My First 18650 Battery Pack - KFF

Talk about anything and everything here within reason.
Post Reply
User avatar
mauimart   100 W

100 W
Posts: 215
Joined: Nov 10 2009 2:08pm
Location: maui

My First 18650 Battery Pack - KFF

Post by mauimart » Dec 21 2016 7:02pm

This is my first attempt at a 18650 pack build. The pack will be fitted to a Specialized Big Hit running a first generation MXUS in a 24" wheel. I still have to build an enclosure for the pack.

Specs are as follows:

- 20S8P using Sanyo NCR18650GA cells (from tumich)
- Custom designed and 3D printed battery holder (solvent welded ABS)
- 0.2mm x 8 mm pure nickel strip
- >2600 welds at 8ms pulse using custom Arduino controlled spot welder (based on Riba design)
Attachments
18650 battery spacer _ 20x8 ASM-page-001 (Small).jpg
18650 battery spacer _ 20x8 ASM-page-001 (Small).jpg (61.38 KiB) Viewed 3040 times
IMG_4098 (Small).JPG
IMG_4098 (Small).JPG (100.94 KiB) Viewed 3040 times
IMG_4110 (Small).JPG
IMG_4110 (Small).JPG (106.37 KiB) Viewed 3040 times
IMG_4140 (Small).JPG
IMG_4140 (Small).JPG (149.67 KiB) Viewed 3040 times
IMG_4304 (Small).JPG
IMG_4304 (Small).JPG (115.92 KiB) Viewed 3040 times
IMG_0161 (Small).JPG
IMG_0161 (Small).JPG (114.02 KiB) Viewed 3040 times
IMG_0149 (1) (Small).JPG
IMG_0149 (1) (Small).JPG (103.54 KiB) Viewed 3040 times
IMG_0141 (Small).JPG
IMG_0141 (Small).JPG (99.92 KiB) Viewed 3040 times
20160223_105404 (Small).jpg
20160223_105404 (Small).jpg (98.23 KiB) Viewed 3040 times
IMG_9700 (Small).JPG
IMG_9700 (Small).JPG (123.44 KiB) Viewed 3040 times
schematic.jpg
layout.jpg
20160209_171707 (Small).jpg
20160209_171707 (Small).jpg (92.63 KiB) Viewed 3040 times
Last edited by mauimart on Jan 06 2017 2:57pm, edited 1 time in total.

Tats   1 kW

1 kW
Posts: 417
Joined: Apr 17 2014 9:51pm
Location: NOR Perth, worlds best kept secret, Australia

Re: My First 18650 Battery Pack

Post by Tats » Dec 21 2016 7:43pm

Impressive - I have the same frame and that's gave me some ideas.

Bayareapilot   1 µW

1 µW
Posts: 1
Joined: Dec 04 2016 5:37pm

Re: My First 18650 Battery Pack

Post by Bayareapilot » Dec 23 2016 2:25am

Looks pretty nice. I sent you a PM.

User avatar
mauimart   100 W

100 W
Posts: 215
Joined: Nov 10 2009 2:08pm
Location: maui

Re: My First 18650 Battery Pack - KFF

Post by mauimart » Jan 06 2017 2:17pm

I made a small amount of progress on the pack, just prior to a significant setback. I soldered the end connections to a strip of nickel plate and then spot welded the plate to the terminals of the pack. I was quite pleased with the connections and confident that it would hold up to the expected 80A max current during operation.
IMG_0296 (Large).JPG
Positive Terminal End Connection
The next step was to route the wires and terminate with a XT90 connector. In the process of routing the 10AWG cable through some zip ties, near the cells, I inadvertently allowed the negative cable to make contact with the can of a cell near the positive terminal (18th in the series so ~60V) and you can guess the rest. A giant ball of plasma and heat materialized from the short. The pain was instant yet I could not immediately see the carbon buildup on my fingers or the damage to the pack as my pupils were constricted from the flash. The episode was quite spectacular. My pain was quickly overshadowed by discontent when I saw that the wall of the cell had vaporized. What a PITA it is going to be to replace the cell(s).
IMG_0293 (Large).JPG
Shit!
IMG_0298 (Large).JPG
There Are Better Ways To Arc Weld.
Some lessons learned:

The heat shrink insulation on 18650's is quite thin and cannot be relied upon to actually provide insulation. Yes, it is true that in hindsight I should not have used pliers to pull the wire through the zip tie near the can of a cell. Before proceeding with the routing I was well aware of the danger and that if the end of the cable (which was flush cut) were to compromise the battery wrapper there would be trouble. Knowing this I continued the routing anyway, with the precision of a surgeon.

