Lithium Polymer Batteries -- How to wire and what to buy.

[hailrazer]

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/polymer...wh-10a-rate-ul-listed-un38-3-passed-ndgr.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/smartcharger12afor74vli-ionpolymerrechargeablebatterypack--ullisted.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

 

[Mako321]

Hail hasn't been online since 4:43, how was this posted at 5:22?

 

[snowpenguin]

Don't rock the boat, mako.

 

[bud]

Okay SS's charge and play diagram is gone now, but I need to look at it. Could someone repost it?

Also is it possible to get three or so of these and wire two to get the 7.4v then wire the others to increase the mah. If so how would I do this? A diagram would be nice.

Thanks

 

[chrisperson94]

Okay SS's charge and play diagram is gone now, but I need to look at it. Could someone repost it?

Also is it possible to get three or so of these and wire two to get the 7.4v then wire the others to increase the mah. If so how would I do this? A diagram would be nice.

Thanks

here you go

 

[bud]

I saved it so it will never be lost.

 

[Mario]

Or, if you only need 3.7v (like using a step-up to get 5v) you can get a 3.7v battery and one of these: http://www.sparkfun.com/commerce/produc ... cts_id=726

Or, you can just buy a MAX1555 chip yourself.

 

[wooothooot]

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/highpowerpo ... arate.aspx

uhh, when checking out it says to purchase a 25 D LLAR haz mat shipping box--is this required for this purchase?

 

[cfc_12]

there are no pics, darn it

 

[ttsgeb]

Well, that's unfortunate. :/
He's not even banned here. I guess he just didn't think to update this post whenever that happened.

 

[Kickback]

How childish

 

[ttsgeb]

How childish

To be fair, this is an appropriate response when dealing with Bacteria.

 

[hailrazer]

Guide updated.

 

[Shank]

Do you need some kind of cooling system for the batteries?

No? In his comment, he says nothing about running a cooling system to batteries. He is expressing his concern for someone putting sensitive lithium batteries right on a heat source, while not having a cooling system for said heat source.

 

[Shank]

So Li-Po batteries don't heat up?

They have an equivalent series resistance, so they can heat up when high currents are drawn, but this amount shouldn't be that high in the average portable. If your cell is heating up on its own under low current draw, then your battery is not functioning properly.

 

[ttsgeb]

If you need heatsinks on the battery for your portable, you're doing something horribly horribly wrong.

 

[Prog]

If you need heatsinks on the battery for your portable, you're doing something horribly horribly wrong.

Wrong? Or right?
Maybe someone is finally making an Xbox portable :awesome2:

Seriously though, LiPos will generally heat up relative to power draw as Shank said, but you probably have to go well-beyond the max discharge rate for that to be a problematic amount of heat. A bigger risk is putting the batteries close to something hot like a CPU.

Also holy flax Hail is alive