my 18650 frame pack build

Batteries, Chargers, and Battery Management Systems.
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izeman   10 GW

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my 18650 frame pack build

Post by izeman » Jan 29 2018 10:18am

my lipo battery is aging, and is about 4 years old now. it's down to 80% capacity, and it is time to replace it. i never had a single issue with any lipos over the years, be it in my bike or in the quadcopter, rc car ....
still the 18650 cell looked interesting to me, and i thought how a switch could happen.

the current configuration is 8 packs of 6s 5.000mAh zippy 20c rc-lipos cells. the pack weighs around 6.2kg and has a nominal capacity of 3,7V * 12s * 5.000mAh * 4p = 888Wh.

i took a lot of measurement of the available space in my self-made frame, and the space available is 370x50x110mm. thanks to the great help and support of maddin88, we found a very good solution which uses the space ideally. totally i can fit 150 cells into the frame. 2 packs of 75 cells in a 15s3p configuration. the cells will be arranged in a 3s5p honeycomb layout and then folded. this will give a long pack of 50x105x350mm.

150 cells will make the capacity much larger. from 888Wh to 3,6V * 15s * 3.000mAh * 10p = 1.620Wh (almost double the capacity), at 6.8kg. the pack is more heavy because it has more volume, and fills the room much better then the lipos which needed a connection pcb in the middle.

the sag will be much worse than before, but due to higher voltage (44.4V compared to 54.0V) the current will come down and range may be doubled.

this is what the bike looks right now:

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Re: my 18650 frame pack build

Post by izeman » Jan 29 2018 10:26am

the new batteries from nkon have arrived. 150x samsung 30q and some meters of 25mm and 10mm wide 0.15mm thick nickle. and some heat shrink and end cap's savers as well as kapton tape.

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first of all they were arranged in groups of 5 and glued together with hot glue. i 3d printed a little box where the batteries fit in quite tightly and are perfectly aligned before fixing them in 5p packs.

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then some kapton tape is wrapped around each end to reinforce the very thin heat shrink:

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these are the 10x 3s5p packs that will make the two big packs

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Last edited by izeman on Jan 29 2018 10:40am, edited 1 time in total.

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Re: my 18650 frame pack build

Post by izeman » Jan 29 2018 10:34am

a friend of mine bought a spot welder from Aulakiria https://endless-sphere.com/forums/viewt ... &start=250.
after some initial issue of too weak welds, and the great support here we found out that the battery was too weak. it's important to use a strong battery directly connected to the welder - no adaptors, no long wires in between.

after that, the welds came out beautifully and very strong:

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each cell got a little black self adheasing paper ring. the whole cell is the negative pole, so if the heatshrink anywhere is damaged there is a high risk of a short circuit.

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the batteries where stacked and glued together with regular silikone glue and let cure over night

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then i could start welding the packs together:

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you may notice some different color heat shrink. these are all the same cells from the same charge. but during glueing them together, i did it too slowly or used too much pressure, and the hot nozzle of the heat gun destroyed the heat shrink. so i had to replace some.

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Last edited by izeman on Jan 29 2018 10:37am, edited 1 time in total.

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Re: my 18650 frame pack build

Post by izeman » Jan 29 2018 10:35am

the big pack has solder fins for the balance wires:

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Last edited by izeman on Jan 29 2018 10:39am, edited 1 time in total.



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Re: my 18650 frame pack build

Post by e-beach » Jan 29 2018 10:55am

Looking very nice so far! Subscribed.

:D
Favorite Quote: "This is L.A., sugar. There is no 'over the top." --- Chris Erskine

Current build: Liahona w/ cheap front suspension and suspension seat post. Yescomusa 36v 800w generic front hub motor. 15ah Headway triangle mounted pack. Tronsung 30 amp,

Previous Build:1992 Trek Antelope 800 - Bone Crusher (no suspension) - Yescomusa 800 watt 36 volt front wheel kit. Don't do it! Get suspension!!!

