I've been jump starting my little snapper rear engine rider/14.5 hP briggs lately off a car. Pull it out of the shed and roll it back beside the car.

Until I get time to go shopping for a battery that's hopefully less than the one I hesitated buying at $45.

QUOTE: "Someone tried to tell me the 12volt in the tractor would get screwed up because of the stronger 12volt in the vehicle"

That "someone" is full of BS (no offence intended).
12V is 12V.... incidentally, the truly correct way to say it is: 13.8V is 13.8V

I remember when Kevin Beitz used to post here. He not only jumped off his lawn tractor.....but also had to jump off his big Kubota a time or two.

WAIT!!! ...what's this about batteries?

No more or less of a problem than jumping a car.

Be aware that most cars that use an electronic regulator recommend against jumping, and the same thing will be true of most tractors. Odds are it will be fine, but it will NOT be covered under the warranty.

It has been decades since the car companies started putting this warning on vehicles, and I have yet to see one blow up.

One caution. Since the car alternator puts out more than a tractor alternator, don't leave the jumper cables left for an hour or you *could* over charge the tractor battery. Not too much of a worry, but that is the biggest caution.

You will not overcharge it. The alternator in the donor vehicle is self regulating to the voltage level in the electrical system. When you connect a donor vehicle to a dead or weak battery (using booster cables), the dead or weak battery then becomes a component part of the donor vehicle's charging system. The moment you make your last connection with the booster cable, the voltage level in the now combined electrical system drops (because the dead battery draws power from the donor battery). The voltage regulator in the donor alternator detects this voltage drop and adjust the alternator to increase it's output current (amperage) to make up for the deficit. As the increased current recharges BOTH batteries, the system voltage will rise. The regulator then adjusts output to a lower value as the electrical system returns to it's ideal voltage of 14.2.

Okay, thanks guys. I kind of thought it was a non-issue, so to speak. I was trying to jump it off the other day and heard low-toned pop. Have no idea which vehicle or battery it came from but I'm still trying to work through ignition problems with this tractor, so I thought maybe I screwed something up after that comment.

Still won't start (haven't checked the new battery charge yet), so maybe it's the soleniod or starter...already changed the spark plug. I have another tractor to use. I'm kind of engine testing illiterate, so it may take a while unless I can get my BIL to help.

The 2 most critical issues about jump starting are: (1) Make certain that you have correctly identified the polarity of all 4 battery terminal posts (2 on the dead & 2 on the good) and always connect Positive to Positive and Negative to Negative. Hooking any other way will almost always damage one or both alterntors and potentially explode a battery. (2)When jump starting, you should always connect the Positive booster cable to both batteries FIRST. Next, connect the Negative booster cable to the Negative post of the dead battery. Last, connect the other end of the Negative booster cable to a good, solid, unpainted ground (metal) on the engine of the donor vehicle. This last connection will be the one that causes a spark and you DO NOT want to make a spark near a battery. (explosion hazard). After the dead vehicle starts (or refuses to) unhook the Negative booster cable from the ground surface on the donor vehicle first (same reason..sparky). Then unhook the Negative booster cable from the boosted vehicle. Last, unhook your 2 Positive cables in any order. Exception to this procedure is: If you have a set of "Safety" booster cables that plug together in midspan, you can hook the cables to the battery posts on both vehicles BEFORE connecting the 2 halves of the set together. After the boost, separate the 2 halves of the set BEFORE disconnecting the cables from the batteries. If you take a moment to put some safety goggles over your eyes you'll be glad you did if ever a battery explodes near you. Battery explosions are relatively rare but still occur often enough that you need to be protected just in case.

12V is 12V, but if the dead battery is internally shorted, it may be 0V.

Thanks for the indepth, mownie. Always good to know proper procedure. I knew most of that from growing up, but some of the sequence I've been faulty at not following.

I'll do ya one better. I have jumped my truck, off the lawn tractor. My son even took the battery out of the lawn tractor and put it in his Ford F150 300 cid inline efi, and used it for about a week.

I would remind everyone that running on dead battery overworks alternator it over heats the stator and burn up. A battery should charge up after cranking and give the stator a break to cool. You slowly bake stator trying to charge a battery with one dead cell two dead cells and engine heat on stator if don't fry stator you loose the ampere output of alternator to lesser degree results are new battery want last as long battery shelf life is 9 months so buy ones closes to delivery truck as possible batterys have month and year date on them when put in stock.

