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Archive for January 14th, 2014

FC1002 Frequency Counter Battery Pack

The main reason for taking the FC1002 frequency counter apart was to replace the failed quad-AA NiCd battery pack. Rather than buy new cells with tabs, I recycled some low-discharge “ready to use” NiMH cells from the heap. Back in 2009, they looked like this:

Tenergy RTU Pack A Tests - Aug 2009

Tenergy RTU Pack A Tests – Aug 2009

Nowadays, they’re a bit less peppy:

Tenergy RTU - 2014-01 - loose cells

Tenergy RTU – 2014-01 – loose cells

The red blooper shows that you can’t trust a smart fast charger to get the right answer; it concluded that pair was fully charged. After the discharge test and an overnight C/10 charge, they regained as much enthusiasm as they’ll ever have.

They have slightly less capacity than in 2009 and also a somewhat lower terminal voltage. That shouldn’t matter here, as the frequency meter has a power supply to take care of that problem.

Although I’ve sometimes been able to (quickly!) solder directly to ordinary AA cells, a trial run on a defunct RTU cell showed that wasn’t going to work on whatever variety of steel they used, no matter how much I scuffed it and despite using aggressive flux that normally blends silver solder onto stainless steel.

Fortunately, the top half of a four cell case fitĀ exactly in the space available, so I used woven copper fabric tape inside the case to interconnect the cells, then lashed everything together with the obligatory Kapton tape:

FC1002 Frequency Counter - battery pack

FC1002 Frequency Counter – battery pack

That cracked faceplate isn’t the nicest thing to confront, but it’ll suffice until I get more motivation:

FC1002 Frequency Counter - repaired

FC1002 Frequency Counter – repaired

I’ve misplaced my stack of Round Tuits again…

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