The Paseo gets an alternator disabling switch

Discussion in 'Toyota' started by Daox, Jun 14, 2009.

  1. Daox

    Daox Well-Known Member

    I've wanted to do this for a while after seeing results from others. I decided to go the route of killing the alternator field wire with a switch (for now). This seems to work great. Its a very low current wire instead of the huge alternator cable going to the battery, so small electronic components work just fine.

    First, I found out where the alternator field wire enters the cabin. I really didn't want to be running more wires from the engine bay back into the cabin if I could find one that was already inside. The pin is pulled out of the connector in this picture because I tested the setup this way.


    Next, I cut the wire, and soldered in another length of wire to go to a switch.


    With it all soldered up, things went back together.


    On the other end of the wires, I added ring connectors.


    I then found a switch I had laying around, tapped the terminals for a #6-32 screw, and bolted the rings down to the switch. The reason I did things this way, was if the switch ever fails on me, I should be able to just unscrew the leads and connect them together on another leg of the switch.


    Last, but critically important if you're going to disable an alternator for anything more than a short duration is the deep cycle battery. This battery I got from the same guy who gave me the chassis for my mower. It is a group 24 deep cycle battery (70-85 Ah), and just fits in the engine bay. I had to finagle it around so it wouldn't hit the hood. It had been sitting for 2 years or so. It seems to hold a charge alright. We'll see how it holds up over time.


    I took it for a drive earlier today with the wife. We went about 15 miles with the connector like you see in the first picture. The car ran great, but the voltage was dropping down to 11.9V by the end of the trip. I'm hoping the battery just needs to be exercised a bit.

    Here is a shoddy video I took when I was all done with it. You can't really see the voltage numbers on the scangauge, but you can certainly hear and see the difference in RPM.
  2. vtec-e

    vtec-e Celtic MPG Warrior

    Good job. It'll be interesting to see what mpg improvements you get.

  3. The Fridge

    The Fridge Well-Known Member

    Nice looking job!
  4. bomber991

    bomber991 Well-Known Member

    I'm not sure what you're doing exactly. The alternator doesn't charge the battery anymore when the switch is flipped? But the belt still spins it right?
  5. Daox

    Daox Well-Known Member

    Yup. The switch interrupts the signal that tells the alternator how much juice to spit out. The alternator will still be spinning, but it won't put any load on the engine.

    The deep cycle should last me long enough to get to work and back. When I get home, I have to charge up the battery. So, technically the Paseo is now a plug in hybrid. ;)
  6. cpeter38

    cpeter38 Right Lane Dweller

    Before I do that modification, I have some crucial changes to make:
    1.) I need a DC/DC converter to provide a stable 13.8 volts to vehicle electronics.
    2.) I need to figure out a switching/relay concept that allows me to use both a deep cycle battery and my normal automotive battery depending on usage scenario.
    3.) I need to recover my Kill a Watt meter from my uncle to make sure that I am correctly accounting for my electrical usage.​
  7. Daox

    Daox Well-Known Member

    I disagree that it is crucial to do most of those things.

    1) The car runs great at 12V. Electronics don't seem to mind in the least. If you are worried about things pulling more amps since voltage is lower its really not a problem. There are guys who have run without alternators for quite a while and have never had electrical problems. I agree 13.8V would be better, but I have yet to find a ~60A DC to DC converter.

    2) Unless you have a huge engine and live in a extremely cold climate, I don't see a reason why you'd need both a starting and deep cycle. Did you have another reason besides starting?

    3) A gallon of gasoline has 36.6 kWh worth of energy. The average car uses ~25A. If you drive for 1 hour a day you have effectively used .3 kWh, or .8% of a gallon of gas per day. Now, if we take my example, I have my engine off half of the time. So, I'm using more like ~13A, and I'm down to .4% of a gallon of gas per day's worth of energy. I have yet to actually verify this with a kill a watt though.

