So I read on here about buying a deep cycle battery and ditching the alternator. What experiences have people on here had with this? On a side note I drive a 92 civic HB and I drive 150 miles roundtrip everyday, 5 days a week for work. I'm not using A/C but I am using the radio and I get off of work at 11 at night, so i would be using my lights on the way home.
If you want to make it work for your car and driving conditions, I'd recomend some LED running lights to reduce electrical consumption, install a switch for the alternator so you can turn it on when the battery needs some charging, and a voltmeter so you can keep an eye on batt volts. Then install a battery charger under the hood and park next to an electrical outlet so you can plug in your car when you park. If you can get all of that arranged, you might save some gas. Darin at MetroMPG.com saw 10% improvement in FE when he removed the alternator, but the savings were offset by the cost of running a batterycharger. It was still a gain.
There's a user here who runs no alternator and it seems to be working well for him. Here's what I had to say about the idea in another post:
Originally Posted by 1cheap1
I think i saw a guy on the net who had taken out the generator and ran all electrical off a deep cycle extra battery, then charge the battery at night. It add FE to his car. Of course he is an electrical engineer.
I am currently driving a 2005 Jeep TJ with an onboard custom built switching (solid state) battery charger, Group 24 Gel, no alternator and electric fan. My best MPG so far is 17.1MPG but that was before I removed the mechanical engine fan.
I've been considering a more mild form of that, where I don't remove the alternator but just disconnect it, and I don't have to invest in an expensive battery but I can just use my existing starter battery and maybe a deep cycle battery I have for my boat too.
That thread did include this response to my post:
Originally Posted by RoadWarrior
You could try to do a kind of "mild hybrid" thing with the alternator, and have a relay keep the field coils disconnected while the throttle is open. As soon as you lift off the gas, it cuts the field coils back in again. Would probably get you a flat battery on long highway hauls though, so rigging a manual bypass would be wise.
However, many ECUs modulate the field current according to state of battery charge, electrical load or other factors... so as soon as you're fully charged up and not using many electrics, the alternator should be in minimal drag mode. This is why I doubt the overall FE potential of underdrive pulleys on vehicles that have this, it just prolongs the charge time.
if you look at This Page you will find a list of all of the electrical loads that I tested with an amp meter on my 1992 civic vx, so figure out what all you are going to have running on your car while you drive, how long they are going to be running for then find a battery that has at least twice that capacity so you don't drain it down past 50% full (shortens the life of the battery a great deal), you will then be able to figure out if this is practical for you to do.
It all depends...
A fully charged lead-acid battery during the daytime running nothing but the engine... No turn signals, no brake lights, no fan no radio no lights no wipers no washer no nothing...
Can go around 400 miles on a charge.
That's assuming the battery is in good shape, and the correct one for the car.
It helps further if the battery is a size bigger than the car needs.
I usually run 1,000 cca's in all of mine, but not for this reason
But you take a risk, that and once the voltage drops a little your mpg suffers because the battery is no longer sending as much juice to the ignition coil(s), hence your spark plugs deliver a weaker spark.
And on a rainy night, with headlights and wipers and at least some fan?
You might make it 200 miles, maybe not... Maybe 100, maybe 50...
It all depends.
It would be my opinion that it would be better for that kind of money to see about installing some high performance 10mm spark plug wires.
A FE gauge should be standard equipment in every vehicle.
I imagine the range would be even shorter on a modern small car with electric power steering and a million electrical features. Still, rgathright seems to be successful, though it sounds like he probably invested more money in it than he would save. However, he bought a really expensive battery and such.
I just wonder how well I would do in my VW on my 80 mile round trip commute. Obviously I would charge it every night, and if the voltage got too low while drivig I could always abort for that day and plug the alternator back in (or switch it back on or whatever). rgathright is using a voltage regulator which would mean you could drain the battery more; but you'd want an expensive proper deep cycle battery for that...
I'm pretty sure that the stock VX battery is a 40amp hour battery, so without damaging the battery you can drain 20amp hours out of it.
In my '92 civic vx turning the key "on" but with the engine off (dash lights completed with self check, door closed, lights off, radio off, fan off) gave a reading of exactly 2 amps, so in my figures I subtracted that number from the total reading.
Heater fan 1st setting 3 Amps
Heater fan 2nd setting 5.4 Amps
Heater fan 3rd setting 8 Amps
Heater fan 4th (highest) setting 11 Amps
all of those numbers were fresh air coming in, switch to recirculation and it added .4 amps to the highest setting due to added air drag.
Brake lights 3.2 amps
55-watt low-beams (110 watts for the pair)... 110/12volts=9.167 amps
65-watt hi-beams (130 watts for the pair)... 130/12=10.833 amps
After market Radio varied from about .6 up to 4 amps depending on volume.
Cranking for about 5 seconds gave a starter draw of about 138 amps.
I don't have any numbers yet on the wipers, but I can check that as well, also the 2amp draw from the key being on is just the cars computer running, and the coil, but the coil should draw more when it's working and firing the plugs, I also now have LED tail lights, and as soon as I find my turn signal flasher under the dash I'll switch the turn signals as well.