Will I damage my lawn mower by using a car battery for its ignition?

As long as you're sure that the mower system is 12V (and the car battery is 12V!) the higher capacity of the car battery won't harm the mower.

Just make sure you get the + and - connections the right way round!

Hi,

If all of the information you supplied is correct, there should be no problems with utilizing a much large automotive battery. As pointed out by JohnDG you want to be very sure of the polarity when you hook it up. This caution would be valid regardless of the size of the battery and it could to prove to be quite damaging and even dangerous if this is NOT correct!

The only difference will be is that you will have a much greater power reserve and the battery won't become discharged anywhere near as fast as the small original battery will if you are having difficulties getting the engine to run.

A couple of IMPORTANT cautions:

1 - Electric starters have a very low 'duty cycle'. They are only designed for a VERY short period of time between usages. Typical specifications is a ten minute cool down period after 15 seconds of the starter operating before you make another attempt to start it

2 – You may significantly damage the electrical system by trying to operate it WITHOUT a battery installed! This applies to Automotive engines as well. Also unless the battery charger is one that is designed to be utilized in starting a vehicle and has enough current to accommodate this, you will very likely 'fry' the battery charger which may subsequently result in damaging the electrical & ignition systems of the garden tractor as well

Has the garden tractor in general and the engine in particular sat for an extended period without being operated? If so there are a number of things to watch out for and that you can do to help prevent things like broken piston rings etc when starting it up after a significant period of disuse. This applies to vehicles as well.

(8 >) . A Happy, Healthy and Prosperous New Year to One and All . (< 8)

Hi,

I got the impression that the tractor was new.

I take exception to your statement, " You may significantly damage the electrical system by trying to operate it WITHOUT a battery installed!"

After the vehicle is started, how does running without a battery damage the electrical system?

Thanks.

"unless the battery charger is one that is designed to be utilized in starting a vehicle and has enough current to accommodate this, you will very likely 'fry' the battery charger which may subsequently result in damaging the electrical & ignition systems of the garden tractor as well ..."

This, obviously, only applies if the battery is installed in the mower and connected to the charger when attempting to start.

Generally it is better to remove the battery from the mower, charge it fully then re-install it (observing polarity!) before trying to start.

Hi,

I concur about the safety glasses. In fact the proper procedure is to hook the final ground connection to something on the vehicle well away from the battery, preferably on the engine; so that if it is venting hydrogen and oxygen gases a spark will not ignite it and blow up the battery and perhaps you along with it!

The ground always goes on last, and comes off first.

This part pertains to both boosting a vehicle and the person disputing the fact that there may be damage to a vehicles or engines electrical system being damaged with running it without a battery installed:

Most modern internal combustion engines utilize integrated electronics, both for the ignition as well as for other (Expensive!) 'black boxes' for pollution controls, ECU Engine management, instrumentation, and other electrical subsystems. Unlike the 'old days' where everything on the vehicle was 'electrical' and had no 'electronics'. The later are generally have much tighter allowable tolerances for the variation in voltages that are still very wide ranging. Even on modern day vehicles, operating voltages from 8 VDC to ~ 18 VDC are not uncommon. A garden tractor may very well have an electronic ignition system as do many even smaller engines such as lawn mowers etc. But there voltage regulation is even worse than automobiles. The battery serves as a significant buffer to soak up and dampen sudden voltage spikes that can and do occur, especially when boosting a vehicle that can and do destroy electronic systems. If you research the procedures for 'jump starting' a modern day vehicle you will likely find that the following recommendations apply to most of them to minimize blowing up 'electronic black boxes' some of which can cost up to $5,000! After the second vehicle has been boosted and started, before removing the jumper cables you are supposed to have both engines at the normal low idle speed, and not at their fast idle speed that many still have when the engine is below its normal operating temperature so that both alternators are at low output levels. The engine of the vehicle that is working properly and being used to start the other one with a dead battery is supposed to be turned off, all high current electrical systems in both vehicles are supposed to be turned on: High beam headlights, electrical rear window defogger, AC / heater fan on high, wiper blade motor on high. ONLY then do you FIRST remove the grounded jumper cable that was hooked up last and is on a place other than the battery to minimize the chance of explosion. All of these particulars are to minimize any sudden power surge that may occur in one or both vehicles that can destroy onboard electronic systems.

The part about not running an engine without a battery hooked up to the system has been SOP (standard Operating Procedures) for decades now, even before the advent and prevalence of electronic devices. This also applies to the comment about having the battery in place when boosting you Garden Tractor if needed. I'm not sure exactly what this comment is specifying, but not vehicle should be boosted without a battery in it.

