EIG Pouch Cell Questions

[Storapa]

Hi folks,

I’ve been lurking about on the forum for a while. It is excellent. Thanks to all who take the time to contribute.

A bit of history. I built up a bike using a BBS02 kit and a Hobby King lipo pack with low voltage alarms. It’s a great kit and I’ve been enjoying riding it. Unfortunately I was surfing E-Bay as you do, and ended up buying an HS3540 rear hub motor. I then bought a 12 FET 4110 Infineon controller from Paul at EM3EV (excellent service) and an 84V bulk charger from BMS Battery.

I’m also a mechanical engineer by trade, so a lot of this is new to me.

A friend gave me a quantity of EIG 20 Ahr pouch cells (ePLB CO20B) in carriers. I also managed to get the data sheet for the cells. They have been used for gentle bench testing but little else. They are all within 10mv of each other at 3.75V. I’ve charged them to 4.1V in groups of 5 (using my BC168 charger). I’ll discharge them to 3.8V this week, rather than leaving them fully charged.

My intention is to build an 82V pack using 20 cells split into two packs. I will then fit them with balance leads but bulk charge the majority of the time. I was considering buying an iCharge 1010B charger to balance charge them in future. I won’t be running a BMS, but rely on the controller to cut the power at a certain voltage.

A few questions.

Does my plan sound sensible.

Should I charge and discharge the cells a few times?

How do you guys produce the graphs with respect to your charge and discharge cycles?

Anything else I need to think about with this set-up?

 

[dnmun]

why would you not just use a BMS instead?

 

[Hillhater]

A friend gave me a quantity of EIG 20 Ahr pouch cells (ePLB CO20B) .......?

..wow !... You have a good friend .!
But you do know that will be a quite a large heavy pack ?

 

[Storapa]

Hi all,

Thanks for the replies.

Dnmun, I don't have a BMS as yet. If I can get one easily enough I'll give it a try.

Hillhater, yup, he's a good friend. The pack for my BBS02 weighs in at 6kg (12 cells). The pack for the HS3540 weighs 10kg (20 cells). As you say, heavy, but the cells were free and the capacity is reasonable.

 

[amberwolf]

My intention is to build an 82V pack using 20 cells split into two packs. I will then fit them with balance leads but bulk charge the majority of the time. I was considering buying an iCharge 1010B charger to balance charge them in future. I won’t be running a BMS, but rely on the controller to cut the power at a certain voltage.


Should I charge and discharge the cells a few times?

On CrazyBike2, I run a 14s EIG NMC pack, using typically about 3-4Ah or less each day for my commute, etc., occasionally longer ones using most of it's capacity, and I don't have to balance it--it has yet to go out of balance by more than a few hundredths of a volt. It is bulk charged to 4.17V/cell (which is a tad higher than the spec sheet max).

I'm sure as they age more it'll get unbalanced, but so far it's fine. I do have the balance connectors on there to do it if I need to.

I also have a 4s pack used for my lighting, which used to be 3s, and the 3s part was once discharged accidentally to 0V, recovered, and even now it doens't get more than a few hundredths difference from the other cell I added to it.

So while it isn't any guarantee that you won't have balance issues with them, so far I haven't.


If you want to test the cells before building a pack, to characterize them, it's not a bad idea. If your charger comes with software that will let you monitor it via USB while charging or discharging, that's one way to get the graphs. I forget the name of the 3rd party software that does this, but if you look up my Venom charger repair thread I think I mention it in there somewhere.



Having a good BMS on there won't hurt anything, and could save the pack if something goes wrong with your charger (or if the controller's LVC fails to trigger for some reason).

I don't have one, but it's mostly cuz I don't have any here that would do the job for these cells both in balancing and monitoring. I *do* have some of the Methods' LVC/HVC boards, which are supposed to go into this pack, but after the non-ebike-related housefire almost two years ago, I'm still finding all the bits and pieces of projects started before the fire to eventually finally get them done.


If I did have a good BMS with a good known track record that had the right set points for these cells, I'd probably get it installed in there.


FWIW, I run the HSR3548 in a 20" wheel on a 40(60)A 12FET controller.


BTW, since you do have the trays and stuff, I highly recommend bolting them together at the corners as designed, and use the bottom mounting plate to hold that end togehter (IIRC it screws into every cell's baseplate?).

If you need a secure box for it to go in, you can fit each half of the pack in a 50cal ammocan with plenty of room to spare. (I think 16 or 17s, maybe 18, is about the max in one if you want to pad the case with anything).

 

[Storapa]

Hi Amberwolf,

Thanks for the detailed reply.

I'll go without a BMS for the time being, but if I find one along the way, I'll install it. I'll keep a set of balance leads on each pack, to check them from time to time. I'll also use the holes at the upper corners to bolt them together and the screws / base plates.

I'm looking forward to trying them as the pack I am using at the moment is very small.