Lawnmower Battery

Are you preparing your youtube video? I would like to see this.

Are the car and lawnmower batteries both the same voltage? If yes, it is OK to attempt. Will it succeed? Probably not enough current available in the lawnmower battery. We will wait for your video.

Depends.

Which car?

Which lawnmower?

I don't think it's going to have enough cranking amps to turn over your car engine.

Assuming everything is 12 volts, you'd probably be better off trying to jump the car from the lawnmower while it's running.

Or you could buy a charger for your car battery if it's good, or replace it if it's bad.

"jump the car from the lawnmower while it's running"

While at first glance this may seem like a good idea, I advise against this practice. It's very likely to result in a lawn mower coated in battery acid when the battey explodes.

Oh, my!

Did KrisDel™ replace that battery under warranty for you?

I guess he would want to don a good HAZMAT suit first!

Hell, the whole thing seems like a bad idea, he needs to go get a car battery.

Hopefully he's not a melted pool of flesh out in his driveway right now.

Why would having the lawnmower running be different than just trying to start the car with the lawnmower battery alone? Seriously.

I could see it if he was trying to jump a small lawnmower battery from a running car.

Answering my own question.....Don't do it, I forgot about output from car alternator.

Whether the mower is running or not, battery in or out.....once the car fires up, the alternator output is too high for the smaller mower battery and it can explode.

Disregard my first post except for the final sentence.

Agreed, The charge circuit monitor in the car will read very low, and adjust the voltage regulator accordingly. Our OP did say "...If i automatically change it back to the regular car battery?" LynDoor® Industries offers an AutoMagic Disconnect for such projects (it will disconnect source battery from charging circuit 0.2 seconds before the engine starts), but he may not be using one.

All kidding aside, using the lawnmower battery is starting to sound like a bad idea. I would amend my vote to 'Do Not Attempt'.

Is this a lawnmower with engine and electric starter/battery/generator? Replies seem to assume this but there are electric motor powered lawnmowers using a car battery.

Whichever it is, I can't see why it should hurt to try it, if the batteries are similar size. I'd disconnect the jump leads quick after starting, but I don't see why it should hurt the mower battery after the car starts. The car charging regulator will limit the voltage to the right level. Perhaps the alternator maximum current is too high for the mower battery if this is smaller than the car's, but it won't output max current if the voltage is at regulating point. And if the mower battery is much smaller it maybe won't start the car anyway.

Cheers.......Codey

It may work, but in situations like this, where we don't know all of the details and there is a chance the OP could get hurt, it's best to err on the side of caution.

He needs to find a friend with a car that can give him a jump, buy a charger or buy a battery. Why take the risk?

Lynch gets it right once in a while.

Looks like you have a lot of good advise. I would like to throw in my two cents just to make it fun. But do keep in mind you have left out a lot of needed information in order to get a good answer. I will not get to complicated, I will just keep things in simple terms.

The battery in your lawn mower can be different in two ways, voltage and amps. If the voltage is the same on both batteries, they can work together in getting your car started. That is if the lawn mower has an actual charging system.

But first, this is the precaution part, make sure that the car battery is not frozen. When a battery looses it's charge the electrolyte changes from an acid to a water. And this makes it easy for the battery to freeze over. When the battery is in this freeze over state any chemical change in the battery the gassing, while being charged or jumped, will have no where to escape to. The pressure will build and the battery will go "boom". Other problems like warped plates due to freezing can create some interesting issues.

So if this is the case, please do nothing yet! Take your battery inside where it can thaw out. Then you can proceed with getting your car started. I have seen to many batteries explode and it isn't pretty.

A regular car battery is sized to produce an amount of amps over a period of time. The amps it takes to start your car is not as much as some think it is. The reserve capacity of a battery is enough to start a car under normal conditions.

The battery in the lawn mower will most likely not be enough alone to start your car, but it can assist. The charging system in the lawn mower will act as a battery charger for your car if you just start the mower and use jumper cables to connect the two batteries.

Let the battery charge for about 10 to 20 minutes and give it a try. If after a 20 minute charge and no real progress, dump the idea. Your battery is probable to far gone. If the car started, great, remove the jumper cables. If not, but it was close, charge another 20 minutes. If the condition improves you can give it one more shot.

I once used a motorcycle to jump a Dodge Ram. He had left the lights on while camping and I was handy. It was more of a charging than a jump, but I am sure it was a collective effort.

The best overall solution is Sears and a new Die-hard. But in a jam you have to do what you have to do.

Some people think they can start a car with one battery, and once the car is running take out the starting battery and put in the old one, so to charge it up. This is a recipe for disaster. Any modern car with an alternator will promptly self-destruct the whole electrical system when this is attempted. You can lose the alternator, computer, and anything else the system chooses to destroy to punish you for your folly.

Hey Mike, if I may, I think that is not all correct. Once a car is running you can remove the battery and the car will run just fine. A lot of mechanics will check the charging system that way. They will start the car, remove one of the cables, and turn on the head lights and the heater blower motor while the engine in in idle. If the engine is still running the charging system is considered working OK.

If a discharged battery is connected to a running car there will be no issues unless the battery has some defects or is frozen over.

The battery is just there to start the engine. It is connected to the alternator so it can be recharged. It is the alternator that runs the electrical system.

"Once a car is running you can remove the battery and the car will run just fine. A lot of mechanics will check the charging system that way. They will start the car, remove one of the cables, and turn on the head lights and the heater blower motor while the engine in in idle. If the engine is still running the charging system is considered working OK."

This was a poor test when we had generators. When we went to alternators, that test became useless. I watched a co-worker pull that test on an AMC Matador, when they were new. The Presto-lite alternator had no voltage regulator system with no battery. The voltmeter read about 100 volts. The Presto-lite ignition control module fried, the headlights and tail lights burnt. Some of the dash lights burnt, and of course, the voltage regulator shorted out.

But, that was back in the 70s,when there was not so much electronic equipment on cars. "So, you have to ask yourself 'Do I feel lucky', Well, do you punk"

I've used this test myself, granted on older cars and never had a problem.

I'm not questioning what you're saying, but I'm confused. No voltage regulator system without a battery? Is this common? I can't get my brain wrapped around it.

Maybe that's part of the reason AMC is out of business.

I don't mess with anything on new cars beyond changing oil and brakes, the rest of it is above my pay grade. Too many electronics involved.

Without a battery to send a voltage signal to the regulator, it never sees a voltage high enough to tell the regulator to limit charging voltage. It might have been Motorola alternators, not sure now. But that may be why AMC went to GM, and Ford alternators soon after.

If you want an easier test to see if an alternator is charging, take a steel washer, and hold it to the rear alternator bearing. If the washer is held there by magnetism, the alternator is charging.

Hello bob c

It depends on the system. Some alterrnators are battery sensed - battery voltage is fed to the regulator so there's a chance that if the wire breaks or battery disconnected it could overcharge. But the ones I'm familiar with are wired (inside the regulator) so that in this event there is no excitation so no output, ie it fails safe. Other alternators are internally sensed so in theory should not overcharge.

But I wouldn't risk diconnecting the battery with either type, all the manuals advise against it.

Cheers.......Codey

Lets all think about this for a second.

#1) The OP has told us almost nothing about the particulars.

#2) The latest thing being sold to allow homeowners to start cars with batteries that are low is these small jumper boxes. These jumper boxes are nothing more than small batteries that are matched to the starting voltage of the car,(12 volts) The lawn mower batteries that I see sold most often are larger in capacity than the batteries in the jumper boxes. The smallest lawn mower battery I see is much stronger than the jumper box batteries, so what is wrong with the plan, IF done correctly?