When I hit the road, I carry my cell phone, PDA and MP3 player, at a bare minimum. That means I need to carry three power cords and adapters. And, sometimes, power isn't readily available -- or there isn't enough of it. For instance, on car trips, I can use the cigarette lighter to charge my devices or listen to music, but not both.

Enter portable power supplies. We're not far from the time in which devices have rechargeable fuel cells but, in the meantime, other technologies will have to suffice. For the last couple of weeks, I've been using two recently-released alternatives: The Titan I portable power supply, which adds a twist to traditional battery technology, and the Soldius1 solar power supply.

For reasons that are often out of the control of the vendors, neither alternative power source is the total answer. However, of the two, the Titan I is the most useful.

Titan I uses a lithium ion battery but with what the vendor calls "nontechnology energy management circuitry" that enables it to both keep the device small and to provide far more concentrated source of energy in a small package.

I'll buy that. The Titan I is svelte -- a bit longer but narrower and thinner than a deck of cards -- and, like so many things these days, it looks like an iPod and, at about 4.8 ounces, weighs about as much, too. It's much smaller and lighter than other alternative power supplies I've seen and is simple to operate. Initial charging took about three hours; when it was fully charged, its three blue LEDs stopped blinking and shined steadily.

To charge a device, you attach an included adapter or cable to, usually, the Titan I's USB port and press the start button on the side. It can charge either one device or two simultaneously and stops automatically when the charge is complete. It also has a FireWire port for charging devices that support that technology.

But the "attaching" part leads to a problem that the Titan I shares with all portable power sources: A lack of standards for how mobile devices connect to power supplies. To overcome that problem, Titan I comes with a fist-full of adapters, including a particularly clever one -- a cable with three separate adapters at the end, enabling charges of more than one device at a time. In addition to the adapters that come with the charger, more adapters are available via the company's Web site.

I emptied my closet and tested the Titan I with a variety of devices. Some devices charged perfectly, such as the Creative Zen Touch and Samsung YP-T7 MP3 players and an ancient iPAQ 3750 PDA. An old Nokia 6100 mobile phone wouldn't recharge at all, but it would operate while it was attached to the Titan I.

However, some devices just would not re-charge or operate while connected. One reason for that was that there was no adapter, which was the case with my LG VX6100 phone and with the Palm Treo. The adapter fit into my old Nikon Coolpix 880 digital camera, which uses rechargeable batteries, but it would not charge. Such a spotty track record is probably inevitable in a world in which standards don't exist.

Overall, I recharged the Zen Touch and the Samsung YP-T7 twice each, the iPAQ PDA once and used the Nokia phone for about 20 minutes while attached to the Titan I before one of its LCDs started blinking, indicating that it was almost out of juice.

My primary objections were that the Titan I's included adapters could have been better labeled and that, at $149, you'll need to make sure there are adapters for all your devices before you buy.

Titan I; $149.99; Big Wave Power; www.bigwavepower.com In theory, the Soldius1 solar recharger is a lovely idea, charging devices with clean, politically correct solar power. In practice, though, it use is limited.

When it worked, it was easy to use. Folded up, the device is roughly a third larger than the Titan I. When you open it up to expose its solar panels, its size naturally increases. You attach the power cable, aim the solar panels at the sun and it starts charging. Soldius1 comes with adapters for most iPods and many popular brands of cell phones and Research In Motion's BlackBerry. While that covers a lot of territory, it had no adapter for the Palm Treo, the LG VX6100 phone or for my MP3 players, although the cable that came with the iPod Nano worked fine.

Now for the yes-buts. For one thing, the Soldius1 only works in direct sunlight -- it wouldn't charge on cloudy days or when the sun was still visible but low on the horizon. Nor does it have any storage capabilities, so you can't charge the charger and apply the charge at a later time, such as overnight. Plus, it's often not particularly handy to use. In a car, for instance, you'd have to figure out some way to prop it up on the dashboard so that it doesn't fall off. This combination of shortcomings means that there are significant limits on when you can recharge your device.

Bottom line: It's hard to argue with solar energy, but Soldius1 isn't the most practical portable power supply, even if it is one of the most socially responsible. For specialized needs such as backpacking with your cell phone and iPod -- a niche market at best -- Soldius1 is a good idea. For most real-life situations, though, results are mixed.

In any case, before you buy any portable power supply, make absolutely sure that it will work with your devices. If they do, you can reduce cord clutter while you travel and insure you never run out of juice. If they don't, you'll still need some power cords, which defeats the purpose of the portable power supplies altogether.

SoldiusI, starts at $89.99; mysoldius; www.mysoldius.com