You don't have to take my word for these 'details' but you do so at your own risk: both to personal injury and even death &/or (significant expensive) damage to one or both vehicles in the case of boosting a vehicle. In many modern vehicles the SOP is NOT to jump start the vehicle at all and doing so may void the warranty!

FYI: I live in northern latitudes where it can and does get very cold in winter. If your vehicle is parked outside the battery is very cold and has less power available to start the vehicle when in fact it needs more to overcome the thickening of the lubricating oil and the significant increase in the coefficient of friction when trying to start it. Even in this day and age of computer systems on vehicles, some people will still bring their battery inside a heated building so that it is warm when they go to start it.

FYI: Leaving an acid battery sitting on a concrete floor will not only run it dead, but will actually render it useless and destroy it. I don't know why this is, but know it to be so. If you want to know, do your own research on it and let me know why as well. If you can't find the explanation but still want to test the hypothesis, buy a new acid battery and leave it sitting on the concrete floor for a few months or a year and let me know how that works out for you (< 8)

When the battery is very cold, it will not take an electrical charge and any excess electricity produced by the alternator that goes into the battery goes only into warming the battery up and does not charge it at all. This is why in such places and under very cold conditions you will see even new vehicles not running along the road as the battery never gets a chance to actually charge. In such conditions this situation is usually compounded by heavier than normal electrical loads turned on to cope with the numerous problems of the extreme cold. Often this is made even worse by the fact that road conditions may be very bad, &/or blocked by such vehicles that have stopped running from the deficit of electrical energy needed to operate it and the increased number of traffic accidents. All of which contribute to often just idling along or sitting still with the engine at idle and the alternator does not produce enough under these conditions to operate everything and in slowly but inevitably drain the battery dead.

My vehicles have all of the following items on them that I use selectively depending on the conditions:

1 - A block or coolant heater, perhaps even 2 if it is a v shaped engine configuration and there are 2 separate banks of pistons.

2 – A battery blanket to keep the battery relatively warm.

3 – A low amperage (~ 2 amps) 'trickle charger' to help keep the battery both warm and fully charged.

4 – An oil heater: Either of the dipstick replacement type or a higher capacity one that has magnets on it to 'attach' it to the side of the oil pan. I use the latter configuration with the heater also being 'strapped on' and the oil pan is cleaned and degreased before I attach the external heater that has the face that comes into contact with the oil pan liberally covered with a silicon heat transfer compound such as is used in computer CPU coolers.

5 - An in car heater.

I also exclusively use a synthetic 5W-50 engine oil that has a much wider temperature range and doesn't thicken up as much in cold weather nor thin out as much in very hot weather and conditions and as such is suitable for all conditions.

Engines wear more in the first 15 ~ 30 seconds after they are started than in 8 hours of driving due to the lack of lubrication on the parts that require them. This is compounded by cold weather and after an oil change. I ALWAYS fill the new oil filter up several times with new oil until it will not soak any more up to minimize this excessive wear, even if I am paying someone else to actually do the oil change. I always bring my own new oil and high quality filter along with me. The oil should also be relatively warm to reduce the lubrication lag due to cold, thick oil. You can hear for yourself how noisy the engine is when first started up, especially when the oil filter is installed dry, and how much it quietens down as the oil starts to reach the lubricated surfaces. Likewise if the oil is very cold and thick when first started up under such conditions.

Many high end race cars and large expensive diesel engines have auxiliary subsystems that flood the lubricated surfaces with oil BEFORE starting them up to avoid this very problem, even in summer when the oil is much warmer than in winter. There are aftermarket add on systems that can be installed on vehicles for this very same reason.

Oil is a LOT cheaper than engines and your engine without oil, or the delay before it actually starts getting lubricated, will run for about as long as your body will without blood!

You can search for other submissions by myself in regards to both using your Air Conditioner as the Heat Pump that it is in winter to get the passenger compartment starting to heat up within a minute before the engine and the coolant that is used to heat it are warmed up. This also prevents damage to the AC system from the water that condenses into the refrigerant over the winter if it is not used.

Likewise you will find submissions here by me about how your engine is being worn out at a VERY high rate if your engine never gets heated up properly in winter from driving stints that are too short to heat the engine and the oil up sufficiently to drive the water out of the lubricating oil.

Take good care of your vehicle and it will take care of you !

