Battery Charge Level for Long Term Storage??

Logically, why wouldn't it be the maximum charge? As the charge goes down, it will eventually reach that level of charge other people will tell you are the best. I know for lead/acid (car) batteries, charging them to the max before "storing" a car for awhile is the best option.

I'd fully charge it before placing it in storage. Then every month or two take it out and fully charge it.

For Lithium batteries, its best to run them down (ie use the unit till it shuts itself off), then fully charge the battery and safely store away for a month or two. There is no need or benefit from storing Lithium batteries (or Ni-MH for that matter) in the freezer, they are not alkaline batteries which is where that old holdover comes from. Lithium batteries have a very low self-discharge rate when sitting unused, *but*, because the Nuvi is always using power, even when off, you will need to cycle the batteries (discharge and recharge) on a regular basis (the one to two month I mentioned above). Do not simply put the Nuvi away and forget about till many moons later. A Lithium battery once it has passed a certain low voltage, it will no longer hold a full charge and will quickly die, in many cases it will not even charge up.

You might like to peruse this article: http://www.batteryuniversity.com/parttwo-34.htm

I think you got it right, keep it at 40% charged, in a cool place. Btw, if you put it in a fridge, doesn't the moisture ruin the internal circuitry? It's a different story if the battery is removable and you only put the battery in the fridge.

I would be very concerned about storing it in the fridge. The cold/warm cycle will cause condensation which will eventually destroy the electronics.

With humidity levels here in Tucson usually below 20% and often in single digits, there is no condensation. Point well taken though. If you keep the item sealed in a zip lock bag without much air surrounding it, and let it warm before removing it, any condensation forms on the bag an not the unit. (Years of experience with expensive optics and electronics coming in from the cold gives me no concerns about ruining the GPS' electronics here)