For emergency use, a "crank flashlight" can be ideal because it needs no replacement batteries at all. Instead, you turn a handle for about a minute at a time, which recharges the internal battery. Crank flashlights, also called windup flashlights, are an especially good choice for a disaster-preparation kit. The main caveat is that we didn't find any windup flashlights with lifetime warranties or tight weather seals.
As the most useful crank flashlight, two reviews recommend the five-LED Electrilite (*est. $20), because it can also charge your cell phone. At DigitalReviews.net, reviewer Mike Regtien confirms that one minute of cranking is enough to get a bright light for 30 minutes. After that, the brightness gradually declines. For even more runtime per windup, you can lower the light level by using fewer than all five LEDs. You can also get a version with four white LEDs plus one red, so you can use just the red LED for night vision.
Reports say that it takes three minutes of cranking to get eight minutes of cell phone usage -- not bad for emergency calls. A voltage regulator protects the cell phone, and the Electrilite comes with adapters for various cell phone brands. At 3.5 x 2.25 x 1 inches in size, this flashlight is just barely pocket-size, and it isn't waterproof -- but it's a good choice for a glove-compartment flashlight. That way, if you're stranded on a highway with a car that won't start and a cell phone that's lost its charge, you can still make emergency calls.
For light alone, without cell phone charging, the three-LED Wind 'n Go flashlight (*Est. $13) gets high ratings from owners reviewing it at Amazon.com. Owners say it fits comfortably in the hand and is bright enough for a nighttime walk. For longer runtime, you can use just one of the LEDs. Most owners say cranking the Wind 'n Go flashlight for one minute gives an hour of bright light (followed by several hours of dimming light). There may be an occasional lemon, since one owner complains he gets only a few minutes of bright light. The warranty is for one year.
Also at Amazon.com, one especially useful review of the Dynamo Illuminator (*Est. $10) provides a detailed comparison with the Garrity Power-Lite (*Est. $10) . Both get average 4-star ratings from owner-reviews at Amazon.com, but the Garrity Power-Lite -- though a bit harder to crank -- provides bright light much longer, and it focuses the light into a stronger beam. It's fairly big -- 1.1 x 6 x 2 inches -- and weighs over a pound (about as much as a can of soda). However, the rubberized grip makes the Garrity Power-Lite reasonably easy to hold, and owners also give it high ratings at Wal-Mart.com. The lifetime warranty doesn't cover the internal NiMH battery, and we found a few reports of quality-control problems.
Shake flashlights recharge an internal battery when the user shakes them vigorously. This might seem easier than hand cranking, but we read disappointed owner-written reviews of quite a few shake flashlights. Owners say this type of flashlight produces too little light for the effort, recommending it only as a children's toy. For that purpose, a shake flashlight does, indeed, save batteries.
The main drawback to windup or crank flashlights is that they're not built for durability, and warranties are short or even unspecified -- which lessens their value for emergency use. It would be wise to keep a more durable "lifetime" flashlight on hand as well. Note that some crank powered emergency radios also include flashlights and cell-phone chargers. These are covered in our separate report on weather radios.