I have opened the pack and it's
filled with 12 sub c size batteries.
So I guess they are full but two of them have
"gone high impedance".
I am not familiar with "gone high impedance"
or battery failures so could you point me to
Those packs are effing expensive. When I tried to buy new packs for my portable power tools, they were more expensive than I originally paid for the tools! I've given up on cordless tools till they come up with reasonably priced replacment packs.Why bother...the pack has had it...buy another and move on...
Treat your battery packs carefully and they might last a bit longer
I didn't know about the hard freezing! Wonder how well it would work if I went to the welding supply shop and got a thermos of liquid nitrogen to bathe them in, something 300 below.two other ways to remove battery memory, 1) hard freeze the battery for 24 hours (below 0F) this breaks up the crystallization that causes battery memory. 2) repeated hard charges and discharges through near short circuits. the internal heating also breaks up the crystals that cause battery memory.
Here's a pic of 12 cells soldered together.I rebuilt a 4 year old worn out 3000mAh 15.6V (13 cell) NiMH Battery pack with higher capacity 3800mAh tabbed cells after finding that the least expensive replacement pack was ~$90 with shipping. I purchased the tabbed cells from an eBay store for 1/2 the price. They have all types and sizes of cells.
eBay Store - All-Battery Center: Battery Charger Kits, 8.4V, Nimh Nicd Batteries
I'm an electronics technician and it took me 4 hours to take apart the old pack and rebuild it. You have to be so careful not to accidentally short out any cells. I drew an arc once while soldering 2 cells together when the soldering iron touched something it shouldn't have. I used a small piece of mylar to keep from melting the plastic directly below the tab areas.
[/QUOTE]Here's a pic of 12 cells soldered together.
I wasn't sure that soldier would stick to the plated battery terminals. Maybe I'll try that with my pack. I saved the plastic shell in case I got inspired to try to replace the cells.