Building a small (36v/8ah) bottle battery with BMS

[Warwick]

Can someone here advise me or show me a link to a way of building a small bottle battery for a kit I have lying dormant?

Someone on here once built a very small bottle battery, but I want to use a vruzend kit, or something similar to keep things simple. I want to do the least amount of soldering possible.

I am a novice on such matters, so have no idea of how to proceed, but a willingness to try.

 

[Woosh]

maybe with 20 U-tagged ncr20700b cells?

https://www.nkon.nl/rechargeable/21700-20700-size/sanyo-ncr20700b-lithium-battery.html

 

[Nealh]

Small bottle battery you will need all the room to utilise, Vruzend kit bits will make things to bulky.

d8veh it was who made one with 20a HG2's, 10S 2P I believe.

Here's the thread.
http://www.pedelecs.co.uk/forum/threads/how-to-make-a-lightweight-battery.28437/

 

[Warwick]

That's the thread, thank you. Looks a bit beyond my very limited skills on reflection.

 

[Woosh]

you can't solder directly wires to the cells, the prewelded nickel tags solve that problem for you. Each cell weighs 63g, 20 cells + BMS + wires add up to about 1.5kgs. The good thing is they are small so can be hidden inside a normal bottle and still pack enough punch for a typical e-bike.

 

[Nealh]

When my 2 x 29E Dolphin batteries have had their day on my commute/town errand bike , I shall most likely build a drinks bottle replacement. A 10s or 13s 2p with VTC6 cells or hg2 most likely for a handy 216 - 297 wh, ideal for 10 - 20 miles.
Though for 13s a taller size 80mm dia drinks bottle will be needed as 13s in cylinder is an awkward number to put in series so 3 tiers is easier to weld and connect up allowing a bms to sit on the side.

 

[KirstinS]

When my 2 x 29E Dolphin batteries have had their day on my commute/town errand bike , I shall most likely build a drinks bottle replacement. A 10s or 13s 2p with VTC6 cells or hg2 most likely for a handy 216 - 297 wh, ideal for 10 - 20 miles.
Though for 13s a taller size 80mm dia drinks bottle will be needed as 13s in cylinder is an awkward number to put in series so 3 tiers is easier to weld and connect up allowing a bms to sit on the side.

Have you found a suitable bottle Neal?


Sent from my iPhone using Tapatalk

 

[Nealh]

I have found an 80mm dia 1000ml ali bottle on AliEx and a couple on UK sites, need to buy one to see if internal length is enough for 3 tiers of cells.
I reckon I need about 205/210mm internal space, bottles overall length is approx. 260mm.

For the bottom plate d8veh had a new one made up 3D, I have found an 80mm rubber bung/grommet that may do the job or one of those plastic desk cable tidies that fits a 80mm desk hole. And some 0.4mm grp sheet for cell separation.

Haven't yet looked for bms to complete items required.

I reckon 10s2p build will be about 1.4kg and 13s about 1.8kg.

 

[awol]

These are only about 70mm dia but the large version of this is about 220mm long and will fit 30 cells in, the smaller version is about 170mm and will fit 20 cells in, but not a bms in either unless it's very small and can lay in the top spare space of about 25mm spare.
https://www.amazon.co.uk/Zefal-Unisex-Adult-Tool-Bottle/dp/B00RN48ESG/ref=sr_1_1?ie=UTF8&qid=1537645222&sr=8-1&keywords=zefal+tool+bottle&th=1&psc=1

These are about 70dia and 190mm long so will fit 20 cells in with no bms again but about 50mm spare space at the top.
https://www.amazon.co.uk/Lixada-Storage-Cycling-Bicycle-Container/dp/B071NH328Q/ref=cts_sp_4_vtp

How small can a bms go?

 

[Nealh]

10s is the easy option but I don't like easy and want 13s, so have ordered a 1000ml /80mm bottle from AliEx.
Same style as d8veh used with the neat charge socket hidden in the lid cap.
Also plan on mounting a panel mount fuse at the bottom for easy access.

Smallest 13s 30a bms I have found is 78mm x 60mm.
or 25a bms 67mm x 53mm with peak 60a max should do nicely. 4.18v balance & 4.19v balance release voltage.