Li-po batteries

[Nick Gardner]

Hi,

Just wondering if any of the folks that are smarter than me about batteries have any info on why we aren't using these for everything. Seems like they totally fit the bill. They have the capacity for dumping huge amounts of amps quickly, charge fast, and are super light. I don't think they are that much more dangerous than Li-ion. Is there a reason I shouldn't make a 4 cell pack in an AB housing? They work great in my RC helicopters.

Nick

 

[Vinny Duwe]

Lithium Ion and LiPo cells require control circuitry. If you just put 4 packs in series, you'll get the desired voltage to operate the camera, but the key with Li is balancing the cells. Without a battery control board, the cells will not charge and discharge evenly. Uneven charge/discharge can lead to explosion/fire/etc. be careful.

 

[Nick Gardner]

The charge evenly part I understand, and of course you have to use a li-po charger. But the hi-cap batteries being used in RC aircraft don't seem to have any special electronics other than the user settable low voltage cut off which is not in the battery, but the electronics of the aircraft. They just seem like wonderful batteries.

Nick

Edit-afterthought - OK, so why doesn't somebody make a board for theses things and make a big old block battery out of them?

 

[Vinny Duwe]

There is a circuit board shrink wrapped underneath.

 

[Bob Gruen]

What do you think the Red Bricks are???

 

[Nick Gardner]

Lithium Ion, not lithium polymer.

Nick

 

[Bob Gruen]

There is little distinction between the two (in terms of cost vs performance anyway). I've run both of them in various applications and the only real distinction is that the Li-Po batteries are more volatile if something goes wrong. Red already has issues getting Red Bricks through the mail, if they were Li-Po it would be even worse.

Bob

 

[Nick Gardner]

I use both, and the weight to power ratio difference and the ability to deliver large quantities of power quickly, are not inconsequential. That's why they are going into cell phones and computers, and that's why they are the battery of choice for RC aircraft where weight is a major concern. We'll agree to disagree then.

Nick

 

[Bob Gruen]

Example from MaxAmps:

A123 - 2300mAH * 6.6V = 15,180J @ 170 grams
Li Po - 2000mAH * 7.4V = 14,800J @ 120 grams

...but the Li-Po battery above is a soft cell while the A123 is by its nature a hard cell. The A123 would require less structure in an exterior case than the LiPo would so by the time you had a finished product (akin to a Red Brick) there wouldn't be a significant weight difference between the two chemistries.

The A123 cells also have had a burst rating of 60C since they were first offered on the market while the best Li Pos are only cresting 60C now (not that electronics like the Red put out major amperage spikes). A123 cells can also be charged/discharged more aggressively without damage. In fact, the Red Brick charger has the deep cycle charge feature that allows you to use more of the battery than you could safely do with a Li Po. (Personally I pull the battery from the camera when it hits 30% as the deep cycle charge section in the charge cycle is very slow.) Also, Li Ion also has a tighter voltage range during discharge which makes them better for electronics.

Red really did their homework in every element of their solution, their battery system is probably the best design on the market today for the purpose which it is intended...

Bob