Split ebike battery

Batteries, Chargers, and Battery Management Systems.
LegacyCode   1 mW

1 mW
Posts: 17
Joined: Oct 10 2020 4:23pm

Split ebike battery

Post by LegacyCode » Oct 11 2020 6:45am

I found this forum through google when looking into creating a battery pack for my bike, I've been trying to build up an electric bike for a while and I've ran into the problem that pre-built packs just wont fit, since then I've been doing alot of reading on how to make a pack myself i'm just stuck on a few thing that i'd like the input on from those more experienced before i begin and order all the stuff (i've got a spot welder on the way)

On the bike i have a Bafang BBS02b 750w and would like to put a 52v 14s4p pack but due to the size limits i wanted to split it up into 2 packs however I'm not sure what would be the best way to go about this

I was thinking about putting the BMS in pack 1 an run 2 cables with connectors between the packs one for the positive and negative and the others for the S8~S14 wires, I'm not sure what issues this would bring the only one i can think of myself is cables breaking but that should be okay if i use some thicker insulated ones


(didn't add in all the bms wires)
B2.png
B2.png (128.36 KiB) Viewed 844 times

or would it be better to create 2 packs each with a BMS and put those in series


I'm also not 100% sure what BMS i should get, I've been looking at daly BMS 100a


Possible parts being used
Enclosures : Extruded aluminum case's
Plugs : Aviator 7 and 2 pin
Cells : Samsung 30q / 40T (depending on what works size and price wise unless there's better options)
BMS : Daly BMS 100a??

eMark   100 W

100 W
Posts: 299
Joined: Nov 02 2019 11:53am

Re: Split ebike battery

Post by eMark » Oct 11 2020 8:20am

Have you checked out UnitPackPower's triangle packs ... https://www.aliexpress.com/item/3291458 ... 5614%23546

... OR ...

https://www.amazon.com/QZF-Battery-Elec ... KE8020VN1T

What about fabricating your own DIY rear rack for your 14S4P ... https://www.aliexpress.com/item/3284714 ... 5608%23177 ...
and your own 14S4P DIY build. Doing a split pack is too much bother (IMO) ... You can always make your own split pack at a later time if you're still really convinced that's your best option. That will give you plenty of time to figure out the best configuration and best cells for your use. You may decide that a 14S5P (or 7P) would be a better DIY build for your use.

goatman   10 MW

10 MW
Posts: 2327
Joined: Jun 23 2019 6:50pm
Location: Surrey, B.C.

Re: Split ebike battery

Post by goatman » Oct 11 2020 8:44am

the s14+ doesnt go to bms, it is the P+, the bms is P- negative.

you could go 2-14s2p in parallel

LegacyCode   1 mW

1 mW
Posts: 17
Joined: Oct 10 2020 4:23pm

Re: Split ebike battery

Post by LegacyCode » Oct 11 2020 9:25am

eMark wrote:
Oct 11 2020 8:20am
Have you checked out UnitPackPower's triangle packs
I've spoken to them they have nothing that could fit my bike.
eMark wrote:
Oct 11 2020 8:20am
What about fabricating your own DIY rear rack for your 14S4P
I've looked into rear racks, it's not really an option either
goatman wrote:
Oct 11 2020 8:44am
the s14+ doesnt go to bms, it is the P+, the bms is P- negative.

you could go 2-14s2p in parallel
Went based on this image!
Bwiring.png
Bwiring.png (156.49 KiB) Viewed 819 times
14s2p with each their own BMS? (7s bms)

goatman   10 MW

10 MW
Posts: 2327
Joined: Jun 23 2019 6:50pm
Location: Surrey, B.C.

Re: Split ebike battery

Post by goatman » Oct 11 2020 10:36am

each with their own 14s bms

you could go with 14s3p of a 21700 cell like a samsung 40T for a 40amp bms and about 12ah.

in your pic above you see the battery is P+. the battery negative goes to B- of bms and leaves out bms as P-

eMark   100 W

100 W
Posts: 299
Joined: Nov 02 2019 11:53am

Re: Split ebike battery

Post by eMark » Oct 11 2020 11:11am

eMark wrote:
Oct 11 2020 8:20am
Have you checked out UnitPackPower's triangle packs
LegacyCode wrote:
Oct 11 2020 9:25am
I've spoken to them they have nothing that could fit my bike.
eMark wrote:
Oct 11 2020 8:20am
What about fabricating your own DIY rear rack for your 14S4P
LegacyCode wrote:
Oct 11 2020 9:25am
I've looked into rear racks, it's not really an option either.
The time will come when you'd like to have a backup 14S4P pack charged and ready to go when you need to make another significant journey the same day. Also by alternating between both a unitpackpower and DIY 14S4P pack they should serve you well for five years ... with reasonable care/use.

