yet another solderless DIY battery pack via NIB's

Hummina Shadeeba said:
Are u doing just one strip of .05" for all the connections or is it folded over and how many times? How many amps do u do?

My batteries, magnets, and copper are still sitting here and waiting for the answer to that question..but much more so really waiting to finish the skateboard
With the cavity im still set on potting the battery in...w 50duro silicone.
Click to expand...
I was thinking of ways of how to answer this question. I think most importantly if your not an adult then make sure you seek adult supervision when making a pack like this as potentially serious fire/smoke damage can be done.

My main goal is still just on average 500watts of power.. I have a Bafang 500W CST hub motor.. and a S12S 500watt controller.. It can go up to 1000watts on take off though.
The reason I have made a somewhat large battery pack of 7P is because I only like to have to recharge maximum of once per week, mainly because I have no access to power outlets to where I keep my bike.

I currently rebuilt my pack with two layers of the adhesive copper foil. The biggest pain in the arse with using the copper adhesive foil is I had to remove at least some of the adhesive glue on the inside so that it wasn't pointlessly insulting the two layers..
To remove some of the adhesive glue I dipped the copper foil in acetone and then scrapped it off with a coin.. Once submerged in acetone the adhesive glue expands and discolors.. The amount of adhesive they put on the one side of this copper tape has to be seen to be believed once its dipped in acetone. I scraped off all of the middle adheasive and left the sides in tacted so I can still fold the second layer over and have some stick.
IMG_0157b.JPG

For just one 2S7P link I decided to use the ebay "Copper Sheet 0.05 x 100 x 1000 mm" that I ordered, cut to size, the massive upside to this is there is no adhesive but its still thicker..
http://www.ebay.com/itm/181443383724?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
It feels way more 'springy/less contouring' against the postitive terminals as at least for Samsung 29E cells the positive side sits a bit inward from the round top edges of the 18650 cell.

I was thinking that for most folks who build their packs they draw enough current that the links get very hot to the point of BBQing.. So I was thinking that if your going to be drawing a large amount of power that creates a lot of heat then theres no real point of building a nib pack as your going to be putting your cells through the same or more amount of heat over time then just using them in the first place.
In other words if your going to draw heavy amounts of power out of them you may as well just use a soldering iron and solder your cells together as theres not going to be any difference in the heat they endure in the first place.

https://endless-sphere.com/forums/viewtopic.php?f=14&t=83505&start=75#p1234810
https://endless-sphere.com/forums/viewtopic.php?f=14&t=83505&start=75#p1236850

getting hota.jpg

So in that case you might consider building a pack soldered together like this guy did.
https://endless-sphere.com/forums/viewtopic.php?f=14&t=65719#p988212
 
I think I've posted about it before but why not use copper strips or wires glued on isolated nibs (ex: nibs enrobed with slim silicon sleeves or a rigid high temp polymer)?

Main source of heat and current limit with no solder joints is how much of current goes through the magnets or how close the warm tabs / wires are from the magnets right? Too much heat = no more magnet strength, too much nickel = limited current. And useless distance = higher resistance and lower magnet strength.

My main issue with pure copper is corrosion... Your conductive grease though could do a great job to protect it no?
 
Vanarian said:
I think I've posted about it before but why not use copper strips or wires glued on isolated nibs (ex: nibs enrobed with slim silicon sleeves or a rigid high temp polymer)?

My main issue with pure copper is corrosion... Your conductive grease though could do a great job to protect it no?
Click to expand...
Thats a good idea, I think a nib thats 'enrobed' with copper foil but barely any bigger then its existing physical width would be great for the positive side of the cells. The negative side is very easy to deal with as its surface area is roughly 4-5 times as much and its perfectly flat and even, a 12mm x3mm magnet has incredible clamping force on a few layers of copper foil, its the positive side of cells that is difficult.

I think copper foil enrobed for about 2-3cm then soldered onto a wire would make it very easy visually to see if your positive cells are well centered on the positive side, currently for me with the whole 2SP7 copper foil tabs I can only verify they are centered on the postive side of the cells by feel or by lifting the tab up and visually inspecting.

I don't know if this is exactly how you envisioned it but I just created a quick real concept of enrobed copper nib with two layers of copper foil wrapped over a 8mm neo magnet which is a good size for positive terminals.
I think if you can solder the wire onto the copper from at least 2cm away from the nib the heat wont transfer over to the nib and destroy its magnetic properties. Alternatively using a crimp tool and crimping the copper to the wire could be used as a solderless method.

