Hello sorry I know this is not a battery forum but I need help from more advanced minded people with actual education and experience to answer this question with confidence and not from what a buddy told them was ok...

So my Question is can I confidently use a magnet on the negative end of a flat top 18650 battery so it will fit in a flashlight designed for button top 18650 batteries ?

Cube magnet vs round flat vs polarity are also areas of concern, protection of battery and housing contact are already taken into account.

I do not want to put the magnet on the positive end due to the protective plastic wrap could get scraped and leave the negative body exposed shorting out the battery and causing a dangerous situation so I have been using a tiny cube magnet on the but end cap against the negative end of the battery with a piece of hard density foam around the cube to keep it in place.

I`m unsure if the position of the polarity of the magnet matters ether this is definitely out of my league to grasp...

The flashlight can be 2 or 3 cells long it has a body section that can be removed, I did have the cube magnet between the 2nd and 3rd cell and not sure why the 3rd cell was being drained and the others not as the 3rd ran empty while the other 2 remained 90%, I tried again with a different brand ( NCR ) but have moved the magnet to the very end of the 3rd cell against the end cap and not sure if this will be safe as the LG that ran empty popped and hissed when it reached full recharge many times faster than normal, faster then the two 90% cells.....

I`m using the S4 Inlife smart charger not a cheap dollar store no name fire hazard and not sure what happened, it read 0% but the voltage was still 3 volts then started to trickle up in voltage and then the percentages started to rise once the voltage was high enough.

Here is the flashlight I`m using and very pleased with over all, up grades it could have are a temperature cut off as it does get hot to the touch when left on high for about 1 hour and a low voltage cut off to protect the delicate 18650 batteries ... !

https://www.amazon.ca/gp/product/B071ZLHTX8/ref=oh_aui_detailpage_o04_s00?ie=UTF8&psc=1

Thank you for your time it is much appreciated !

 

Hello,

There was a lot of discussion about this maybe 10 years ago on another site.
The general outcome was that the magnet could slip off the top and touch the sides of the case or the inside of the battery case if the case is metal. This could happen if the device is dropped.
So if you do it, you have to be sure you have a way to keep it from moving off the battery top if the device is dropped or moved quickly.

Another idea is to make tiny triangle pieces using sheet metal from a steel can. You then bend the corners under the top piece that is already there. You have to be very careful not to short the cell out, and having it discharged while doing this is better.
It's not easy to do though, and has to be done just right.
Some cells may not accept a triangle piece either it depends on the exact makeup of the top of the cells as they are before the mod.

Keep in mind that this is a modification of a cell that already could have problems. If you dont do something right, the results could be very bad.
When they make button top cells they weld them i think. You can get them on the web.

 

Thank you for the reply, all great insights.

I`m hoping to get a more educated technical explanation in re guards to the direction the positive and negative ends the magnet is facing and if that matters also if the magnet is between 2 cells or on ether ends how is that affecting current draw, limiting, lagging, slight boost ?

Is it safe can it harm the battery ?

Please don`t clutter the thread with chatter like other sites it`s rude and drags everyone down, lets wait until we get a solid answer, thank you !

 

The polarity of the magnet will definitely not effect things ....

This a problem I've also encountered , you would think battery manufacturers would be able to prevent this from arising...

I've solved it by jamming aluminium foil between the contacts ... also soldering onto the +ve terminal a round blob of solder , this is the best way ...

 

How about a magnet and glue ro hold it in place?

 

How about a magnet and glue ro hold it in place?

Hi,

Well i have mixed thoughts about this. It sounds interesting.

FIrst, when the magnet makes contact it does so due to the attraction between the magnet and the steel of the cell top. That is what makes the contact stay connected.
However, if we then add glue, and assuming that it's on the outside of the magnet and not between magnet and cell top, then the glue becomes the thing that determines the contact pressure between magnet and cell top. This means the magnet can not react as easily to expansion and contraction as it would if there was no glue. The glue holds it in place. Maybe it would work anyway? It might, but it may also cause a bad connection which could heat up. If we are lucky, the heating would cause a better contact again.

What makes sense is some kind of donut, that keeps the magnet from roaming too far off. That would restrict the magnet position but not hold it tight in one place.

Not sure what i would do yet if i had to use a magnet. Still more thought i think might help.

 

How about a flexible adhesive - RTV perhaps - on only one side of the magnet?

 

Thank you for the insight guys.

High engine temp gasket maker might be a viable solution if only used sparingly at the sides of the magnet,
I`m using high density foam I cut out into a donut already and it is working fine but has shown some wear due to the heat of the flashlight so now I only use it with the magnet at the end cap...
a thick plastic washer or stacks of them design is probably the safest way to hold the magnet in place though.

So definitely no problems using the magnet spacer in-between cells ? no matter if say a 4 cell flashlight and I only use magnet between cells 2 and 3 ? Or what ever configuration or multiple configurations this will not cause heat to build or one cell to drain faster than the others ?

And a cube magnet posses no issues in the same above situations ?

 

How about a flexible adhesive - RTV perhaps - on only one side of the magnet?

Hi,

Sounds like a good idea. Maybe test by dropping it a few times.

 

Here is a better look at my original question as to why maybe a cube magnet might cause implications in the electron travel and create a heat sink... ?

A cube magnet splits the flux field when facing one way vs the other, so if the north and south ends are not in line with the flow of the electrons can this create a build up of heat ?

You can see in the pictures below some have the magnet facing with the poles up or down and the others the poles are facing side to side causing a split and the magnet field lines...

https://www.dropbox.com/s/3k61211lsvhljle/20181225_131632.jpg?dl=0

https://www.dropbox.com/s/cs99n2kv7ferxvp/20181225_131719.jpg?dl=0

https://www.dropbox.com/s/srl33ymkwd4dw8f/20181225_131310.jpg?dl=0

https://www.dropbox.com/s/b74rgbsy5vqjtyr/20181225_131357.jpg?dl=0

 

Here is a small disc magnet I had laying around they are just to large in diameter to use with my 18650 cells.

One picture it is flat and the other on it`s side.

https://www.dropbox.com/s/epqn4alhvpatdfz/20181225_131800.jpg?dl=0

https://www.dropbox.com/s/3dxc7h7r2qxm1p1/20181225_131922.jpg?dl=0