AlphaSmart Dana Power Hack

alphasmart_dana_sony_cycleenergy

Here’s a little hack for the AlphaSmart Dana that will both improve battery life and allow you to future-proof your Dana’s power needs in the event that AlphaSmart someday stops selling replacement battery packs.

AlphaSmart rates the life of Dana’s rechargeable battery pack at 25 hours, but users generally do not see that kind of life since the Dana’s battery pack gradually loses its charge when sitting. The actual run time varies widely, depending on how soon the device is used after being charged and how long the device sits between uses. A freshly charged Dana will still last far longer than a laptop computer, but the gap between the two will narrow the longer the devices have been sitting.

There are two reasons for Dana’s power drain. First, as an older Palm OS device, Dana needs a constant trickle of power to preserve the contents of RAM. The second reason is the nickel metal-hydride (NiMH) cells used in the Dana power pack. One of the disadvantages of NiMH batteries versus traditional alkaline cells is their slow self-discharge, which gets more pronounced as the cells age. The gradual self-discharge is probably responsible for more dead-battery surprises than the power needed to keep the RAM alive. Happy Dana users are frequent users and frequent re-chargers.

In the last few years, developments in battery technology have led to a new type of NiMH battery that has a miniscule rate of self-discharge. Manufacturers claim that these “Low Self-Discharge” (LSD) batteries retain 85% of their charge even after a year of storage. The LSD cells can be recharged 1000 times and are completely compatible with any charger or device that uses the older NiMH batteries, including the AlphaSmart Dana. As a bonus, the new NiMHs also have a larger capacity than the older cells used in the Dana battery pack. Dana’s cells are 1600 MaH, while LSD batteries are usually 2000 MaH. The larger capacity, combined with the almost non-existent self-discharge, make LSD NiMH cells the ideal choice for powering Dana.

Unfortunately, you can’t simply plug the new NiMH cells into Dana’s battery slot. The battery slot is wired for alkaline batteries, a feature that allows users to slap in a set of standard AAs when the rechargeable pack goes dead. The Dana does not correctly read the voltages of NiMH cells plugged into the battery compartment, nor would the device recharge cells through the compartment wiring. Instead, there is a separate power connector for the rechargeable battery pack. In order to use the new LSD cells, one needs to get them plugged into this separate power connector. One way to this would be to rebuild the battery pack with the new cells. A second way is to wire the alkaline battery compartment to the power connector used for rechargeable packs. I chose this second method, essentially turning my battery compartment into an open-door rechargeable battery pack that I can install new cells into whenever I like. Of course, I must be careful if I ever decide to put a set of alkaline cells in the rewired compartment. They’ll run the device fine, but it could be dangerous to plug in the charging cable while the compartment contains alkaline cells. Not a problem for me. Most of my gadgets are recharge only anyway. I’m used to it.

alphasmart_dana_motherboard_back

To re-wire the battery compartment, you’ll first need to take apart the Dana case so you can remove the motherboard. You can see the power connectors from the battery compartment, and the separate one that plugs into a rechargeable pack. What we’re going to do is clip the black compartment wires off of the board, and wire those connectors to the wires used for the rechargeable pack.

alphasmart_dana_power_connector

Closeup of the pre-snipped wires.

alphasmart_dana_snipped_power_cords

Here we are with the wires cut. You will also need to strip the plastic coating from the ends of all wires.

alphasmart_dana_re-wired_power_cords

Next we have to wire the flat battery connector to the red recharge line. With the wire ends stripped of their plastic coating, you can twist the two together pretty easily. For the spring connector, I had to add some extra wire to the black line since it wasn’t long enough to reach the other end of the battery compartment. I took an extra length of wire, stripped the ends, and twisted it together with the short black wire. I twisted the spring connector onto the end of the longer black line.

To finish up, I covered the exposed sections of twisted wire with a bit of electrical tape. One must be careful not to use too much tape; it could thicken the wires to the point where they can interfere with the case halves fitting back together.

dana_with_sony_cycleenergy

And here we are with the case put back together and the new cells in the regular battery compartment. The compartment now serves as a rechargeable battery back that can have its cells replaced anytime. Based on how well the LSD cells (Sony CycleEnergy) work, I do not think I’ll ever even need to rely on a spare set of alkaline cells. The battery life that I’m seeing with this hack is really quite incredible. I’ve let this Dana sit for three weeks at a time, and can come back to a system that still has a bit of juice remaining. No more dead battery surprises!

alphasmart_dana_battery_meter