I just had to replace my 3 year old battery (a “72 month battery”) after replacing my alternator. Is it realistic to believe that a bad alternator can destroy an otherwise good battery?
thanks
Yes
Yep.
To elaborate on the above (correct) answers, one way would be that if the alternator is not recharging the battery as it should, the battery will (sooner or later, probably sooner) go completely flat. While some batteries may revive on a full recharge, some may not, There may be other ways for a “bad” alternator to wreck a battery, but I reckon this would be by far the most common.
The natural life of a modern car battery is about 4 years based on normal driving. If you use a car at a greater than normal rate that number goes down. This is without any other factors that affect battery life.
How did you determine the battery had to be replaced. If it was deeply discharged, it may have needed more charge than it received from running the engine for a short time after replacing the alternator. Some newer cars need a nearly full charge to start the car. Changing the alternator would be a good time to clean the corrision from battery terminals and cable clamps. I’ve known people that replaced perfectly good batteries that weren’t charging because of poor conductivity at the connection because of corrosion.
A car battery is several cells of lead and lead oxide plates with an electrolyte of water and sulfuric acid between them. As the battery discharges, both the lead and the lead oxide plate get converted to lead sulfate, and the sulfuric acid gets converted to water. Charge the battery and this reverses.
If the battery is left discharged for too long (like the alternator that charges it isn’t working) then the lead sulfate hardens and turns into hard crystals which insulate the plates and prevent the battery from holding a charge (this is called sulfation of the plates). Normal recharging will not turn these lead sulfate crystals back into lead and lead oxide, so at that point the battery is pretty much shot.
There are ways to remove the sulfation on the plates but simple recharging isn’t going to do it.
How would you remove the sulfation?
I think the common technique to remove sulfation on the plates is to over-charge the battery with a constant current source at a high enough voltage to break down the crystals. The battery will tend to overheat when you do this so it has to be done in conjunction with careful temperature monitoring to make sure you don’t boil the electrolyte.
There are some pulse chargers that claim their high voltage pulses will break down the crystals and remove the sulfation as well, but I’ve read conflicting information about how well they work.
thanks all.
the dead battery was identified by the shop. It is a reputable if expensive shop so that I trust their conclusion. But it is good to have some confirmation.
NO this is not how you break down sulphation. This would however be an excellent way to destroy a battery.
There are two ways to break down sulphation on a car battery. the first is to charge at a very low current for a very long time, the other is to employ a charger that is designed to monitor the current, and voltatge and do this automatically. I have one like this one and it did reverse a badly sulphated battery of mine.