IMG_0170.JPG


So far from test riding at only a low assist level my pack does feel like its delivering more power than it did before.. I have the controller/LCD set to not draw much above 400watts, I want to allow the CW7100 conductive grease that I placed on each cell to cure a bit longer as it seems to greatly increase its conductive properties the longer out of its tube and applied thinly.

All up I think I am done with my pack, I don't think I will be changing it again, I should be able to use this for many years now, I already been using it this whole year, but now its been upgraded I think I can safely get more out of it...
I think the amount of stuff I bought to build it and the time it took probably outweighed its benefits of just buying a spot welder or even soldering.. I got 3 different thickness sets of copper sheeting I ordered that I barely used.. $50 on the CW7100 conductive grease which I still have plenty left over so that can be used for something else.

I think if your the type that uses recycled cells then this magnet connector approach is probably quite practical, otherwise your mileage may vary.
 
i soldered the copper foil to the wire and then wrapped the magnet in the copper

Thebeastie why do you say your milage may vary or that this method is better suited for recycled cells?
 
I'd like to test magnet and copper connectors by getting the cells connected to them to discharge 5 amps continuously "on the bench". Is there a way...integrating a resistor of the right size i guess, that I can get my 5 cells in parallel to discharge 5 amps each continuously? I'd like to see how hot they get.
How badly does a battery's internal resistance affect voltage sag?
 
I had a couple of reservations about using magnets to hold the busses onto the cell ends, in the beginning. I recently came back to this thread to see if there had been any more developments, and I am impressed. I finally looked at the button-magnet 12mm X 3mm prices, and I am somewhat shocked at how cheap they are. (also 10mm X 2mm, 100 pc for $7)

This is now something I actually want to try. Copper for the busses

Who's a good supplier of magnets for USA? Earlier I read that ebay seller "l-che27" was highly regarded. If I have one magnet per cell-tip, a 12S X 6P pack would be 72 cells, so... 144 magnets (probably need to order 150 to allow for a few damaged)...

edit: I now believe (June 2017) that these mmagnets holding a copper ribbon onto the negative end is the best DIY way to go. However, for the positive nipple, I like the soldered fuse-wire.

xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

edit: soooo...these exist...0.20mm thick copper busplates that fit the common plastic cell-holders.

SpotWeldCopper1.png

If the series portion of the strip is 10mm wide, then it is 10mm X 2mm = 20mm in area (cross-section), which is 4.5mm sq, which equals 10.5-ga. The three shapes below would all carry the same current, although the flat plate has the most surface area, and "might" shed heat a little better?...

SpotWeldCopper2.png
 
I cant find l-che27 when I try to find the seller in Advanced Search in ebay.
I think its best to put a little bit of epoxy to secure the magnet in place so it doesnt move around along with a plastic clamp. Either that or straight up solder to the cell.
 
I don't know if that pic is from a legit supplier, so I apologize for teasing. However...as stated earlier in this thread, the parallel connections can be a very thin wire, which is cheap and easy to do. The series connections carry the current, and that is the part that needs to be thick copper. I am certain that strips like that can be made from a roll of 10mm wide copper ribbon. I will investigate this further, in order to find out exactly how much crap I am full of.

One parallel wire is shown at the far left, in the pic below. Click on it to enlarge...

BatteryMagnets.png
 
Here is an E-motorcycle, (small 50cc size) with a 14S 19P pack (52V). The pic shown is one P-group of 19 cells. I see copper busplates? (waiting for a response from the builder for details).

Cell is the LG HG2, factory rated as 20A peaks and 3000-mAh, so 19 in P is 57-Ah and 380A peak...this guy looks well-researched and he chose copper, so...

https://endless-sphere.com/forums/viewtopic.php?f=10&t=85758

file.php


file.php


BatteryPackLooseCell1.png
 
looking at that thread and the pics he posted I'm confused by how he had that copper positive terminal bar made (it isn't flat and has a lot of curve to it) and I'm also wondering if there's more parts he hasn't shown because otherwise it seems that same curved positive terminal part has "tabs" coming off the side of the busbar without any support and their not being steel I can't imagine there'll be much spring and pressure. looks like a good nibs candidate.

all this nice design work might go out the window when it's shown duct tape, hand cut 2mil copper, and nibs work well

whats the math to know how much current is flowing through the p connections?



https://endless-sphere.com/forums/download/file.php?id=209296
 
There are several similar threads, but this one seems to have the most info and interest about using magnets to clamp the bus-strip to the cell end. I contend that the positive end of an 18650 cell can easily handle having a fuse-wire soldered onto it safely and consistently, with the proper technique. However...the broad and flat end of the cell is the most vulnerable, as shown on several youtubes of soldered cells that were dissected.

