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40T, neodymium magnets, plasti dip cycle test


10 MW
Jun 23, 2019
Surrey, B.C.
Im getting ready to life cycle a 40T @ 7.5 amp discharge, 5 amp charge 1000? times. I don't have everything I need yet but im going to start playing with what I do today and share. these magnets are 3/8 diameter 1/8 hole, 1/8 thick. I have more magnets coming with 1/16 hole and smaller diameters and thickness
my tester

40T magnets wire

12 gauge/19 strand wire

attached magnet to 40T and ready to plasti dip

spraying plasti dip didn't work, the force of the spray got into the air gap between button and magnet but that's ok, im just playing, you can get pourable plasti dip, my plan is copper electrode

with the copper wire you cant hold the battery sideways, it will fall off but with copper electrode you can and you can solder a fuse wire to the electrode. im going to start playing with the tester on the 40T today, ill share more later
tried soldering the wire into the hole, gave it a scrub on emery cloth. the magnets are nickel/copper/nickel coated and you cant really see it in the picture but that halo around the hole is copper

it worked, sort of. the heat from soldering probably took half the magnetic pull away, battery can still hang from the magnet but I used to be able told the battery horizontally and the wire would stay horizontal but not now, it flops down and hangs at a 90

I guess ill have to glue a copper electrode in the hole


Just spitballing here but how about a flat head machine screw through the hole, then crimp the wire to the threaded end and slather the wire side in non conductive epoxy or something?

Another idea, less screws though possibly more screwy. Take that electrode and put it in a vice with say 1mm sticking proud then whack it with a hammer and hopefully mushroom the end. Then slide the magnet on from the other end of the rod, little shoe goo on the back side, and hope to hell your mushroom holds I guess.

These may not be good ideas necessarily. but I try. :)
ya I was thinking of of whacking 1/8 copper rod like a rivet/mushroom it to lock it in place but now that I know what a 40 watt solder iron does to the magnetism? just now I grabbed some UV activated glue I had and glued the wire in then a sanding on the cloth for a flat mating surface


goatman said:
ya I was thinking of of whacking 1/8 copper rod like a rivet/mushroom it to lock it in place but now that I know what a 40 watt solder iron does to the magnetism? just now I grabbed some UV activated glue I had and glued the wire in then a sanding on the cloth for a flat mating surface



Awesome, looking forward to the results.
i pulled the sticker off

Plasti dip is waterproof and electrically insulates and as it cures it tightens up. I know people have mentioned that magnets move from vibration on the batteries but this should stop any kind of movement.



now I need to figure out how to use the tester
I received the N52 magnets I was waiting for


I used 14 gauge copper wire, it was too thick to fit in the hole of the magnet so I stuck the wire in the freezer for 30 minutes to let it contract and then I was able to tap the wire into the magnet.


it has pretty good holding power


if I try to hold the battery any more to level the battery will fall off the magnet



now ill start the test
this is a picture of 16 gauge copper strand wire, I was thinking conductive adhesive could hold wire in the hole and still get 1/8x 3/16 contact with magnet


just did the 7.5 amp discharge from 4.1v to 3.0v battery and magnets didn't get hot 35 Celsius and delivered about 3ah. doing the 5 amp charge then ill try to upload the charts before starting the cycle test
I was curious about 10amp continuous and the temp of the cell. Docware did a test and shared

but im cycling 4.1v to 3.0v, if you look at endothermal and exothermal most heat is generated on discharge from 3.2v to 2.5v


I have the tester so at 10 amp continuous 4.1v-3.0v the battery temp hit 108f/42c on the 3/8 magnet 40T with plasti dip

I would not leave the strands all "umbrella splayed" like that.

I assume the magnets are strong against a compression force?

A fully flat smooth / parallel crimp, getting the strands as flattened out as possible, greatly increasing the mm2 contact surface area

would be my approach.

But I have to say I'm not sold on the magnets idea, but thanks for experimenting!

