I recently received a personal message about mining lamp batteries that was a response to a post somewhere on the ironminers forums. It was intended for someone named Mike, but I am not sure which one. Hopefully the right Mike(s) will get the message, which is enclosed below:

Mike- saw your post about those rechargeable Edison mining lamps on the mining site. They MAY be Ni-cads as Edison was fond of them. I think they are 1.2 volts per cell versus 2.0v for lead acid. They use NaOH as a electrolyte. There is a lot of info on the web about them. They also last a long time so with care, you and your buds may be able to get some to work long-term. Hope this helps.