I believe that button magnets holding a thin copper strip against the negative is a useful configuration to use. I just got some 12mm X 3mm button magnets, neodymium, N48 strength, very cheap, and they hold the strip onto the cell very well. I will add compression too, but when it comes to heat expansion, cold contraction, and bumps/vibration, I believe the magnet pressing down will work very well. The copper is not magnetic, but the 18650 shell is nickel-plated steel, and the magnet wants to pull towards the steel.

The strip I used is 0.20mm copper. Flexible enough at the neck to move slightly if needed to maintain flat contact. The round pad is 12mm, and since the bottle-neck is the 8mm slots on the common black plastic cell-holders, if the 0.20mm strip is 7mm wide at its narrowest, that is 7mm X 0.20mm = 1.4 square mm of area in the copper cross-section. Copper will create less waste-heat when carrying current, and any warmth that happens will be easily shed. It's 1.4mm squared cross-sectional area is equal to 16-ga wire.

The highest-amp cell right now is the LG HB6, factory-rated at 30A each. If we are only hitting 30A per cell on occasion, then 16-ga wire/ribbon per cell should be fine for this as a minimum thickness.
 
spinningmagnets said:
There are several similar threads, but this one seems to have the most info and interest about using magnets to clamp the bus-strip to the cell end.

I just got some 12mm X 3mm button magnets, neodymium, N48 strength, very cheap, and they hold the strip onto the cell very well. I will add compression too, but when it comes to heat expansion, cold contraction, and bumps/vibration, I believe the magnet pressing down will work very well. The copper is not magnetic, but the 18650 shell is nickel-plated steel, and the magnet wants to pull towards the steel.
Click to expand...
Yeah this thread has a lot of good info in it and folks that want to build a "neodymium pack" should really read the whole lot as its just riddled with good tips.
Yeah 12mmx3mm are great for the negative side of 18650 cells, I found myself grinning in amazement when I first placed one of those sized magnets on the negative cell terminal, and yes if you use the common black 18650 cell holders you can't actually fit 12mmx3mm magnets on them as the little plastic tabs get in the way.
What I did was merely snap them all off with long nosed pliers, they break/snap off easily in a quite convenient fashion.
You can see from this pic posted below from a few pages back in this thread that after snapping those tabs off I was able to push through the whole black plastic cell holders down and out of the way of the cell terminals. While this adds more convenient access for good contact to the cell terminals it also comes at the price of having to ensure good manual alignment of magnet/copper contacts.

I think looking back if I was going to make a new pack in this style I would still snap off the tabs but try and leave the cell holders sitting on top. The reason I didn't do this originally was because I was experimenting with different thickness level copper sheets/foils before deciding that the skinniest copper foil possible with 2 layers was the best overall approach for me, as it allows more contour while still providing thickness/gauge and flexibility just like why stranded copper wire exists.
file.php


As discussed in this same thread back here ( https://endless-sphere.com/forums/viewtopic.php?f=14&t=60517&start=100#p949962 ) when the neodymium magnet is heated it practically loses all its magnet strength, the change is so extreme I recommend you sacrifice one of your magnets to see the dramatic change by just putting under a flame for 5 seconds or so.
This is where I hope this style of pack design works out to be like a fuse. As if one cell goes bad hopefully the heat will only be big enough for the nib to lose its magnetic strength and disconnect/blacken the copper connection from the terminal.
This is only logically most likely going to happen if the pack is on its side in a frame bag, which is the position of how my pack is kept on my ebike.
 
2 seconds is enough. I soldered magnets to balance wires to make charging harnesses for my iCharger. It's rapid. That said, 36v and 48v Battery Blocs running up to 30a controllers have never heated up a properly sized battery, enough series cells, sufficient to fail.
 
Epoxy the magnets on, using epoxy on the top and sides of the magnet and not the bottom where the contact is.