    Good points, but really not crucial.
  8. cpeter38

    cpeter38 Right Lane Dweller

    1. I have read that the coils do not deliver quite as much spark energy and that the combustion efficiency suffers as a result. However, you are raising a VERY good point. I think that is the only system which would have a significant benefit from the 13.8V. I'd like to hear your opinion on that. As far as the whole 60A DC to DC converter thing goes, that IS a problem. I'm thinking that it may make more sense to just power the coils with a smaller DC/DC converter. I am thinking that you could run a couple of smaller ones in parallel into a cap (to filter the ripple). Thoughts?

    2. If I take the deep cycle down a lot, I do not want to have to charge it with the engine. I would like to have the conventional battery available as backup. Also, I have 4 L16 batteries in my garage and no use for them.

    3. I already have a Kill A Watt - I just have to ask my uncle to return it to me. That IS important for the FE challenge ...
  9. Daox

    Daox Well-Known Member

    I just got the car off the charger for the night. The kill-a-watt recorded .48 kWh used. When I put the battery on the charger, the charger said the battery was still at 70%. So, I have tons of capacity left in the battery which is great! I think it can be safely said that my charger is fairly inefficient since the total capacity of the battery is only .9 kWh. Anyway, today's commute was pretty bad compared to normal (accident on the way home had things really backed up), so this is about as bad as it should get.

    I'm still wondering if I'm going to track the energy usage day to day. I mean, I don't think anyone logs energy usage for block heaters either, and those use quite a bit more juice.

    As for #1, I think it will be fine as is. I'm sure the spark is weaker. The lower the voltage going into the windings the lower it will be coming out. However, ignition systems are usually most stressed at high rpms and high engine loads. It will never really see high rpms, but it will see high engine loads.

    The alternative that has been discussed on ecomodder is to use two 8V batteries in series. This brings the voltage up fairly high, but the electronics should be able to handle that too. One of the guys over there tested his van out with three 6V in series for 18V total! He did end up blowing out his headlights though. So, I think I'll just stick with my 12V.
  10. Elixer

    Elixer Well-Known Member

    I guess I'm with the others and I don't really see the point of the switch. The main source of losses from using the alternator are from the mechanical friction involved in the belts and shafts. Turning off its electrical load will not eliminate these losses. You can drain the battery and then charge it from an AC charger, but most of these chargers tend not to be that effecient and then you're dealing with charge/discharge losses as well. If you're looking to save the environment I doubt you're going in the right direction because of:

    charge/discharge losses (A lead-acid battery has an efficiency of only 75-85%) (which you don't normally deal with as the coils can more or less draw straight from the alternator)
    relative inefficiency of battery charger (Probably on the order of 75%, maybe worse)
    additional impact of larger required battery

    Though you won't be using a lot of electricity, it's worth comparing your fuel savings to the amount of electricity you use and calculating out CO2 use to see if something really is worth it.

    From a cost perspective I think it's pretty clear that the investments aren't going to add up when you're only saving .4% of your fuel. That's like saving 1 cent a gallon, which would mean driving 200,000 miles at 40mpg to save $50.

    However if this is a test run to see if you can run your car with the alternator mechanically disconnected I salute you as that will yield fairly significant gains in FE.

    Personally I would work on a system of leaving the alternator disconnected, and then leave a socket wrench set in your car in case you need to reconnect it. The alternator in my Camry is extremely easy to swap out.

    Also - According to my car friend, most cars will produce a large enough spark to run the engine with a voltage above 7V. So 12V is no big deal. Most 12V lead-acid batteries fully charged will have voltages well above 12V - ~12.6 is typical
  11. MnFocus

    MnFocus hanging member :)

    way back when I used a product called "NuCharge" to do this very thing. Easy plug and play "black box" affair - wired in between the alternator plug and battery and used a vacuum sensor routed to full manifold vacuum to kill the alt field. There was a decent bump in fe if set correctly. iirc the company was based in Colorado.
  12. Daox

    Daox Well-Known Member

    Belt losses are really not that large. Did you watch the video? The engine rpms drop at least 300 rpm when I enable the alternator. The engine quickly starts to recover to get the rpms back up, but you can see its a fair load. Most alternators are ~50% efficient, couple that to a 30% efficient engine and you have a horribly inefficient source of power.

