High output alternator

smartcarfan71 said:

Hi guys ive veen putting some sudio into my smart car like a sub and a couplr conpsct monitors. But ive noticed that the power draw is too great and causes the monitors to shut down to in audible levels. Is there a high outpur smart car alternator i could put in to make sure theres enough power to go around?

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If I am remembering correctly the factory alternator is 90 amps. It takes some horsepower to run a larger capacity alternator. 90 amps seems like an alternator large enough for a Cadillac, but the Fortwo uses alot of electrical amps to run the automated operations of the car like clutch engagement and gear shifting. The factory alternator puts out a fairly high dose of amps even at idle

Possibly you could run an auxillary battery and run a battery isolator to charge both batteries. What kind of amperage draw is your audio amp pulling at a high volume? Monitors that are LED shouldn't be an excessive draw. Electronic computerized equipment and such as your monitors are really suseptable to "dirty" power. Output directly from the alternator is a little on the dirty side in that if you were to connect an oscilloscope to it you could verift this by looking at the wave onscreen.

For test purposes run the power wires from your monitors directly to the starting battery terminals where they will get close to 14 to 14.1 volts when the car is idling and the battery will pacify some of the voltage spikes, and your monitors should work okay. Your amp will be much more forgiving of voltage spikes but may have some hum or buzz from the alternator. Try this and see if it helps and let us know. DCO

I drive often at night and bear in mind that I have replaced every last bulb in my Fortwo with LED's and in many cases have added extra LED's when the running lights are on. But it is common for me to drive at night with HID headlights on, the radio is always on and running the A/C which also switches on the radiator fan to run continuous. At idle my voltage never drops below 13.2. The digital voltage gauge I added to my fortwo samples voltage once per second and it is not uncommon to see the voltage fluctuate about .5 (half) a volt. So normally I am running 14.2 to 14.3 during daytime driving, no lights, A/C or not and always the radio. During the time it is 14.2 or 14.3 it occasionally reads 13.8 or 13.9, but most of the sampling times it is on 14.2. I'm sure the fluctuation is from the voltage regulator working at maintaining a full charge on the battery. My feed wire for my voltage gauge is from one of the accessory terminals on the fuse box. The 12.3 you are seeing is perfectly acceptable if the ignition is turned on but the engine isn't running. There have been so many cases of quirks in the electronics and they ended up being a weak battery as proven time and time again here on the forum. I think I would dig out your reliable multimeter and take some voltage readings in the system and logically look at it to determine where your problem actually is. There is already some great advice on this thread already, and they are giving great advice too. DCO