General battery/charging question

[Bonnewagon]

My neighbor went away for a couple of months and neglected to have someone start his car so the 4-5 year old battery was stone cold dead on his return. A jump wouldn't do it so I offered to charge it. It needed water as well so I figured at minimum an overnight charge. After a couple of hours it was not even half charged but a storm was coming so I said lets try jumping again so we can get it off the street. That got it started and he went to fill it with gas and I said not to shut it off for fear it wouldn't start again. He was gone maybe 15 minutes and when I went to recharge it, the meter read fully charged. Stopped and started it several times and the meter jumped right back to fully charged each time. I was floored. 15 minutes of alternator charging, with the headlights on? Unbelievable! This was like an early 2000-2001 or so Nissan Maxima I think. I know modern alternators are way superior to our old junk but DAMN! Is this normal?

 

[454muscle]

It might have been a connection issue.

Both ground straps are needed in good condition to start the car. Now, if one or both of them are corroded, and many do, the plastic jacket can wear off and expose the metal which over time can cause some rust and reduced current flow, enough to the point it won't start, but with a boost it would start due to the extra voltage.

So it may not have been fully discharged...

 

[Bonnewagon]

Oh no, it was dead. All connections were good, but nothing worked. Not lights, horn, wipers, nothing. Dead. It had caps so I filled the cells with distilled water and used a soap solution with baking soda to wash the acid and dirt from the terminals and case. When I got it partially charged things began working and the motor even cranked just on battery power. But it took the jump to get it to fire up, and I always put the ground clamps on good engine grounds, not the battery terminals. When it did fire, it smoked and shook a bit, then smoothed out and ran great. At that point the charger read just under 1/2, then 15 minutes later, full charge. I know that chargers limit the amps so as not to harm the battery, and that an alternator will commit suicide trying to charge a battery with a poor circuit which the alternator will interpret as a dead battery. But 15 minutes? Today he came by to thank me again, and said it ran fine even in all day rain with the lights, wipers, and heater on.

 

[454muscle]

Damn, that's crazy. Stumped.

 

[Pontiac455]

The max amp the charger puts is prob 8-20, depending on what u had it set at. The alt will pile the amps to a dead battery. Reason why it went with a boost is because yer alt was drivin the amperage to er like a New York wh*re.

 

[bill]

Good alternators will eventually charge up low volt batteries.. and if the battery is in good condition, even though its old, it will produce amps. Its not easy to fully grasp the whole battery/alternator relationship, and I sometimes have troubles with it from time to time when I see something that doesnt make a lot of sense at work. But, from what I have been told and trained about batteries and alternators, especially newer ones, is that the battery must have good levels of distilled water to prevent shortages and boilovers. And, if theres voltage, there can be amps...but not the other way around. Batteries that dont have over 12.5volts must be charged up before a good test can be performed because they are in a state of discharge and, if, after charging for a while, it will not hold that voltage under a load, it will not last very long. Good batteries, even though they may have very little voltage, will make amps when recharged. However, a battery with voltage, but a dead cell, will not hold charge or produce good amps, no matter how much you charge it or how often. What tends to burn up an alternator is when its trying to charge a dead battery that has very little voltage at all or a battery that will not hold a charge. Most old fashioned chargers were great at quick charging a battery, but they were likely to overcharge batteries too if left on too long. Newer chargers are usually automatic and those will never overcharge a battery. Many times in my line of work, Starters, bad cables, and bad terminals are to blame for a no start, hard start issue. Often, the battery is weak from trying to start a car with a bad starter. Or its dead from a bad alternator or bad wires. I always tell people when they buy a battery from me....its only gonna be as good as the other parts of the car that its relying on or working with...... :wink:

 

[Bonnewagon]

The guy was trying to jump it before I stepped in. The battery was so dead that it was draining the donor car, and all he could get out of it was a faint click. That's why I offered to charge it and when I saw the water low I knew it would be a long time charging after I topped it off. Bill I'm right with you on that. "Good alternators will eventually charge up low volt batteries." Key word is eventually. That's why I am amazed that after he ran to get gas and back, it was fully charged. All I can figure is that after the battery was charged enough to run the car, the alternator went nuclear to roast the battery, and being healthy it responded because as 454muscle said, "yer alt was drivin the amperage to er like a New York wh*re." Then I used one of these on her and it checked out that all was well like nothing was ever wrong.