DIY build my own E-bike battery - tips?

[Emsflea]

Hey guys.
I was informed that my BAFNAG needed a 52v 25amp battery to reach 1800w peak (thats bafang 1000w)

I was wondering if there is any templates to go off kind of like a lego set instruction manual to build my own batteries like this?

Or a template calculator where by you put in your desired V and amps? Then it shows you how to set up the batteries, and where the strips go.
I am somewhat clued up (but still novice - have experince in soldering and other electrical stuff)
LG 21700 4800mah at 14A should do the job for me. for this build.

What can i read up on or watch to improve my theroy?

thanks guys.

 

[Chazmo]

I’ll bet there is a calculator somewhere for this. In any case, the battery needs to supply the nominal voltage, but you need to figure out how many Watt-hours you need to size the battery for the amount of riding time you want. I’m pretty sure my Juiced RipCurrent S was capable of ~2000W peak with the upgraded power controller, but stock I don’t think it ever gets barely over 1000W. It’s pretty much up to the controller how much power the motor can draw.

I don’t know if this helps you, but my bike came with 52Vx19.2Ah battery (~1000Wh). This battery has 84 cells in a 14Sx6P configuration. I can get 50-60 miles of my kind of riding on a full battery, and I usually ride under 35 miles charged up to 80% and never getting near 20% on discharge. This is very well-suited for me, but definitely not if you are riding mountains or longer distances.

 

[harryS]

Samsung 50S, a 5AH 21700 rated for 25A if you can keep it cool. Otherwise, should push 10A easy and if you had a 14x4 array, that's a 52V20AH battery capable of 40A. Make it 14x5 for a 25Ah battery,

In any case, go with a 5AH cell that's rated for at least 14A of continuous current. You will use either a 14x4 or 14x5 array, called 14S-4P and 14S-5P. P x the cell Ah is the battery AH, That's all the calculating done, The rest is craftmanship.

You can buy a rectangular cell holder and put your cells in it. Then shrinkwrap. put in a hard case, and figure out a way to mount on the bike, Or you can buy a plastic battery case/cradle with cell holders. EIther approach needs a BMS. A bluetooth model is nice, but yu need a case bug enough for it,

It's a lot of stuff to learn and needs lots of tools and supplies. The early guys that did youtube videos on it are pretty much all obsolete, using techniques 5-7 years ago that are deemed unsafe today,

Batteries capable of 50A require some thought in how you get that kind of current to the motor w/o melting things. Helps to have a background in power and and to be afraid of fires.

 

[Gionnirocket]

Hey guys.
I was informed that my BAFNAG needed a 52v 25amp battery to reach 1800w peak (thats bafang 1000w)

I was wondering if there is any templates to go off kind of like a lego set instruction manual to build my own batteries like this?

Or a template calculator where by you put in your desired V and amps? Then it shows you how to set up the batteries, and where the strips go.
I am somewhat clued up (but still novice - have experince in soldering and other electrical stuff)
LG 21700 4800mah at 14A should do the job for me. for this build.

What can i read up on or watch to improve my theroy?

thanks guys.

Easy... Just buy a battery.
To build a battery requires precision spot welding so as not to damage the cells and it requires specialized equipment and a bit more knowledge and experience. Building one battery in just buying what's needed will cost you more than buying a pack already built. Forget about the learning curve and possibly ending up with something dangerous.
Unless you plan on building multiple batteries... I would not go down this path.

 

[Emsflea]

Yeah i plan on building quite a few e bikes so the tools will be ok for purchase - not necessarily will my own batteries be sold with my finnished builds, its more of a skill set id actualy like to learn and get down.
People round here for whatever reason are starting to see me as "the e bike guy" and im like - woah. I dont know that much lol

 

[Emsflea]

Found this too and understand more now.

 

[PCeBiker]

Yeah i plan on building quite a few e bikes so the tools will be ok for purchase - not necessarily will my own batteries be sold with my finnished builds,

I think you should build ebikes with batteries provided by a Quality Battery builder with complete UL certified batteries.

You could advertise your ebikes as having UL certified batteries.

, its more of a skill set id actualy like to learn and get down.

It ain't just something you learn.
You need to spend Lots of money getting UL tested and certified.
Let the professionals do it and take responsibility for the batteries.

People round here for whatever reason are starting to see me as "the e bike guy" and im like - woah. I dont know that much lol

There's too much to learn, too much to spend, and too much responsibility building batteries, (buildings could burn).

Spend your efforts learning how to build proper safe ebikes mechanically and everything else electronically from the battery down.

 

[gromike]

Battery building is a great skill to have, but a terrible hobby. Kind of makes you a pariah nowadays.
Selling your batteries, on or off the bike, is a huge liability risks. So it's best not to have any traceable assets.
That being said, you can build a safe, capable battery. It will take building a few before you get there, and maybe a few cheap battery spot welders before you buy one of those that doesn't turn into smoke.

 

[PCeBiker]

Battery building is a great skill to have, but a terrible hobby.

