For vehicle dwelling I'd much rather have a 14500 or 18650 lithium based battery flashlight and recharge it from the vehicle.
These:
https://www.amazon.com/Hausbell-Ultra-Bright-Flashlight-Tactical/dp/B00CEOII9K/ref=sr_1_3?ie=UTF8&qid=1508782110&sr=8-3&keywords=14500+led+flashlight
can run off of an Alkaline AA battery but are about 25 to 30% brighter on a lithium 14500 cell. The AA and the 14500 are the same physical dimensions, 14mm diameter and 50mm long. One is 1.5v the other is 3.7v nominal
I like the zoomable factor, and these can concentrate the beam to a nice small square of light.
I have an 18650 battery based zoomable flashlight that is OK, not worthy of a link.
I also use a Nitecore HC50 headlamp which uses an 18650 battery. It recently has become unreliable, and In a moment of flashaholic weakness, I ordered the Olight H2r headlamp. 2300 lumens available for about a minute when the battery can still support that rather tremendous light output. It has regular low medium and high settings as well as a moonlight mode.
The 1 minute is because of the tremendous heat it generates, but 2300 lumens is more than most vehicle's headlights on low beams
One neat product I really like is this portable USB source. It will charge a 18650 battery from a USB port and will act as a USB source too.
https://www.amazon.com/ThruNite-C2-Small-Sized-Fast-Charging-Flashlights/dp/B01MPWHSCM/ref=sr_1_1?s=electronics&ie=UTF8&qid=1508782495&sr=1-1&keywords=thrunite
A couple ofextra 18650 batteries and my existing headlamps and It would cover the backpacker needs as well as the renogy solar flashlight, for several days at least.
Problem with solar recharging of such devices is one either needs to set it outside in the sun and risk driving off with it on their roof, or place it in a sunny window and account for sun movment and lesser solar radiance through glass.