Idea: Hybrid laptop batteries. (tummy.com, ltd. Journal Entry)
tummy.com: we do linux

Tuesday July 21, 2009 at 15:08
Subject: Idea: Hybrid laptop batteries.
Keywords: Batteries, Ideas
Posted by: Sean Reifschneider

They now have "carbon nanotube" (what can't they make better?) capacitors called "super capacitors" which are very high capacity for their size. Unlike regular batteries, they don't really age out, but they don't quite have the capacity of regular batteries. But they can also charge very quickly.

I could imagine a hybrid laptop, with a regular battery and a supercapacitor, either co-located with the battery or or as a separate battery pack, which the system could use as a "front line" power buffer in front of the battery. This may allow longer battery life through fewer cycles of the main battery (only depleting the main battery if the super capacitor ran out), and very quick charging for a "topping off". Benefits that both laptops/netbooks and other electronic devices like phones could benefit from.

Many laptops include the ability to take two battery packs -- like my current laptop can take a second battery in place of the DVD burner, and it will drain from and charge to that in preference to the main battery.
(Post Reply)

Comment
Tkil
Subject: The problem with supercapacitors

Hm. It could work, but a few things that get in the way:

  • 1. Self-discharge rate is worse than Li-Ion. For the application you're specifying, that's not a big deal, as we expect to charge it every day.
  • 2. Linear voltage curve. Unlike most rechargables, the discharge curve is linear -- which means that you can only use the very first part of the discharge curve without expensive (and inefficient) DC/DC voltage regulators. Not sure how that compares to the circuitry already required for Lithium-based cells, though.

Not the end of the world, but not quite as simple as "strap a capacitor in front of a battery"...

Comment
Author: Sean Reifschneider
Subject: Indeed...
I didn't mean to imply that it would be as easy as just dropping a capacitor into the battery, but it seems like it'd be doable for the charging circuitry they have to design into laptops to support this sort of a hybrid.

Sean