Alternator delete consequences
 

So I have been messing with the alternator on my 2005 Honda Civic out of boredom, as well as educational purposes. But I have been wondering about the consequences of running the car without the alternator functioning. And if you were wondering, I have not seen any definite efficiency gains from disabling the alternator. Maybe 2 and 3 explain this?

I have an Optima Yellowtop D34 deep cycle battery in the trunk, which can run this car for quite a while as long as accessory usage is minimized. I have driven this car for 2 hours on the highway running off the battery before no problem, although I didn’t use any accessories. But the bad news is that I’m not sure how much efficiency I actually gained, if any.

I have been wondering what the negative effects could be though. I know that the battery life may be shortened by charge and discharge cycles, but I am not worried about it because it is a deep cycle battery and I don’t usually cycle it that deeply, so I am more concerned about how the lower voltage can affect the car’s overall performance.

In no particular order, a few ways I can think of that a lower voltage can adversely affect performance:

1. Reduced accessory performance, such as somewhat dimmer lighting. All of my lighting is LED, but the brightness of some of the bulbs seem to be adversely affected by lower voltage. My fog lights actually flicker a little bit when the alternator is disabled, although I am not sure why. The windshield wipers also run a little slower, the HVAC blower isn’t quite as strong, the power windows aren’t as quick, and the rear defroster seems to take a little longer to clear the window.

2. Reduced ignition coil performance. I am not sure if the ignition coils lose performance when fed a lower voltage. I have heard that the spark wouldn’t be as strong, and I have also heard that the coils will work just as well and will just draw a little more current to compensate. I am not sure

3. Reduced fuel injector performance. The fuel injectors will not open as quickly when fed a lower voltage, potentially throwing off fuel delivery timing and adversely affecting the engine’s performance. But for all I know this ECU may have voltage compensation since the car has a dual mode charging system and is designed to run on lower voltage when commanded by the ECU.

4. Reduced fuel pump performance. When fed a lower voltage, the fuel pump won’t be able to pump as much fuel. This doesn’t seem to be a problem for me, but worth mentioning nonetheless.

Did I forget anything? Thank you in advance! Any input would be greatly appreciated :)

How are you recharging the battery?

Use a lithium battery.

Agree with the lithium battery. It will hold it's charge at approximately its nominal level until just before depletion whereas the lead acid will slowly but continuously decrease in voltage the entire time it's being used. It should also be much lighter than the deep cycle.

You might see decreased performance with accessories because even though the battery is rated at 12 volts, it will normally being getting charged from the alternator at the higher level between maybe 13.5 to 14.5 volts. Normally a fully charged battery should show between 12.6 and 13.2 volts on a volt meter.

Have you measured your voltage levels before and after yet? That would be useful information.

JJ

I have a Battery Tender Plus charger mounted in the trunk hat I plug in when I get home. I don't usually run the battery down that much, so it's usually charged by the next day when I drive it again. Also, I always make sure that the battery is fully charged or very close to it before I re enable the alternator because I don't want to overheat the alternator.

Great advice to get a lithium battery! I never thought much about them, although I knew that they existed. I will look into it, but I imagine that a lithium battery with a comparable amp hour rating would be prohibitively expensive though.

This alternator seems to have a temperature compensated regulator, so it will produce less voltage the hotter it gets. When it is started cold on a cold day, it will produce around 14.8 volts in high charge mode regardless of electrical load or RPM. However, on a very hot day after driving for a while, the alternator only produces around 13.6 volts in high charge mode. With the ELD plugged in, low charge mode always seems to be around 12.7 volts though regardless of temperature.

You can get a 5 Ah lithium battery for about $20. I imagine 50 Ah would be about $200 then.

The difference is you can use more of the capacity without harming the battery compared to a lead acid.

Another difference is you can't charge them below freezing.

I don't think you risk overheating your alternator. I haven't in seven or eight years.

On the fuel savings, it is hard to test with our imprecise equipment and methods. I am confident it is worth about 3 mpg to me, but I cannot prove it in any rigorous sense of "proof."

I didn't mean I risk overheating the alternator if it is spinning without producing electricity, I meant it might overheat if I enable it with a nearly dead battery because it would be running at maximum output for quite a while trying to recharge it. This battery can pull a lot of current when it is dead, much more than a stock size battery. It can push this (larger than factory) alternator hard enough that it can't get the battery above 12.5 volts with 110 amps of current going into it! That couldn't be good for the alternator to run it that way for long.

I did a test to see how much current this large alternator that came with my JDM D17A engine out of a Honda Stream can produce, and it looks like it can produce around 80 amps at idle and it peaks at around 110 amps or so. By comparison, the stock alternator could only produce about 45 amps at idle and it peaked at around 70 amps.

Thanks. I wish I could get a 50 Ah for $200 LOL. I found a 50 Ah battery that weighs 15 lbs, but it is almost $700! https://www.amazon.com/GreenLiFE-Bat...r=8-3-fkmrnull