Back to track, complete brompton maintenance

[jerrysimon]

I guess the epoxy will hold for a while.

Can't you just get a new bag frame ?

Brompton S bag frame only

Jerry

 

[cwah]

I could get a new frame, but this is the second I broke.

I think the weight and vibrations tends to crack the plastic. It needs some sort of stronger encasing, especially when it's a bit loose.

Hopefully epoxy should make it for now... maybe buy another one and add some aluminium sheet to renforce the plastic?

 

[jerrysimon]

Or rethink your battery ?

Do you need to carry that amount of capacity for every trip ?

Jerry

 

[superDove]

Do you put the bag strap around the steering column to stop wobbles?

Down the Pacific coast by Brompton / Clevercycles Blog

 

[cwah]

Or rethink your battery ?

Do you need to carry that amount of capacity for every trip ?

Jerry

My next battery pack will be some LG or Samsung 230wh/kg pack. I'm waiting for some test from endlesssphere before purchase. It will divide the weight of my pack by 2 with 1000wh for only 5kg.

I probably do most of the time between 20-30km. But because of the motor power, I usually use at least 400wh daily at 22mph (I'm slower now because my A123 20AH has been reduced to 17s).

Later I'll go back to 28mph and I expect 600-700wh daily. So 1000Wh seems to be a good number.

 

[cwah]

Do you put the bag strap around the steering column to stop wobbles?

Down the Pacific coast by Brompton / Clevercycles Blog

Since I epoxied the plastic bag frame, wobble has almost stopped

 

[cwah]

it's time for me to upgrade my battery pack with the new 18650 cells. I decided to test the sony US18650V3:

They seem to have life cycle comparable to lifepo4:

But are much more lighter:

44g for 8.1wh / cell means 184wh/kg. Lipo usually average at 140wh/kg and lifepo4 at 120wh/kg. So around 25-30% lighter than conventional cells.. without the hassle

 

[cwah]

I decided to cycle them 100 times to see if the lifecycle mentioned was true. But because I have an icharger, I couldn't discharge to 2.5V as it was done during the tests:

Capacity decrease was related to increasing resistance on the cell after 100 cycles at 5A. I discharged them after at 0.5A and still had 2000mAH capacity.

 

[cwah]

I decided to move my battery pack to the frame:

I use 5mm pvc foam sheet as they are good insulator and easy to shape:

About 600g for the box.

 

[cwah]

I decided to make my own pack of 20s5p for a total of 72V11.25AH:

 

[cwah]

Finalised pack weight 4.6kg:

Currently my brompton weight 26kg.

With the new battery box I'll have:
- 4.6kg battery
- 600g box
- 500g controller
- 200g DC adapter
- 100g wattmeter+fuse
- 100g wiring
- 100g light
- 4.3 kg mac motor

total of 10.5kg added weight.

With an 11kg brompton, I'll have a 20.5kg brompton with able to reach 30mph and 25 miles distance at high speed!

 

[patpatbut]

Hi cwah,

Do you have a photo that shows the battery after unfold?

Pat

 

[cwah]

Not yet, will post it when it's a bit more finalized

 

[Deleted member 4366]

Really good work Cwah. How much did you pay for the cells?

 

[cwah]

Thanks Dave. I managed to get them at 2GBP/cell shipped by buying a big order (350 cells) from Keeppower.

This pack of 72v11.25AH costed me 200GBP. I think it's an excellent price.

If anyone from the forum want some cells I can ship some to them for the price I paid because I owe so much to this forum. Or you can order directly from Keeppower

 

[jerrysimon]

cwah,

Nice offer but it seems that postal services are getting harder and stricter with batteries/cells.

I have heard that many cells shipped from China are being returned when they get to HK for shipping. Many Chinese suppliers on ebay will no longer ship to the UK.

Regards

Jerry

 

[cwah]

Jerry, is there any issue for shipping lithium from France to UK?

 

[jerrysimon]

It seems all air freight shipping of batteries is getting stricter.

Jerry

 

[patpatbut]

It seems all air freight shipping of batteries is getting stricter.

Jerry

Hi Jerry,

I am planning to get the battery from Cellman. Would that be a problem?

He ships via DHL

Pat

 

[jerrysimon]

I think its the cheap HK post that is mostly effected. Suggest you check with him first.


Jerry