Best way to Freeze items in a PU

[azpopup17]

I am trying to figure out an economical way to freeze ice packs for hiking trips while camping.  My application is medical supplies that need to be kept ~85 degrees.  I know you can purchase a portable freezer which can be pricey.  I have seen some in the $400 - $500 range.  Has anyone tried using dry ice in the ice box to freeze items or have any shared learning on this?  

Thanks.

[beacher]

The only dependable way to freeze something, especially for medical use, is by using a freezer.

The three-way fridge in my PopUp will maintain frozen items in it if they are placed on the very bottom.  Things like Ice Cream, or frozen steaks will stay frozen indefinately, (well, at least as long as four days, .....as long as we have ever "tested" it).  However, it will not freeze the items if they were not previously frozen.  I would never depend on by refigerator's ability to keep things frozen for medical purposes.  It's more of a fluke!

[AustinBoston]

I am trying to figure out an economical way to freeze ice packs for hiking trips while camping. My application is medical supplies that need to be kept ~85 degrees.

Does "kept ~85 degrees" mean "kept near 85

[azpopup17]

Thanks for the info.  The medical items (insulin) do not need to be frozen.  They just need to be kept < 87 degrees which will not be a problem dry camping at the PU.  It will be a problem if we venture off from the PU in warmer temperatures.  So if it is 95 degrees outside and we go fishing or hiking I would like to be able to bring a small cooler and throw in a couple of ice packs to keep the stuff cooler.  I may test the dry ice in the ice box method.  Since it is at -70 degrees it would be the best chance to freeze something.  I am not sure if it would freeze an ice pack that is not already frozen though, which would be my special case.

[Ribs1]

Thanks for the info.  The medical items (insulin) do not need to be frozen.  They just need to be kept < 87 degrees which will not be a problem dry camping at the PU.  It will be a problem if we venture off from the PU in warmer temperatures.  So if it is 95 degrees outside and we go fishing or hiking I would like to be able to bring a small cooler and throw in a couple of ice packs to keep the stuff cooler.  I may test the dry ice in the ice box method.  Since it is at -70 degrees it would be the best chance to freeze something.  I am not sure if it would freeze an ice pack that is not already frozen though, which would be my special case.

Dry ice will freeze an icepack that is not already frozen.  It will also freeze anything else.
http://www.dryiceinfo.com/