A truly 'dead' battery is much easier on the alternator than a good battery which is just deeply discharged - The alternator will have to put lots and lots of amps into the discharged battery, while the 'dead' battery won't accept a charge, so it puts very little load on the alternator

Worst case for the alternator is a discharged battery and then having all the accessories (blade clutch, lights, etc) turned on - Your alternator will never be working harder than it is then . . . . a 'dead' battery is very easy on it by comparison

Don

I had an old Murray and usually put cheapo WalMart batteries in as replacements. When they started to die and before I got a new battery, I always used my car to jump start it. As the other posts said, 12v (or 13.8v) is 12v. Once when the battery cable to the starter solenoid ended up badly corroded from a bad battery, I was able to jump start the tractor by putting the jumper cable on the solenoid post where the battery cable is attached and successfully jumped it without any damage.

I'm gonna have to test my ignition system or have someone do it and let me watch. I have the instructions to check-test the battery, the solenoid and the starter, but don't feel really comfortable sticking something here and there.

Just so I could eliminate it, I put a slow charge on it and it still wouldn't start. I get a couple of errrr...errrr's, but then nothing. I think it's either the solenoid or starter but can't prove it yet.

I don't have a trailer, but I may get my BIL's truck to transport to the local repair shop if he can't figure it out either.

You don't say WHAT you are trying to start, but many engines have an automatic compression release on them.
IF the valve lash is too excessive, the ACR doesn't engage.

Also, why not just remove the battery and get it tested?

bill_kapaun - I will, but haven't had time because of work.

I do have a multi-testor that I got as a gift. Looks like a cheapo, but I wonder if I could test this battery with this testor? It's a Cen-Tech multimeter #90899. Is anyone familiar with this model? This thing seems to read in ohms and amps, so I'm back in left field again. Damn shame to be a dumass at my age with so many simple things.

Just a few comments to supplement the good info already provided....

Mownie - it is possible to overcharge the battery... not in terms of charging it to a voltage that's over the limit, but the "rate of charge". A car alternator is capable of producing a lot more current than what a small tractor battery can safely absorb as charge. If the charge-current is too high, you can damage the battery by heating it up and even boiling it in the extreme circumstances. It's OK to do it momentarily, and particularly when the battery in question is in good shape - it will accept charge easier (ie less heat generated) than a half dead battery.

don21 - a battery can be dead by 2 means... open circuit or short circuit / shorted cell. When the battery is open circuit, then yes - the alternator will not work as hard, but in many "very simple" regulators (such as a lawn tractor), the battery is necessary to create a load - to stabilize the regulator - otherwise you can get some wild voltage swings... When the battery is dead by means of short circuit - that's really bad... in fact, if only 1 cell is shorted, you create stress, but when the whole battery is shorted, you will fry the alternator (diodes) in a very short time.... unless there is a fuse. Again, that is because lawn tractor alternators do not generally have a current limit function like your car.

One last comment: whenever boosting a dead battery, make sure that the vehicle with the "good" battery is NOT running at the time... reason is that the starter can draw 100's of Amps at starting, and that stresses the crap out of any alternator.... hook up the cables, let the dead battery get a bit of charge for 5 minutes, at elevated donor-vehicle RPM, and then shut off the donor vehicle and with the cable still connected, try to start the dead one....

I agree that too high a charge rate will damage a battery, but remember, when "jump starting", the dead or weak battery becomes an integral part of the donor vehicle's charging system for as long as the booster cables remain connected. If you are jumping a small battery from a larger vehicle, the low voltage condition of the small battery is mitigated by the higher voltage of the good battery in the donor vehicle (relatively higher because it is near full charge). With this factor in play, the total voltage value in this 2 battery system will be something higher than the small, "dead or weak" battery alone, and something lower than the larger, fully charged battery alone. A GREATER difference in size between the small weak battery and the large charged battery will result in less of a VOLTAGE DROP when the 2 batteries are connected together. So the alternator in the larger donor vehicle will not react and begin charging at max output. From a practical stand on the topic of jump starting a lawn tractor (or any equip of comparable size) from a much larger donor vehicle, it is hardly necessary to have the donor engine running at all, just to get the smaller vehicle cranked. A note here as to charge rates on lawn & garden sized batteries. 10 amp is about the MAXIMUM charge rate these batteries should be subjected to. You should not charge this size battery for longer than a few hours at the 10 amp rate. If you want to "slow charge" (preferred) one of these batteries, a rate of 2 to 3 amp for 2 weeks or longer is needed. Battery chargers that "cut back" or "cut off" when the battery reaches full charge are the best way to prevent "over charging" a battery. If you don't have a self regulating battery charger you need to check the votage of the battery often during the charging (turn off and disconnect charger from battery to measure voltage). The nearer to 13.2 volts that you can get the battery charged to (for a 12V system), the better. If you don't trust your short term memory (and who can?) with numbers, keep a charging "log" note pad nearby and record the voltage when you begin charging. If you are charging at a 10 amp rate, check the voltage every hour or so, if at the 2 to 3 amp rate, check it every day or so. When the battery reaches 13.2 (or refuses to after much time on charge), Remove and store the charger. At this point, you could have the battery load tested (with the appropriate sized tester and the correct procedure) or you can just let the battery sit (don't connect the vehicle's battery cables for this evaluation period) and begin measuring the voltage drop of the battery over a period of time. You need to record the voltage loss or drop just as you did with the charging. If your battery got close to 13.2 but refused to reach that high (say it got to 12.8 or so), your battery is likely showing it's age and useage. Record the battery voltage immediately after charging and again the next day. If your next day reading is less than 11 volts, your battery is shot. In fact, if a battery drops to 11 volts within 2 weeks after being fully charged, it's a goner. If your battery loses less than a tenth of a volt (o.1 V) in a week, it is in excellent shape. Always leave the battery cables disconnected for this kind of test because your vehicle MIGHT have a "parastic drain" on the battery. Parasitic drain can be caused by anything that draws current out of the battery while the vehicle is off. Ignition switches, or any other switch that can operate a device with the ignition turned off, can potentially cause parasitic drain (especially if these switches have internal corrosion from repeated exposure to moisture). The topic of parasitic drain could well justify a new thread because of all the diverse ways it can occur.

