Quote:
Originally Posted by mattW
The electrical drag will just be your voltage x current draw / efficiency, so a 12.8V battery at 50 Amps with a 60% efficient alternator will take 1.07kW. 50 amps was just a guess but you could measure your amp draw if you want an accurate measurement.
According to Wikipedia "Very large automotive alternators used on buses, heavy equipments or emergency vehicles may produce 300 amperes. Very old automobiles with minimal lighting and electronic devices may have only a 30 ampere alternator. Typical passenger car and light truck alternators are rated around 70 amperes, though higher ratings are becoming more common."
So it looks like my 50 A guess was pretty close, somewhere around 1hp (38A) - 2hp (70A). |
My guess is, you would need to have a LOT of stuff turned on, before drawing 50 amps.
But, if your ignition(spark-plugs), OBC, clock, GPS, SGii & radio are drawing much more than 10 amps, I would be very surprised. (10a*13v=130 watts).
IIRC, a car battery wants to charge up to about 13.6V (at least they used to) and the alternator wants to feed it about 14V all the time you are driving.
So, the amount of load on the alt is going to partly depend on the charge state of your battery.
Have you been sitting with the engine off with the radio cranked up to 300 watts?
Look at your SG2 while driving and with the engine off. The battery is getting some charge voltage even if it doesn't need it. But, if it's already up to par, the current drain isn't that much. Maybe less than an amp or two.
Unless, you are driving at night!! Then you are going to need some major amps.
-----
I read an interesting post today. The idea proposed was to install a relay in the alt output, so the car could run on battery alone.
The relay would pull in, only when the driver hit the brakes.
My idea is to use a smart charger on the battery. Measure it continuously and only charge it, when it started to get low. You could tailor the off-on settings for best fe.
Of course having a 3A 15V solar array might help too. (If it didn't have a lot of drag).
Or, you could just plug in a smart charger in the garage every night. (& use the alt less the next morning).