View Full Version : O/T Tractor Battery Problem, electrons disappearing

07-04-2010, 09:14 AM
I may have missed "electric 101" somewhere along the line. I have this on-going problem with my old farmall tractor for years. The battery goes dead all by itself. It was orig 6 volt positive ground and had the problem. I thought it was because the generator was not producing enuf current to keep it charged. A couple years ago I converted it to 12 volts positive ground and installed a single wire alternator / regulator on it. I also installed a knife switch right on the top of the neg. terminal of the battery. I have a new battery in it, and it still goes dead.

I have not noticed any spark of any kind when I open and close the knife switch and when I put the 30 amp charger on the battery it is able to start in a very short time.

There is front and rear lights on the tractor that have the original switch that functions as its should and I have looked at the exterior wiring and lookedfor anything that would lead me to believe there may be an issue . nothing visible.

How can a disconnected battery discharge itself with the negative terminal totally removed from the circuit ? where the he!! could this thing be leaking ? or have all 5 or 6 of my new batterys over the years, been bad ?

07-04-2010, 09:35 AM
Assuming your knife switch fully disconnects the battery from the electrical system, lead acid batteries will self discharge with time (weeks to months). When not in use, it's best to keep a trickle charger on the battery (IE: Battery Tender brand). It will save you lots of batteries (and grief) in the end.

That being said, contaminants on the battery surface can also provide a discharge path for the battery.


07-04-2010, 10:18 AM
If you live in an area where there is humidity and changes in temperature that would cause the battery to "sweat" giving a water film to discharge the battery over time. Dust on the battery would help as well. Obviously if you disconnect the battery then there is some other thing going on. I find I must start my rigs once a month and get them warm enough to drive off moisture, usually 1 hr. Removing the battery and keeping it in a warm dry location would be one solution. I remember seeing batteries on top of a chunk of wood to keep them off concrete floors, I don't remember the reason.

Deja Vu
07-04-2010, 10:33 AM
I remember seeing batteries on top of a chunk of wood to keep them off concrete floors, I don't remember the reason.
That was mainly for preventing acids from the battery (should it let some out) getting into the concrete and disintegrating it.

07-04-2010, 11:36 AM
Long ago, batteries has cases made of something other than impermeable plastic. Leaving them on a concrete floor allowed them to absorb moisture from the concrete, which caused current to leak through the case between the cells.

I'd say your problem is a combination of dust and moisture on top of the battery. How long are you going between uses/charging?

07-04-2010, 11:54 AM
I think the problem is two fold

One, battery self discharge/water discharge/whatever..

Two: you are never properly charging the battery in the first place, leaving it with only a tiny amount of power to discharge before its dead again.

Lead acids can NOT be charged in an hour, Let alone the 15 mins that most people seem to think there alternator/battery charger can charge it, even if it happens to be able to start the motor at that point, its not nearly charged.

for a typical lead acid it takes at LEAST 2 hours to get a decent charge (75%) and up to 8 hours to charge the last 25%. Could be even longer depending on the charger. If its an automatic float charger id leave it on there 24 hours to charge it up.

Furthermore, if you leave a lead acid in the discharged state, it quickly will ruin the battery. If its been a year at a low charge state, it might allready be down to as little as 20% of its total rated capacity, And may of grown partial shorts in cells that can discharge a cell in hours. (1 cell discharged = whole battery seems dead), Or cells may of fallen apart internaly.

Some chargers overcharge batterys too. Iv seen batterys RUINED by being left on supposidly 'Automatic' chargers for a week. Not a drop of electrolyte left in the battery. a proper charger should drop to 13.6~13.8v once fully charged. Infact its safe to fully charge a battery by only using 13.8v (Takes 24+ hours however. Aka a 'trickle' charger, these types of chargers can be *left* attached for months.

Note, a trickle charger will output less then 13.8v when first connected due to the battery loading it. But it should eventualy hit 13.6 to 13.8v and stop rising.

J Tiers
07-04-2010, 02:14 PM
Quite possibly BM is correct......

But how LONG does it take? Many starting batteries will go dead in a few months..... they are NOT for "storage" but only for "starting", the maximum plate area, and so current capacity, in a small box. Leakage is larger than for a quality battery.

I suspect that your charging circuit is really DISCHARGING the battery, charging it to 11 or 12 V instead of 14+.

You start with a nearly dead battery, and it doesn't get better with time. It may be sitting there at 25% of capacity state of charge, or LESS.