Don't route the power cables near cells.

Submerse the charred parts of your flesh in cold water as soon as possible. I made sure to do this prior to snapping the photos.
IMG_0291 (Large).JPG
It Burns!
IMG_0294 (Large).JPG
That's Gonna Leave A Mark.
IMG_0294 (Large).JPG (219.48 KiB) Viewed 664 times
Next update should hopefully show the repaired pack. I should probably have a camera running while I do the repair...
Last edited by mauimart on Jan 06 2017 2:54pm, edited 1 time in total.

Voltron   1 MW

1 MW
Posts: 1837
Joined: May 02 2013 4:53pm
Location: Santa Barbara CA

Re: My First 18650 Battery Pack

Post by Voltron » Jan 06 2017 2:41pm

Yikes...

Lurkin   100 kW

100 kW
Posts: 1409
Joined: Jan 18 2015 4:31pm
Location: Melbourne, VIC, AUS

Re: My First 18650 Battery Pack - KFF

Post by Lurkin » Jan 06 2017 3:48pm

Your cell holders are perfect/sweet.

Did you print them or order them from someone else?

User avatar
amberwolf   100 GW

100 GW
Posts: 25089
Joined: Aug 17 2009 6:43am
Location: Phoenix, AZ, USA, Earth, Sol, Local Bubble, Orion Arm, Milky Way, Local Group
Contact:

Re: My First 18650 Battery Pack - KFF

Post by amberwolf » Jan 06 2017 4:46pm

That's pretty bad. :shock:

Interesting that while it vaporized parts of the cell itself, the ziptie millimeters away appears undamaged (though your skin is not). Two other zipties on either side appear to be broken (or were they cut afterward?


It is very fortunate that the cell damage did not cause an internal short leading to a fire....

User avatar
skeetab5780   10 MW

10 MW
Posts: 2127
Joined: Jun 15 2009 10:58pm
Location: MA
Contact:

Re: My First 18650 Battery Pack - KFF

Post by skeetab5780 » Jan 06 2017 5:00pm

Ouch thats something most people would overlook at first glance, I had to double take and think what shorted the positive lead?...then realized the cell can!!! DOH

Wow

User avatar
Ykick   100 GW

100 GW
Posts: 5558
Joined: Nov 26 2009 6:10pm
Location: San Diego, California

Re: My First 18650 Battery Pack - KFF

Post by Ykick » Jan 06 2017 5:53pm

Painful and potentially expensive lesson learned...

Heal up quickly!
Talent must not be wasted.... Those who have talent must hug it, embrace it, nurture it and share it lest it be taken away from you as fast as it was loaned to you.

- Frank Sinatra

User avatar
mauimart   100 W

100 W
Posts: 215
Joined: Nov 10 2009 2:08pm
Location: maui

Re: My First 18650 Battery Pack - KFF

Post by mauimart » Jan 06 2017 5:57pm

Lurkin wrote:Your cell holders are perfect/sweet.

Did you print them or order them from someone else?
I designed the holders using Onshape, which BTW rocks, (search '18650 battery spacer') and printed in ABS on a Prusa.
amberwolf wrote:That's pretty bad. :shock:

Interesting that while it vaporized parts of the cell itself, the ziptie millimeters away appears undamaged (though your skin is not). Two other zipties on either side appear to be broken (or were they cut afterward?


It is very fortunate that the cell damage did not cause an internal short leading to a fire....
All the zip ties survived the initial blast. I later cut them to get the cable away from the cells as soon as possible. I am lucky that short did not cause a fire and/or propogate. Voltage measurments indicate that only that cell is bad. I also moved the pack out doors as soon as I could.
skeetab5780 wrote:Ouch thats something most people would overlook at first glance, I had to double take and think what shorted the positive lead?...then realized the cell can!!! DOH

Wow
The part that is most frustrating is that I was clearly aware of the danger prior to routing. I just thought that with my "delicate touch" and the insulating wrapper the risk would be minimal. DOH!

User avatar
amberwolf   100 GW

100 GW
Posts: 25089
Joined: Aug 17 2009 6:43am
Location: Phoenix, AZ, USA, Earth, Sol, Local Bubble, Orion Arm, Milky Way, Local Group
Contact:

Re: My First 18650 Battery Pack - KFF

Post by amberwolf » Jan 06 2017 10:03pm


User avatar
liveforphysics   100 GW

100 GW
Posts: 13941
Joined: Oct 29 2008 1:48am
Location: Santa Cruz, CA, USA

Re: My First 18650 Battery Pack - KFF

Post by liveforphysics » Jan 07 2017 1:51am

KFF happens.
Each carcinogen vapor exposure includes a dice roll for cancer.

