My dual battery transmitter is operating for less than the claimed number of hours. What is wrong? Open


Here's a reply to a customer who had an SMd that would only run for 6 hours on lithium batteries.

Hi Tom,
There have been four problems with the SMd battery setup. Here's the problems:

  1. The screws that hold the contact leg to the board were not tightened properly at the factory. Resolved by giving the assemblers a torque screw-driver just for those screws.
  2. The spring behind the contacts was not cut properly. The "spring" is a piece of silicone tubing which is very stable and long lived but was being cut by hand, sometimes at an angle. This can be detected by looking at the battery height above the case with the door open. Commonly one battery would stand proud of the case and the offending battery would be 0.050" below the case edge. This was resolved by cutting the springs with a machined fixture that cuts the springs squarely and at a constant length.
  3. The battery polarity protector inside the case was a hair too thick and kept some batteries with short nipples from touching the contact. The offending battery just happened to be the Eveready lithium batteries that we ship with the product. This was resolved by molding a thinner polarity protector.
  4. The diameter of the machined ring on the inner surface of the battery door, also just happened to fit inside a circular depression on Eveready batteries of all types. This reduced the battery pressure and could cause a loss of contact if the SM's were shaken or dropped. This would cause the unit to shut down.

All of these are considered to be our design fault and come under the extended "we blew it" warranty and will be fixed at no charge or automatically upgraded if a unit comes in for other things. Also, these fixes have been in the units for some time. However, not all were done at once since we didn't find them all at once and they didn't fail on most units.

As far as battery life, the lower capacity "Advanced" lithium batteries run an SMd for 12.7 hours. We will have the "Ultimate" lithium numbers in a day or so but they should be around the 15 hour number.

Posted 3 years agoby LectroAdmin

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