calculations just 30km range on 1 battery. Will post some pictures tonight once I get all side panels and everything out. Its not looking great.

If I dont fit it as 20s2p I may have to squeeze everything I can out of it so was thinking about 2x 22s1p charging up to 3.4v and having 74.8v just before my controller goes to overvolt. What a mess . Not happy at all

There's different schools of thought on which is better, top or bottom balance. Here's a discussion on the topic.

Building two separate xxS 1P packs instead of one xxS 2P has the advantage of making it lighter& smaller, make the build process simpler, make trouble shooting and repair of a bad cell down the road much easier.

Do you plan to include a BMS?

 

[99t4]

Completely insulate your ratchet with masking tape to prevent blowing it up if you drop the ratchet.

Electrical tape might work better?

 

[broskioski]

Yes indeed I have jkbms already.

Damn I have a lot of space down there, more than I thought.

Could order extra 20 cells and go for 20s3p for better range? Take a look guys I guess it would be a tight fit.
First pics are with space holders inside for 60 cells and later for 40 cells for comparison.

 

[dominik h]

If there is enough space, go for 3p.
Less current per cell and less voltage sag.
And why not build 21s?.

 

[broskioski]

What would be the thinnest, strongest material to build cover box for such battery? I dont have much space around the sides of the battery where the side panels go.

Was thinking 8mm foam for inside and 10mm abs sheets to make the box?

Why 20s? Already had jkbms 20s laying around... But..

If I want 3p - max I can fit is 20s.
If I were to go for 2p I would think about getting 21s.

Also as you can see on the pictures the 20s3p has 4 cells at the top of the pack so I would definitly have trouble making good schematic for series/parallel connections.

Im gonna have to sleep with the idea of going for 3p, its doable but really tight on space, so would need good idea for battery box.

Pics for space at the sides so you can see.

Im really glad I decided to get some help here. Thank you everybody.

 

[broskioski]

Would anyone kindly please try to make connections and sections for me in this format? 20s3p. Bms is next to those 4 cells at top.

 

[chuyskywalker]

That's a tough thing to get 3's into; as far as I can see, there is no clear, simple way to make that work. You *can* fit is all in there and make a loop, but it's going to have some odd series connections which will require adding thicker connections in some spots where the group-to-group connection point is limited.

Purple lines are the groups, blues are one side of the battery.

Also, current path:

 

[Zambam]

Original battery is 60v26ah 18650 that is 6 years old now and it simply does not hold its range

What's the voltage of your old battery fully charged? If it's 16S NMC should be 67.2V.

 

[broskioski]

That's a tough thing to get 3's into; as far as I can see, there is no clear, simple way to make that work. You *can* fit is all in there and make a loop, but it's going to have some odd series connections which will require adding thicker connections in some spots where the group-to-group connection point is limited.
View attachment 378573
Purple lines are the groups, blues are one side of the battery.

Also, current path:

Great stuff. Which connections should i make with thicker plate? And how thick?

 

[broskioski]

What's the voltage of your old battery fully charged? If it's 16S NMC should be 67.2V.

Its 70v when fully charged.

 

[dominik h]

Sometimes you have to be creative to get what you want.

Here is a design 24s2p with the Eve C40 cells where plus and minus had to be next to each other ,where the BMS sits, to have only one point to acces for disconnecting the battery, the bms and the controller.

Connections were made of 3mm copper. It was only made for 100A peak current.




Don't ask how often we checked the cells and their direction , before getting the second sheet on top.

 

[broskioski]

Sometimes you have to be creative to get what you want.

Here is a design 24s2p with the Eve C40 cells where plus and minus had to be next to each other ,where the BMS sits, to have only one point to acces for disconnecting the battery, the bms and the controller.

Connections were made of 3mm copper. It was only made for 100A peak current.
View attachment 378589

View attachment 378590

Don't ask how often we checked the cells and their direction , before getting the second sheet on top.

View attachment 378591

That looks very neat. I was just gonna use the busbars that came with the pack.