PDA

View Full Version : 18650



EVGator
07 August 2012, 1620
Has anyone got any personal stories with 18650 cells, used them in a project, etc.?

I had forgotten about them until reading about them recently. I would assume that the lack of a decent C rate is the reason that these cells aren't widely used in motorcycles. I remember seeing a company called SAFT that was designing a high C rate cylindrical cell similar to the 18650, but can't seem to find any for sale.

These cells peak my interest as far as an idea I had for placement on my bike goes, but I am afraid that the power is not there. With a C rate of 0.5, some major paralleling would have to take place...

frodus
07 August 2012, 1819
They're a PITA to put together. It's not the C-rate.... that can actually be pretty high. The issue is, you need to weld them to bussbar and they're a lot of work to put together a pack. Not many people have a tab welder.

I've built several 26650 packs and wouldn't wish that on anyone to do DIY.

Nuts & Volts
07 August 2012, 1836
We have some Sanyo cells that are second hand from Tesla. We also have a spotwelder which has made assembly a breeze. These cells are the best in terms of energy density both in weight and volume, but most don't like C rates above 5-6C peak. The Sanyo cells will do about 2C continuous, but will get way too hot at 3C. Tony Coiro's buddy, Sean, has a 11kWh pack of these cells in a thermal material and uses them up to 5-6C peak.

But it is possible to fit 20kWh on a bike that weighs about 250-300lbs (pack weight) and can do about 100kW peak. That would give you a bike about 500-550lbs. I don't know prices but they are the cheapest cell per energy according to Tesla. You should email panasonic directly and try to get their 3.4Ah cells. They are about 250Wh/kg. This is my guess on the cells that Mugen uses.

Issue is you will have 1000+ cells to quality control. But they are easily paralleled if you have a nice spot welder and then you need a good scheme to series them. If they had more than 500cycle life and could handle the heat better I would use them.

EVGator
07 August 2012, 2135
Travis, you're definitely right about the tab welding. A pack would absolutely suck to put together. I've seen guys build their own tab welders with big car audio capacitors and such, but I'm not really sure I want to go through the trouble of even doing all that work. Didn't know the c-rate could be that decent. Guess I've been looking in the wrong places.

And Kyle, thanks for the info. I'd only be building a 5kwh or lower pack to begin with since this one is just a commuter bike, so less than 400 cells. Still a lot to watch though. Maybe I can come up with an efficient way to monitor them after reading this book by Davide Andrea. Or just buy a BMS system to match, although I feel like that could get expensive. Alot of the websites claim upwards of 1000 cyclesif the cells are babied I assume.


There are two reasons that these cells are attractive to me. Battery systems are usually "boxy" and I want to have a curvy, natural looking battery system. Not that I am trying to emulate an ICE bike necessarily, I've just been playing around with the configuration of these cells and it will be different. Price point is another factor. This is a bad example, but with the Ultra Fire cells, they're about $2 each, and 3ah each. So 20 of these in series gets me about 84volts charged, 18 in parallel gets me 54ah, and all together gets me around 4.5kwh, which is only 3.6kwh if I want a decent cycle life out of them. So, $720. Although I'm not sure if I would go with that brand, just an example. A broke college student cares not that spot welding make take a few sleepless nights at school if he can get an entire battery pack for under $1000, thus getting the bike on the road quicker.

Another side note, has anyone ever used pressure to secure these cells in place? Sort of like dropping batteries into your flashlight and then screwing the cap on to compress batteries in series? Obviously it would be much more complex on a motorcycle, but what if this were done in manageable sections?

Harold in CR
08 August 2012, 0545
Be VERY cautious about those Ultra Fire cells. Guys on Endless-Sphere have found they are recycled or rejected, with new wrappers.

Here is a quote, "I don't want those recycled or rejected ultrafire batteries!"

Go to Classifieds USED on E-S and find Makita packs. They don't require balancing and you can get 8+ good cells from eack pack, for $15.00 + S&H. They are Sony Konion 18650 cells. MANY people buy these and use them.

ALSO, they will already be tabbed together, so, DO NOT cut them apart, except to get rid of the 1-2 bad cells. There are several whole threads on how to do this and build the packs into crazy kwhrs.

Dicey
08 August 2012, 0621
To reiterate what others have been saying, 18650 is very nice for packaging reasons, though you need to leave a certain amount of space between them for cooling, maybe 3-5mm. The C rate is honestly really so so compared to some of the LiPo chemistries, but the shelf life and cycle life is very good. I know of several vehicles with 70k+ on 18650 packs with 5000+ cells that are still running very well. There are ways to electrically connect them without having to full on weld the tabs. I think cell pricing can get in the $1-1.50 per cell range. Also, good luck getting Panasonic to part with 3.4 Ah cells. Tesla is using 2.8 Ah.

