I have an 11watt, 12v sealed beam light. So, its pulling a little less than 1 amp.

I see small 12v 4 amp hour batteries on ebay (security camera type). Does this mean they will power this light for about 4 hrs?

Also, this is for filming underwater (only two feet or less) anyone see why this wouldn't work assuming all was kept dry?

There must be a reason it won't work, because I can't find anyone else doing it.

Thanks so much for any replies.

 

There are many kinds of battery chemistries that have different spec's. You forgot to say if your battery is old lead-acid or one of the newer better ones. Look at the spec's on its datasheet.

An old lead-acid battery that is rated at 12V/4Ah can supply only 0.4A for 10 hours or only 0.2A for 20 hours. It might supply 4A for half an hour or less.

A Lithium, Ni-Cad or Ni-MH battery can supply 4A for 1 hour.

 

Nah a 4amp 12v/lead acid sealed would only probably give around 3 hours, something due to the fact that when lead acid battery deplete they discharge faster than to begin with, basically you don't get the rating... try a 6-8ah for 4 hours of runtime.

 

I'm only looking for 1 -2 hrs run time before recharging.

Yes, I'm talking about the "cheaper" lead batteries used for scooters, security cameras and such.

If this works, it is a much cheaper alternative to expensive dive lights.

Of course, I could use a deep cycle marine battery, but they are so heavy to carry.

Thanks for the replies.

 

A home made dive light I made a few years ago consisted of a led array and battery inside of an camera housing for diving. I set up the shutter release on the underwater camera case to turn the light on and off. You don't have too much to worry about above 2 atmospheres, deeper that that and you have pressure to deal with.

I got a cheap underwater housing for $10us for a cheapie 35mm removeable camera. That allowed me to keep everything dry to about 30ft.