What is so unique about the design of your bike that neither a 14S4P triangle or rectangle pack is doable? Having a difficult time imaging a bike that doesn't have room for a triangle or rectangle pack. Are you building a 3-wheel trike? If so isn't there room enough for a rectangle pack in or under the cargo basket/container between the rear wheels? If a recumbent possibly below the seat. That way you'd be sitting a few inches higher for improved vision :thumb:

999zip999   100 GW

100 GW
Posts: 9747
Joined: Jan 10 2010 1:40pm
Location: Dana Point So. Cal

Re: Split ebike battery

Post by 999zip999 » Oct 11 2020 1:36pm

How about a picture of your bike so I can help you out a little better. Ping does his 20ah packs split with one BMS for years.

markz   100 GW

100 GW
Posts: 11417
Joined: Jan 09 2014 11:38pm
Location: Alberta Canada

Re: Split ebike battery

Post by markz » Oct 11 2020 1:47pm

999zip999 wrote:
Oct 11 2020 1:36pm
Ping does his 20ah packs split with one BMS for years.
Bulky and Heavy compared to the new stuff out now.

John in CR   100 GW

100 GW
Posts: 14797
Joined: May 20 2008 12:58am
Location: Paradise

Re: Split ebike battery

Post by John in CR » Oct 11 2020 2:55pm

Be sure not to make the series connection like in your pic with cell 7+ wired to cell 8+.

LegacyCode   1 mW

1 mW
Posts: 17
Joined: Oct 10 2020 4:23pm

Re: Split ebike battery

Post by LegacyCode » Oct 11 2020 3:19pm

eMark wrote:
Oct 11 2020 11:11am
What is so unique about the design of your bike that neither a 14S4P triangle or rectangle pack is doable? Having a difficult time imaging a bike that doesn't have room for a triangle or rectangle pack. Are you building a 3-wheel trike? If so isn't there room enough for a rectangle pack in or under the cargo basket/container between the rear wheels? If a recumbent possibly below the seat. That way you'd be sitting a few inches higher for improved vision :thumb:
None of their packs can fit the triangle, the smallest one was too big, it's full suspension MTB i'll put a picture below.
I'd like to go with some premade enclosures that can just be modified to go on the bike, i have neither the tools nor the knowlage or skils to make a full enclosure by myself or have something custom made.
goatman wrote:
Oct 11 2020 10:36am
each with their own 14s bms

you could go with 14s3p of a 21700 cell like a samsung 40T for a 40amp bms and about 12ah.

in your pic above you see the battery is P+. the battery negative goes to B- of bms and leaves out bms as P-
I've thought about using those, not 100% sure what cells to use yet, 56 40T compared to 70 30Q cells has a price difference of over a 100 euro.
999zip999 wrote:
Oct 11 2020 1:36pm
How about a picture of your bike so I can help you out a little better. Ping does his 20ah packs split with one BMS for years.
Are there any threads you could link me to that show off those split packs? Putting a picture below
John in CR wrote:
Oct 11 2020 2:55pm
Be sure not to make the series connection like in your pic with cell 7+ wired to cell 8+.
It's supposed to go to 8-, butchered the image a bit, cells are top down view


Image

goatman   10 MW

10 MW
Posts: 2327
Joined: Jun 23 2019 6:50pm
Location: Surrey, B.C.

Re: Split ebike battery

Post by goatman » Oct 11 2020 3:56pm

3p of 40T is the same as 4p of 30q except you only need 42-40T. you only need to fit 42/21700 cells in the triangle

compare the real mah available

40 T cycle test

viewtopic.php?f=14&t=106550&start=25

30q cycle test

viewtopic.php?f=14&t=108547

John in CR   100 GW

100 GW
Posts: 14797
Joined: May 20 2008 12:58am
Location: Paradise

Re: Split ebike battery

Post by John in CR » Oct 11 2020 5:19pm

I've done saddlebag-like batteries over the top tube on a couple of bikes, and while it works fine they can get in the way and it's hard to make look good. You have a pretty big triangle area, so I'd put the pack there if possible, and the little bit that doesn't fit I would put on top of the top tube or under the downtube, whichever fits better for a cleaner mounting as well as better protection of the pack.