Just a thought.
 
Was thinking about build a 18S 4P Vruzend kit of below.
https://endless-sphere.com/forums/viewtopic.php?f=31&t=87434&start=350

But then I thought about the fact I have to order 2 kits for a 72cell build, then there is shipping and then there is talk it can't handle a big amps.
So I wondered if I should turn to my magnetic pack build again..
Some of the inital input costs.
60mm wide x10meter long copper tape $10
http://www.ebay.com/itm/Various-Size-Guitar-Shield-Screening-Copper-Foil-Tape-Noise-Conductive-Adhesive-/272116333522?var=570925191526&epid=1973684762&hash=item3f5b65bbd2:m:mkmEv7LMS8Pdlw1V7ykdaPw

4 x cell holder bracket sets $5.60
http://www.ebay.com/itm/2PCS-4x5-Cell-18650-Batteries-Spacer-Radiating-Shell-Plastic-Heat-Holder-Bracket-/253031364822?hash=item3ae9d838d6:g:cU0AAOSwicJZXj0c
50 x 10mmx3mm neos $7.69 (negative side)
http://www.ebay.com/itm/5-100Pcs-Super-Strong-Round-Disc-10x1mm-10x2mm-Magnets-Rare-Earth-Neodymium-N35-/282388785539?var=&hash=item41bfaee983:m:mgyvXNxl_HL69Z710h-8E4g

50 x 7mmx3mm neos $5.88 (positive side)
http://www.ebay.com/itm/Diameter-7-mm-series-Disc-magnet-N35-neodymium-rare-earth-magnet-/142423774260?var=&hash=item21291e5434:m:mf2IdtCrglZlennctAP63Sg

$29.17 total cost, and the value of having a battery pack that makes you look like a half nut mad scientist? priceless. The price of having a considerably dodgy looking more awkward battery pack? Hard to measure.

Might update the urls prices etc as I go over it all.. One of the most annoying things about this pack build from memory was the positive side on Samsung cells, because the positive terminal sits almost inwards around the rim I am thinking 7mm is better than 8mm. I have noticed Sanyo cells positive terminals sit about a good 2mm above the rim almost like a button top cell but they are considerably more expensive cells.

I guess the bigger question for me is does this type of build allow more or less current than the Vruzend kit which do look pretty cool.
Or just solder, I got a pretty good soldering iron but I am just ok with soldering skill wise, I wonder if anyone soldered an 18650 cell and have it blow up in their face or notice with conviction any damage to their cells?
Also I verge on just buying a spot welder but I only ever build a new pack every few years, what to do.
 
andy1956 said:
what about flat tinned copper braid direct to battery with magnet on top??
Click to expand...

Might be too thick and not have enough "staying" force or shall we say contact force.
How thick is it?
:lol:
 
The problem with tinning a braid is that it loses all flexibility.
How about stuffing NIBs inside a braid? Stretch the braid on both sides to keep the magnet in place. Only half the thickness of the braid will be between the magnet and the pole.
 
Hi everyone!
Since several years I assemble DIY ebike.
I came to this interesting 3D since I'm going
to try assembling DIY lithium battery by using
Sony VTC5 cells and neodynium magnets without BMS.
Many people are assembling custom batteries by
the mentioned cells without BMS with no problems.
I'm not expert in this matters but if I undestood properly
it seems charging the battery the Sony VTC5 cells
do not overvoltage despite they are not singularly
controlled by the BMS.
Using this feature my idea is to create rubber tubes 10s
by cells connected by magnets connecting than 3 or 4
tubes in parallel.
I contacted one year ago a USA company which patented
a magnets based lion battery assembling but due to high
delivery cost to Italy (65$ delivery over 50$ staff) I gave up.
Have you similar info on Sony VTC5 cells?
Sorry for errors, my English is a bit rusty...
:lol:
I'll keep you posted, at this moment I'm waiting
for receiving the magnets.
Ciao!
 
http://www.batteryblocs.com/

This is the link of the company I mentioned;
Assembing videos are on Youtube.

And one of my DIY ebikes.

