Sounds great, I would love to a have portable power supply so I've been using a Heath Robinson lash up with a lm2596 and two lithium 18v cordless drill batteries in series and it works great. If you used protected cells there wouldn't be any worries about over discharging and subsequently killing the battery. Please don't use any of those garbage 18650 on ebay with ***fire on the label but you probably know that already.