The Hundred Dollar Ebike Battery

George S.

Well-Known Member
The Hundred Dollar Ebike Battery

You can build an ebike battery in an hour if you understand the basic concept of ‘series’ power. The parts are simple. You buy 7 of these. You cut off the connector and carefully do a series connection (black to red) on each pack. Tape it up.

https://batteryhookup.com/products/lg-chem-7-4v-11ah-81wh-module-w-bms

If this is too much trouble, you can buy this on Ebay and have it in a week, from California. This is an 8 amp hour battery, according to the spec sheet. These are 18650 cells. So, with 39 cells, you are talking 2 bucks a cell and a few minutes in the robot welder. It has a protection board.

Battery hookup is giving you 70 older and used cells, but name brand. Ebay is giving you the generic cell of the day.

https://www.ebay.com/itm/48V-8Ah-10...hDarwoV3BBEV2b&_trksid=p2047675.c100005.m1851

How good are generic Chinese cells? Who knows. This Ebay vendor has moved stock to the US and has good feedback. You want a vendor who is building a name, and having a US presence is really a key.

I’d like to know how these things spec out. One way or another, I think ebike batteries could be like power tool batteries, or Dyson batteries, or robovac batteries -- Easy to clone and sell on Ebay and Amazon. The only proprietary thing is the connector point, but maybe that can be fudged.
 

ki11a

Active Member
From what I understand about batteries, you need high quality cells from reputable dealers mainly Japanese and Korean.

The lower quality Chinese cells just dont match up to the high amps and drainage that these higher quality cells are known for and these ebike motors consume. I am sure you can make an ok battery with chinese cells but to say how long they will last and how much steady power they will give is an unknown.

To where quality cells have proven specs and reliable data. But I also would like to see these Chinese cells spec'd out for curiosities sake.

I have a 'free' hookup of unknown relatively cheap and unknown Chinese 18650's...but to build a series battery out of them, I dunno...
 

ki11a

Active Member
That batteryhookup link is interesting to say the least though, if I had expendable cash to just play around with Id for sure test out building a battery out of those LG cells.

not going to risk my house or bike to cheap cells. hoverboards anyone??

Bwahah seriously, or the Samsung Note?!
 

fooferdoggie

Well-Known Member
That batteryhookup link is interesting to say the least though, if I had expendable cash to just play around with Id for sure test out building a battery out of those LG cells.



Bwahah seriously, or the Samsung Note?!
but we are talking using cheap cells and building a battery yourself.
 

FezUSA

Member
I'm a SCUBA diver and dabble with underwater photography. I have regular lights for diving purposes and also underwater strobes for photography. They all use name brand batteries. Last year there was a catastrophic fire on a dive boat during the night that resulted in ALL passengers dying. One possible (likely?) cause is that the fire was started by all of the batteries and equipment being charged. The threat is real. There are specific bags available on the Internet that you can put your charger/ batteries in and even if it catches fire the bag will provide fire resistance. The bottom line is that recharging these batteries can result in fire. Can it happen to name brands? Yes. Is it less likely? Possibly, maybe even probably. Tinkering with these cells and chargers is not something I personally would want to be involved with. Leaving cells on a charger out of sight, nope not going to do it. Putting a smoke detector close to where you're charging is probably a good first step!! Using quality components should be a given.

Just my 2c!
 

Dallant

Well-Known Member
Yeah like these...
 

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AHicks

Well-Known Member
I'm thinking the cells in a pack should match in voltage pretty closely. That would certainly be something I'd want to discuss prior to buying a bunch of bateries I was going to solder together. Simply ask the question "will you guarantee these cells are matched?" PRIOR to the sale. My bet is some will pretend to not know what you are talking about....
 

FezUSA

Member
Honestly, a Lipo fireproof bag may be ok, but maybe not. There are plenty of YT videos out there that test a whole bunch of them with varied results, and most of those are using small RC battery set ups, nothing anywhere near the size of an ebike battery. An ammo can is probably the next best step up from the Lipo bags. After that you'd be looking at a Bat-Safe, then a Zarges battery safe. However they can get quite expensive. Probably the best solution for home is to get a sheet of cement board and some thin-wall cinder blocks and build your own battery bunker for under $25. Put a section of the board down as a base, build a wall around the perimeter ON the board using the blocks and then put another piece of the board down on top while charging. I would add a fire detector to the mix and make sure there's a bucket of sand (play sand will do) close by. The sand will extinguish a lipo fire much much quicker than water.

