Does use of cig lighter reduce leisure battery charging?

[Sixty-nine Chevy]

Hi. If I am using the cigarette lighter port to charge a battery pack at say 100 W, will this significantly reduce the charge going to my leisure battery? Definitely yes? Definitely no? Or maybe depends on my exact set up. Any comments appreciated!

 

[Emmit]

Definitely maybe?

It depends on your set up.

 

[David and Sally]

Is it connected to the van starter battery or leisure battery?

100w at 12v is about 8 amps draw so any charger will have to exceed that before starting to charge the battery assuming we are talking about the cigar lighter being connected to the leisure battery.

 

[Jimbohorlicks]

I doubt it would affect anything as the cig socket is powered via the starter battery and then from the alternator,which will just compensate for any reduction in charge,whilst the engine is running.
If you use the cig socket whilst the engine is off then this will take current from the starter battery only.