18650 cell questions

ultralight01

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Oct 30, 2016
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Hood River, Oregon
Hi there. I'd like to build a 48v electric bike with an 18650 cell battery. What layout will give me the most range with how may batteries? I'm willing to buy 50+, anything is cheaper than a $400-$1000 manufactured 48v battery.

Thank you! Also, how do you charge a homemade pack like this?
 

culvercityclassic

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Sep 27, 2009
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Culver City, Ca
You would be better off buying a pre-made pack. To do your own pack right you would need a spot welder made to link all the batteries together along with a battery management system to manage the charging and discharging. It's not an easy task for a first time builder and if done wrong could become dangerous and expensive. Check out a couple youtube video's to get an idea.

My choice would be a pack from this company: https://lunacycle.com/18650-ebike-battery-pack/
 

cannonball2

Well-Known Member
Oct 28, 2010
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Colonial Coast USA.
Heres a link to one of my builds. I used recycled 18650 laptop cells. I used a normal 48v SLA charger and monitored the charging with a volt meter. Packs worked well but were not long lived(several months) because of the used cells. Had decent range, are a pain to build, for most folks(having to solder versus a welder), and sketchy on life unless spending mucho$$ on new cells. Don't believe the AH claims on the cheaper 18650s.

I have since moved to lipos and run two 10ah 6s in series(50.4v off charge) these work extremely well have excellent range and cost(at the time) less than $100 a pack. I also run 5ah 4s in various combos up to 63v. These are cheaper still.

In over 10yrs of using lipos in R/C and Ebikes I have never had an issue, but I am very careful. It seems the 18650s are more volatile at least in Ecigs and hover boards. Probably bad handling which is usually the issue.

http://motorbicycling.com/showthread.php?t=53965
 
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cannonball2

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Oct 28, 2010
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Colonial Coast USA.
4 are both big and heavy. They average 7lbs each, or 28lbs. Keep em very low on the build!

They are cheap and forgiving as far as charging. I used them in a couple of builds.

A good Ebike is a delight to use. One with SLAs not so much!
 

biknut

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Sep 28, 2010
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Dallas
Just buy one. Prices have gotten so reasonable that unless you're going to buy a really large number of cells in bulk, and start building a bunch of packs you can't beat the prices of Chinese factory's. Plus do you really want to take a chance on making a mistake and burning down your house? My original plan was to build my own battery, but when I started looking around at prices I figured out that for the trouble, and risk if you're unexperienced, it's not worth it.

This is a 48v 30ah made with Samsung cells. It's rated for 30 amp continuous, 60 amp burst. That's good for up to about a 1500w motor. It was $625 shipped. You can't even build one for less if you have to buy all the equipment necessary to build it, like a spot welder. This one came with 1 year warranty too.

 

KCvale

Well-Known Member
Feb 28, 2010
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Phoenix,AZ
Just buy one. Prices have gotten so reasonable that unless you're going to buy a really large number of cells in bulk, and start building a bunch of packs you can't beat the prices of Chinese factory's. Plus do you really want to take a chance on making a mistake and burning down your house? My original plan was to build my own battery, but when I started looking around at prices I figured out that for the trouble, and risk if you're unexperienced, it's not worth it.

This is a 48v 30ah made with Samsung cells. It's rated for 30 amp continuous, 60 amp burst. That's good for up to about a 1500w motor. It was $625 shipped. You can't even build one for less if you have to buy all the equipment necessary to build it, like a spot welder. This one came with 1 year warranty too.

The important thing in any LI pack is the BMS (Battery Management System).
It is what manages power in and out and keeps the thing from exploding.
I am a CET and leave it to pros too.

Save
 

ultralight01

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Oct 30, 2016
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Hood River, Oregon
Ok, thanks for the advice. That looks like a great battery. When I get serious about electric I may buy a high power electric bike. I've been looking at he stealth and zero motorcycles. Trying to find the best combination of weight, acceleration and range for the price and difficulty level.
 

cannonball2

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Oct 28, 2010
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Colonial Coast USA.
Not trying to start a battery chemistry discussion just offer some insights with my experiences.

I went the 18650 route both with building and buying. I actually bought a 15ah pack from a trusted seller on the west coast. The home built packs worked well but as I said were fairly short lived due to the cells being recycled.

With the bought pack I had a BMS failure which was warrantied.
Several months into the bought pack I had cell failures. It would have been warrantied but I just recycled the pack and moved on to lipo.

I have been running these two 10ah 6s packs about a year. They see daily use. If one is being conservative the range is in the upper 20s. Current cost is $89.67/pack.
There are 16ah and 20ah packs(20s I think are out of stock) Heres a link to the 16s. These are only rated a 10c(160amps) with 20c(320amps) bursts. Who knows if thats a reality. Who cares most common Ebikes don't pull close to half that.

This bike is a distillation of my ideal set up. Runs a 350w 36v geared rear hub paired with a 48v controller. The 6s packs come off the charger at 50.4v. I some time for fun add a 10ah 3s in for 63v. Its pretty quick on 63. Just have to be careful not overloading the gears too much on take off. The caps in the old controller are 63v. I added several more in parallel. Have yet to blow the cheapo controller. This bike is very light and rides like a Lexus over the rough roads on the island here.I have two other Es this is my favorite.


https://hobbyking.com/en_us/multistar-high-capacity-6s-16000mah-multi-rotor-lipo-pack.html
 

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cannonball2

Well-Known Member
Oct 28, 2010
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Colonial Coast USA.
While that is possible you might want to consider that these are only rated at 5c or 20amps. Depending on your controller you could exceed this rating with results like seen on the news.

The construction is 18650s. If you are going to run Li based batteries I would stay with The LiPo based battery. More power density, more C rating and from what is seen recently less of a hazard. I think the issue with the hover board packs is the use of inferior cells. I bet the sellers are dumping these type of packs.

Be careful!
 
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cannonball2

Well-Known Member
Oct 28, 2010
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Colonial Coast USA.
Run two of these for $156.

http://www.ebay.com/itm/Taotuo-22-2...988089?hash=item5440893a79:g:JZkAAOSwj85YONps

These would be great for a 48v system because the low cut voltage usually around 42v is in line with the 3.5v/cell generally used a max discharge. You can run em on a 36v or even a 24v if you use a voltage alarm to alert you on the low voltage cut. Cost about $11 and runs off one of the packs balance plugs. The motor doesn't care how much voltage is put to it with in reason, usually depending on phase wire size. Most controllers have 63v caps so they easily handle close to that. Its just the LVC that is different and of course max amperage output. A 24v controller will have slower acceleration and hill climbing than a 48v because the 48v has a higher max amperage. However the 24v controller will still give the max voltage.

I have one total(motor/controller) 24v system that I run on 12s which is 50.4v off charge. Never had an issue with it.

Moral of this story is with in parameters you can pretty much do what you want with the systems. There are some modded 9c 48v hub motors running over 100v over at the Sphere.
 

ultralight01

New Member
Oct 30, 2016
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Hood River, Oregon
Cannonball, That looks like a great battery. More affordable than an ebike battery for sure.

It was interesting to learn how you can modify electric motors to basically run any way you want, you've just gotta be a science nerd to figure it all out.

But I'm half gearhead, half nerd.

I see electricity in my future.