DIY 14S10P lasercut full wooden enclosure/cell holder

Batteries, Chargers, and Battery Management Systems.
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BotoXbz   10 W

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DIY 14S10P lasercut full wooden enclosure/cell holder

Post by BotoXbz » Feb 03 2019 7:28am

After thinking about different ways to build my 14S10P triangle battery for my BBSHD hardtail I arrived at the following design:
https://a360.co/2Utuo6G
I have access to a lasercutter at uni and am planning to cut the shape from 4-8mm poplar plywood sheets and glue them together to form one big solid block.
The size of the holes was chosen so the cells fit very snug and don't move, I've only tried it with one 4mm sheet so far though.
I will be using Panasonic NCR18650PF cells.
The cells will be spot welded with 8mm x 0.2mm pure nickel strip.
The distance between the cells is 1mm in the design and is around 0.76mm when lasercut (laser kerf).
The battery pack will then go into this triangle bag: https://www.aliexpress.com/item/48V-36V ... 59950.html

What do you guys think about this idea?
The wood is very lightweight but should be very strong glued together and with all the cells inside.
Can you think of a better suited material for this? A different kind of wood?
Thermals should not be a problem since I'll be running the pack at 30A max.
The bike will be used for commuting, climbing hills and long distance trips.

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Re: DIY 14S10P lasercut full wooden enclosure/cell holder

Post by john61ct » Feb 03 2019 8:55am

G10 FR4 laminate board

BotoXbz   10 W

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Re: DIY 14S10P lasercut full wooden enclosure/cell holder

Post by BotoXbz » Feb 03 2019 9:56am

john61ct wrote:
Feb 03 2019 8:55am
G10 FR4 laminate board
It's a 60W CO2 laser so I'd only be able to cut very thin sheets of this material at slow speeds from the info I found on the net.
Might make sense to use this as the first and last sheet if I can source it easily.

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spinningmagnets   100 GW

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Re: DIY 14S10P lasercut full wooden enclosure/cell holder

Post by spinningmagnets » Feb 03 2019 10:08am

I am unable to view the picture of the plywood section, but I think I have the idea from your description.

Rather than ending up with a solid block, consider the option of using perhaps four of the 4mm sheets to allow for air circulation and to save some weight.

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multifrag   100 W

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Re: DIY 14S10P lasercut full wooden enclosure/cell holder

Post by multifrag » Feb 03 2019 10:11am

Why do you need a laser cut cell holder when hot glue would do the job? You're spotwelding them so it's not like you will be able to disassemble the pack easily for repairs. You're getting a battery bag as the main enclosure. I can understand if it would be done out of silicone to protect it from vibration as that will damage your battery over time.

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Re: DIY 14S10P lasercut full wooden enclosure/cell holder

Post by BotoXbz » Feb 03 2019 11:00am

spinningmagnets wrote:
Feb 03 2019 10:08am
I am unable to view the picture of the plywood section, but I think I have the idea from your description.

Rather than ending up with a solid block, consider the option of using perhaps four of the 4mm sheets to allow for air circulation and to save some weight.
It's an interactive 3D viewer from autocads fusion 360, here's a screenshot:
Image

Air circulation is a moot point when the battery will be in an insulated bag, air also has worse thermal conductivity than wood.
But as said the cells will not get warm at 1C max, more like 0.3C cont.
I'm actually more afraid of the cold getting to my batteries over here in Austria.
The whole plywood construction will be less than 500grams, negligible for me.
multifrag wrote:
Feb 03 2019 10:11am
Why do you need a laser cut cell holder when hot glue would do the job? You're spotwelding them so it's not like you will be able to disassemble the pack easily for repairs. You're getting a battery bag as the main enclosure. I can understand if it would be done out of silicone to protect it from vibration as that will damage your battery over time.
I used automotive construction glue on a previous battery ( https://cloud.botox.bz/apps/gallery/s/94drnBJfjacBDnr ) and it works really well, I can lift the whole pack on a single cell, it's super rigid but still flexes a little to allow for vibration damping.

However on a pack of this size and weight and simply because I have the possibility, I'd like to go with a full enclosure for safety, longevity and build simplicity purposes (gluing 140 cells is harder than letting the laser cutter draw some circles on wood and stacking that).

I was also thinking about using only a few sheets of wood on the sides and potting the middle of the battery with silicone.
But that would be more effort, more expensive, more weight and make replacing cells much harder in the rare case.

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spinningmagnets   100 GW

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Re: DIY 14S10P lasercut full wooden enclosure/cell holder

Post by spinningmagnets » Feb 03 2019 12:00pm

Well done. Looks good, and I like it.

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Re: DIY 14S10P lasercut full wooden enclosure/cell holder

Post by BotoXbz » Feb 07 2019 1:57pm

Status update:
Image

Sadly ran out of time, can cut the remaining 4 pieces (2 plates x 15min) next Thursday.
The cells hold super well, they need like 5-10kg of pressure to get in.
So I'm not even gonna glue the wooden sheets together, no need.

