Originally Posted By: 440Magnum
Originally Posted By: Vikas
If you are trying to get more life out of battery by putting the new alternator in, I am banging my head against the wall. Replacing battery is cheap and easy. Replacing the alternator is expensive and usually lot more work.
As long as alternator voltage is higher than the battery voltage, the power requirement of the car is being satisfied by the alternator. While the car is running, the power should be coming from the alternator.
True, but the alternator has the secondary job of maintaining the charge of the battery. Car electrical systems are actually fairly terrible at that. To properly charge a battery, it should be done slowly and in stages. Beginning with a discharged battery, there should be a constant-current bulk charging phase, where the voltage slowly ramps up over time. Once that is complete, there should be an absorption phase where the current ramps down and the voltage is held constant over time (this is typically 13.5-13.8 volts for a flooded lead-acid battery). Finally, there should be a very low-current and higher voltage finishing charge at about 14.5 volts.
Car charging systems only approximate this, because there can be no assumption that the engine will be left running long enough to do the job. So they bang the voltage to the absorption phase voltage (often compensated for ambient temperature), and call it good. That results in a much faster than ideal bulk charging rate. And it also forgoes the finishing charge, which gradually sulphates the battery. Also, flooded batteries periodically need a time-limited, high-current, high-voltage "equalizing" charge where the voltage is pushed well above normal and the electrolyte boils. The individual cells tend to recharge at slightly different rates over time, and pushing a high current through all of them tends to equalize the state of charge as well as de-sulphate them. There's no way for a car to automatically do that, since it would push the system voltage high enough to pop headlamps and damage other components.
That's (plus the vibration and heat) is why car batteries don't last 10 or 20 years like the same type of battery in a more conrolled re-charge environment can. AGM batteries are much more tolerant of non-ideal recharging, never need the equalizing step, and hold up a lot better in automotive use IMO.
Out here in sunny California people typically get around 5-6 years with standard automotive lead acid batteries. My motorcycle is known for just murdering them with most people barely getting more than a year before it no longer has enough grunt to turn over the engine on chilly morning.
I think all charging systems should be load and temperature compensating. Seems a lot smarter and a better use of resources.
Originally Posted By: Vikas
If you are trying to get more life out of battery by putting the new alternator in, I am banging my head against the wall. Replacing battery is cheap and easy. Replacing the alternator is expensive and usually lot more work.
As long as alternator voltage is higher than the battery voltage, the power requirement of the car is being satisfied by the alternator. While the car is running, the power should be coming from the alternator.
True, but the alternator has the secondary job of maintaining the charge of the battery. Car electrical systems are actually fairly terrible at that. To properly charge a battery, it should be done slowly and in stages. Beginning with a discharged battery, there should be a constant-current bulk charging phase, where the voltage slowly ramps up over time. Once that is complete, there should be an absorption phase where the current ramps down and the voltage is held constant over time (this is typically 13.5-13.8 volts for a flooded lead-acid battery). Finally, there should be a very low-current and higher voltage finishing charge at about 14.5 volts.
Car charging systems only approximate this, because there can be no assumption that the engine will be left running long enough to do the job. So they bang the voltage to the absorption phase voltage (often compensated for ambient temperature), and call it good. That results in a much faster than ideal bulk charging rate. And it also forgoes the finishing charge, which gradually sulphates the battery. Also, flooded batteries periodically need a time-limited, high-current, high-voltage "equalizing" charge where the voltage is pushed well above normal and the electrolyte boils. The individual cells tend to recharge at slightly different rates over time, and pushing a high current through all of them tends to equalize the state of charge as well as de-sulphate them. There's no way for a car to automatically do that, since it would push the system voltage high enough to pop headlamps and damage other components.
That's (plus the vibration and heat) is why car batteries don't last 10 or 20 years like the same type of battery in a more conrolled re-charge environment can. AGM batteries are much more tolerant of non-ideal recharging, never need the equalizing step, and hold up a lot better in automotive use IMO.
Out here in sunny California people typically get around 5-6 years with standard automotive lead acid batteries. My motorcycle is known for just murdering them with most people barely getting more than a year before it no longer has enough grunt to turn over the engine on chilly morning.
I think all charging systems should be load and temperature compensating. Seems a lot smarter and a better use of resources.
