problem 12v to 5v conversion

[idoporges]

im in the idf (3yrs mandatory...) and all i know is high school physics.
im using a generic idf battery of 12v (15v when full 11v depleted) to charge cell phones.
i took a cheap car charger (which is supposed to get 12v-24v from the car itself) and soldered wires to its inputs - and connected the wires to the battery.
it works fine, for many charges, but when the battery is "depleted" it still gives out 14.7v and can still power the idf machinery it is supposed to power, and for a long while too!

I make DO, but i cant help but wonder if there's a huge unlocked potential to these things.

so why wont the charger work with 14.7v? is the charger faulty? (it is rather cheap...) is the battery simply not enough? will building a quality converter solve the issue? (educating myself on regulators! :thumbsup
please help!

 

[ARQuattr]

What type of battery is it (what chemistry)? Typically equipment is designed to not use batteries at low voltages to avoid over-discharging them, which can lead to shorter life or complete failure. It depends a lot on the type of battery.

 

[idoporges]

What type of battery is it (what chemistry)? Typically equipment is designed to not use batteries at low voltages to avoid over-discharging them, which can lead to shorter life or complete failure. It depends a lot on the type of battery.

its a lithium battery (its a packet with about 4 of them inside).
inside the packet there is also a chip which connects the inputs and has some unidentified parts in it (they are some army made parts, made to be more resilient). might the chip be another regulator? if it is, might it be the problem?

 

[D.A.(Tony)Stewart]

Cheap chargers do not have the 3rd stage to reduce to float or autoshutoff preferred for LiPo to prevent self-heat which ages the chemistry.

Can you add a timer to charger input?

Also define common abbrev. like idf (Indian Defence Force or Israeli Defence Force)

also rename your question title or add relevance to 5V

Google Images has schematics (hint)

 

[idoporges]

Cheap chargers do not have the 3rd stage to reduce to float or autoshutoff preferred for LiPo to prevent self-heat which ages the chemistry.

Can you add a timer to charger input?

Also define common abbrev. like idf (Indian Defence Force or Israeli Defence Force)

also rename your question title or add relevance to 5V

Google Images has schematics (hint)

i really dont know what to search in google to get those schematics >_<
auto shut off is probably way above my skills anyways. will a heatsink help? are there 12v 3cm fans?