Welding in Battery Mfg. - Nimh (Nickel Metal Hydride)

Batteries for electric cars or hybrid vehicles are a hot field right now due to the global fuel issues. What should be interesting for folks is that there is a heck a lot welding in batteries.




I had the opportunity to work on Nickel Metal Hydride (NiMh)battery manufacturing and was involved in developing and implementing some of the welding processes. The materials involved are exotic such as Nickel foam, Nickel Wire Mesh, Copper and welding becomes a challenge due to the sheer limitations of the components involved.

How do you weld Nickel sheet electrodes to Nickel Foam (spongy) using resistance welding? Typical resistance welding (AC) works quite well except its a challenge to ensure contact between tips and parts. Our goal was to be able to achieve good electrical conductivity and maintain suffient pull and peel strength.

Welding nickel leads to copper terminals in the battery was challenging until laser welding came about. The leads were quite thick and the laser was the best option to get enough penetration and produce a weld with the copper terminal. Ni and Cu do not produce any intermetallics and hence the welds very sound.

In short, the sheer volume of electrodes in a battery cell is large and it is an interesting challege for welding engineers.