Advice on premade battery pack

[Vbruun]

Hello

I have got an older cargo bike, a "Long John" that i have modified to fit a bafang swxk front wheel motor coupled with a 20a PAS activated controller. IT is currently fed by a 36v LiFePO4 battery pack.
The front wheel is however only 20" and the swxk is a slow wound motor so the bike tops out around 17 km/h, which is too slow to be practical.

A Friend of mine recently bought and ebike with 48v battery and since I read online that it might add some speed, we tried to fit it to the bike. What a difference!
The bike had a significantly faster top speed and felt just the way we wanted it to, so now we are on the hunt for a 48v battery.

We have made a box to house the old battery and preferably, we could reuse this, as that would make things easier in our part. This limits the battery size to max 105x120x450mm
We would like to have a big battery so we cam shallow cycle IT to improve the lifespan. Maybe 20 ah or so.

I have already contacted unit pack power on aliexpress as I have read that they should be decently reputable.
So my questions to you are;

1:
Should I contact other battery manufacturers to have this battery made

2:
What cells and bms should I ask for?

Also, if someone is living in DK or northern germany and willing to help me with a DIY build, I am very interested, but I don't have the time to this project myself.

 

[flippy]

what can your controller take?

"just" adding a 48v battery to a 36v controller might simply pop the controller on the spot.
if you have a really slow motor you might want to simply replace the controller to a 72v model and 72v battery so you can set a top speed manually and it will always reach that speed even if the battery drains.

what kind of life expetancy are you aiming for? china cells are still china quality. buying EU is more expensive but also gives the lifespan/performance you need/want.

fitting a battery inside that box should not be a problem for a battery builder.

 

[Vbruun]

Hi flippy. Thanks for the reply!

The controller is also suitable for 13s batteries and as I stated earlier, I have already tried to fit a 48 v battery to it and it worked wonderfullly!

I am hoping to have the battery pack hold 40 km/charge in 5 years.

At the moment, the bike Will do 30 km, but at a horribly slow pace. I recently bought a battery tester and plan to measure the capacity og the current battery tomorrow.

What EU vendors should I look at?

 

[Vbruun]

To elborate on the controller; it's this unit

https://s.click.aliexpress.com/e/2jwsPqNE

So far it has worked like a charm

 

[john61ct]

What cells are made outside China these days?

Or do you mean just more trustworthy sellers & pack builders?

 

[flippy]

i do not know any "offical" german vendors, this is a quite a nice market.
if you want solid lifespan i would do a partial charge, so up to 4.05V, that requires a customized charger and smart bms. nothing special and can be made to order with pretty standard parts for a battery builder.

you can eiter find a local DIY guy or get a company to do it but i dont think you will find one near you if you dont "know a guy".

What cells are made outside China these days?
Or do you mean just more trustworthy sellers & pack builders?

panasonic just to name 1, and yes and yes.

 

[Vbruun]

Alright so I should look for a local DIY Guy or a thrustworthy european vendor?

Could I post a thread in some subforum here to help me Find that? Or should I look elsewhere?

 

[Vbruun]

Hello again!
I am currently working on two different plans to realise my need for a new battery pack:

1.
I got in touch with a local guy who is willing to help me make a battery pack if I supply the materials needed. He makes the packs without soldering but via a system of 3d printed enclousures similar to the NESE system.

2.
I am still in contact with unit pack power in china to see if they can make this happend. It seems that they might.

So I have a few questions, especially in regards to method #1

1.
Regarding my previous wishes to shallow cycle the battery to max 4,05 or maybe 4,1 v per cell, I am looking for a BMS and charger that will function at those voltages. Is that something that is available or does it have to be custom made?

2.
I read other places that the samsung 29E was a decent cell for making battery packs for e-bikes. Now I just tried to do a quick run-over of the amount of cells i might need.

I want 20 AH, 20/2,9=6,9 I round up to 7

7p*13s = 91 cells. Is that correct?