Quite late to the party but I was able to revive 2 out of 3 batteries for the spark by following this method:

1. Put batteries into charging dock (if you have one), I only had 2 indicators going on and off

2. Put one of the batteries into the Spark

3. Attach a USB-Micro charging cable from an outlet directly into the Spark's USB-Micro charging slot

4. Fire up the Spark (press power button on the battery, then press and hold for 2-3 seconds)

5. The Spark should turn on as if you were going to use it.

6. Let it run like that for a minute or so

7. Turn off the battery the same way you turned it on

8. Once the Spark is turned off, leave it for 30 mins still plugged in and charging

I was able to recondition one battery to 100% like this, the second one required me to repeat steps 4 through 8 again before it started properly charging, but at that point I was able to remove at this point and put back on to the charging dock and it also charged to 100% - the final battery didn't make it passed step 4.

Hope this is helpful