eMark   100 W

100 W
Posts: 299
Joined: Nov 02 2019 11:53am

Re: Split ebike battery

Post by eMark » Oct 11 2020 5:44pm

LegacyCode wrote:
Oct 11 2020 3:19pm
None of their packs can fit the triangle, the smallest one was too big, it's full suspension MTB i'll put a picture below.
Image
Can't envision that split pack lookin' cool in your very cool looking bike. Isn't a 12S4P fast enough and cooler-lookin' in that allowable triangle space than your two split 7S4P layout design packs.

It would be helpful for 999zip999 and other DIY designing members if you could post a diagram of the triangle dimensions plus the dimensions of that other space above the rear suspension gizmo. Being you've already ordered a spot welder there should be a way for your DIY build that those two spaces will accommodate-shelter a 14S4P... Interesting challenge :)

If an existing 12S4P (or 3P) triangle pack will fit in that space it will serve as a beginning pack and future backup pack. Assuming your 14S controller will function at 40V (12 p-groups are at least 3.35V). That way you can take your time designing your own 14S4P unique layout with your own custom protective enclosure to fit within that inside space.

The last thing you want is to feel rushed with your first DIY build; especially being it's your first spot-welder build. If you post a diagram with the dimensions of those two inside areas there are some very talented members that should be able to come up with the best 14S design for that available space.
John in CR wrote:
Oct 11 2020 5:19pm
I've done saddlebag-like batteries over the top tube on a couple of bikes, and while it works fine they can get in the way and it's hard to make look good. You have a pretty big triangle area, so I'd put the pack there if possible, and the little bit that doesn't fit I would put on top of the top tube or under the downtube, whichever fits better for a cleaner mounting as well as better protection of the pack.
Agree
markz wrote:
Oct 11 2020 1:47pm
999zip999 wrote:
Oct 11 2020 1:36pm
Ping does his 20ah packs split with one BMS for years.
Bulky and Heavy compared to the new stuff out now.
Agree

Michael B   10 mW

10 mW
Posts: 22
Joined: Oct 03 2019 10:56pm

Re: Split ebike battery

Post by Michael B » Oct 12 2020 2:32am

Play around with this battery shape configurator.

https://e4bike.ru/page/battery-shape-co ... 6336197183

LegacyCode   1 mW

1 mW
Posts: 17
Joined: Oct 10 2020 4:23pm

Re: Split ebike battery

Post by LegacyCode » Oct 12 2020 3:46am

eMark wrote:
Oct 11 2020 5:44pm
LegacyCode wrote:
Oct 11 2020 3:19pm
None of their packs can fit the triangle, the smallest one was too big, it's full suspension MTB i'll put a picture below.
Image
Can't envision that split pack lookin' cool in your very cool looking bike. Isn't a 12S4P fast enough and cooler-lookin' in that allowable triangle space than your two split 7S4P layout design packs.

It would be helpful for 999zip999 and other DIY designing members if you could post a diagram of the triangle dimensions plus the dimensions of that other space above the rear suspension gizmo. Being you've already ordered a spot welder there should be a way for your DIY build that those two spaces will accommodate-shelter a 14S4P... Interesting challenge :) .

This is about the space i have roughly might still replace the spring with one that takes up a bit more space in the future wich would make it smaller
btriangle.png
btriangle.png (287.58 KiB) Viewed 719 times

Problem still remains, i don't have the skills/knowledge or tools to make something like that, I wanted to go with some premade extruded enclosures and at most drill a few holes (don't want to do that to the bike itself) in it where needed and mount those where the red squares are.
batteryplacement.png
batteryplacement.png (445.43 KiB) Viewed 719 times
Enclosures like this
bhousing.png
bhousing.png (226.33 KiB) Viewed 719 times
Running some durable cables between them with plugs like these https://www.aliexpress.com/item/32821634581.html (might need to look for smaller versions)

for the BMS i was looking at these (the 80/100a versions) i'm not sure they work since they are listed as 48v
https://www.aliexpress.com/item/3292112 ... 1460O4dPFx
https://www.aliexpress.com/item/1005001 ... 8c6bWSjmC1

goatman wrote:
Oct 11 2020 3:56pm
3p of 40T is the same as 4p of 30q except you only need 42-40T. you only need to fit 42/21700 cells in the triangle
The 14s4p was based of the 40T, could do 5s 30Q and it would be cheaper, it's quite the price difference, i can't check the 30q right now they went out of stock (looking at nkon)
40t.png
40t.png (31.88 KiB) Viewed 719 times
Michael B wrote:
Oct 12 2020 2:32am
Play around with this battery shape configurator.