:)
 

Attachments

  • 2017-11-10 20.05.17.jpg
    2017-11-10 20.05.17.jpg
    125.1 KB · Views: 2,790
I'm pondering using 20700 or 21700 cells instead of 18650.
Perhaps someone can help me building a list of pros and cons? For info, my needs are 14S and ~20A of draw for a Bafang BBS02 and this will be my first battery build. Her's a start for the pros/cons:

Presumed pros:
1. The wider cell diameter and cell holders leave more room for the conductive sheets to flex and lay flat over the positive terminal.
2. (related to 1. ) The possibility of using larger magnets might improve the connectivity when clamping sheets directly over terminals, without needing to use a second magnet
3. (related to 1. ) Assuming the diameter of the positive terminal is larger than in a 18650 (can't find a reference proving so) then the conductive potential at the positive terminal is increased
4. I can achieve the desired capacity (~12.5Ah) with 3P instead of 4P. However TheBeastie was saying we should use at least 5P for a 500W+ build, so maybe I'm completely unrealistic here?

Presumed cons:
1. A configuration with less cells in parallel infers more current on each cell and thus require ever better connectivity at the terminals. I'd love more input here to help me realize if 3P or 4P is realistic for my build. If I need 5P the cost of the battery would become too high and I'd fallback to 18650 cells.
2. Choice of a cost effective 21700 cells is rather limited

I liked radad's version 5.20 idea with the parallel connections acting as fuses and thought maybe soldering these could be ok. However how do I know what thickness/material of wire would be a good material to operate as a fuse?

For reference, here are the dimentions of the 21700 endcaps. I think I would use these even if I'd go with the Sanyo 20700B and potentially stack several rows of them around the cell using TheBeastie's « cat-inferred revelation » (breaking the caps tabs that prevent the cells to go through).

p8rwGq4.png
 
respire said:
I'm pondering using 20700 or 21700 cells instead of 18650.
Perhaps someone can help me building a list of pros and cons? For info, my needs are 14S and ~20A of draw for a Bafang BBS02 and this will be my first battery build. Her's a start for the pros/cons:
Click to expand...
I used this battery pack I built for 2 years (pic below), it worked fine, due to the glue etc it was more robust then it looks, but looking back I don't think they are worth the trouble, its a lot of tedious work for something that looks ugly. The only upside to these neodymium battery packs is they are so ugly I think most thieves trying to steal it would elect to just dumping it after extracting it from your ebike rather than using it as it looks so weird.
I think this did save the battery once from being stolen 1 time actually, the frame bag and been forced/pulled open, and just left, its like the thief just went "eew, no thanks". I did have a vibration alarm on my ebike as well so that may as much been the saving factor.

Just buy a cheap spot welder and build it with that.
I bought a spot welder for a new project. I did, after 2 years, spot weld the battery pack below (with no noticeable increase in performance).
After using a spot welder I can't believe how much faster and easier it is to use, when you watch youtube videos of cells being spot welded it really is as easy as it looks.
Also in general advice on pack building, I think its important for any battery pack to use cell dividers, I really don't think packs that don't use cell "holder/spacer/brackets" are very safe, because they allow for the cells to slightly wiggle around and or trap more heat, and increase the chance of short circuits to occur..

Like I said before, the neodymium build may look straightforward but its painfully tedious way to build a pack..
The JP spot welder, or Arduino prebuilt spot welder, or the Kwelder etc are so cheap, that there is little logic to not just buy one and use it. Sure its technically cheaper to do a neodymium build but if you value time and quality and if you think you will build another battery in a few years time these spot welders pay for themselves in so many ways, a spot welded build will always be safer anyway I would think.
https://endless-sphere.com/forums/viewtopic.php?t=68865
https://endless-sphere.com/forums/viewtopic.php?t=89039
file.php
 
Did anyone think about aluminum strips?

should be a better conductor than nickel and not have the same tarnishing issues as copper?

as it's not being welded it should no oxide?


https://www.aliexpress.com/item/High-quality-18650-battery-holder-For-big-power-battery-pack-50A-100Ah-200Ah-Lower-price-is/32837557299.html?spm=2114.10010108.1000023.1.62fe261eNWayt2

these also look interesting plates can be screwed on
 
You must log in or register to reply here.

Similar threads

Kodin
Tank Bike - (Previously: Yet Another Genesis)
2
Replies
28
Views
11,911
Kodin
Kodin
DrkAngel
Homemade Battery Packs
67 68 69 70 71
Replies
1,769
Views
651,758
Lucifer
Lucifer
oldswamm
An economical Hi Amp DIY BLDC controller
2 3
Replies
65
Views
13,428
kevbo
K
Back
Top