Solderless Battery Pack

[safe]

Most Lithium and NiMh packs have historically been built with the laborious practice of soldering tabs together. Other than this being tedious it also makes the packs fairly brittle to damage if a severe shock strikes the pack. (as in a crash)

The new idea is "Solderless Battery Packs" using silver paste:

Anyone tried this yet?

(I'm planning to try it on my next project)

http://www.modelelectronicscorp.com/products/SPTs/powerpaste.html

 

[NickF23]

I looked into it at one point but I'm now happy soldering batteries. I think its a great idea for lithium cells or for those who want to make they're own pack but don't feel comfortable soldering.

I've heard that you need to put fresh paste on once a year.

Other possible issues:

Allowing for expansion of cells in a tube when hot.
Effective cooling and waterproofing.
preventing the paste dispersing and shortcuiting a battery.

Keep us posted if you do experiment.

 

[safe]

I've heard that you need to put fresh paste on once a year.

Other possible issues:

Allowing for expansion of cells in a tube when hot.
Effective cooling and waterproofing.
preventing the paste dispersing and shortcuiting a battery.

Keep us posted if you do experiment.

There is paste and then there is an epoxy glue option as well. My guess is that just a microscopic amount would fill in the pores in between the battery surfaces. It's all so microscopic and below the level that the human eye could sense. Even if you got little improvement the difference between "raw" batteries and soldered isn't that huge anyway. So if it lands somewhere equal and not better than soldering then it's still a "win" in my book. (less effort equals a "win")

I was thinking of using pvc pipe which should transfer heat well enough.. I guess I'll find out...

 

[bobmcree]

conductive epoxy is a suspension of conductive particles like silver in an epoxy base. it will not have a very low resistance. none of these materials is intended to carry a lot of current, and there could be electroplating issues where the metal comes out of the paste and deposits on the contacts, reducing the quality of the connection. soldering is just not that hard...

 

[safe]

There is silver epoxy and there is a silver paste. I'd prefer to use the paste because it would flex as the batteries flexed keeping things tight all the time. (you need to keep everything spring loaded of course) If the measured results are as they seem to be (above) the idea is a "winner"... but it does force you into using "tubes". In many cases it's impractical to use "tubes" so the biggest argument against it is that it limits your pack shape. (long and narrow doesn't work for everyone)

Look back up to those numbers above... even the "no-paste and no-solder" (bare) option isn't that far off. The fact of the matter is that soldering is a bad idea because you would have to take your pack apart if a single cell went bad. (xyster is presently in a sort of "nightmare" where his pack is giving strange results and he has few options as to how to diagnose the problem) With a "tube" based approach you can always take it apart every once and a while and test each cell individually. If one cell is going bad you can replace it or rebalance the pack overall. (not to mention replacement which is a snap)

It just seems smarter to do "tubes" in my opinion... but that's just me... keep using the old way if that's your thing...

 

[bobmcree]

if you measure the resistance of your silver paste junctions over time and it does not increase significantly i would say go for it. i fear vibration would push the particles out of the way and resistance would increase. of course you could redo the connections periodically if this was a problem.

i mounted my 68 D cells on a triangular frame in the bike frame so i can have access to all of them to check voltage or replace a bad cell. this has the added advantage of giving each cell some airflow and keeping temperature constant. (photos on bobmcree.com)

i would be very interested to learn if the impedance of your pack varies much over time using the silver paste. it sounds like a good idea if it does not plate out or get pushed out of the contact area.

 

[safe]

...it sounds like a good idea if it does not plate out or get pushed out of the contact area.

Yeah, well right now it's just "big talk" because I "imagined" the concept myself and then found over the internet that the idea does work. I will be trying this on my next project. Other people have tried it and the biggest "error" is to not "spring load" the batteries. Since the batteries expand with heat if you tried to simply hold the "tubes" together with threaded ends you will end up with a pack that would get loose over time because of the expansion and contraction.

Otherwise, the RC people seem to be able to pull it off already and I'll be trying to scale it up to the electric vehicle level and see how well it works. (I'll have 10 "D" Cells per tube)

Epoxy would break... so I'm certain that paste is the way to go...