When reviewing the link about the Ivation battery powered shower it reads "consistent 2.5i/minute". I know of no liquid measurement in the U.S. system or metric system that has the abreviation of "i". What nuance am I missing?
When trying to do a comparison with Zodi I found the following.
Zodi™ has a self-contained portable Battery Powered Shower for rinsing dishes, cleaning up, hand washing, washing pets, showering etc. Powered by 4 D-cell batteries and place the compact pump in any water source.
The Zodi™ Battery-Powered Shower, "flow rate for the pump is ½ (.5) GPM, the water pressure is not available" per Cabela's website found under customer questions and answers for Zodi™ Outback Gear Zodi™ Battery-Powered Shower section about this product. The ½ (.5) GPM figure I verified with Zodi Customer Service.
Zodi™ has a portable 12 Volt shower. Place the pump in any water source and connect the 12 volt plug to a convenient 12 Volt power supply. The 12 Volt pump "delivers up to 1 gallon of water per minute" per the description on the Zodi™ website, i.e., pumping through a Zodi shower unit because the coils in the heating element restricts the water flow.
Zodi™ 12-Volt Pump and Washdown Hose "Up to 3 gallons of water free flow per minute" per the description on the Cabela's website. I verified with Zodi Customer Service. the "up to 3 gallons per minute" is with no restrictions on the flow of water.
These Zodi™ units runs at .5 (½ ) GPM and 1 GPM respectively.
As a point of reference your home shower runs at 2.5 gallons per minute.
The Ivation battery powered shower is interesting.