Fix the charging circuit.

BTW, a start takes little out of the battery...... most are maybe 60 AH..... So a "long" crank of 10 seconds before starting, at 600A (rare, unless diesel, or very cold) actually amounts to less than 2 ampere hours of discharge..... leaving a fully charged battery at 97%+ charge state.

if you are "resting" at 20% state of charge due to low charge voltage, that start, if it were even possible, would take you down about 20% on the existing stored ampere hours........to around 16% remaining.

Long storage will also drain them pretty dead from a starting point of 20% charge.

Your Old Dog
07-04-2010, 02:52 PM
Dog's suggestion would be to keep the top of the battery free from oil and sludge. I've measured 6 volts from one end of the battery to the other without touching the lead post but just thru the grease. I wet the top, sprinkled Arm and Hammer Baking Soda, letting it foam and then rinsing it off with the hose.

I'd also go to NAPA and buy a battery tender for about $30.00 and keep it plugged in. The tender samples the battery every 5 minutes or so and gives it a light charge when it see's it's needed. My ATV isn't used enough to keep the battery charged and then I have all the power drawn by the electric plow. The tender is the answer.

Mine looks pretty much like this. It is hermetically sealed with short leads. Mine all (I have 3) came from NAPA Auto parts store.


The Artful Bodger
07-04-2010, 04:57 PM
If a lead acid battery is left discharged, or in a low state of charge for long it forms quite hard sulphate deposits on the plates which stop the battery from working, officially such a battery is really past practical use.

However, there are various battery 'zappers' that give the battery tiny high voltage zaps over a period of days, weeks or months and these can restore some life to an old or otherwise sulphated battery.

We had various tractors, Fordson, Massey Harris etc, on our farm that we did not bother to keep batteries in as if the engine is in good tune and you can crank start the battery does not provide much benifit. Diesels are a different issue though!

07-04-2010, 05:07 PM
How old is the battery? As batteries get older they tend to flake off plates, when the sediment gets high enough it will short out the plates causing the battery to go dead by itself. My tractor sits all winter with the battery disconnected from nov till april and always starts. Question #2, Why did you go pos ground? I converted an 8N to neg ground and used a 12V GM int reg alt (1975 to about 1980) with a 1 wire setup, just had to rev the engine a little to energize it. Seems to me a 12V pos grd alt would be hard to come by. Jan

07-04-2010, 05:39 PM
2 other things I have learned to check. Check engine running charging voltage at the battery posts. (not cables) A 12v battery should charge at 14.5 v. Also check for terminal corrosion, a little goes a long way toward causing problems.

07-04-2010, 05:46 PM
Like they said, a battery goes dead through slef discharge. Even a brand new battery will go dead in less than 6 months if it's not charged periodically.

My truck was sitting unused for many weeks at a time. The battery was always dead when I needed to use it. I replaced it twice. Disconnecting the battery helped some, but that screwed up other things (like the radio).

A $15 1.5 watt solar battery charger on the dashboard fixed the problem. It made up for the internal drain as well as the drain from the alarm and radio.

It was the best $15 I've spent in a long time.


07-04-2010, 06:05 PM
Well, I've had my problems with smaller lead acid batteries. All were 'starting' batteries meant for motorcycles, lawn tractors, etc. None of the ones I bought lasted more than about six months of non-use. I didn't use a trickle charger or any other maintenance charger.

The original battery in my Land Cruiser was good- it could sit for months and still start the engine. All the replacement batteries I've had couldn't do that. Now I have a marine battery in it, and I can come back after a year and it will still start the engine. Three years, and I have to charge the battery first. Fair enough. I don't even disconnect the terminals-

I've tried to find the smaller sized batteries (to fit the motorcycle for one) in a marine version, or do we call it 'deep discharge' type, but it seems that whatever you can find in the small size is a fake if it's given the 'marine', or 'deep discharge' designation. The one I have in the bike right now was new last year, and I charged it before starting the bike in april. Of course our weather being what it is, I didn't get to ride again for two months. The battery had only enough juice to kick the engine over once, and that was it. The bike sits inside in a heated space.

I seldom use a trickle charger, but maybe it's time I did. Last time I parked the Astro van for several months, the battery kept its charge, but it may not be able to continue to keep a charge for awhile once it gets older. It wouldn't be difficult to put a solar panel on the roof of it, but for the motorcycle that would be more difficult. Where would I put it?

