Req: Information about Li-Ion accu

[cube007]

Hello,

I'm looking for information about Li-Ion accus. For example, is it possible (good) to switch the cells parallel to increase the capacity?

by,
cube007

 

[Smanetto]

As I know, battery pack use parallel cells to increase the capacity, but you must be carefull.
Li-ion batteries have a very high energy capacity and low series resistance, so if you short 2 batteries together it could be dangerous.

Battery pack use almost identical cells and some protection: a diode in parallel to avoid voltage inversion, a series PTC to limit the maximum current (and sometimes a lo-esr capacitor in parallel to the cells).
When there are also cells in series (7.2V, etc...) a circuit is necessary to equilibrate the charging voltage and to avoiding the voltage across every cell goes above a maximum of 4.1 or 4.2V (depending to the chemistry).

If you have to parallel them, put the cells at the same voltage (with a resistance for a quite long time) and then join them.
Charging the batteries is not a huge problem, because the li-ion cells limit the current automatically at the end of charge (constant voltage charging).

A few warnings: limit the maximum charging current, do not exceed the maximum charging voltage (4.1 or 4.2V), use identical batteries and remember that the last 20% of capacity is in the last 100mV of charge!

Search in Internet for Li-ion batteries manufacturers and you will find these informations more clear and with images!

Bye

 

[cube007]

Hello Smanetto,

thank you for the information. I will take a look at the homepages of the "big" manufactures like Sanyo and Panasonic to get more stuff.

by,
cube007

 

[beuch]

Hi,

careful, it's very very very hard to obtain LiIon batteries from, as you say, "big" manufacturers Sanyo or Panasonic.

I suggest you to buy standard batteries for camera or video recorder.

bye