Also, balanced batteries are much less likely to catch fire. The reason for this is that if there's not a balancer in play, then some of the cells are being overcharged while the undercharged ones are being brought up to level. It's these overcharged ones that will then be a problem.
 

Dallant

Well-Known Member
Honestly, a Lipo fireproof bag may be ok, but maybe not. There are plenty of YT videos out there that test a whole bunch of them with varied results, and most of those are using small RC battery set ups, nothing anywhere near the size of an ebike battery. An ammo can is probably the next best step up from the Lipo bags. After that you'd be looking at a Bat-Safe, then a Zarges battery safe. However they can get quite expensive. Probably the best solution for home is to get a sheet of cement board and some thin-wall cinder blocks and build your own battery bunker for under $25. Put a section of the board down as a base, build a wall around the perimeter ON the board using the blocks and then put another piece of the board down on top while charging. I would add a fire detector to the mix and make sure there's a bucket of sand (play sand will do) close by. The sand will extinguish a lipo fire much much quicker than water.

Also, balanced batteries are much less likely to catch fire. The reason for this is that if there's not a balancer in play, then some of the cells are being overcharged while the undercharged ones are being brought up to level. It's these overcharged ones that will then be a problem.
Great thoughts. I’ve wondered what is best and why it’s tough to find purpose built fireproof containers for these batteries. Seems like a natural money maker especially considering how popular these ebikes are getting.
 

Dallant

Well-Known Member

FezUSA

Member
None of those are long enough to hold my Bosch PowerTube batteries. Gotta be at least 19” inside length.
Looking at the price of the bigger boxes (I think Zarges will also custom size you one) that's a little expensive. The best route is to make your own "battery bunker". Very inexpensive, you custom size it to whatever works for you.
 
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Timpo

Well-Known Member
There are tons of YouTube channel testing out those cheap Chinese cell packed batteries.

To make a long story short, they don't give anywhere near performance that's promised.

For example, 48V 15Ah pack may actually be 48V 6.5Ah.
 

George S.

Well-Known Member
The Chinese want to own electric cars, so they are 'encouraging' the Koreans to manufacture in China. So, there are a lot of Chinese cells that blend with the Korean names. LG Chem will have major production in China (56%). There are some technology transfers, but people need to deal with China. I noticed the Honda Inverter generator uses unknown Chinese Cells, and so do several other large, high amp power packs. These cells are everywhere, and the push has been over the past two years. You can't say what the cells really spec at, but they are getting better and the Chinese want to make it so their cells are LG spec and vice versa. The fires are pretty rare. You can charge outside or in a protected box. The are bad misrepresentations on Ebay by Asian vendors, but there are sellers with longer histories and excellent feedback. People griped about Chinese solar, but they have a tremendous presence, exacty what they want from lith.

The stuff Tom at Battery Hookup sells is usually very solid. He got started 3 years ago selling thousands of new/old stock hoverboard packs. I bought 5 and used them for a year, ight out of the box with one adapter. I still have 50 loose cells. They were branded. People tore the packs apart, made multiple YouTube vidoes. They analyzed the BMS in the packs. Everything seemed to check out. The construction was flimsy, but 3 years later everyone seems happy enough. Twenty cells for $30. Why not recycle cells? It's sad that there are no great ways to assemble cells, and now they use robot welders and cheap new cells, which drives down the value of old cells. You have to be careful to make them work, but the pack on offer is assembled and the BMS might be useable. There is going to be a lot of stuff to recycle. How long do they last, even at 50% of capacity? Battery Hookup is an experience.

The safest chemistry is LiFePo4. The Chinese pretty much own LFP. Tesla is looking at LFP, but it's not new. It doesn't catch fire or explode under any normal circumstances. I have an LFP ebike pack that is 5 years old. It's 500 wh and as of last month 450 wh were still useable.They are rated for 2000 cycles. You can find LFP ebike packs on Ebay. Some of the vendors have been around for years, and the 4 month boat ride is less common, to get one delivered. You can get them out of California. If I wanted a safe pack I'd go with LFP. It's taking over the RV market, and US companies tend to try to brand the Chinese stuff, which isn't a great long term strategy.