07-04-2010, 06:28 PM
I seldom use a trickle charger, but maybe it's time I did. Last time I parked the Astro van for several months, the battery kept its charge, but it may not be able to continue to keep a charge for awhile once it gets older. It wouldn't be difficult to put a solar panel on the roof of it, but for the motorcycle that would be more difficult. Where would I put it?

On the seat! Its only used when your not riding it :)

Or just on a nearby bench or in a window cill, whatever.

Or just get a trickle charger that plugs in and well, plug it in..

07-04-2010, 07:25 PM
Its too bad modern batteries do not have cell access plugs like they used to, otherwise a S.G. reading should give you an idea what is happening.

07-04-2010, 08:46 PM
'on the seat'- why didn't I think of that- Actually, that gives me an idea- black vinyl formulated to keep itself cool by dissipating heat electrically- :)

Ok, how about making thread that consists of series connected photovoltaic cells- weave enough of that together and you have a fabric to cover the seat with. Make the hookups on a few seams, and wire it to the controller. Careful how you sit-

07-04-2010, 09:19 PM
The next time you install a battery, buy an Optima. I don't know the reasons why, but they don't seem to self-discharge as fast as the flat plate type. We have a modest collection of old cars that don't get driven much. Before we switched to Optimas we were always fighting dead batteries. Now, we don't even bother putting trickle chargers on them. We park the cars in the autumn and next spring the Optimas spin the engines over, just fine.

When my youngest son was in the Coast Guard, at one of his duty stations they were plagued with dead batteries in their emergency equipment. He persuaded his Chief to switch to Optimas and they never had a problem after that.

There's another thing that's very important in old equipment: adequate grounding. Often, the battery is just fine. It's the ground connections that are bad. Rust is a poor conductor of electricity. The ground strap's connection to ground should be bright shiny metal touching bright shiny metal. Anything less and you're screwed. Don't forget the structural parts of the machine; very often they are part of the ground circuit!

The other day SWMBO told me the taillight was burned out on one of my old-timers. Seeing as how both the tail and stoplights were out I first checked to see if there was continuity from the light assembly to the frame. There wasn't. After dismantling everything and abrasive blasting all connecting surfaces, the lights were brighter than they had been in years.

You will be well rewarded by shining up every nut and bolt that holds that old Farmall together, especially the ones on the starter and ground strap.


Mike Burch
07-04-2010, 10:20 PM
Wierd things, lead acid batteries.
To charge a battery fully, you need to get the voltage across the terminals up to around 14.5v. But once it's there, if you keep charging it at that voltage for any length of time, you'll damage it. So a smart charger will allow the voltage to rise to 14.5, hold it there for a little while, and then drop it back to 13.8 volts, at which voltage you can happily charge the battery forever without doing any harm (the so-called float charge).
Unfortunately, most if not all automotive charging systems are not smart – they merely set an upper limit on the voltage the alternator terminals can rise to. Because the car/tractor/truck manufacturer has no control over how long you're going to run the engine, this upper limit will always be 13.8v, so that you can't overcharge the battery.
Alas, at 13.8 volts you will never fully charge the battery – no matter how long you run the alternator, you'll get the battery up to only about 2/3 of its capacity. (Which is why all engine makers specify starter batteries much bigger than would otherwise be needed – they know that the battery will never be more than two-thirds charged.)
Another point to be aware of is that lead-acid batteries are not 100% efficient – they require about 1.4 amp-hours charging for every amp-hour's discharge.
And yes, they self-discharge at about 1% per day when not being used.
Dirt between the terminals is the commonest cause of excess "self"-discharge – it absorbs atmospheric moisture and becomes conductive. Dirty terminals (and not just just those on the battery itself) are the commonest cause of starting and charging problems. Starter motors draw very high currents, and Ohm's Law (Volts = Current x Resistance) tells us that the slightest resistance will therefore cause a correspondingly high voltage drop.
I note that the OP admits that despite his having little knowledge of electricity, he himself converted the tractor from 6 to 12 volts. Auto-didacticism is a wonderful thing, but it might pay him to get his handiwork checked. And I'm very suspicious of the "positive ground" – every alternator I've ever seen has been negative ground, and without some pretty advanced knowledge, they're not at all easy to convert.
"Marine" batteries are usually a compromise between starter batteries (designed to supply high current for a short time) and "deep cycle" batteries (designed to supply modest current for a long time). They are neither fish nor fowl, and really do neither job very well. Deep cycle batteries should not be used for starting, as they will fail sooner than a proper starting battery.