A D-sized battery doesn't have enough volts to shock you enough to even notice so don't worry about that.

I use the chemical toe packs from Wal-Mart and they are awesome! I've totally converted my entire hunting family and friends over to them for all outdoor activity when it's cold out. Around $2 for 2 pair at Wal-Mart, I will buy a case next time I can find them on sale.