Each mutagen vapor exposure includes a dice roll for reproductive genetic defects in your children.

Each engine start sprays them into a shared atmosphere which includes beings not offered an opportunity to consent accepting these cancer experiences and defective genetics life experiences.

Every post is a free gift to the collective of minds composing the living bleeding edge of LEV development on our spaceship.

User avatar
spinningmagnets   100 GW

100 GW
Posts: 10645
Joined: Dec 21 2007 10:27pm
Location: Ft Riley, NE Kansas

Re: My First 18650 Battery Pack - KFF

Post by spinningmagnets » Jan 07 2017 10:44am

Glad you're OK, and thanks for being honest and posting the carnage. That is the most valuable way to show newbies about why the experienced builders do things a certain way.

I'll post a pic later, but I was an idiot (what else is new?) and rode without a helmet recently. Fortunately I was wearing safety goggles (that look like sunglasses), and took a spill. My pride was the part that suffered the most hurt, but I also now have on extra scar with which to impress the ladies at the rest home for the elderly. If I hadn't been wearing safety glasses, I might be typing this through one eye.

I'm impressed by the plastic cell-holders in a honeycomb layout. That is the way I would do it. This is ES, we need to be the ones to lead the way in providing links and resources so a builder can get on a website and easily draw two plastic side-plates for holding 18650's, and then paypal a separate website to 3D print them out and ship.

edit: I added you to the KFF index in the battery section stickey:

https://endless-sphere.com/forums/viewt ... 7#p1254427

Hillhater   100 GW

100 GW
Posts: 9224
Joined: Aug 03 2010 10:33pm
Location: Sydney ..(Hilly part !) .. Australia/ Down under !

Re: My First 18650 Battery Pack - KFF

Post by Hillhater » Jan 07 2017 5:50pm

Hindsight but,....
Battery building is at its safest if all cells are fully discharged before assembly.
It wont prevent an arc, but it will minimise the power discharged.
This forum owes its existence to Justin of ebikes.ca

User avatar
Cowardlyduck   10 MW

10 MW
Posts: 2429
Joined: Jun 26 2011 8:41pm
Location: Canberra, ACT, Australia

Re: My First 18650 Battery Pack - KFF

Post by Cowardlyduck » Jan 08 2017 1:06am

Thanks for sharing.
This makes me scared of my current build now. I was somewhat relying on the cell insulation to shield my cells from each other as I'm just gluing them directly to each other. I think I'll start adding a layer of un-shrunk heat shrink between each group now.
Image

Cheers
High Power LiPo wiring harnesses - 4P - XT90, HXT4mm, 5.5mm. 200Amp+ capable. Global shipping.

Modified Stealth Fighter - Force air cooled motor @ 6KW, Heat-sinked Adaptto Mini-E. 49AH, 52V 18650 - 2.5Kwhr
Cowardlyducks - Stealth Fighter Videos

BikeE recumbent commuter - 9C, 6Fet Grinfineon, internal 17AH, 52V, + on-board solar.

The stuff I make and modify.

User avatar
fechter   100 GW

100 GW
Posts: 12885
Joined: Dec 31 2006 3:23pm
Location: California Bay Area, USA

Re: My First 18650 Battery Pack - KFF

Post by fechter » Jan 08 2017 1:54am

It was looking really good before the accident.

In the pack building process, it's important to plan the steps to avoid having the potential for accidents as much as possible (easy to say with 20/20 hindsight). Things usually go pretty smoothly until you get to attaching the main wires and balance wires. Attaching the BMS is the really scary part. Strategically located connectors help a lot.
"One test is worth a thousand opinions"

whereswally606   100 kW

100 kW
Posts: 1098
Joined: Jun 19 2011 2:11pm
Location: Cheshire, UK

Re: My First 18650 Battery Pack - KFF

Post by whereswally606 » Jan 09 2017 6:13am

So I was having a conversation with a friend Bobc about modifying his loose cells in soilpipe design to up the cells in series and reducing parallel (more volts, less capacity, same length. The new design ends up having cells/cans running parallel which are quite a bit of potential difference apart. This KFF incident has further made me think about the necessity for printed spacers so that we aren't just reliant on the battery cell insulation for insulation. Thanks for posting, hope you heal well. Btw its still a great looking pack.
Distributing "Lebowski" FOC Controller PCB (Through hole) since 2016
Moped: Emax 110s 2009

