User manual

11. Charging Lithium Rechargeable Batteries

Test setup: USB-cable, plug board, red LED, 2 diodes 1N 4001, resistor 1 kΩ,

cable with alligator clamps red and black, lithium rechargeable battery.

Most mobile phones and Smartphones, notebooks and tablet PCs work with lithium

polymer (LiPo) or lithium ion (Li-Ion) rechargeable batteries.

This rechargeable battery type has a high energy density at a low weight. The re-

chargeable batteries are replaceable or rmly installed (soldered in). One problem

is that this rechargeable battery form has many different types (at, round, square,

etc.), rather than a consistent standard as in disposable batteries (e.g. mignon and

micro cells).

The energy density is at 95–400 Wh/l, depending on materials and use. If the

rechargeable battery is only partially charged and then partially discharged again,

the number of possible charging cycles is strongly increased. The usable energy

density drops at the same time, though.

The charge type is less complicated than is frequently assumed and generally

looks as follows: If the rechargeable battery has been discharged very deeply, start

with a very low charging current. In regular charging, the cell can be charged at the

constant maximum current in the 0.5–1 C range, though.

The nal charging voltage is 4.1–4.2 V, depending on type, and should never be

exceeded. It serves longevity of the rechargeable battery to keep the nal charging

voltage a little lower. 3.9–4.0 V (depending on rechargeable battery type) are

sensible.

Of course, LiPo and Li-Ion rechargeable batteries can also be charged at a lower

charging current. This also increases the number of cycles that can be reached

(the number of charging and discharging processes).

The rechargeable battery is completely charged (full) at a nal charging voltage of

4.1–4.2 V, the charging current will drop to about C/10. This is also the technical

measuring evaluation for automatic chargers to end charging.