Hi Again,

It is important that all battery connections and especially the very high current ones for and to the starter be snagged up tight. There will be a fine oxide/corrosion build up between such electrical connections over rime that will cause resistance and impede the current flow. This is especially important to the starter with its very high current and low voltage that can and does make a significant difference. Be sure to remove the ground wire from the battery before tightening up any positive connections so that you don't get a dead short if your wrench comes into contact with anything that is grounded, which is most of the vehicle. Be careful not to over tighten the large hot lead to the starter as it is usually attached to a brittle insulating material that will crack and break easily. All significant power and ground connections should be tightened up just a little bit to break this oxide/corrosion that builds between such electrical connections. Some WD40 or MG Chemicals 'Super Contact Cleaner' on these electrical connections including the fuses it a good idea.

The fact that a battery will lose it's charge and be destroyed when left to sit on a concrete floor has been around since the 30's. It is not absolutely true. In those days the lead acid batteries were sealed with pitch and the charging regulators on the vehicles were quite crude. They tended to overcharge the batteries and the boiled off acid would collect on the pitch and eventually create a path between the + and - terminal thus discharging the battery. Placing the battery on a concrete floor meant that you were placing the battery in a high humidity location and this aided the process of establishing the conductive path aiding the self-discharge. That's about it. After all, when the battery is in a vehicle it is placed on a metal frame which is a lot more conductive than a concrete floor. It is the humidity and damp that does the damage. Modern batteries are sealed much more so they don't accumulate a spray of acid between the posts and the solid state regulators don't overcharge so this old myth does not stand up now.

Hi,

It all sounds good to me and as I stated, I don't know why putting batteries on concrete floors destroys them, but I do know that having been in many storage warehouses of large & specialty battery shops that they NEVER store or keep any (Lead) Acid batteries directly on the concrete floor even to this day, regardless of humidity.

Hi,

Regarding the Lead-Acid battery failing while being left on a concrete floor: To my knowledge, there are mainly two things that are happening:

1) the battery will hold less of a charge as its temp. drops. I have seen charts that show the capacity will drop as the temp. goes down, but will rise back up to a point as the temp. goes back up. The optimal temp. for lead-acid is 77 F Being on a cold floor will drop the temp. and drop the stored power accessibility.

2) the batteries internal resistance/conductance will cause the power to gradually drop. Unless it has a constant charge, this discharge will happen. Note: when the battery receives a constant flow of power, its life tends to drop, due to overcharging. The best way to keep a lead-acid battery functioning is to follow these steps below:

1) use a charger that uses pulsed current, so the plates can charge without overcharging.

2) use a thermally suitable location if possible for storage. As the temp. drops below around, say, approx. 50 to 60 degrees F, the cells won't cycle properly, and it will be much easier to overcharge.

3) consider getting a deep-cycle battery for certain applications. They use nylon stockings for longer life, such as marine batteries and other applications where reliability is important

4) check water level of maintenance batteries, use only distilled water, other water will cause permanent damage to their chemistries

5) avoid dropping or other undue shock. This can cause internal shorts and possible explosion elevated risks.

6) consider using a solar panel that sends a pulsed current into the battery, especially in colder northern climates.

Some folks say and provide details on using low internal resistance NiCad batteries, claiming that NiCads are great to supplement the Lead-Acid power to start a vehicle. I personally do not know much about this, but I feel it is noteworthy. The NiCads have such a low internal resistance that, in an emergency, they can provide significant wattage to a starter system when a lead-acid cell is unable to work.

My education has been focused on battery technology since high school. In college, I wrote a 12 page essay on battery chemistries, and now use Lead-Acid, NiMH and solar together. I enjoy answering questions related to batteries, and hope my response here has been somewhat helpful.

I studied some Electrical Engineering Technology before switching majors to Computer Science. I still practice EET seriously as a hobby and hope I can be helpful for others.

Regards,

Eric

Thanks!

I defer to your expert knowledge on the subject.

Back on the farm, we never worried about...........................oh, never mind, you're right.

Cheers.

Just a quick note from a computer technician, if you're applying that stuff liberally you're probably not getting as much benefit as you could be. Steel on steel conducts heat much better than that stuff does. It should never be applied liberally if your goal is better heat conduction.

it's used on CPUs because the surfaces have tiny imperfections. The goal is to apply a very very small amount, and then scrape it across the surface so it gets in all those little dips and grooves. That way, anywhere you don't metal to metal contact you still have /some/ contact, thus improving the overall transfer of heat.

If you take those off, scrape them off, and then reattach I bet you'll have better performance from those heaters.

Only note I have to add is that safety glasses are highly recommended with hooking up or disconnecting batteries, and especially when using jumper cables.

