How to calculate the Ampere Hour Ratings?

Agreed, but I no experience with Lithium Iron Phosphate. Additionally, battery “capacity” (how long you
can use it before you have to charge it) is not really the same as energy density (how many amps you can discharge it at) so it is possible that what you (rockwallaby, since we are the ones having this discussion) said is true with regard to 80%. Perhaps draining the battery at 60 mA for 64 hours instead of 83 hours
will increase battery life. Battery life isn’t always the highest priority. Sometimes being able to run
something longer is more important than how often you need to replace the battery, especially when
your are talking about something like the difference between 100 discharges and 300 discharges before
needing to replace the battery. All in all , I would have to say that since you have LiFePO4 experience and
I have LIPO experience, we are talking apples and oranges, and the OP will have to decide for himself what to use.

All the OP wants is to know how to calculate the capacity of a battery and solar panal to power his very small gadget, as he says:

Where did you get the “solar panel” reference from the OP ? I don’t see any mention of solar panel in his
questions.

It looks like one of you is talking Ah capacity, and the other is talking discharge rates.

It looks like one of you is talking Ah capacity, and the other is talking discharge rates.

We are actually trying to correlate one with to the other (Is that possible ? I don't know)

The OP is interested in Ah capacity and discharge time.

The questions are :

1- Does a battery with a higher discharge rate have longer discharge time (Ah capacity) ? 2- Which battery technology offers the longest discharge time (best Ah capacity) in a small package ? 3- ? [fill in as needed]

Check out this thread: Choosing batteries