https://e4bike.ru/page/battery-shape-co ... 6336197183
That seems like a pretty handy tool

999zip999   100 GW

100 GW
Posts: 9747
Joined: Jan 10 2010 1:40pm
Location: Dana Point So. Cal

Re: Split ebike battery

Post by 999zip999 » Oct 12 2020 10:23am

Here is a 40t pack https://bicyclemotorworks.com/product/5 ... e-battery/
Yes Ping is heavy and big and does a split pack with one BMS

Voltron   100 MW

100 MW
Posts: 2687
Joined: May 02 2013 4:53pm
Location: Santa Barbara CA

Re: Split ebike battery

Post by Voltron » Oct 12 2020 1:12pm

I just run a backpack battery on my full suspension builds, esp during the early days of a build when you're not even sure if you'll love the ride.
It's the hardest part of the setup to get right, and I've had several times I was excited about a particular bike, and all the getting the battery turned out to be a waste of time as I didn't like the handling or fit or whatever.
The handling of the bike is so much better too... I've done back to back comparisons of the same bike with the battery in the frame, then taking it out and running with it in a back, and it's a big difference if you're going sporty riding.
Wearing it actually saved my spine one time too...I got car doored by the passenger side of an Uber, and went over the bars and landed on my back with the curb right across the middle of my spine, but the flat case of the battery spread the hit out...

john61ct   100 GW

100 GW
Posts: 6710
Joined: Dec 18 2018 2:06pm

Re: Split ebike battery

Post by john61ct » Oct 12 2020 1:33pm

999zip999 wrote:Here is a 40t pack https://bicyclemotorworks.com/product/5 ... e-battery/
Yes Ping is heavy and big and does a split pack with one BMS
He might do custom? If doesn't usually offer the higher-density LI cells, ask if you could have them drop-shipped to him?

LegacyCode   1 mW

1 mW
Posts: 17
Joined: Oct 10 2020 4:23pm

Re: Split ebike battery

Post by LegacyCode » Oct 13 2020 8:24am

Spot welder just arrived

Image

eMark   100 W

100 W
Posts: 299
Joined: Nov 02 2019 11:53am

Re: Split ebike battery

Post by eMark » Oct 13 2020 9:45am

Voltron wrote:
Oct 12 2020 1:12pm
It's the hardest part of the setup to get right, and I've had several times I was excited about a particular bike, and all the getting the battery turned out to be a waste of time as I didn't like the handling or fit or whatever.
Couldn't have been expressed better by someone with years of experience.

First question is does LC really need a powerful 14S4P for his primary biking interests? Many years ago I just had to have a 1970 T-bird with a 428 cu in V8. Likewise, many younger bucks think what their e-bike needs is a 14S7P pack. Simon Cowell broke his back riding his speedy e-bike toooo fast for conditions. Your leg watt power and gear ratios should provide you all the speed you need.

Asssume the primary need is for occasional pedal assist with his IDEAL bike (especially for hills) for easier pedaling NOT going 35mph. Thus a DIY build as light as necessary with pedal assist. Those that may have used a secret motor assist in the 2015 Tour de France only used what they needed which wasn't much. What will actually suffice (IMO) is just a 12S3P triangle pack in that space.
Voltron wrote:
Oct 12 2020 1:12pm
The handling of the bike is so much better too
With a lighter one piece 12S3P build inside the triangle space :)

This is my fatherly suggestion which makes more sense, less expensive, lighter, and by far cooler lookin' (1865 or 2170)... https://e4bike.ru/page/battery-shape-co ... 0200600400 ... probably just as enjoyable and more practical ... than a split 14S4P pack which is overkill (JMO).
Michael B wrote:
Oct 12 2020 2:32am
Play around with this battery shape configurator.
https://e4bike.ru/page/battery-shape-co ... 6336197183
What a valuable post! ... THANKS
LegacyCode wrote:
Oct 11 2020 3:19pm
i have neither the tools nor the knowledge or skills to make a full enclosure by myself or have something custom made
The REAL (IDEAL) challenge of your first DIY build is acquiring the knowledge and skills to build a triangle pack (12S3P) to fit in the available space. You'd be pleasantly surprised at what you can accomplish when you give it your all; even more so now with Google and this ES forum. You've already got a spot-welder, so begin acquiring the knowledge and skills to build a 12S3P triangle pack that will be a cool fit/addition to your IDEAL bike and a satisfying/fun cycling experience. Maybe a 13S3P triangle build would also fit in that space. My bet is that if you do you'll realize that a 14S4P split pack wasn't the best solution or really necessary.

