I'm looking at buying a clock for my van. It's an LED "always on" type so will be pulling current all the time. Draw is quoted at 11mA. Is this OK? Would it drain the battery too much?
http://www.ebay.com.au/itm/CAR-CLOCK-12-VOLT-LED-DIGITAL-DASH-PANEL-MOUNT-12V-12-HOUR-LQ1200L-/251385304447?pt=AU_Car_Parts_Accessories&hash=item3a87bb557f&_uhb=1
Thanks
I gather 11maH
so 11 millionths of an amp every hour
sp extrapolate out to 24hrs, or how long it takes to drain a battery - no you will be fine if you drive it regularly.
your right its fine to use . . .
. . . but not a million mA in 1 amp
11ma is mili lilke in milimeteres so 1000 mA in one amp
so if you run it for about 90 hours you will use 1 Amp Hour of stored power which is next to nothing in practical terms
edit :
the title of the threas says 100mA this will use one amp hour of stored power per ten hours of use if this is the real draw currrent still quite a low amount
not sure how handy you are with auto electrics but it would be pretty simple wire the led back light off of a switched source and the rest of the clock wired direct. . . just a thought
It would be my first foray into car electrics. It will make an interesting learning exercise.
Yeah I agree with above. Milli amp is thousandth of amp. So I am not the best at electronics but my car battery says 180 amp crank power. I assume crank power is like a burst rate. So let's say your car battery has 100 amp to be safe. That's 100000 milli amp. The bit I always remember is it isn't just amp it's amp per hour. Your draw would be 11 milli amps an hour. Let's say 10 milli amp for simpler math. It would take 1000 hours to completely flatten the battery if you never started it. The car would need a lot of amps to start though so you couldn't leave it for all that time but generally that thing draws bugger all
I think from memory the average car battery is around 40Ah, ie you can draw 1 amp for 40hrs or 40amps for 1 hr. or 100ma for 400hrs and 10ma for 4,000hrs. Given of course, it's a fully charged battery in very good condition
The after market immobiliser the state government makes you install draws about the same amount. If it's your everyday drive no probs.
Every modern car has the same kind of clock. Will take well over a month to use 1/4 of a typical car battery.
Select to expand quoteStuthepirate said..
I have a watch
You're a dying breed. Watches are being displaced by mobile phone these days. 
Select to expand quoteHarrow said..Stuthepirate said..
I have a watch
You're a dying breed. Watches are being displaced by mobile phone these days.
yeah my grandad had a monicle and fob watch he kept in his top pocket...
ikw
Batteries with lead acid chemistries have a working range from 66% to 100% capacity. If you go below 2/3rd, you start damaging the battery and reduce it's capacity/life***.
Car battery manufacturers no longer specify battery capacity (in their specs) for legal reasons, since their batteries are designed for starting cars, not "up time" (yep, the world is getting sillier and sillier). Decrepit is right, about 40-70Ah capacity depending on brand/model of battery.
When you calculate up time for lead acid batteries, you have to use the 66% > 100% capacity. Take the capacity, divide by 3 and use that. 11mA is fine.. but be aware, if you have your car parked up for more than a month, you need to disconnect your car's battery (probably a good thing to do anyway).
Mark: stick to fixing boards ! hehe 
*** Always refer to the specs for actual product characteristics. The "2/3rd" rule is a rule of thumb.
Everybody is quoting the capacity of new batteries, which is fine if you're always going to have a new battery.
When the battery is 3 or 4 years old, your new 40 amp hour battery will have a capacity of about 15 amp hours at best.
Even at 15 amp hours it will still do the job of starting the motor provided you use it every few days.
If you leave it a few weeks, even a small constant drain load is enough to drain it sufficient that it wont start.
Most cars now have a whole lot of stuff that leaves a small load even when turned off.
Things such as immobilisers, clocks, radios, can add up to about 25 milliamps.
Well,.. that's not much is it?
Only 25 milliamps?
25 milliamps for 24 hours adds up to 0.6 amp hours. Still not a lot.
For 2 weeks, that adds up to 8.4 amp hours. 
For one month it's 17 amp hours. (double )
On an old battery, that adds up to a 'no start'. 
Not because the battery is dead flat but it has taken the top off it to the extent that it wont start.
(Yes,. I know,.. just buy a new battery. 
)
Lets compare
Your smallest light on the door or celing in the car may have 2W max 5 Watts bulb.,
This clock will use something like 0.15 W light bulb or we could say during one day will use the same amount as your car lighting bulb use in 1 hour.
For a week suck clock will drain about 2.5 Ah from your battery for a month more then 10 Ah and that is substantial amount for any car standing, not running.
To compensate any loss in your car you could but the smallest solar panel say 2 Wattts 12V and hard wire to battery. Such small solar panel could be also useful for any car standing long time and not used to keep the battery in shape.
Pweedas is absolutely spot on in every point of his analysis.
Except for deep cycle batteries, your car battery is not designed for deep discharge. You should only ever plan on using a fraction of it's actual capacity.
Select to expand quoteikw777 said..
It would be my first foray into car electrics. It will make an interesting learning exercise.
just dont let the smoke out of the wires, its a real bugger trying to put it back without the proper kit- and these are getting scarce.
www3.telus.net/bc_triumph_registry/smoke.htm
stephen
edit: you will need the whitworth to metric adaptor to use this kit.
Select to expand quotesn said..ikw777 said..
It would be my first foray into car electrics. It will make an interesting learning exercise.
just dont let the smoke out of the wires, its a real bugger trying to put it back without the proper kit- and these are getting scarce.
www3.telus.net/bc_triumph_registry/smoke.htm
stephen
edit: you will need the whitworth to metric adaptor to use this kit.
Ha ha ha!. I'm not THAT wet behind the ears...
Excellent point Pweedas. I own an automatic car, and live in an area where it drops below 0 in winter, so I'm extras vigilant about replacing my battery regularly (every 3 years).
Select to expand quoteikw777 said..
I'm looking at buying a clock for my van. It's an LED "always on" type
always on 11.05pm Saturday 24 November 2007 ??
Southern Cross painted on the side of the van with ALP 001 number plates ??
Select to expand quoteCarantoc said..ikw777 said..
I'm looking at buying a clock for my van. It's an LED "always on" type
always on 11.05pm Saturday 24 November 2007 ??
Southern Cross painted on the side of the van with ALP 001 number plates ??
ALP 007, I think.
