iPod Toch 5G (iOS 7.0.3) charges way too fast?

I made a second test...

from "full" battery (around 95% after some testing) to absolutely empty I needed roughly 38 hours -- playing music, wlan on, display off... as supposed in one of the support documents. This means, the battery is okay and was nearly full charged. Therefore the "100% calibration value" must be in the correct range. And it shows that the battery is okay and not drained (by usage / mishandling).

To mention: Before I unplugged the iPod, when 100% of charge was reached... and therefore havn't "overloaded" the battery (e.g. to push up the 100% calibration value). I have the idea, that 0% and 100% values are calculated/measured whenever the iPod is charged and discharged fully (maybe as an average value over time).

So I guess: 0% and 100% of this iPod are in the right value region.

Now I charged the iPod with my MacMini -- Lightning cable in USB Port. This time no wall plug.

a.) From discharged/0% to 80% it needed around 1 hour.

b.) From 80% to 100% (just reached) it needed around 30 Minutes.

The (a) chargind is around twice as fast as it should be.

The (b) charging is around four times as fast as it should be.

(support document says: 2 hours for the first 80% and 2 hours for the remaining 20%)

There is no decline in charging speed between 80% and 100% -- as written in a support document about batteries. The charging is roughly linear between 50% and 100%...

BTW: The outer shell of the iPod hasn't warmed in this test.

What is going on?

From my technical understanding this couldn't be good... because if the Li-Ion-Battery is charged too fast it will drain bevor its 400 full-charge-cycles... and this means, the iPod will live only halve its lifetime!

And as a hazard, a too fast charged battery could catch fire?!

Am I correct or am I wrong?

Is the (hardware) charging-regulator inside the iPod defective?

Nevertheless I'm a little bit worried...

This 2hrs + 2hrs = 4hrs for full battery charging time which is stated in the product description has been set to maintain a long life of the product.

If it would be okay to charge it fast apples technicians would have implemented this for every iPod. They didn't... with good cause, I think.

This iPod should live around 400 full charging cycles until a costly battery change or a new product should be neccessary. Maybe it will live as long with "fast charging"... but if not, then what?

And if I would charge my rc-flight-LiPos with double or quadruple their supposed charging current, I guess they would simply explode. Li-Ion are not LiPo batteries... but nevertheless, one should be carefull with things which could catch fire.

So... what to do?

Send it back to Amazon? Contact Apple (besides this board)? Do nothing?

BTW: The charging time hasn't anything todo with the power source. This time I used the MacMine, last time a 5W USB wall-plug. Before a 12W/10W iPad charging-plug. Always the same...

FYI - A final update ...

I fully charged my battery for around 8 hours -- so it should be on it's limit (and the 100% mark should calibrated right).

I did a test with movie playing and came to the same result: after 4 hours (continous playing, screen on, wlan on, loudspeaker on) the iPod was at 50% . Thats within the specification given for the iPod and that means: The battery is okay.

So I charged it again on the MacMini.

After 15 minutes the charge was risen from 50% to 80% ...

after 15 minutes more it was risen to 90% ...

after 15 minutes more it was finally at 100% ...

So I will send the iPod back to Amazon... even if it's more than half a year old, this is a (maybe critical, because of catching fire) defect.