Look at it as a blessing that you don't have enough space in that triangle for a 14S4P build. Whatever you decide after all is said and done you may realize that a 14S4P split pack wasn't the best solution for your riding need and enjoyment.

Voltron   100 MW

100 MW
Posts: 2687
Joined: May 02 2013 4:53pm
Location: Santa Barbara CA

Re: Split ebike battery

Post by Voltron » Oct 13 2020 12:54pm

Re. using thicker balance wires, thin ones are somewhat self fusing, and will melt if shorted...usually anyway. When you go bigger, then you also have to start thinking about individually fusing each one, in case the harness shorts in a crash, for example...

999zip999   100 GW

100 GW
Posts: 9747
Joined: Jan 10 2010 1:40pm
Location: Dana Point So. Cal

Re: Split ebike battery

Post by 999zip999 » Oct 13 2020 2:11pm

Does the Samsung 40t pack I gave you a link to fit ?
Or will it fit ? It's 12 in
It gives you dimensions all you have to do is get some cardboard and some tape tape the battery mock-up and see if it fits you were going to have to do it anyways you're going to have to make a maca more that bike the time you thinking about it battery you might have to make three of them before you get it right

LegacyCode   1 mW

1 mW
Posts: 17
Joined: Oct 10 2020 4:23pm

Re: Split ebike battery

Post by LegacyCode » Oct 13 2020 2:25pm

999zip999 wrote:
Oct 13 2020 2:11pm
Does the Samsung 40t pack I gave you a link to fit ?
Or will it fit ? It's 12 in
It gives you dimensions all you have to do is get some cardboard and some tape tape the battery mock-up and see if it fits you were going to have to do it anyways you're going to have to make a maca more that bike the time you thinking about it battery you might have to make three of them before you get it right
It's too big, Ordering from the US would become very expensive shipping and tax wise too.

Did that for the different hailong packs and some other options all too big!
Voltron wrote:
Oct 13 2020 12:54pm
Re. using thicker balance wires, thin ones are somewhat self fusing, and will melt if shorted...usually anyway. When you go bigger, then you also have to start thinking about individually fusing each one, in case the harness shorts in a crash, for example...
Would still use thin wires internal if that makes a difference, will have to read up on this!
eMark wrote:
Oct 13 2020 9:45am
First question is does LC really need a powerful 14S4P for his primary biking interests? Many years ago I just had to have a 1970 T-bird with a 428 cu in V8. Likewise, many younger bucks think what their e-bike needs is a 14S7P pack. Simon Cowell broke his back riding his speedy e-bike toooo fast for conditions. Your leg watt power and gear ratios should provide you all the speed you need.
I'm honestly not 100% sure what i need, kinda going based on what unitedpackpower had listed in their descriptions.

i will mostly just use it as round bike to get where i need to be, we don't really have any hills here. will limit it to 25km/h (legal limit) and no throttle because you need a license for that, my normal trips are going from my town to a nearby city which is about 15~20km to and back but might want to take trips to the larger city someday which is 50~60km to and back.
upp.png
upp.png (21.47 KiB) Viewed 563 times

Michael B   10 mW

10 mW
Posts: 22
Joined: Oct 03 2019 10:56pm

Re: Split ebike battery

Post by Michael B » Oct 13 2020 4:10pm

That Malectrics spot welder is the one I bought. It worked fine for me.

As an example this is the 18650 (LG MH1 - 3200 mAh) 13s3p triangle shape I made.
Bluetooth BMS (~150 x 65 x 12mm) sits along the top where it says 142.
You should be able to come up with something in 52V flavour that will fit.
13s3p50.png
13s3p50.png (96.33 KiB) Viewed 535 times

999zip999   100 GW

100 GW
Posts: 9747
Joined: Jan 10 2010 1:40pm
Location: Dana Point So. Cal

Re: Split ebike battery

Post by 999zip999 » Oct 13 2020 5:48pm

On your I n neither- land.

Post Reply