Instruction: Extract information from the supporting document to answer the given question.

Input:
Question: What size battery does the unit use. Is It built in or does the battery have to be inserted?
Document: One other issue I read in an early online review was that the backlight could not be turned off, but that is not true, a brief press on the power button toggles it on/off.The only other issue I have with the unit is a philosophical design issue with outdoor electronics - I do not like built in rechargeable batteries. I would much prefer replaceable batteries in a battery compartment, so that I can replace depleted rechargeable AA or AAA batteries in the field and have the unit continue to work. In a few years, the battery will go bad and the unit will need to be sent back to Bad Elf for replacement, or I will need to go through the cheaper but riskier process of figuring out how to do it myself.
I do not have an issue with the built-in battery because I know I can get support if I need it.Again, I am pleased because the product works, it is easily updated, and Bad Elf's competent technical support staff is readily accessible via email, online workorder system and social media.Update 1-4-2014: The app and firmware updates have SIGNIFICANTLY improved the unit's utility.
I bought this product because the ipod touch 5 doesn't come with a built-in GPS chip. The feature of GPS route logging is very useful, it saves lots of battery for logging on my ipod. The accuracy is as good as the ipad (3G). The reasons I give it only 4 stars are that it often takes a long time (2-3 minutes) to lock with satellites and a couple of times it gets disconnected with my ipod.
I am a pilot and needed a GPS that would give my non-3G iPad the ability to have a moving map while flying. This Bad Elf 2200 is PERFECT for this need. It has a built in bluetooth function that will connect to 6 different devices! I was able to save major dollars by not having to go back out and buy the higher cost iPad plus a Data Plan!! This product was well worth the price and it has functioned perfectly! Another function I needed was a LONG battery life...well... this one has it!!
I use the Bad Elf GPS antenna when 4 wheeling out far beyond cell service. The antenna and accompanying app allow me to synch with previously downloaded topo maps to know exactly where I am and where I'm going, even in the tall brush. the large screen size of the IPad allows for quick glances rather than conscious study of the map.Great product, highly recommended.
I was looking for a small GPS that I could leave in my bag and have it track my travels. This unit has a great battery life and I can use my iPhone as an interface while leaving the GPS in my bag. I find that it is surprisingly accurate even in an urban environment where others I've tried have difficulty keeping in sync w/ enough sats to keep an accurate history.
I bought the bad elf pro as a replacement for my previous bluetooth unit (the one you could never turn off). I am a pilot and use it to connect my ipad to GPS in flight and it works perfect. Connection and the acquiring of satellites is immediate and I've had it for months and I have only charged the battery once. I have probably flown 10-15 hours with it on and still have 3 bars on my battery. Love having the display to ensure accuracy too! Great product, HIGHLY recommend!
The unit functions as described but the setup was a bit off from the documentation. When pairing, you are instructed to wait for a code window to appear on your iPad or other compatible device. After several frustrated attempts to pair with no window to type in the pairing code appeared, I just simply hit the gps button again on the unit and it paired instantly with the iPad. I am using an iPad with the Retina display and IOS 7.0.3. Had the same issue with my iPhone 5. Other than that it works well.Pros:Easy to use once you figure out how to pair it with your device.Good battery lifeCharges quicklyNice and smallCons:Downloading the data is a bit confusing, you have to have data logging turned off and it takes a while.The &#34;elf-port&#34; USB connector cover does not stay corked.
I purchased this to use with ForeFlight on my iPad, and it works great. Connects via bluetooth within a few seconds. I only had a problem once getting ForeFlight to recognize the location data, and restarting the iPad fixed it.The GPS unit on its own is actually pretty nice as well. It locks onto the GPS signal quickly (unless I'm in my basement, but even then it locks on after a minute or two). The cover for the charging cable is easy to remove, but seems like it will stay put even if I'm running with it.I'm a little surprised it only came with a car charger, I would have preferred a wall charger as the battery life should take me through a full day just fine.One other thing: I like that you can record tracks with just the device!
I'll stick with Skobbler GPS Nav 2.It is about 4 times larger than the previous version - some friends have asked me why I'm carrying a pager around and then I have to explain what it is. LOL. But it fits handily in a pocket. The larger size I'm sure is to accommodate the bluetooth.It could use a second lanyard - the one provided is for wearing around the neck. A small lanyard for someone who normally keeps it in a pocket would be more convenient and add less bulk.The rubber cover for the charging jack does not stay closed.
Answer: The battery is built-in.   It lasts an insanely long amount of time.  I fly with it weekly for several hours per flight.  I only need to charge it once a week or every other week.  Charges via USB cable.