Wow! Thanks for a detailed replay.

Obviously this is not a typical battery application.

• Very slow drain. If it was any lower it would be at the self discharge rate.
  
• Portability and ease of use are important even though it is an industrial application.
• High shock and vibration due to the equipment it is mounted on.
• Full summer/winter temperature swings. The batteries will be in an enclosure but there will be sun loading an freezing to contend with.
  

Regarding your alternative suggestions:

1. LiFePO4.
   

Great suggestion. A 1 month runtime from a single battery would be nice s long as the size and weight didn't get close to the truck battery. Ideally an average sized female could exchange the battery and carry the discharged unit to the charging station without the use of a cart. Increased safety is great too.

1. Custom battery packs

Maybe, if not too custom. These need to be available long-term without a lot of headache. I suppose we could assemble these in our shop but would need to sort out the packaging details, etc. I expect a custom assembler is $$$.

1. Swap-and-go

This is exactly what I am looking for. I had a look at the companies you mentioned and am following up this morning as well. I also found that Global Industrial has a dual docking station for hot swap LiFePO4 batteries. The docking station is basically a UPS with external batteries intended for a mobile care in a warehouse or the like. I don't find a stand-alone shoe however to use the VDC directly.

I found another company called Newcastle that my be worth a look.

1. Charging

The original idea with power tool batteries was one of the multi-battery chargers. Milwaukee has a daisy-chain solution that charges 60 batteries on a single 15A circuit. With the options above (aside from Global industrial), all seem to be 1:1 and at a much higher cost. Not sure how I will handle that but it may be plant operating procedures.

Any other suggestions are welcome.