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Car Headlight Power on Generator


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Hi all,

Doing a night exterior shoot and for most of the film's story, a car is left unattended and running with the headlights on. My question is: how would I go about running the headlights off of an external power source like a generator? Just so that we are not relying on the car's battery, as the headlights will have to be on throughout our days.

Would love to hear your advice.

Best,

Sam

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If the car is running, won't the inverter power the headlamps.

Otherwise I guess you'd be able to use an external power source with a rectifier and step down transformer to give 12V DC and patch that in parallel to the battery. Maybe a car battery charger would do the trick if the drain of the lights isn't too much. The fast chargers are about 100W - so if the lights are less then that might be do-able.

Or just have a couple of spare car batteries you could swop out and charge up

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I've used the external car battery technique, but you may need a few to swap out while charging the others.  But, if you can keep the car running during takes, you can just turn on the headlights when needed I would think.  

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18 hours ago, Sam Holling said:

Hi all,

Doing a night exterior shoot and for most of the film's story, a car is left unattended and running with the headlights on. My question is: how would I go about running the headlights off of an external power source like a generator? Just so that we are not relying on the car's battery, as the headlights will have to be on throughout our days.

Would love to hear your advice.

Best,

Sam

A battery charger of sufficient size will charge the battery from an AC source at the same rate that the lights deplete it.  Put an amp probe on the positive lead of the battery to see what the headlights draw.  Then go to a boat supply store to find a charger that will charge the batteries at the same rate.

Guy Holt, Gaffer, ScreenLight and Grip, Lighting Rental & Sales in Boston

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Why do the lights need to be on outside a take or lighting check?

Car headlights in the UK are 55W, so two with sidelights will draw about 10A. If you need a genny anyway, that's no problem.

Surely if the sound of the car running is necessary that will go on afterwards. The sound man can get a recording as atmos anytime and he may curse you for running the engine during a take.

Edited by Mark Dunn
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