4P4S soldered solid core house wire 12 Volt battery FTW,..

Hasn't blowed up yet.
It's been 10-15 years on the shelf.

 

[Gionnirocket]

Yeah i plan on building quite a few e bikes so the tools will be ok for purchase - not necessarily will my own batteries be sold with my finnished builds, its more of a skill set id actualy like to learn and get down.
People round here for whatever reason are starting to see me as "the e bike guy" and im like - woah. I dont know that much lol

Decent video as most I've seen are complete hacks. Though he didn't mention anything about the welder he is using and that's probably the most important piece of hardware needed.
Still think it's not worth the effort as tech advances/changes and prices drop.
That said it is interesting and I did research it myself but ultimately decided against. Mainly because of the previous statement and that a quality battery should last at least 5 years and how many could I possibly need as I would not take on the liability of selling to anyone.
A few things that I will say if you do decide to go forward.
Make sure you buy quality batteries from a reputable source as counterfeits are out there.
As somewhat mentioned in the video, a quality safe pack will have cells built with matching voltage. But you also want to buy batteries of the same manufacturer lot so the chemistry and performance will be as equal as possible. They need to work as one.
The nickel strips need to be of the correct gauge.. I'm not sure I agree with doubling up on it.
And do some more research

 

[harryS]

Found this too and understand more now.

FYI. He needs insulating washers over the positive terminals. It's for reliability over time, and also good insurance if your weld is done off center. There's a real chance one could put the weld tips down off center and short the positive terminal to the side of the cell. I probably would have but I used the washers. Otherwise, seems like a well done video,

 

[Emsflea]

I think you should build ebikes with batteries provided by a Quality Battery builder with complete UL certified batteries.

You could advertise your ebikes as having UL certified batteries.

Yes this is the way i was already going to do that thanks for your input.

4P4S soldered solid core house wire 12 Volt battery FTW,..

View attachment 198761

Hasn't blowed up yet.
It's been 10-15 years on the shelf.

Hahahah - oh my, its like a drug addict had just enough spares found a few vape pens in the street - and sold it for $20.

 

[Emsflea]

FYI. He needs insulating washers over the positive terminals. It's for reliability over time, and also good insurance if your weld is done off center. There's a real chance one could put the weld tips down off center and short the positive terminal to the side of the cell. I probably would have but I used the washers. Otherwise, seems like a well done video,

if it shorts like this - does the battery simple fail to run? and fail to charge?

 

[PCeBiker]

Hahahah - oh my, its like a drug addict had just enough spares found a few vape pens in the street - and sold it for $20.

I bought a used ebike about 10 years ago that was already 10-15 years old.
It came with new SLA batteries but the guy was experimenting with making a lithium battery for it using lithium cells from old laptop computers.
He gave me all the lithium cells including the ones he soldered together.

I never did get around to making a battery, but I bought a 36 V BMS to help make it a little bit safer.
He would charge the pack with a 12V battery charger for a car.
Another neighbor at the time set his garage on fire charging his homemade battery that way.

 

[Emsflea]

I bought a used ebike about 10 years ago that was already 10-15 years old.
It came with new SLA batteries but the guy was experimenting with making a lithium battery for it using lithium cells from old laptop computers.
He gave me all the lithium cells including the ones he soldered together.

I never did get around to making a battery, but I bought a 36 V BMS to help make it a little bit safer.
He would charge the pack with a 12V battery charger for a car.
Another neighbor at the time set his garage on fire charging his homemade battery that way.

Jeez - I'm actually buying a fire proof box to store the battery im buying and for when i charge in doors.

 

[Emsflea]

K weld seems to struggle if doubling up

so deffo need the big boys toys for that.

 

[Gionnirocket]

That's what annoyed me when researching this.
Seems most are using toys or some hacked up equipment.
The proper spot welder and how to set it up shouldn't be a mystery.
And I've learned that the proper tools no matter the task make all the difference.

 

[6zfshdb]

I considered building my own batteries for a time. Obtaining the necessary skills, equipment and materials, plus my time, made me change my mind. I would never save any money. The only advantage would be the known build quality. With UL standards being applied to e-bike batteries now, that worry is much less. With newer, safer technology on the horizon, the equipment investment would be obsolete in the near future.

If I were in business, it would make far more sense. For now, I'll continue to shop out quality replacement batteries.

 

[Gionnirocket]

4P4S soldered solid core house wire 12 Volt battery FTW,..

View attachment 198761

Hasn't blowed up yet.
It's been 10-15 years on the shelf.

That's what I use to burn my crack pipe... The intense arch makes it glow niiiiiiiiiiice

 

[Slaphappygamer]

if it shorts like this - does the battery simple fail to run? and fail to charge?

If a cell shorts out, it starts to get hot. This may impact the surrounding cells. If the surrounding cells also get hot. Then thermal runaway could begin.

Me personally, I’d never build a battery. It doesn’t make financial sense. If I did, then I’d follow this build.