Have you spec'd a way to check the resistance added by these connections, compared to spot welding?
the resistance, the tester can do resistance was going to start playing with that next.
splayed wire, I only splayed the wire on the 16 gauge for the picture to show that im using this as a serial connection. I mentioned conductive adhesive to glue the wire in hole and then id sand it flush.one of the first posts already cancelled out splaying, the rapid fix UV glue id never use, that was just for playing around til my magnets came.

heres the 10 amp discharge with numbers

then started charging at 5amp with 0.5amp cutoff but im going to change the cut off

it was charged in about 45 minutes but the volt dropped to 4.06v
if I do 0.10amp cut off it takes 90 minutes to reach 4.1v and stay
I might try 0.4amp c/o next
Looks like a great project, good luck with it.
I used my neodymium magnet battery for a good few years with absolutely no problems. The only problem with it was how dodgy it looked, it looked incredibly dodgy but it was in fact remarkably robust..

The only thing about my neodymium battery pack project was how other folks just didn't really get it, they tended to go off talking about copying with super thick copper etc, when I used something remotely similar "aluminium foil" level thinness copper foil wrapped in my magnets.

People seem to forget that the Tesla EV battery pack runs off this level of thinness connections, clearly the philosophy of Tesla battery packs is "many hands make light work".

Here are my main two last posts talking about my battery pack with photos before I spotted welded it all together after years of using it like it was. The only real reason I later spot welded it all together was because I came into the possession of a spot-welder for another project so I figured I may as well make good use of it, but the performance of the pack never changed.

Basic pic of the concept connected the cells together.

The way I aligned the magnets with the copper and cells was with the 18650 backet holders, this worked well and was important for accurate alignment of the magnets, the right sized magnets would center on the cell more or less.

The other thing that was unusual about my pack was my pure parallel balance charger, where I used extra thick heavy duty "7 Pin Round Male Plug Trailer" connectors https://endless-sphere.com/forums/viewtopic.php?f=14&t=60517&start=150#p1172125 , probably same level of thickness that EV use.
I still use this charger exactly as photoed.

I think the other thing that confused people looking back was my use of kapton tape, which made the whole thing look goldish, not only the copper by the neodymium magnets etc.

Whole battery pack, again I used this YEARS with no problems, but I was on a 500W bafang kit, not a 6KW Stealth Bomber doing 50foot jumps in the air, if someone wants that level of power draw then perhaps this probably isn't the solution for them, but it might work OK I don't really know.

In some ways this battery pack is a reflection of me, lol, it was like "this is how everyone else is building packs" and for me it was like "nope, I am not doing it that way, I am going to do it like this..."
thanks beastie, copper, I was looking at the copper foil tape with conductive adhesive to put on the magnet where it contacts the battery and electrode but the nickel/copper/nickel coating on the magnet seems to be fine, thought about silver paint also.

I can easily be wrong, the magnets during discharge are the same temp as the copper wire and battery, when discharge stops, magnet and wire temp drops right away below cell temp
I also thought someone could use a fuse wire embedded in conductive adhesive in the magnet hole for cell level fusing and if someone did that, might be able to use 3/16x1/16x1/16 magnets I have some to try

I tried doing the resistance and it isn't working, had to take the battery to 4.2v to try. the attempts dropped voltage to 4.16 so discharged to 3.0v quite a bit of ah

im trying to find the right charge settings so I can do discharge/charge in 2 hours for 12 cycles a day.
charging to 4.12v@5amps with 0.4amp current cut off, its done took 59 minutes to 4.12v and settled at 4.1v. don't mind the chart title forgot to change the title.

That CB86 line from Radiolink are a great "node" charger, like 6/8 completely separate chargers, each cell / group gets its own independent cycle through its balance wiring

so strictly speaking no balancing going on

just that they all have the exact same stop profile, so the cells are in fact balanced once they are finished.

Makes it much faster than the usual stop/start resistive bleeding method.

Balance leads / connectors are usually only spec'd at 3A or so, but these units push 6A, seems to be OK.
this tester doesn't do a true resistance test? it just gives you an idea if cell is good or bad. I really don't know what im doing. but I put in 3900ma or 1c with battery at 4.2v click test and it would show 0.3amp on tester screen and click off and no result would appear. so I left it alone, don't want to break anything til I get atleast 1 lifecycle test done.

I was thinking of adding a dab of some conductive liquid between magnet and battery. ive got it doing a 5 cycle test right now. I need to figure out how to make the chart Docware uses wich puts a mah dot every cycle onto a chart