Pedego Comfort Cruiser Battery rebuild - missing cells?

[marcexec]

I need some advice:
Flatmate's bike is Comfort Cruiser – Electric Beach Cruiser – Pedego Electric Bikes.
She's very happy with it just the battery is getting weaker and was only 10Ah to begin with. I'm contemplating rebuilding the pack with better cells for her, keeping the BMS etc.. I had it open briefly, see below.

So the pack is 5P10S, i.e. 50 cells but (without taking it apart as it's in daily use) I count 4 rows of 12 cells =48 cells with 5 paralleled at connections. WTH are the 2 missing ones?

Also (probably the main question), can I re-use the plates if I want to solder the new cells in the same place, has anyone tried that before?
As a favour, please don't try to convince me to get a spot welder and practise with it, it's soldering or outsourcing as I'm a bit time-poor. If I can't use the plates I'll likely use braided solder wick which is is holding up well in two 13S packs I did, just have to stock up before Christmas.

BTW, I'll use LG MJ1s which are also 10A

 

[Chalo]

While it's good to recognize the limitations of your ability/budget/patience etc., please understand that soldering your pack with normal tin-lead electrical solder will damage the cells and reduce both their lifespan and their reliability. If you must solder them, I recommend a low temperature electrical solder like 42% tin 58% bismuth. If you use that with a good powerful iron or gun, and take care to get in and out of the joint quickly, it should be okay.

I just rebuilt one of those bikes at work. I removed the battery and its receiver, replaced with a surplus stick-shaped battery of slightly larger capacity and smaller size, and used a soft bag sitting on the battery shelf brackets to hold the new battery and old controller.

My point is you don't have to build a new battery into the same case. You only need one that fits into the available space. Doing that could save you both time and money.

 

[docw009]

The cells are staggered with 12 on top and 13 on the bottom. That's 25 cells on each side, for 50 altogether.

You have to be pretty good to be able to remove the nickel plates without damaging them. I think it's impossible, unless you were to machine away the welds. You can buy it in rolls, something like these nickel plated 2P strips on aliexprress Solder at your own risk.

 

[marcexec]

Thanks guys, noted.
I'm adding 2m of this strip to the MJ1 order from NKON. I'll report back in a couple of weeks as I'll have to discharge the cells before soldering (130W Ersa iron with a big tip).

 

[Chalo]

Thanks guys, noted.
I'm adding 2m of this strip to the MJ1 order from NKON. I'll report back in a couple of weeks as I'll have to discharge the cells before soldering (130W Ersa iron with a big tip).

Don't discharge the cells below 3.0v each, because that damages them. You'll have to guard against short circuits while putting the pack together.

 

[marcexec]

Don't discharge the cells below 3.0v each, because that damages them. You'll have to guard against short circuits while putting the pack together.

yep, that's empty as far as I'm concerned - as opposed to the 3.6V or so they'll be at for storage/shipping.