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Battery Contacts R Us

I was recently contacted by a customer unhappy with his current manufacturer. He regaled my with that age old tale of woe regarding battery contacts that had failed to meet application specs. The customer related to me his frustration at locating a knowledgeable source for this seemingly straightforward commodity. He also said that before he contacted Peridot, his company had been through three suppliers, two stateside and one offshore, and they had all failed to meet requirements.

I must admit I LOVE getting calls like this as I have been a spring maker for (gulp) 30-plus years. So it’s only naturally that I have a connection with battery contacts.

The design was a typical base plate with two helical/conical springs attached with rivets. The application was for a portable electronic device a soldier would carry in combat. The problem was that the springs failed during drop testing, causing the device to unexpectedly reset. Not good. As the thirty seconds it took for the device to reboot could be critical for the soldiers.

At first glance nothing seemed to be amiss with the samples provided, but a stress analysis quickly revealed that the springs were way over-stressed. The G-forces from even a waist high drop caused the springs to yield and fail to return to contact length. We redesigned the spring to a configuration that would withstand much higher stress and deflections, then submitted samples for the customer to evaluate. We received word back quickly that the new design had passed testing. We pointed out to the customer that the current 5 part assembly (plate, 2 springs and 2 rivets) could be reduced to to a 3 part assembly (plate and two springs) by using an extruded hole in the plate for the springs to fit around and then cold heading the extrusion to lock the plate in place. Here is the resulting example:

Spring to Plate-Look Ma, no rivets!

Note in the above photo the small serrations on the plate. These serrations dig into the plastic ribs in the molded battery case and lock the assembly into place with no additional fasteners involved. The springs in this case are pre-nickel plated Music wire and the plates are nickel plated 1075 spring steel. This combination provides high strength and corrosion resistance at a reasonable cost. We hard tooled the plate on a punch press and have had several re-orders in the 5000-10,000 pc range.

 

Here is a good closeup of the joint between the spring and the plate that can eliminate an external fastener:

Gold plated battery contact assembly

Let’s look at a few more examples of the types of battery contacts Peridot routinely produces in both short run and high volume. This little guy is a coin cell contact made from gold plated beryllium copper:

Coin cell contact

Want to save some money on a non-spring contact? Consider pre-tin plated cold rolled steel as a cost saving alternative. An example:

 

Negative terminal

Have a sliding contact application? Gold plated beryllium copper is KING! Don’t forget to spec a nickel under-barrier and hard gold.

AU plated BE CU C172 alloy 1/2 HT Temper

Here is a “jumper” design with both positive and negative terminations:

Jumper

Our multi-axis CNC wire forming equipment can produce wire jumpers complete with no second ops:

Economical jumper solution

These same CNC wire formers can make all kinds of end details for attaching to circuit boards etc.

 

Battery spring with pigtail

Or if you wish simple legs that go straight into thru holes and are soldered to the board:

Simple tail

Need to get more elaborate with your shape? We know elaborate!

4-slide battery contact
Gold over Phos Bronze

 

We can offer many solutions to battery contact problems. We can prototype, short run and also handle high volumes of these types of components and assemblies.

So if you want to know when to use Beryllium or Phos bronze and which plating is best please consider consulting the experts at Peridot.

 

 

 

 

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