Can a Car or Truck Run with No Battery How Vehicle Alternator and Electrical System Works

All right. I got to get this battery out of here so I can replace it. It still runs.

Hey friends, it's Len here from 1A Auto. So today, I want to talk to you about whether or not your vehicle can actually run without a battery in it. To answer the question, can it run without the battery in it? Well, yes, it can. Okay. So I hope you liked the video, I hope you learned a little something. You did, you wanna talk about it, leave it in the comment section below...wait a minute. I haven't even talked about it. I got more to say.

Firstly, how's the car even running without having a battery in it? Well, it comes down to this little piece right here. This is called your alternator and it's powered by your serpentine belt. So what is an alternator and what does it even do? The alternator is supposed to be able to generate energy and transfer it over to the battery and the battery acts as a storage area for that energy.

So essentially, when your car's battery voltage is low like this one right here, 11.5, that's technically low. At that point, the alternator's gonna try to do its job, which is, of course, to try to charge up this battery to its maximum capacity, which is approximately 12.4 to 12.6 as long as it's not under load. Now, I can think of three main reasons why you'd wanna have a good battery inside of your automobile. Obviously, you wanna start it up. You hop inside, you want to start right up, and then, of course, run. Once the car is started, the alternator is gonna create voltage, which, of course, is gonna create a current leading to the battery and that's gonna keep the battery charged up. Of course, the battery is also gonna store some energy. That's what it's for. And lastly, it's gonna act as a surge protector for the electrical system overall.

Since we also mentioned that the battery technically works as a surge protector, the reason why that is because the alternator can technically put out different current to the battery to try to ensure that it stays charged up. If it finds that the battery has a low amount of charge or it's getting worn low, it's gonna try pumping out more amperage to that battery to try to bring it up. If it feels as though it's up where it needs to be, the alternator's gonna push out a little less and it's kind of just gonna send out a little bit of a trickle charge to that battery just to keep it topped off. But if your alternator doesn't find that it's getting a reference point from the battery to figure out exactly where it's at, it's just gonna try to send out maximum current because it thinks that the battery is completely dead and it needs to do all the work.

So why does this even matter? Because the alternator itself is gonna be able to push out different amount of currents at different RPMs or how fast the engine's actually running. And, of course, this could cause voltage spikes. And the battery right here is meant to absorb those spikes, as opposed to having them just get sent right out to your electrical components. So now let's have a look at the multimeter while the battery is disconnected. As you can tell looking at these numbers right here, the voltage is spiking or fluctuating. It's going up and down all the time. If the battery was in this, it would be pretty much constant and that voltage is, of course, gonna be available to any of the electronic components inside the car. Right now, any electronic components are gonna be looking at this and they're gonna go, "How much voltage am I actually getting, 12, 13, 14? I never know what I'm gonna get." And this can cause major electrical, especially in most modern cars that have a lot of electrical components. And this is just while the car is actually sitting here idling, not doing anything. Let's go ahead and rev it up like we're driving down the highway. Scary.

Now with the battery is still disconnected, let's go ahead and turn everything on inside this car and see exactly what this does. Well, I guess the alternator just couldn't keep up. So now let's have a look at what might potentially happen to your battery as you start turning on the accessories, but not actually having the car running so the alternator can't start charging it up. Maybe you still wanna listen to the radio, maybe you wanna have your headlights on for some reason, you got to hit the horn, or even you've got four ways on because there's some sort of emergency. I'm gonna turn on the headlights. Let's go ahead and turn on that air conditioner/blower motor. Obviously, it's not gonna blow any cold air. Four ways. Step on the brakes. What else do I got? Horn. And some wipers. Now, obviously, looking at this battery and the starting voltage, you could tell that this battery wasn't necessarily in the best of condition overall to start. After we start adding some loads to this, you can see how much the voltage dropped on this battery. And it's definitely not bouncing right back up like it should. And this is definitely not gonna be enough voltage to start this car. I'm cranking. Nothing. It's got nothing.

Okay. So now we have our battery back inside the car. We started it right back up. And as you can tell looking at this multimeter, the voltage is pretty much sitting steady exactly where it should be. It's not jumping all over the place, so you're not seeing a whole bunch of surges. I guess now let's put a load on it. So here we go. I'm gonna step on the brake, put on those headlights. Why not some wiper blades, four ways, and, of course, we're gonna start off this air conditioner because it's hot out here. Not bad. So now as you can tell, as I started loading this up with the car still running, you did actually see the voltage start to fluctuate a little bit, but it really didn't fluctuate very much and when it did, it came right back up to where it's supposed to be. As you saw, once I turned it on, the initial voltage that was getting sent to the actual apparatus or electrical component drew off the battery, it took a little bit of juice from it, and that's great and everything, and then the alternator said, "Whoa, whoa, whoa. I gotta help this guy out." So it started sending some voltage and here we are again, looking great. Every time those wiper blades move or something tends to happen, it draws it right down. Of course, right now, the car is just idling. So the RPMs aren't necessarily spinning that alternator very fast. Let's go ahead and rev it up a little bit.

So now as you saw with the loads on there, even with the RPMs, the alternator was really only pushing out approximately 14 bolts to the battery to try to charge it up. Why is that? Because inside the alternator on this particular application, it has an internal voltage regulator. Essentially, what that's gonna do is it's gonna make sure that the alternator can't just put out 1,000 volts just because I'm jamming on that accelerator pedal. And, of course, that's for the safety of all the internal electrical parts of your passenger vehicle. Okay. So, in conclusion, will the car actually run without having a battery in it? Yeah. Obviously, it does. Is it gonna start without having a battery in it? No. It's not gonna start unless I have something to be able to actuate all of the circuits and be able to start up the actual engine itself. Once the engine is running, obviously the alternator can take care of business, but as I start adding loads to it, it could potentially put more of a drain on the system. In that case, you're gonna notice more surging. All that surging could potentially cause damage to your electrical system. Let's take this for a road test. All right.

This one's for Matt. Now let's do this hill. Oh, yeah. Plenty of power. It doesn't need that battery.

Okay, friends, so I hope you liked the video. I hope you learned a little something. If you did and you wanna talk about it, or you have a story of your own, leave it in the comment section because I'd love to hear it from you. Of course, if you liked the video or loved the video, please feel free to go ahead and smash on that like button for me. It would mean the world. While you're at it, go ahead and subscribe, ring the bell that way there you can be kept up with all of our latest content. Thanks. Oh, don't forget to share. Where the heck are we? Better turn around. Oops.