Nuts & Volts
08 August 2012, 0631
To reiterate what others have been saying, 18650 is very nice for packaging reasons, though you need to leave a certain amount of space between them for cooling, maybe 3-5mm. The C rate is honestly really so so compared to some of the LiPo chemistries, but the shelf life and cycle life is very good. I know of several vehicles with 70k+ on 18650 packs with 5000+ cells that are still running very well. There are ways to electrically connect them without having to full on weld the tabs. I think cell pricing can get in the $1-1.50 per cell range. Also, good luck getting Panasonic to part with 3.4 Ah cells. Tesla is using 2.8 Ah.

The Roadster used the 2.8Ah cells and the smaller Model S pack might use these cells too. However the large Model S packs actually use the newer 3.4Ah cells.

The cool thing is that the newer cells are actually better chemistries and are no longer LiCo. So they are safer and more reliable.

jonescg
08 August 2012, 0735
Actually, building a pack out of high energy density cells regardless of their format such that I could slot them into my new race bikes battery box would be an option for when the racing is done. 250 Wh/kg is truly amazing. The C rate would need to be upwards of 10 C continuous, even on a commuter bike though. Might be EiG cells before long though. A bunch of us West Aussies are looking into a big purchase of their 20 Ah cells.

Nuts & Volts
08 August 2012, 0908
Actually, building a pack out of high energy density cells regardless of their format such that I could slot them into my new race bikes battery box would be an option for when the racing is done. 250 Wh/kg is truly amazing. The C rate would need to be upwards of 10 C continuous, even on a commuter bike though. Might be EiG cells before long though. A bunch of us West Aussies are looking into a big purchase of their 20 Ah cells.

Why does a commuter need more than 1C if you can build a 20kWh pack that weighs only a little more than your LiPo pack? 20kW continuous would have you riding at 80mph+ for an entire 100-150 mile ride. This is essentially Tesla's battery model. Take the cheapest and highest energy dense cells and put them in a huge pack so that power density and cycle life is no longer an issue. Oh and the size factor will always be the same so as tech increases you can use the exact same bussing, modules and pack size for the next 20 years :D

We almost went this route with our OSU bike, but QC and power just isn't quite there. Cooling would have also been an issue for us

lugnut
08 August 2012, 1136
It is a huge task to weld up 20 kWh of these cells. And you need a quality welder. And then you end up with a very large assembly of several thousand cells and BMS hardware. All it takes is a single cell failure to short to ruin your day.

I strongly recommend that you use a modular design of sub-packs such that a problem doesn't require surgery on the whole beast.

jonescg
08 August 2012, 2043
Why does a commuter need more than 1C ?

Cause I ride like a hoon :D

EJ Williams
08 August 2012, 2159
Hi guys!

I'm new to El Moto but I've been reading up on different threads for awhile now. All this 18650 talk motivated me to make an account.

I worked with Tony Coiro and the Purdue Electric Vehicle Club this past year to build a kart for the third annual Purdue evGrand Prix. We ended up using the Sanyo 18650 cells that you guys are talking about also donated from Tesla. The cells performed excellently as you can see here:

http://www.youtube.com/watch?v=DYhVzDMH5aA

We had two custom built packs that were 20s30p. Each pack had 600 cells with 4 tab welds per cell (two positive, two negative). Let me tell you the tab welding took awhile. About two months in all to make the packs. Only evacuated the Chemical Engineering building once!

But if you are looking to package the cells. I highly recommend what we used. The company is called AllCell and they're based out of Chicago. Its a phase changing material (graphite infused with paraffin wax) with holes drilled out to hold the cells tightly in place. I've got pictures of the setup if you are curious.

Here's to my first post!

EJ Williams
Purdue Student

Nuts & Volts
09 August 2012, 0532
Cause I ride like a hoon :D

Hahaha alright then get a 30kWh pack :D

jonescg
09 August 2012, 0601
Yeah, if they weren't a PITA to put together I would look into it for the post-race comuting, or even for the CRX. I worked out I can fit over 50 kWh worth of EiG cells in the CRX if weight wasn't an issue. The race bike will have an internal volume of 32 litres for batteries. Pick your chemistry and fill 'er up!

Allen_okc
09 August 2012, 0920
:cool: i dont know about you fellows, but the last thing i need is another PITA while building a EV...

EJ Williams
09 August 2012, 1658
Hi guys!

I'm new to El Moto but I've been browsing the threads here for awhile. All this talk about 18650's pushed me to making an account.

This last year I had the chance to build an electric go kart with Tony Coiro and the Purdue Electric Vehicle Club to race in Purdue's evGrand Prix. We ended up using the Sanyo 18650 cells (also donated by Tesla) that you guys are talking about. They performed excellently! Check out the video:

http://www.youtube.com/watch?v=DYhVzDMH5aA

For the race we built two custom battery packs that were 20s30p. The 600 cells each needed four tab welds (two positive, two negative) onto the nickel sheeting we used. Let me tell you that the tab welding is a long process. It took about two months to build the packs but in the end they followed through.

In terms of packaging the cells. We used the phase change material that was mentioned above. It is a graphite material infused with paraffin wax made by a company called AllCell out of Chicago. They are basically bricks with holes drilled out to hold the cells tightly in place. I've got pictures if you are curious.

Here's to my first post!

EJ Williams
Purdue Student