6. Inside A Nickel Metal Hydride Battery Pack

Here's a nice Toshiba battery pack, 9.6V 3000mAh Nickel Metal Hydride. While this is old tech, I'll be comparing the battery to a Dell Lithium-Ion later on so you can see the differences. This battery pack doesn't have visible seams; however, the underside looks like this:

There are five very telling openings, which are really very small:

But I think is just big enough so it might fit a screwdriver:

Ahh! Here we go. Knock, knock! As you can see, the screwdriver is not the ideal tool, as it left some gnarled edges on the opening, but it does work. Now that the battery let us in, we'll gently pry up around the edge of the panel to reveal the cell packs.

Toshiba does very nice clean work inside. Nearly ever cubic inch of space inside is packed with NiMH cells. Let's peel away the layers of the onion.

As you can see, the four battery terminals on the right are hooked up directly to the battery cells. NiMH tech is very safe and so no protective circuits are needed inside. The connections are done on top of the wax paper to avoid any metal accidentally shorting a battery cell. Let's now peel away the waxy insulation paper:

This is a layer of red vinyl insulation covering 4 NiMH cells in a single set. There are two sets of four NiMH cells all wired in series of eight cells. The interesting bit here is that Toshiba used custom looking cells made in the shape of a box. Usually, battery cells are cylindrical, like AA, C, and D alkaline cells. In this case, Toshiba chose to fill every bit of space inside their pack with NiMH and really push for performance. Since this entire pack is rated at 9.6V @ 3000mAh this tells me there are two individual packs rated at 4.8V @ 3000mAh each. Each boxy cell is probably rated at 1.2V @ 3000mAh each. This battery pack is from an older notebook.

A single one of these AA NiMH cells is also rated 1.2V @ 2700mAh but is exactly half the size of those boxy older cells. In theory, placing these cells into the same laptop battery case would yield a battery pack rated at 9.6V at 5,400mAh or roughly 2 times more running time. And the battery still would essentially be compatible with the original. Is it truly possible to mod the Toshiba battery to twice the running time using off the shelf AA batteries? Do they even fit? You bet! Take a look at the next photo. But this is a mod for another time.