Outer Limits 4x4 Board

Installed some 55w spotties as side lights today for light when setting up camp, looking for house numbers at night etc. Used to have some halogens but they never worked (crap build quality) and it only just dawned on me, how much power will these things suck? I'd like to be able to leave them on for a fair while, maybe an 1hr or so at a time? ATM I only have my standard cranking battery which is a big sucker but I'd still love to have a rough idea of what these might draw in amps per hour.

They are 55w and have a H3 globe if that helps

Power = voltage * current

Assuming a voltage of 12.5 ish.. and that power consumed is 55 W (is that for one or both?)

You are looking at around 4 and a half amps...
(need to double that if its 55W per lamp)

Check the Ampere hours for you battery A/H

if your battery was a 100A/H (for example) you subtract 4.5 each hour you run your spotties.

Theoretically you could get about 22 hours, but that would dead flatten your battery which lead acid batteries cant handle...(shouldnt discharge them below 70-80 percentish from memory.. correct me please someone if wrong)

An hour at 55 watts should not be a drama for a good quality car battery.

the_smoo wrote:
An hour at 55 watts should not be a drama for a good quality car battery.

for one, but how many you planing on hooking up? or are you going to have these seperately switched?

you should get away with two spotties off a good battery for one hour..

I would recommend running spotties whilst the engines not running for manual vehicles only

Heheh, yeah its 2 spotties, one on either side of the car (but I can unplug 1 easily enough), and its manual . And my NRMA battery's warranty ends in about 8months so hopefully it will die b4 then

Thanks.

They will draw just under 10 A after you factor in losses. (That's for the pair of 55w).

A battery shouldn't be discharged over around 50% too many times or it won't last long. (Especially a cranking battery)
Then again, a battery usually only get charged to around 80% capacity from the car's charging system. That leaves you not much to play with.
Then try to start your car.... maybe not

Dual Batteries

HotFourOk wrote:Then again, a battery usually only get charged to around 80% capacity from the car's charging system.

Where's Mythbusters when you NEED them?

Where does this crap come from?

Both internet and auto-eleccy.

He told me yesterday, that a charger is needed to get the battery right up to full capacity.. especially in my car with a povo alternator.

I think you've asked me this before

-Scott- wrote:

HotFourOk wrote:Then again, a battery usually only get charged to around 80% capacity from the car's charging system.

Where's Mythbusters when you NEED them?

Where does this crap come from?

I’ll second Scott on that.

Even with a small alternator, providing all your electrics are up to scratch and your battery is OK, there is no reason why your battery can’t be charged to at least 95% capacity off your alternator under normal driving conditions.

If you only drive for a few minutes every day then you WON’T fully charge the battery but if your doing reasonable driving times, the battery(s) will fully charge.

HotFourOK, this is not aimed at you, but so called experts that make that statement usually have ulterior motive, like trying to sell you something you don’t really need or they are trying to make themselves sound knowledgeable about something they quiet obviously haven’t got a clue about.

Cheers