| Electronics > Beginners |
| Car battery confusion. |
| (1/5) > >> |
| andrewlapham:
Hey, I've been drawing up plans for an led light bar I'm designing for my car. the only thing that is bugging me is the source voltage. I'm yet to take a multi-meter to the car to test the output but is it really necessary if it fluctuates so much? i know that lead acid batteries are pretty much dead at 12v and fully charged at 14v ish. I'm currently using sets of 4 LED's in series with a 10ohm resistor. is calculation is running of the idea that my car (on average) will be outputting 13v. is assuming 13v as a standard voltage the right way to go about this? cheers. |
| cur8xgo:
--- Quote from: andrewlapham on June 21, 2019, 03:42:20 pm ---Hey, I've been drawing up plans for an led light bar I'm designing for my car. the only thing that is bugging me is the source voltage. I'm yet to take a multi-meter to the car to test the output but is it really necessary if it fluctuates so much? i know that lead acid batteries are pretty much dead at 12v and fully charged at 14v ish. I'm currently using sets of 4 LED's in series with a 10ohm resistor. is calculation is running of the idea that my car (on average) will be outputting 13v. is assuming 13v as a standard voltage the right way to go about this? cheers. --- End quote --- Battery voltage in a car swings from say 8.5V during cranking to maybe 14.5V charging. If you use just a resistor you will have to deal with that entire range and make sure nothing breaks. So resistor will be oversized at low voltage and undersized at high voltage. Could use a voltage regulator to protect it from the high voltage swings and some kind of low voltage cutoff circuit to prevent it from operating at too low a voltage (presumably thats non-ideal as well) |
| rstofer:
I think the float voltage supplied by the alternator is 13.8V It will be up around 15V when charging. Maybe you should look into constant current circuits. |
| Nerull:
Any device meant for '12V' automotive use needs to be able to deal with voltage drops to almost nothing during cranking, widely variable 'running' voltage, and spikes up to 24V+. |
| Benta:
--- Quote from: Nerull on June 21, 2019, 04:31:32 pm ---Any device meant for '12V' automotive use needs to be able to deal with voltage drops to almost nothing during cranking, widely variable 'running' voltage, and spikes up to 24V+. --- End quote --- Actually, an automotive circuit should be able to withstand +/- 60 V, this can happen during a load dump. |
| Navigation |
| Message Index |
| Next page |