Oh, you're right...I didn't mention the tractor. It's a 2002(?) Murray Select #4250000x8A, 16.5hp Briggs I/C OHV Engine, 42" cut. It's the one that came with the little cart from HD. Oddly enough, it has a really nice cut and I like to use it for it's lightness and turning.

Mownie,

You're right, but you missed my point. Assuming that you can cause no harm to a weak / discharged battery, by connecting it to a large alternator / battery combination is wrong.

Yes I know that the weak battery gets inserted into the (larger) circuit of the donor vehicle.... but that does not help in the scenario I am referring to....

If the small tractor battery is discharged, it will draw whatever current from the source - the only limit will be the battery ESR and the resistance between the current source (donor vehicle's system) and the dead-battery's terminals. Typically, both resistance values are much lower than what is necessary for a safe charge-rate control.

When you hook up your dead battery to a fresh battery and an alternator (in your truck for example), the alternator may not be supplying the high current because the voltage drop created by the dead battery on the system, is insufficient to turn the alternator to full steam... however, the dead battery will still draw the current from your larger truck battery, which is capable of supplying way more amps than what the dead battery can handle. So... either the alternator, or the truck battery will source potentially 100's of amps into your dead battery.... wanna know what happens next?... it's about the same as short circuiting that same tractor battery when it's fully charged (ESR is ESR).... I wouldn't recommend trying it.....

A small tractor battery may be able to handle a boost when it's not fully drained... because the charge current the battery will draw is a function of existing charge, so if the battery charge is not zero, the the charging voltage is much lower than 13.8V, therefore the max current draw is lower. But if the tractor battery is nearly totally dead, or short-circuited, then look out!

9 times out of 10, the few minutes it takes to boost a battery will not cause any harm... so for pratical intents and purposes, it's OK... however, there is always a risk.... and althouhg rare, if the dead battery is outright shorted, just putting the booster cables on, will blow a really nice hole in your cable clamps..... if one does not know how to determine if a battery is right shorted, or totally discharged, then it's better to play it safe.

"I do have a multi-testor that I got as a gift. Looks like a cheapo, but I wonder if I could test this battery with this testor?"

You can't do a load test, so you can't really prove a battery is good.
However, if after charging, the battery falls below about 12.6V, you can assume it's bad.
If it's the original battery, it's EXTREMELY suspect. After a couple years, batteries start getting "suspect" in L&G equipment.

Wally, you are correct in pointing out that any large donor system "charging" a smaller battery can have detrimental effects on the small battery. And even though I myself have been pretty windy (and strayed from the topic of the thread) we need to accept that "charging" and "jumping off" are 2 different things (and not interchangable either) If you have a dead battery, it would be preferable to charge it up at the appropriate rate instead of jump starting......but so long as we keep suddenly finding a battery has become discharged, we humans will continue to use the jump start, we just need to use what we learn, to keep us on the safe side when these unplanned set-backs occur. And I will reiterate that it is hardly necessary to run the engine at all when boosting a small battery from a much larger battery. Your point of "wrong to connect a small battery to a large system" is well taken and I agree. Boosting or jumping should be done conservatively and carefully.

agreed... in fact, to add to your comment of "not needing to run the engine" when jump starting... in fact, it's not a good idea to run your engine when boosting, because of what I said earlier - the draw of the starter can overload and fry the alternator... always shut off the engine on the donor car, before turning the key on the vehicle that is being boosted....

HANDSHAKE !

Strange thing about amps. Amps aren't forced or pushed in a circuit. They are drawn and no matter how many amps are available a circuit will only draw the amps it requires. I'm talking about a working circuit. A dead short will draw as many amps as your have available but it won't work.