Optician friend of mine told me one of his patients was blinded in the course of jump starting a car, and said it happens much more often than you'd think.

Don't know where you bought this lawn tractor, or how long it might have been on the sales floor. Don't know if it was properly assembled in the first place.

Is the Ground wire firmly in place?

Did you put a voltage meter on the charger contacts?

I believe some do not recommend metering small batteries as some drain is induced, but don't think it is so terrible for batteries of that sort.

No.

It would help to ensure that the car battery is fully charged.

When you say that the mower is not functioning, does that mean that it will not start? If it is trying to start (engine is turning) but won't, make sure that it has fuel and that if it has a fuel shut-off valve that it is turned on. There is also a switch in-line with the ignition to prevent start-up when the clutch pedal is not depressed. This is a safety feature that prevents the mower from moving forward if it is left in gear when starting.

It would be much easier to use a DVOM check the voltage then put on your charger and check the voltage. A good battery should be around 12.8 volts. With the charger on it should be above 13 volts. If the battery won't charge use your warranty and exchange it for a new item.

I was warned a few years ago about jump starting a mower with an automotive battery. I was told that it would destroy the diode in the lawn mower electrical system. This advice came from my brother who owns a repair shop and has replaced several diodes due to this. I just called him to double check this. He said it is just to much power for the lawn mower electrical system. If needed you MIGHT be able to boost the mower if the car is not running. Better still just connect the cables and let the weaker mower battery soak up some power from the car battery. Then disconnect the cables before trying to start the mower.

As for the safety glasses,

I helped a cousin jump start a minivan. His van so he was under the hood. The battery exploded. It turned out the battery post was cracked at the base. When the ignition switch was turned to start the van the resulting spark set off the explosion with the gases in the battery. After a few hours at the hospital getting his eyes washed out he ended up ok. We both grew up on a farm and had jumped several batteries. This was the first time we had a problem.

Hi there Mechanic et al,

What you are referring to with the diode trouble doesn't fit what experience or what I know about electricity and ignition systems, but I've come across many other such things that didn't make sense either but were just what they were and would or wouldn't do what they did do.

One such instance was what was otherwise a plain Jane 35 amp alternator that was built by Ford to VW specs. It looked EXACTLY the same as the 'Ford' model except the mounting tabs were oriented a little different. My jobber cost on the OEM rebuilt Ford model was ~ $35. (This was more than a couple of decades ago) The VW OEM spec one was over $350! There was one other 'minor' difference that was also a VW spec: when the field wire on the alternator was fully energized to test the full output capacity reading on the alternator as is SOP, the rectifying diodes wouldn't handle that much current (Amperage) and blew the diodes out of it! Nice little 'invisible' touch eh!

Better to be safe than to be sorry.

In that regards we all seem to be in agreement about the dangerous of exploding batteries. There have been airplanes blown out of the sky and people killed by exploding, overheated and overcharging NiCad batteries as well.

Keep on Keeping On!

I am not much on electrical components so I have to rely on what I can get from the pros. My brother has been in business for over 25 years. My dad had a small engine repair shop before that. By the time I came along Dad was moving on to better things and had his fill of running his own shop. Maybe the diode issue is the result of something else that occurred while jump starting a dead mower. From what little I know about electrical components, I would suppose the diode could have gone bad or was at least weak before the jump start attempt. Regardless, I avoid jump starting mowers because of what I have been told.

Hi Blink,

An excellent, well informed, comprehensive response Blink. The rest of us did overlook the aspect of the Magneto ignition. I did consider it but ruled it out because of the presence of both a battery and an ignition capacitor. However these were assumptions on my part and you know what they say about 'assumptions'.

Regards,

DougRH (< 8)

Thanks, Doug.

I note that others also referenced the various interlocks -- some of which can be almost infuriating. Perhaps the original poster will return to clarify what he meant: No engine rotation at all? Too slow rotation? Rotation but no start? Coughing, sputtering? No presence of spark at the plug?

As this is a new tractor remember you have to be sitting on the seat in neutral with the clutch depressed. My small riding mower shuts off power to the solenoid with these safety relays. This would make think you have a bad battery.

And the blade(s) must be disengaged. Mine also has a switch connected to the reverse on the transmission. If you try backing up with the blades engaged it kills the motor. That is very annoying unless you know which wire to remove and tape off.

I got sick of the short battery life with my ride on mower (lawn tractor), so finally fitted a car battery. No problems since.

dont have the car running or you will fry altenater and or regulator on mower from 65 amp altenater from car to 3 to 16 amp alt in mower