Instruction: Given a question and the related document, and generate the answer to the question based on the information provided in the document.

Input:
Question: Since the main unit has a battery, is there two separate power adapters for the car or does one cable power both?
Document: Fine. But, if you want to use both, you plug a car adapter into the main unit, then connect a power cord (and A/V cable) from the main to the second. I think it's also supplying the main unit with power so that the battery isn't drained, but it was quite a hassle figuring out which unit had to go where because of the power cord.
>> ?!?!?! So once that's done it's good to go. There is a cable for feeding video and power that plugs into the second unit. This is a bad thing. Kids like cables, cables that dangle. These cables dangle. My kids liked them and pulled them and tore the video cable out of the second unit leaving the plug so that's #2 down the drain. Making the DVD players able to play separate movies would have been ideal.
First,super pleased with Amazon support. The first unit I got, the second screen wasn't working. Returning it for a new one was super easy. The second unit I received is exactly what I wanted. Perfect for the car, or to take with us. Straps pretty easily to the headrests, or sometimes I just let the kids hold them. Good picture, good size and the battery works well. It only powers the main unit, but that is ok for us.
I purchased this item for a 3 1/2 hour plane trip to FL and for use in our mini-van post vacation. I was disappointed that the battery only powered the main unit and not the secondary unit, but that isn't a big deal. ** I was sure to test it prior to our trip to check this as the reviews were conflicting. ** I can say that NO, the battery does not power the second unit no matter what we tried.
We completed 30+ hours of road travel and this DVD player kept my 1 and 3 year old entertained the whole time. This has a lot of features that some of the others don't have including a remote control, battery power on the main unit, and the ability to play videos from a flash drive. We loaded 20 hours of video onto the flash drive and so we never had to change a DVD the whole trip. We could just change the video on the screen.
The adapter for the car that it came with did not fit into the plug into my car correctly. I had to purchase a separate inverter in order to use it in my car. Also, the internal battery did not keep the unit going at all when I had to stop the car. The ability to use it with a flash drive was amazing, I really liked that feature. I just push play and then drive.
we bought the Sylvania 7-Inch dual screen portable DVD player because of one trip two and a half hours felt like torture with our five year old in the car. We bought a Sony and the power source didn't work so, we took it back and bought the Sylvania.
Our second unit stopped working after a month of barely being used. I opened it up and NOT ONE solder joint is proper. Solder joints need to be heated properly when assembling components. A normal solder joint is shiny. These are ALL dull and grey. NO JOKE not one connection was done properly.Garbage product. Iam trying to upload a picture here. Also, its a stupid function that the battery wont charge wile the unit is playing even wile getting DC power.
This is one of the worst electronic items I have ever purchased. Only used on two separate occasions, when the screens stopped working.Thank God for Amazon's return policy.
It turned out to be what we were hearing was coming from the speakers and would go away when I "tweaked" the AV out connection (the signal cable to the 2nd screen) on the main unit. It kept coming back, but when we next stopped, I changed discs, re-connected all the cables and it never happened again, even on the return trip playing the same disc.
Answer: There is only one cigarette adapter (to the car).  Then there is a connecting wire from the main unit to the second unit to provide power.