Lithium Polymer batteries are the newest and currently one of the best choices for batteries in a portable. They are smaller than other batteries, don't develop a "memory" , and last through more charges/discharges than other types of batteries.

But working with Lithium Polymer batteries can be dangerous and precautions must be observed. Be very careful with polarity when hooking up Li-Po's. Also ALWAYS use a protection circuit (PCB) and a Lithium charger that is appropriate for the number of Li-Po's you will be using.

Lithium Polymer batteries come as single 3.7v cells. These cells can be packed together to get 7.4v , 11.1v, 14.8v , etc Li-Po Packs.
When using a 7.4v pack you will want a 7.4v Pcb and a 7.4v charger. Ditto on the rest.

The following diagrams will be based on wiring the 3.7v cells in series to add their voltages together to get the required voltages we need. Batteries wired in series are wired like so :



This is the typical battery most of us use because it has a relatively high capacity for a very small size and cheap price:
http://www.batteryspace.com/polymerli-i ... isted.aspx


Here is an example on how to wire the different sets of Li-Po packs you might be using :

7.4v pack. (Two 3.7v Li-Po's)


For the Pcb you will need the following :
http://www.batteryspace.com/pcbfor74vli ... limit.aspx

For the charger you will need the following:
http://www.batteryspace.com/smartcharge ... isted.aspx

11.1v pack (Three 3.7v Li-Po's) :


For the Pcb you will need the following :
http://www.batteryspace.com/pcbfor111vl ... ocket.aspx

For the charger you will need the following:
http://www.batteryspace.com/smartcharge ... isted.aspx

14.8v pack (Four 3.7v Li-Po's) :



For the Pcb you will need the following :
http://www.batteryspace.com/pcbfor148vl ... ocket.aspx

For the charger you will need the following:
http://www.batteryspace.com/smartcharge ... isted.aspx

Very nice. I've been wondering how to hook up batteries higher than 7.2v. This is extremely helpful!

Where do you get the charging port for the smart charger to plug into?

I make my own with type M jacks from Radio Shack :
http://www.radioshack.com/product/index ... Id=2102491
http://www.radioshack.com/product/index ... id=prod_cs

Say I wanted to hook up 4 of those 3.7v batteries but still have 7.4 volts total. how would this be accomplished?

EDIT: nvm i think i found out how very cheap.

so, do these pcbs/ smart chargers work with lithium ion cells too?

Yes.

ok good. now i can use this hueg li-ion battery pack i got a the ircuit city closing sale for 2.50$.

How would you hook up two 7.4v Li-ion packs?

The picture on the bottom. Connect them in parallel.

I meant to the board. Would I just buy the first pcb listed and skip over the COM? Or is there another I should buy.

Ah, ok! From his picture for the 7.4v protection circuit, hook up both positives to the B+ part and both negatives to the B- part. The Com (common) won't matter, because that is only for batteries in series.

Awesome! So to be clear;
1) Do NOT parallel them and attach the positives to B+, and negatives to B-
or
2) DO parallel them and attach them as you said?

#2. Parallel, and attach positives and negatives to their respective spots.

These batteries from batteryspace are interresting but shipping it to europe is too expensive... does anyone know where to buy good batteries in europe ?