U've all gotten some good tips on jump starting and charging system function here.. Now heres some info on avoiding most of this stuff to start with... All of us that have been around these mowing tractors for any length of time know that the batteries that they come with, and for the most part the replacements too R pure junk, an at
premium prices too...I've never seen one last more than 1 1/2 - 2 years yet... After the original battery in my GT died after the first season, I found there was room enough for, after a few minor mods, a group 24 car battery... I ran car batteries in the GT for about 25 years after that, getting an average about 5 years out of a decent one, so for 50% more in initial cost, I was getting 2 1/2 to 3 times the life span out of them... About 10 years ago I had the oportunity to pick up a big gel-cell for a good price when I needed a new battery for the GT, so I bought the thing, it was a YUASA NP 38-12, (12V-38AH), an installed it, the in service date on that battery was 3-98... Its STILL in there, over 9 years later.... I was initially concerned whether it would stand the vibration generated by the big old one lunger, but that hasn't been a problem... One this size is too big to fit into most of these things, but they do make an NP 26-12 that is about the same size as Ur average small tractor battery and should drop right into most of them... The bad news is that batteries of this quality AIN'T cheap... However in the long run it'll be a whole lot cheaper than the 4 or 5 crappy replacements that U'll spend $40-50 apiece on over the same time span... I'm currently running a fairly new ZTR with the original battery thats now a year old, an U can bet-Ur-bippy on what I'm gonna replace it with this fall, if it even lasts that long...
Paul R...

Strange thing about amperes is that they ARE pushed through a circuit and it is the voltage potential of the system that accomplishes the pushing. "Amp draw" is a term that describes how much current a device will use or consume but in no way does that imply that amps are drawn or pulled solely by the device using the flow of electrons. An analogy is to compare the flow of electrons in circuits to the flow of water in pipes. If you want to flow a greater amount of water from point A to point B through a pipe system, you can accomplish that in 2 ways (or a combination of the 2). You can increase the pressure pushing the water and leave the pipe size the same and you will flow more water. Or you can increase the diameter of the pipe and leave the pressure the same and you will flow more water. Or you can increase the pipe diameter AND the pressure, and you will flow more water. The analogy here is voltage potential equates to water pressure. Pipe diameter equates to circuit conductor diameter. If you increase the system voltage potential, you can PUSH more amperes through a conductor of the same diameter. Or you can use larger, heavier conductors and push more amperes at the same voltage. This is precisely why the automotive industry decided to go to a 12V standard years ago. With the 6V systems that were in use prior to the advent of the 12V standard, all the components (starters, generators, other motors) had to be much bigger because the internal windings had to be larger diameter to allow enough amps to flow with only 6V potential pushing. All the wiring on these vehicles was bigger and heavier too for the same reason. Another benefit of using higher voltage potential is the fact that the higher voltage systems are less affected by corrosion in connections. Reason: The higher voltage can push or bludgeon it's way right through minor resistance where a lower voltage system would develope an "open circuit" at the point of resistance. On the other side of the coin, consider the military electrical standard of 24 V or 36V in some cases. This standard allows equipment to use smaller and lighter wiring and components while minimizing potential problems from dirt and corrosion, particularly beneficial to aircraft. To finish this analogy, consider that voltage is to an electrical circuit what a pump is to a pipe system. You arrange the pump to PUSH water through the system because it is most efficient to do that instead of trying to suction or draw the water. You can only lift water by suction a few feet, but you can force it up to great heights under pressure. It's the same with amps. You can't draw them or attract them to flow in a circuit, you have to push them along with voltage to get them to do any work. The term "amp draw" really refers to the amount of current that is required to operate a device (or that the device will use) under it's normal design voltage. If the system voltage drops, then the "amp draw" will increase, and catastrophic overheating of the entire circuit will result. One thing you can always count on. Electrical theory will always "spark" a debate.

Just can't help myself:-)

There's no sense beating a dead horse- but if you've reached the point where you even seriously consider that abusing a dead animal might improve your lot in life, I say go ahead and give it a shot. --Anthony Myers

Remind me to phrase my question just a little differently next time. I think I understand what I was trying to find out, but the rest just flew by...pretty dry to. :)

I wrote:
"One caution. Since the car alternator puts out more than a tractor alternator, don't leave the jumper cables left for an hour or you *could* over charge the tractor battery. Not too much of a worry, but that is the biggest caution."

I guess my qualification counts as "charging" so we are all in agreement. And I think we agree its not a usual consideration, mainly a theoretical. Also the term "overcharge" is perhaps a bit misleading in this case since we are talking about over current during charging, not the charging end point.

SHAKE

SHAKE

Boostpacks are super handy for dead lawnmowers. At the farm we've got an old White mower with a bad solenoid. No problem, hook the negative on the boostpack to ground on the mower and touch the positve to the hot lug on the starter. Starts it right up every time. Bungee the boostpack to the back of the seat so its handy if the mower stalls.