    If we add up the power consumption, you can see its a fair load. The average car takes ~25A to operate. That is the equivalent of 300W of power at 12V. Now, the alternator is only 50% efficient, so we must use 600W of power to make 300W. 600W is .8 horsepower. That is a fairly decent load. Now, if we take the engine into the equation, we make that even worse as far as gasoline consumption.

    Others who have done this modification have tested it at a steady cruise. They have measured a 10% increase in mileage with it. Obviously, with pulse and glide you won't see as great of an increase since you are running the engine more efficiently. I am expecting ~5% which is not too shabby.

    This is quite true as I showed in my previous post. Anyone have any ideas on efficient wall chargers? I'd love to go solar, but it won't be able to recharge the car if I need to drive it two days in a row.

    Quite true, and an interesting perspective. I still think I come out ahead. EVs still come out ahead of conventional ICE vehicles, why wouldn't this? I suppose I could always justify this by saying I do pay for renewable energy.

    This is quite untrue. Many people have found places that gladly give up used deep cycle batteries for the core charge which is usually around $5. I got mine for free even. As long as you have a switch and wire laying around, the modification could be completely free.

    At this time I have no plans to mechanically disconnect the alternator. I would love to move it off the engine and onto a drive shaft or off the transmission so I could activate it with a relay driven off the brake light circuit for a very low level form of regenerative braking though... Alas, that is a fair size project and not likely to happen soon. Its also a slippery slope from that point to sizing up the alternator with an AC motor for a mild hybrid setup too...
  13. msirach

    msirach Well-Known Member

    There are mechanical losses with the alternator spinning at no load. If the regulator is calling for more charge for the battery, the alternator supplies it. It's at this point that it starts putting load on the engine. At a low charge rate of 5-10 amps, it will be minimal load on the ICE. Headlights on at night, windshield wipers, defrost on max, the alternator will be heavily loaded. The brake lights on, radio on, turn signal all add load on the alternator.
    A cut-out switch can make a difference and you can regen like on a hybrid when coasting down a hill or to a stop light. This is a much simpler solution than actually removing the alternator belt.
  14. bomber991

    bomber991 Well-Known Member

    I gotta go slightly off topic, but I feel like I gotta mention this.

    I remember watching an episode of Top Gear where they had to do one of their go from A to B challenges. Anyways, the waterpump died in the car that Richard was driving. So what did they do? They hooked up a hand pump, and he was sitting there manually pumping the coolant or whatever it is the water pump pumps.

    Hypermiling, sometimes we do dumb things for small gains. So I wonder what kind of gain this would give you? I'm guess it's just an electrical load, and since you're already using a pre-charged battery it probably wouldn't give any mpg gain. It would just make the battery charge last longer.
  15. Sulfuric

    Sulfuric Well-Known Member

    Tech question. Other than ignition and the ECU, is there any electrical power needed to run the car? Let's say I have no alternator, and I clutch start my car every time instead of turning it on with a key. If I never use any lights, or fans, etc, how long would my car run?

    Short version. Does the engine draw power from the battery once it is started?
  16. aaronl

    aaronl Alternative transportation advocate

    Yes. Fuel pump, fuel injectors, ignition system... Not sure what it adds up to.
  17. Daox

    Daox Well-Known Member

    Just a little update on the battery situation. When I first set it up, I would charge the battery a hour or so after I got home. The next day the battery voltage would already drop down to 12.4V. It stayed solidly at 12.4, but would just not hold a higher charge. So, about a week or so later I put an ebay special desulfator on it. It has been a month now, but the battery voltage is now staying around 12.7V. Previously, when I got home, my charger said my battery was down to 70% charge. Today when I put it on the charger, it said my battery was only down to 90%. So, the desulfator appears to be working.
  18. cpeter38

    cpeter38 Right Lane Dweller

    I tried the same mod on my car. It appears that the ignition system on my SVT does not tolerate the lower ignition energy. I have not given up yet. I am considering running a DC/DC converter to fix this.
  19. JusBringIt

    JusBringIt Be Inspired

    interesting..very ebh plus this mod would kick it up another couple notches...very very interesting.
  20. cpeter38

    cpeter38 Right Lane Dweller

    I am no longer considering the DC/DC. I bought it (actually, 6 x 5 amp DC/DCs). It will take a little time to get here (from China :()

Share This Page