Inverter or solar panel or ?......

[John61CT]

So, let's use the first, with some inefficiencies the DVD player may use 1A, or 2A to watch a movie.

Most older regular Starter batts may store in effect 20AH before too flat to get you started.

So you should be fine.

But a few hours of laptop use may leave you stranded.

 

[DLTooley]

I checked the back of the DVD player and it consumes 9 Watts.

That's pretty good.  Inefficiencies will mostly come from an inverter. 

The secondary battery I linked to above is rated for 150 watt hours, not sure if that is actual capacity or rated, best not to run it below 10-20%, so I'd guesstimate at around 12 hours of use.  Vehicle batteries are rated in amp hours, at a standard 12 volts - so that 20ah should be 240 watt hours.  A Walmart Marine will get you around 50 usable amp hours, and a full basic two golf cart battery setup a bit more than double that.

Making sure you have enough of a charging source to recharge is also important.

 

[wmyers4u]

assuming its a portable dvd player all in one......if not you have to calculate TV power usage.

a portable 12 volt model like this https://www.amazon.com/Enhanced-Bri...ns&keywords=12+volt+portable+dvd+player&psc=1 with a rechargable battery might do the trick.

 

[ZoNiE]

A few hours of laptop use will NOT leave you stranded IF you use the battery IN the laptop and only plug it in and charge it with the inverter while the car engine is running. Not sure you mentioned it, what is your vehicle or planned vehicle?

 

[Gloriahass]

A few hours of laptop use will NOT leave you stranded IF you use the battery IN the laptop and only plug it in and charge it with the inverter while the car engine is running. Not sure you mentioned it, what is your vehicle or planned vehicle?

 

[John61CT]

That's pretty good.  Inefficiencies will mostly come from an inverter.

Electronics like this run directly off DC in the first place.

Plugging into an inverter would be wasteful and inefficient.