Computer Forums Watts / Amps / Volts / mAh / CCA
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 07-11-2009, 05:40 PM #1 Fully Optimized     Join Date: Oct 2008 Location: USA Posts: 2,404 Watts / Amps / Volts / mAh / CCA Alright I'm not new to volts, I understand what watts, amps, and volts are. What I was wondering is... Say you have a 12V car battery, 800 CCA, and 50 Ah. (not in car, just a fully charged battery) Then you have an unlimited amount of LEDs. You have sets connected together of 24 LEDs, 66 mA at 12V(DC). How many strips of 24 LEDs could you connect to the battery and about how long would it last before the battery died? Now, what if the battery was in a car? (car is running, thus battery charging) __________________ __________________ Everyone's Favorite Turd xD ET: "Phone home!" Geek: "ping 127.0.0.1" "If that guy knew half the \$h*t that I know, his fuzzy little head would explode. " - Matthew Farrell
 07-11-2009, 06:22 PM #2 Site Team     Join Date: Jul 2009 Location: England, UK Posts: 3,422 Re: Watts / Amps / Volts / mAh / CCA My understanding is this: I'm assuming here 66mA is the load each set draws, not each LED? CCA is pretty much irrelevant in this case. From those specs it's impossible to say since we don't know the maximum current that can be drawn from it continuously, but the 50Ah rating means you can connect 50amps worth of strips to the battery and expect it to last an hour before discharing. So that's 50/0.066 = around 757 banks of LEDs if you want the battery to last an hour. If you only want teh battery to last half an hour, then theoretically you could connect twice as many, providing 100amps doesn't exceed the maximum current draw of the battery (which in practice it probably will!) If the battery was in a car and charging, then it entirely depends on how much current the alternator is providing to the battery, but if you didn't want to discharge it you'll have to draw less than that current. Also remember that when the car is idling the battery is barely charging, the charge rate isn't constant - the faster the alternator runs, the more it charges, but it's impossible to say how much without detailed specs of the alternator itself. But - you wouldn't connect strips directly to your battery even if it's being charged, you'd connect it so when the alternator was running it'd be powered straight off that. You could run it by directly connecting it to the battery, but it'd wear it out very quickly. __________________
07-11-2009, 11:49 PM   #3
Fully Optimized

Join Date: Oct 2008
Location: USA
Posts: 2,404
Re: Watts / Amps / Volts / mAh / CCA

Quote:
 Originally Posted by berry120 My understanding is this: I'm assuming here 66mA is the load each set draws, not each LED? CCA is pretty much irrelevant in this case. From those specs it's impossible to say since we don't know the maximum current that can be drawn from it continuously, but the 50Ah rating means you can connect 50amps worth of strips to the battery and expect it to last an hour before discharing. So that's 50/0.066 = around 757 banks of LEDs if you want the battery to last an hour. If you only want teh battery to last half an hour, then theoretically you could connect twice as many, providing 100amps doesn't exceed the maximum current draw of the battery (which in practice it probably will!) If the battery was in a car and charging, then it entirely depends on how much current the alternator is providing to the battery, but if you didn't want to discharge it you'll have to draw less than that current. Also remember that when the car is idling the battery is barely charging, the charge rate isn't constant - the faster the alternator runs, the more it charges, but it's impossible to say how much without detailed specs of the alternator itself. But - you wouldn't connect strips directly to your battery even if it's being charged, you'd connect it so when the alternator was running it'd be powered straight off that. You could run it by directly connecting it to the battery, but it'd wear it out very quickly.
Oh Alrighty. Thank you! You are one smart dude.
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