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Re: DIY 14S10P lasercut full wooden enclosure/cell holder

Post by MJSfoto1956 » Feb 07 2019 3:08pm

BotoXbz wrote:
Feb 07 2019 1:57pm
The cells hold super well, they need like 5-10kg of pressure to get in.
So I'm not even gonna glue the wooden sheets together, no need.
I swear, laser cutting is going to change the world. Well done!
Voting has ended: viewtopic.php?f=26&t=102697

Слишком мало, слишком поздно

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Re: DIY 14S10P lasercut full wooden enclosure/cell holder

Post by BotoXbz » Feb 13 2019 10:20pm

Final battery layout:
Image
(didn't draw all the series connection because lazy)

Gonna lasercut the last parts tomorrow.
The layout matters for laser cutting as 50% of the holes for the outermost two plates will be of smaller diameter for the positive side.
The lasercut enclosure will be 65.5mm high, the cells are 65.2mm (with paper rings on + side), will be a nice safety feature so the nickel can absolutely not short out on the cell.

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Dui, ni shuo de dui   1 kW

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Re: DIY 14S10P lasercut full wooden enclosure/cell holder

Post by Dui, ni shuo de dui » Feb 13 2019 10:47pm

Seemed to me like a stupid idea but turns out that it might be a good one.
Kudos on the cuts, they look very clean, nice work so far!

You could even create some channels in the last layers of each sides of the plywood so that the strips are encased and protected, this way they wouldn't protrude out of the surface.
:bolt: :bolt: My electric Ninja 250 clone: 16 000W 72V40Ah A123 cells : :bolt: :bolt:
https://endless-sphere.com/forums/viewt ... 12&t=90032

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Re: DIY 14S10P lasercut full wooden enclosure/cell holder

Post by BotoXbz » Feb 14 2019 5:35am

Dui, ni shuo de dui wrote:
Feb 13 2019 10:47pm
Seemed to me like a stupid idea but turns out that it might be a good one.
Kudos on the cuts, they look very clean, nice work so far!

You could even create some channels in the last layers of each sides of the plywood so that the strips are encased and protected, this way they wouldn't protrude out of the surface.
Was thinking about that too, ideally the channels would only be on the surface of the last plate which is a little thicker, but that's obviously not possible with laser cutting.
So either the last plate will have to be thicker and have the channels fully cut OR
I could just glue a thin plate with cuts on the ends. <- best solution imo.

I could even go further and glue another full plate on top of that so it just looks like a box.
Main discharge wires would still protrude since they are much thicker than the 0.2mm nickel strip and maintenance/inspection is also meh with a full cover.
Insulating the whole thing with PVC tubing is also a good option, as for any battery pack.

And yeah the precision of that laser is really amazing.
16 plates with 140 holes and every hole aligns perfectly and has the same size.

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Re: DIY 14S10P lasercut full wooden enclosure/cell holder

Post by iOn <-+-> uOil » Feb 14 2019 6:37am

BotoXbz wrote:
Feb 07 2019 1:57pm

The cells hold super well, they need like 5-10kg of pressure to get in.
But do the cells not want to expand and shrink while heating or cooling while in use.
It could cause great problems like popping open on top or buttom ?
Truth hurts

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Honk   100 W

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Re: DIY 14S10P lasercut full wooden enclosure/cell holder

Post by Honk » Feb 14 2019 12:44pm

Yes, any holder must have enough space around the cell to allow for expansion during the charge discharge cycles.
At my former jobb we had to redesign the cell area, otherwise the supplier would not deliver any lithium batteries due to unsafe pressure.
Efficiency is king!

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Re: DIY 14S10P lasercut full wooden enclosure/cell holder

Post by john61ct » Feb 14 2019 2:09pm

Wood will have some "give" compared to metal or most plastics. Foam board would be ideal.

I guess without that factor, the ideal would be the "top & bottom" hold the battery tight at the terminals, but holes allow a bit of play.

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Honk   100 W

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Re: DIY 14S10P lasercut full wooden enclosure/cell holder

Post by Honk » Feb 14 2019 2:32pm

Even wood will not allow enough swelling to make it safe in a compact tight fit.
Myself I thought the same idea as you regarding the top and bottom mounted plates.
He could also insert some thin threaded tubes between the cells from top to bottom.
Then simple screws and flat washers could hold it all together.
Efficiency is king!

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Re: DIY 14S10P lasercut full wooden enclosure/cell holder

Post by russ18uk » Feb 14 2019 3:15pm

john61ct wrote:
Feb 14 2019 2:09pm
Wood will have some "give" compared to metal or most plastics. Foam board would be ideal.

I guess without that factor, the ideal would be the "top & bottom" hold the battery tight at the terminals, but holes allow a bit of play.
Not in the direction he's cut the wood. Also the number of layers strengthen the wood even more so it's even more difficult for the wood to expand laterally. In the humid air the wood will swell and the layers may well split.

Maybe removing the sleeves on the cells will help enough but you will still need to protect the wood from humidity.

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Re: DIY 14S10P lasercut full wooden enclosure/cell holder

Post by BotoXbz » Feb 14 2019 5:08pm

As far as I know 18650s don't "swell" since they're in a thick steel can.
The metal expands a bit when it gets warm but I hope that won't be an issue.

