alternator free - Fuel Economy, Hypermiling, EcoModding News and Forum

89HF · 01-09-2010, 02:28 AM

Does anyone happen to have an idea how long a battery will last between recharges if the alternator is removed? I know there are a number of variables but I'm curious how it has worked out for someone that has tried it.

Bicycle Bob · 01-09-2010, 07:11 AM

I wouldn't try it without going to a deep-cycle battery. A starter battery can die in less than a dozen cycles if you push it. There are a few that will do both.

ATaylorRacing · 01-09-2010, 08:51 AM

I had the misfortune of my alternator belt breaking 100 miles from my house a couple of years ago. The belt was ONLY for the alternator. The car was a 98 Neon SOHC that had an underdrive pulley on and none could be found...so I decided I'd hypermile it as far as I could. With 35 miles to go the entire dash died, no speedo, tach, or gauges worked. I barely made it into my drive! Shocked that I made it 100 miles. The next morning I tried to push start it with no luck. I brought out the old stock pulley and belt set up , reinstalled it, charged the battery, and never had a problem again. The underdrive pulley kit made the car get 1.9 better FE, but I traded it a few months later for the SRT4 that I use now. I was impressed with how much more power was freed up without that belt....when the weather gets warmer I will put a alternator kill switch on the Geo and see what kinds of FE gains I can get.

RobertSmalls · 01-09-2010, 08:01 PM

Testing amperage draw - 1997 Paseo

Measurements were taken on three different cars, and anywhere from 5A to 20A was required to run the engine. Lights, fans, and defroster grids draw additional power, especially in the winter.

So, a couple of hours out of a D51R, or maybe 4-5 hours out of a 60lb marine battery. Probably half that in the snow or at night.

Christ · 01-09-2010, 08:30 PM

On my old 1994 Hyundai Excel GL Sedan, the alternator quit working, and I could start, drive 20 mins, start, and drive home 20 mins. If I had to use the turn signals or brake lights excessively, I wouldn't make it home by a good 1/4 mile.

It was also an ECM-Controlled automatic with perf/economy switch constantly put on performance and manually shifted.

bryan11 · 01-09-2010, 08:37 PM

Well, I drove a 1977 Honda for three days and around 150 miles with a dead alternator. No issues and even some night driving.

On a 1996 Ford Explorer AWD, it will go 7 to 9 miles on a fully charged battery. Last year, I drove around 150 miles that way.

thatguitarguy · 01-09-2010, 09:00 PM

The other night I had a 300 mile trip to do and I didn't have to haul anything so I thought I'd dig the Metro out and take him for a drive. I haven't driven him enough to learn his quirks and what to expect, but he started right up. I did have to shovel a lot of snow to get him out, and after I drove 10 miles I turned around and came back. The air was warm from the defroster vents, but there was cold air blowing from where the radio should be. I switched to recirculating the interior air, and that helped a little, but the windows started frosting up, so I had to switch back to outside air and crack the window.

I knew that the van wasn't going to get nearly as good of mileage, but it just wasn't a good night for the MaEsTRO. I usually watch the trip computer in current mpg mode, but I kept cycling through the other modes to watch the temperature, and it was staying in double digits below zero Fahrenheit. I had the seat heater on high, heat blasting out the vents, headlights on bright most of the time, and I was listening to the stereo, and I was glad that I had an alternator that could handle it all.

I may work on an alternator kill switch for summertime use in MaEsTRO, but completely removing the unit just doesn't seem practical to me. You're not saving any weight, because batteries are going to weigh more, and if it dies, a jump isn't going to help. I think a kill switch for the alternator is as far as I want to go in that mode.

Christ · 01-09-2010, 11:57 PM

Actually, a jump will help. That's how I found out the alternator was dead in my Hyundai. Battery light never came on.

When you get jumped, it will give you a few miles of drive time on older cars that don't have ass-loads of electronics to run. Believe it or not, an ECM/TCU and associated circuits can take alot of energy when you don't have much to give to begin with.

89HF · 01-10-2010, 01:08 AM

sounds like losing the alternator all together won't work for me even if I could trickle charge it at work. But is there a link on wiring up an alternator kill switch? That might have potential.

Christ · 01-10-2010, 01:16 AM

There are two ways to do this in your car.

You can either install a high-power relay between the alternator and battery, and switch that, or you can install a switch in the field wire from the ECM. Either way will make the battery light come on while the switch is off, which works as an indicator to remind you to turn it back on. You should couple that with a volt-meter, and turn the alternator back on if you get much below 12VDC on your battery.

I'm waiting for my EF service manual to load up, so I'll post the wire diagram for the alternator in a few mins.