External Li-Ion Pack: More Sawing

Two of the external Li-Ion battery packs I’m using with the bike radios seemed to fail quickly after being charged, so I sawed them open to check the state of the cells. This time I used the fine-tooth cutoff blades, rather than a coarse slitting saw:

Li-Ion pack - sawing case

Li-Ion pack – sawing case

As before, a 2 mm depth-of-cut, done 0.25 mm per pass after the first millimeter, seems about right. I didn’t saw the front of the case near the jack, which proved to be a mistake; the interlocked case halves need cutting.

No cell trouble found, which leads me to suspect an intermittent short in the battery-to-radio cable that trips the battery protection circuit. The spare cables went into hiding during the shop cleanout, so I can’t swap in a known-good cable just yet; of course, the existing cable behaves perfectly on the bench. The suspect cable is now on my bike and, if the problem follows the cable, further surgery will be in order.

For the record, the insides look like this:

Li-Ion pack - interior

Li-Ion pack – interior

The cell label seems to show a 2004 date code:

Li-Ion pack - cell label

Li-Ion pack – cell label

Given that I got them on closeout in early 2010, it definitely isn’t 2014.

Unlike some of the other cheap batteries around here, they’ve been spectacularly successful!

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  1. #1 by Daniel B. Martin on 2016-08-18 - 06:53

    The date code clearly reads “1865.” You bought Civil War surplus. It’s used up!

    • #2 by Ed on 2016-08-18 - 12:34

      Dang, they must be scrapin’ the bottom of the lithium barrel!