What I didn't quiet realize is how heavy 7kg actually are, this thing is MASSIVE.
Pictures: https://cloud.botox.bz/s/X2i2rczA4Sbs2A9 & https://cloud.botox.bz/s/rQq95X6c7gXHizm
I definitely will have to support my chinese triangle bag a bit.

Probably gonna mount the battery at the bottom of the triangle for better gravity and mounting.

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Honk   100 W

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Re: DIY 14S10P lasercut full wooden enclosure/cell holder

Post by Honk » Feb 14 2019 5:41pm

Well, hope you don't end with a bonfire.
Wood and heat, even more heat and so on...
Efficiency is king!

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Dui, ni shuo de dui   1 kW

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Re: DIY 14S10P lasercut full wooden enclosure/cell holder

Post by Dui, ni shuo de dui » Feb 14 2019 8:19pm

BotoXbz wrote:
Feb 14 2019 5:35am
Was thinking about that too, ideally the channels would only be on the surface of the last plate which is a little thicker, but that's obviously not possible with laser cutting.
So either the last plate will have to be thicker and have the channels fully cut OR
I could just glue a thin plate with cuts on the ends. <- best solution imo.
You could use a basic CNC router to mill the channels, it's pretty easy on plywood.
Or, if you don't have a CNC, just use a handheld router, after drawing the channels with a pencil. It's really not that hard :)

People rely so much on fancy machines nowadays they just forget they have hands! :wink:
:bolt: :bolt: My electric Ninja 250 clone: 16 000W 72V40Ah A123 cells : :bolt: :bolt:
https://endless-sphere.com/forums/viewt ... 12&t=90032

:bolt: :bolt: My electric Scooter: 11 000W 72V 50Ah LiFePO4 cells: :bolt: :bolt:
https://endless-sphere.com/forums/viewt ... 12&t=75912

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Re: DIY 14S10P lasercut full wooden enclosure/cell holder

Post by BotoXbz » Mar 03 2019 7:16am

Finally got around to spotweld this beast:
Image
Image

Waiting for some Turnigy 12AWG silicone wire from hobbyking to finish it.
For the negative discharge wire I'll cut 10 short nickel pieces which will go towards the border of the pack.
I'll put a few layers of kapton above the pack, place the nickel on top of that and fix them in their final position with some strong magnets.
Then I'll solder the thick wire to the nickel pieces, remove it after it's cooled down.
Remove the kapton tape and then spotweld the nickel pieces to the negative side, now the thick discharge wire is perfectly attached with barely any heat getting to the cells.
Same thing for the positive but the wire will be in between the cells.

For mounting the pack I've ordered 1.4m of 20 x 80 x 20 x 2mm aluminium U-profile, I'll bend and weld that to a triangle which will be screwed down onto the bike.
Battery is 66mm wide, inside of the u-profile is 76mm wide, so 5mm of padding on both sides inside of the profile.
I'll buy some 1 or 2mm 40-50 shore A silicone plate and glue that on the battery sides for insulation and better thermal conductivity and then probably use wood for the rest, to secure the battery against damage from the sides.
On the outside there'll be 1 or 2mm thin plexiglas glued with silicone to make the thing waterproof and nice looking.

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Re: DIY 14S10P lasercut full wooden enclosure/cell holder

Post by BotoXbz » Mar 22 2019 8:18pm

Slowly but surely the pack is coming together.
Bought 0.5mm thick copper sheet for the main discharge connection.
Went that way instead of normal copper wire to keep the sides of the battery flat.

I cut the copper sheet to the correct shape, tinned the whole piece of copper and soldered pre-tinned nickel pieces to the right spots with a lot of flux.
The soldered connections aren't the strongest I've seen, they can be teared off with pliers and some force, should not be an issue however.

Image

Image

All pictures -> https://cloud.botox.bz/apps/gallery/s/WTBkH9DfDk36T5J

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Re: DIY 14S10P lasercut full wooden enclosure/cell holder

Post by BotoXbz » Apr 25 2019 5:38pm

Update for those that are interested how this battery is holding up:
I used it to ride over 200km from Graz to Zagreb: https://cloud.botox.bz/s/poqrcWPeadoXkQW
Mounted in a triangle bag with a little foam on my BBSHD powered hardtail: https://cloud.botox.bz/s/ykkSJri96XnMLGj
I used about 70% of the battery for this trip, though I did hug the throttle while driving through Zagreb - not the best city for cycling.

Today I rode up on a pretty high mountain here with almost full throttle all the time to test the BBSHD and the battery.
33km with 1250m of elevation (most of it towards the end, started in the city)
BBSHD got mildly warm, controller was definitely warmer than the motor core itself (nice), guessing around 40°C
The battery was 30°C warm at most and I only used around 40% of it, definitely overdid it with the size of this battery heh.

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Re: DIY 14S10P lasercut full wooden enclosure/cell holder

Post by la8rat » Apr 26 2019 9:33pm

Nice :thumb:

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