So, you know, better Chinese cells and decent ways to recycle used cells. Then there is LFP. All things outside the marketing sphere of US ebike companies. Sadly.
 

CdnShaun

Active Member
For my newest builds I have chosen to go with EM3ev Batteries:

High Quality Cells, protection/BMS and a key factor - every cell in the battery is fused - this really sold me on their design at their price point.

My research for capacity per dollar lead me to choosing their configurations with Samsung 35E cells. My first project bike with these batteries has 588 cells, 7,200 Wh @ 52V. The performance has been incredible using the batteries as direct connects to each motor in my 2WD setup and my final step in the project build is to put them into parallel.

I did look at the 'blue wrapped' batteries from AliExpress for example in my initial research - and the YouTube videos of batteries failing/catching fire was eye opening to say the least. After reading all I could around the internet, EM3ev was the price/value/quality I was looking for.

I have 2 more builds in progress with additional EM3ev batteries already purchased. I'm starting to sell off all my Bionx batteries and equipment as I transition to 9C motors and these batteries.

$100 battery? Nope...not even close. But I did find EM3ev to be around 50% of the cost most other top name brand batteries were selling for and yet have the quality/protection/BMS (with bluetooth as a bonus) I was looking for. I wanted to share this experience here in this excellent thread to simply offer up another perspective.

Cheers
 

George S.

Well-Known Member
For my newest builds I have chosen to go with EM3ev Batteries:

High Quality Cells, protection/BMS and a key factor - every cell in the battery is fused - this really sold me on their design at their price point.

My research for capacity per dollar lead me to choosing their configurations with Samsung 35E cells. My first project bike with these batteries has 588 cells, 7,200 Wh @ 52V. The performance has been incredible using the batteries as direct connects to each motor in my 2WD setup and my final step in the project build is to put them into parallel.

I did look at the 'blue wrapped' batteries from AliExpress for example in my initial research - and the YouTube videos of batteries failing/catching fire was eye opening to say the least. After reading all I could around the internet, EM3ev was the price/value/quality I was looking for.

I have 2 more builds in progress with additional EM3ev batteries already purchased. I'm starting to sell off all my Bionx batteries and equipment as I transition to 9C motors and these batteries.

$100 battery? Nope...not even close. But I did find EM3ev to be around 50% of the cost most other top name brand batteries were selling for and yet have the quality/protection/BMS (with bluetooth as a bonus) I was looking for. I wanted to share this experience here in this excellent thread to simply offer up another perspective.

Cheers
Paul is out of that Endless Sphere world, and he's a very knowledgable guy. But he is a bit of a dinosaur. I loved his MAC motor, but I guess it's gone now, not in the catalog. That's too bad. He offered prototypes of different versions trying to push the tech. What won is volume and efficiency. You buy a Bafang hub or something similar, and they are better over time, more torque, maybe not a MAC, but good enough and a lot less. You couldn't build Lectric XP's with the MAC.

My recollection, which dims every day, is that the fuse thing is something Tesla started, then Paul picked it up, Luna probably did, Jehu Garcia talks about it. It surely serves a purpose but obviously it's a marketing point, since there is no real data. I used to argue with Paul (he sort of lectured, but that's cool) about robotic spot welding and assembly line packs. I think he uses that stuff now, and his prices are way down.

The Chinese are building a million or so electric cars a year. Each car has a lot of cells, so every cell really has to be very reliable. And these huge packs really need every safety feature. A 50 cell ebike pack for a 500 watt motor? Gee I don't know, what is the standard? I've used Lipo and Titan packs, old stock hoverboard batteries, blue wrap Lifepo, a Luna Shark. You have a super high perfomance cycle type vehicle, probably not a legal ebike. But if you are talking Lectric XP stuff, the 50 cell pack for 15 amp draws across 4 parallel strings, you can get away with a lot. You need what you need, and Paul is your guy. No doubt. Everything Paul says seems 100% valid, but the market seems to have gone in a high volume direction.