I've heard that these may be one in the same with teh IB4200's of which I have two sets. My experience is that these loose a charge fast. Some times if they sit for a week or so on cell will drop to zero while others will be above a volt. Can you measure the voltage of each cell? (are they side by side). Anyway when this happens one amp doesn't seem to wake that cell up. I usually hit them with 3 amps for a few minutes, you'll see the voltage come up. Then I drop back to .5 if I'm doing a forming charge to balance them out again. If I do the 0.5 right off the bat that cell will not come up to voltage. Ive seen this on 3 of the four 4200 packs that I have.