User avatar
fechter   100 GW

100 GW
Posts: 12885
Joined: Dec 31 2006 3:23pm
Location: California Bay Area, USA

Re: My First 18650 Battery Pack - KFF

Post by fechter » Jan 09 2017 10:50am

That's a good point. If the cell insulation gets a little hot, it may become soft or melt completely if really hot. A space between groups would be a good idea. Something like Nomex paper or fish paper between groups would also be good (won't melt or puncture easily).

Also consider what might happen if the bike crashes or just tips over. The cells need to be securely mounted to prevent things from shorting from impact.
"One test is worth a thousand opinions"

User avatar
amberwolf   100 GW

100 GW
Posts: 25089
Joined: Aug 17 2009 6:43am
Location: Phoenix, AZ, USA, Earth, Sol, Local Bubble, Orion Arm, Milky Way, Local Group
Contact:

Re: My First 18650 Battery Pack - KFF

Post by amberwolf » Jan 09 2017 2:43pm

Or vibration, etc.

I had a wiring fire on the SB Cruiser last summer because of that; a wire got pinched in the space between box and frame (repeatedly, from flex), and becuase *another* wire further down the cable at the rear lights had apparently worn thru, this let the lighting battery pour full current thru the cables, and started a fire under the seat and inside the lighting battery compartment. I was able to rip the wires out by hand and yank the battery itself out before it was damaged or ignited by the incident, but I was burned in the process, and if it had been the traction pack I doubt it would have worked out that well. :(

User avatar
mauimart   100 W

100 W
Posts: 215
Joined: Nov 10 2009 2:08pm
Location: maui

Re: My First 18650 Battery Pack - KFF

Post by mauimart » Mar 17 2017 4:32pm

Some progress in pictures...
Attachments
18650 battery V2-page-001.jpg
CAD.
IMG_0661 (Large).JPG
Water jet cut parts.
IMG_0665 (Large).JPG
IMG_4659 (Large).JPG
Installed on bike.
IMG_4670 (Large).JPG
IMG_0668 (Large).JPG
a01.jpg
Close up of tabs, slots, and T-nuts.
IMG_0682 (Large).JPG
With motor controller in position.

User avatar
fechter   100 GW

100 GW
Posts: 12885
Joined: Dec 31 2006 3:23pm
Location: California Bay Area, USA

Re: My First 18650 Battery Pack - KFF

Post by fechter » Mar 18 2017 12:40am

Looking good.

What is the housing material?
"One test is worth a thousand opinions"

John in CR   100 GW

100 GW
Posts: 13510
Joined: May 20 2008 12:58am
Location: Paradise

Re: My First 18650 Battery Pack - KFF

Post by John in CR » Mar 18 2017 12:51am

Cool battery box, but doesn't that Bomber fork have enough travel for the wheel to hit the battery enclosure?

User avatar
mauimart   100 W

100 W
Posts: 215
Joined: Nov 10 2009 2:08pm
Location: maui

Re: My First 18650 Battery Pack - KFF

Post by mauimart » Mar 18 2017 4:45pm

fechter wrote:Looking good.

What is the housing material?
It's 6061 aluminum, 5mm top plate, 3mm all other plates. Fasteners are M3.
John in CR wrote:Cool battery box, but doesn't that Bomber fork have enough travel for the wheel to hit the battery enclosure?
It does look like the tire will hit under compression yet bouncing up and down on the handlebars with all of my weight I can't get it to touch. I think I'm compressing it close to full travel. If the pack does end up making contact with the tire I can always slide the pack further down the down tube.

User avatar
mauimart   100 W

100 W
Posts: 215
Joined: Nov 10 2009 2:08pm
Location: maui

Re: My First 18650 Battery Pack - KFF

Post by mauimart » Apr 05 2017 11:40am

More progress. I added a bracket for the motor controller and the circuit breaker. Also installed a precharge switch and controller enable switch. Current shunt is also installed via a 3D printed holder.
Attachments
IMG_01.JPG
Mounting bracket
IMG_02.JPG
Current shunt holder
IMG_03.JPG
Circuit breaker
IMG_04.JPG
Switches
IMG_04.JPG (215.77 KiB) Viewed 654 times
IMG_05.JPG
CA

Post Reply