That battery ain't dead yet probably. Hook it up to a car tail light bulb and drain it dead. Then re-charge. Repeat process about 5 times. I bet it works it back into shape. If it doesn't, then if you have access to an aftermarket charger charge it a 1C (an amp rate equal to the capacity of the pack...1000ma = 1 amp). That might bust out any resistance crystals that have formed in it, but sometimes I'll shock charge a pack at say 3C or so, but ONLY for about 5 minutes because that can be risky if you don't know what a pack can handle fast amp wise. After a 5 minute blast I'll put it back on a 1C charge the rest of the way.
If you can't get that pack to recover after about 5 cycles, and blast charging didn't help either, then pretty much you've got two options- A new Minelab pack (the ones for the GT work too), or sending the pack to somebody to have it re-built. I bet that would be a much cheaper option then buying a new Minelab pack. Many companies build custom packs for devices dirt cheap if you know where to look. And the added bonus is you can have them put higher capacity cells in it then the sub-as in it now which are probably 1000ma if it's the same as the GT pack. Tell them you've got 10 sub-As in the holder and want a quote on them re-installing some higher capacity ones. Just remember if you use the stock wall transformer the charge time is now longer. Divide the capacity of the cells by the output amps it says on the wall charger. If it says 100ma and you had them install 2000ma sub A cells, the charge time is now 20 hours instead of 10 or whatever it was before, depending on the output of the wall transformer. I'd much rather just buy a cheap charger for it from them when you have the pack re-built. You'll need to clip it to the two main battery leads and not charge thru the little plug as that has a charging circuit in it that gets fed from the stock wall transformer.