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Re: my 18650 frame pack build

Post by izeman » Feb 02 2018 9:34am

so it goes on. i made the mains connection. a 10mm wide 0.15 nickle strip.
first i cut of 5cm of insulation of the awg12 silicone wire and divided the wires in two parts, twisted those and tinned them.
then i pre-tinned the nickle and soldered the wire to it, pressing it down with a screwdriver bit by bit.

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safety first. it's really important to isolate wires under voltage.

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pre-tinned the battery tabs as well. with a good soldering iron and 400°C this takes less than a second. so not much heat transferred into the battery.

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welded the strip to the battery. i don't know why, but there were some sparks flying and burnt holes in the nickle. so it doesn't look that nice, and i had to weld at some more points to have 6 valid welding dots.

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all done, ready to test :) those are not the final wires. just for testing, to see if the BMS is working - which it does! all cells are within 7mV. not what i expected, but good enough. i thought that 5 parallel cells would level each other out closer than that.

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999zip999   100 GW

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Re: my 18650 frame pack build

Post by 999zip999 » Feb 06 2018 2:24am

What amp rate are you going to use this pack at ?


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Re: my 18650 frame pack build

Post by e-beach » Feb 06 2018 11:36am

Do you worry that the positive solder fins will be a potential short if they cut through the plastic wrapper and ground to the negative battery outer case?

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Favorite Quote: "This is L.A., sugar. There is no 'over the top." --- Chris Erskine

Current build: Liahona w/ cheap front suspension and suspension seat post. Yescomusa 36v 800w generic front hub motor. 15ah Headway triangle mounted pack. Tronsung 30 amp,

Previous Build:1992 Trek Antelope 800 - Bone Crusher (no suspension) - Yescomusa 800 watt 36 volt front wheel kit. Don't do it! Get suspension!!!

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izeman   10 GW

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Re: my 18650 frame pack build

Post by izeman » Feb 06 2018 2:08pm

I don‘t really worry, but there is a) extra capton tape b) paper rings and c) i will add some tape to the inner side after soldering as well. This should keep the risk to a minimum.

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Re: my 18650 frame pack build

Post by 999zip999 » Feb 06 2018 4:16pm

Maybe there was a small air gap between the stiffer pos. End with mutli strand and solder combo. Giving a spark gap blow out. Maybe hold down with a chop stick if you have a third arm with hand attached.

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Re: my 18650 frame pack build

Post by izeman » Feb 10 2018 3:59pm

today i made the isolators. 0.7mm thick gfk. cut into 50x102mm pieces, then sanded and rounded the edges. i also made a slot for the wires.

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then those were glued to the battery with silicone

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before that i attached some additional isolation to the balance tabs. just in case ;)

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then the parts were folded together and held down by clamps to straighen the hole battery out.
now it's time to way for the silicone to cure.

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Re: my 18650 frame pack build

Post by Animalector » Feb 11 2018 10:01pm

looks great, nice work.

Andy

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Re: my 18650 frame pack build

Post by izeman » Feb 12 2018 10:25am

printed endcaps last night, they guide the wires and protect the ends of the battery

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added some extra protection tape. you can never have enough protection, right? ;)

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lots of silicone to glue the caps to the battery. they stick nicely, even with uncured silicone

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i also cut 0.5mm gfk sheets for the sides. they are absolutely necessary as they give stability and also isolate the nickle tabs (at the places were the battery was folded, the nickle sticks out)

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and finally the clamps again. it's vital to make the battery as small as possible as the battery space is very limited. internal width is around 52mm, which is exactly the width of the battery with side covers.

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izeman   10 GW

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Re: my 18650 frame pack build

Post by izeman » Feb 19 2018 7:52am

finished the packs over the weekend, and i'm really happy with the outcome.
i made some small caps to guide the balance wires. there are no sharp dents and the wires won't be bent to much.
the caps were designed with fusion360 and glued to the battery with the glue gun.

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then one layer of 0.5mm GFK was glued to the bottom side.

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one layer of foam to protect the upper side of the battery

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heat shrink with a round hole in it to guide the wires through it

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heat shrink already shrunk and ready to be mounted to the bike

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and here it is mounted on the bike. mission accomplished :)
"fit's like a glove" has never been more true. it's a really snug fit!

