A battery wives' tale?

notjustair

Well-known Member
I'm having some battery issues around the farm (because it has been a whole three weeks since something around here needed a battery) and it got me to thinking.

Growing up if a key was left on and the battery was completely flat on a tractor grandpa would say that it was too dead to charge. We never jumped something unless it needed just a little boost. If it was really low he was convinced that if we jumped it the charging system would not charge it up. We always put those on the charger overnight.

Is there any truth to this? I'm thinking maybe it was partially true back then because everything had a generator and regulator. Is there a situation where the regulator would not turn on the current due to the lack of voltage? With an alternator you need an exciter, but the jumping battery would give you that.

I still follow that rule of thumb but these days I do it because I think it is hard on the generator or alternator to have to put out that much juice. I just use the charger.

So, was grandpa right?
 
some of the older battery types, mantence required styles wont charge back up sometimes, modern batteries are made some different, its not that it wont charge unless it has a dead cell or a direct short, but what happens is a charging system is made to top a battery off, and maintain it, its not built to charge up a totally dead one and there is a real chance of ruining the generator, alternator, regulator ect from too much demand of it over too long a period of time, ive personaly burned up a alternator on my 83 chevy this way , i put a dead battery in it off one of my tractors, let the truck roll down a hill and dumped the clutch to start it and promptly drove it on the hiway for 30 minutes to charge it, alternater overheated internally and i had to buy a battery and a alternator, fortunatly not bad on my old stuff
 
An alternator needs some battery to work, it is better to charge the battery first.
 
Discharging a battery completely reduces its useful life but a fully discharged battery can usually be recharged if it has not been left fully discharged very long.

Dean
 
Having the vehicle's electrical system charge a completely dead battery is tough on the system and even harder on the battery. The typical alternator will be charging a dead battery at rates up to 50 amps or more which can generate a lot of heat. The resulting fast charge will shorten the battery's life.
 
A generator does not need any electricity to get it to charge. It has residual magnetism in its fields and armature. It will charge the battery back up but not as fast as an alternator would. An alternator will charge at a much lower rpm than a generator will. The armature in a generator was built to turn only so fast and is wound differently than an alternator. A generator can loose it's windings on the armature if it's spun too fast due to centrifugal force. The spinning rotor in an alternator isn't as likely to throw its winding so they can spin faster.
 
This speed difference in which each spin is evident of the size of pulleys used on generators versus alternators.
 
The electronic battery chargers we have today are much better at reviving a totally flat battery. The battery is still not gonna like it, but at that point there's nothing to loose.
 
My beliefs:

I always charge up batteries mid winter so they do not go flat. A battery will freeze and brake if it goes flat in the winter, it will have a very short life if clear flat otherwise. I will charge them back up and treat with caution.

I have portable tool batteries that are 5 and 6 years old. I always run them flat then charge them back fully.
 
Grandpa was wrong. The generator or alternator [b:e1f69336b8]will[/b:e1f69336b8]charge em back up but as was stated by other at a very fast rate generating heat inside the battery and causing the charging component to work hard possibly shorting it's life. But what he taught you is the best way to deal with a flat battery. Much better to slow charge a battery and keep it cool and much easier on a tractor or vehicles charging system. So grandpa was wrong....in a good way.

Rick
 
It is common for a lead calcium (maintenance free)battery that is fully discharged, require a higher voltage to begin taking a charge. So, if the regulated voltage of the vehicle is lower than that required voltage to take a charge the vehicle will not charge it. This was demonstrated to us at service schools years ago. A regular lead antimony battery will usually not have this problem unless it has remained fully discharged for several days to the point of sulfating. So, grandpa was correct up to a point.
 
Check out the amperage output on you alternator if it's a 30 amp then give battery a little boost if it up around 80 amp don't worry it bring your battery right up.
Walt
Ps generators are usually very low amperage and not made to bring a battery back from the dead.
Walt
 

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