is a once DEAD battery always going to tax alt?

[dosmastr]

I heard somplace that if you kill a battery DEAD, it damages it in a way that the alternator will always be running at 100% trying to recharge it — even if its charged enough to seem fine.

I do have evidence, I killed 3 alternators with no idea how, and when I replaced the battery, the 4th alternator was good to go.

can I just trickle charge this thing tomorrow and be fine or should I just go fork out the 75 bucks to be 100% sure im good?

fyi, battery in question even passed a load test

Topic

[Jhowe93]

you might be getting the wrong alternator or the battery is too big. some cars had the alternators switched halfway into a production year. for instance my truck has a 90 watt alt, but halfway through the year the switched them to 60 watts.

[dreamer2355]

If you understand the what happens to the battery from a chemical standpoint, you will see why it is not a good idea to completely drain a conventional or maintenance free battery, unless its a gell cell setup or deep cycle.

I would try to trickle charge the battery at 2 amps.

Some auto parts stores can also charge batteries for you for free if needed.

[Matt]

I had a battery in an older s-10 with a LED as a fake alarm system. I kept having to jump the truck to move it, because it sat for months at a time. I pulled it to throw on a cheapy Harbor Freight charger. The charger wouldn’t even engage, and said the battery was toast. I put a meter on it, and it was reading 5v. I put it back in the truck, jumped it again (took awhile), then threw it right back on the charger after the truck had run for awhile. I let it sit on the charger for about a week before I got back to it. (Slow charge, like 2 amps). Threw it back in the truck and worked great while I was in the process of selling it. A slow trickle charge like that or a ‘desulfinating’ charger will often revive batteries that are deemed waste.

[college man]

the problem with running a dead battery is that it over works the alternator. as posted above you can try to slowly recharge it. see if it will take a
charge. good luck and keep us posted.

[commoncoder]

No. A dead battery does not over work the alternator. A shorted battery will kill the alternator but the fuse will not let that happen.

Maybe I can help you in understanding the back end. All batteries and alternators have something called “the internal resistance”. When you buy a brand new battery, its internal resistance is very low. Over time the chemicals in the battery degrade due to normal usage and its internal resistance increases. The alternator doesn’t suffer this way as its internal resistor stays about the same. With that said, here is simple equation you should try to understand. Voltage = Current x Resistance.

Look at this diagram.

So in conclusion, no harm to the alternator. The alternator was supplying 6.5 Amps to charge a new battery in this example and it was supplying only 1.18 Amps to the old battery, thus this is why your old battery is dead. The alternator feels great since its working less.

[EricTheCarGuy]

You should NEVER try and recharge a flat battery with the alternator, if you have an alternator issue and need to replace the alternator recharge the battery with an external charger while you install the new alternator. What happens when you try to recharge it with the alternator is that you overheat the diodes in the regulator and burn it out. Despite what commoncoder stated in the above post I get my information directly from alternator remanufactures as well as my experience with these situations (and now yours). Alternators and most automotive electrical components for that matter are designed to run within specific parameters and if you go outside of those parameters (like when you overtax the alternator beyond it’s limits for too long) then that part is most likely going to fail as a result.

[commoncoder]

Eric, you are right. If you jump start a car that has a dead battery, the alternator components can be damaged due to overloading. When you have a good battery and you crank the engine, the battery drains a little, but the alternator recharges it. If you put a big load on the electrical system, the alternator can’t handle it so in that instant of time, the battery provides the extra current necessary to keep up the demand, then the alternator recharges it again.

If you ever have a dead battery and you get a jump from a friend, you may not be able to still drive it even though the engine is running, the moment you demand more current then the alternator can supply, you will do what eric says, overheat and destroy your alternator or simply your car might just shut off to protect the alternator. I know this because I helped a friend understand why his truck kept shutting off even after he got a jump. He turned on his headlights pulled onto the street, stepped on his breaks and the car shutoff. At that moment he needed a good battery to kick in the extra current demand, he didn’t have any, alternator said, I don’t have any but I will die trying….the car computer said no please I don’t need you to die…let me tell the owner something is wrong by turning off the car…HAHAHHA.

[Trcustoms719]

A big +1 on Erics post!
I’ve seen so many people with dead batterys let their cars run to try and recharge the battery after a jump,
had one lady do it a few times when she had a parasitic draw and she trashed her alternator.

[Author]

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