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Re: my 18650 frame pack build

Post by 999zip999 » Feb 19 2018 3:08pm

Very nice work and it fits in the battery box when you're done that's always a worry to you get it to fit. Good job

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izeman   10 GW

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Re: my 18650 frame pack build

Post by izeman » Feb 19 2018 6:11pm

999zip999 wrote:
Feb 19 2018 3:08pm
Very nice work and it fits in the battery box when you're done that's always a worry to you get it to fit. Good job
thanks! yes, it was a great moment when i let the battery slip in for the first time :)
unfortunately the battery is maybe a millimeter to wide. so i had to add some rubber seal to the inside of the side covers to move them away a bit. but it came out pretty good.

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Re: my 18650 frame pack build

Post by 999zip999 » Feb 19 2018 8:23pm

Yes things change and hard to know the finished product. Good use of a rubber. Please let us know how this pack works out as far as voltage Watts amps and sag. Controller and motor. Thanks good luck

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Re: my 18650 frame pack build

Post by Raisedeyebrows » Feb 19 2018 10:57pm

Thanx for posting this build, feel like I'm getting closer to trying one myself, maybe after several more months of studying I'll be confident enough to jump in the shallow end of the pool.
Yuba Mundo w/BBSHD
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Above all run on 14s4p 52v li-ion
Ecobike folder 36v
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Every trip made with electric bike is one less car trip, saves money, no toxic fumes, less noise, less impact on roads.

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Re: my 18650 frame pack build

Post by e-beach » Feb 19 2018 11:01pm

Nice work for sure!

:D
Favorite Quote: "This is L.A., sugar. There is no 'over the top." --- Chris Erskine

Current build: Liahona w/ cheap front suspension and suspension seat post. Yescomusa 36v 800w generic front hub motor. 15ah Headway triangle mounted pack. Tronsung 30 amp,

Previous Build:1992 Trek Antelope 800 - Bone Crusher (no suspension) - Yescomusa 800 watt 36 volt front wheel kit. Don't do it! Get suspension!!!

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Re: my 18650 frame pack build

Post by richmpdx » Feb 20 2018 3:52pm

Very nice pack build. You do such meticulous work.

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Re: my 18650 frame pack build

Post by jumpjack » Jul 29 2018 7:36am

WARNING!
This pack is very nice... but it's just a "pack", it's not a "battery".

This is a "pack" of cells:
Image

Also this is just a "pack" of cells:
Image

This is a "battery":
Image

The difference is made by these:
Image

Multiple version:
Image


The point is: the "can" of a lithium cell is also its negative pole; it's wrapped with a thin plastic foil; if multiple cells connected together in parallel or series (like in a battery) touch one to the other, only this thin foil prevents short circuits. If it's a stationary battery, that's all you need.
But for road applications (bicycles, motorcycles, cars,...) you must take into account vibrations: the wrapping of two cells in close contact slowly wears out at each vibration; wears out, wears out... until the underlying alluminum bodies (i.e. electrodes) connect together, in an unpredictable position of your battery; and you don't want an unpredictable connection between cells in a battery.

The above shown "plastic things" are called "cells holder", but they also act as "cells separator", and they're a mandatory part in any road-battery (if you want a safe battery).
Of course they increase volume, weight and complexity... but also safety.

Note: if close cells inside a box touch one to the other until insulating wrapping wears out, nothing happens, because cells are not connected together.

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izeman   10 GW

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Re: my 18650 frame pack build

Post by izeman » Jul 29 2018 8:20am

it's nice of you to warn me, and tell me what a battery is. even a single cell is a battery, by the definition of it, but i won't argue on that.
and yes, it's very clear how heatshrink works, and what it does. and it's also clear that the whole can is the negative ground. and if negative and positive touch, bad things may happen. so far, nothing new.
but you may have noticed, each cell is glued to all its neighbors, there is extra capton tape around every cell, and all packs are held together by cfk plates which are glued to the cells again. there is not a single movement of ANY cell. not the slightest. and the whole "battery" or "pack of cells as you call it" is press fitted inside the frame. which by itself doesn't move a single bit.
so no worries. 8)

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