Thanks for all your help, it was the battery, it tested at less than half of its stated cold cranking amps, it still started the car sitting overnight, but just barely. Warmed up however it started the car just fine, I am completely disillusioned with walmarts tire and automotive department, I went to one walmart where they couldn't even tell me what battery I needed. I walked out and went to another walmart that was barely any better but suprisingly they gave me a proration on my old battery after asking about it 3 times, I have no idea how they came up with it but it was $20 and change towards the $49 value battery.
Is a failing battery hard on the alternator?
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Originally Posted By: Jetronic
Originally Posted By: Cardenio327
If the battery has a shorted cell, yes, very hard on the alternator.
If the battery is just weak, no, it is much easier to charge than a strong battery.
A weak battery, however, is harder on the electrical system in general, especially the starter, as the lower the voltage drops while cranking, the higher the current flow and more heat is produced.
erhm, the lower the voltage, the lower the current aswell... P=U².R. If the voltage drops, power drops dramatically...
I couldn't find your formula with Google, who knows what it's supposed to be. I did find this:
Originally Posted By: Random Internet Search
With regard to a DC motor, the voltage across the motor, minus IR losses, is proportional to the speed or RPMs of the motor. The current through the motor is proportional to the torque produced by the motor. Normally the back EMF created by the speed of the motor opposes the voltage being applied and limits the amount of current the motor draws and thus it's torque. As more and more load is applied to the motor, the motor slows reducing its back EMF allowing more current to flow, producing more torque.
With a lower applied voltage to the motor not only will the motor be turning slower, which reduces the back EMF and allows more current to flow, the losses such as the internal battery resistance, the cable loss and the IR drop in the motor become more important. This may mean that the motor may not have the speed or torque to turn over the engine and stall. When the motor stalls there is no longer any back EMF and all the current goes towards heating up the motor windings and that can damage the motor.
From what I've observed in real life, the lower the battery voltage swings during cranking, the more current is drawn, and more heat is produced by the starter, cables, and terminals. This would be caused by the resistance in the circuit and the increased current demands of the DC starter motor.
Originally Posted By: Cardenio327
If the battery has a shorted cell, yes, very hard on the alternator.
If the battery is just weak, no, it is much easier to charge than a strong battery.
A weak battery, however, is harder on the electrical system in general, especially the starter, as the lower the voltage drops while cranking, the higher the current flow and more heat is produced.
erhm, the lower the voltage, the lower the current aswell... P=U².R. If the voltage drops, power drops dramatically...
I couldn't find your formula with Google, who knows what it's supposed to be. I did find this:
Originally Posted By: Random Internet Search
With regard to a DC motor, the voltage across the motor, minus IR losses, is proportional to the speed or RPMs of the motor. The current through the motor is proportional to the torque produced by the motor. Normally the back EMF created by the speed of the motor opposes the voltage being applied and limits the amount of current the motor draws and thus it's torque. As more and more load is applied to the motor, the motor slows reducing its back EMF allowing more current to flow, producing more torque.
With a lower applied voltage to the motor not only will the motor be turning slower, which reduces the back EMF and allows more current to flow, the losses such as the internal battery resistance, the cable loss and the IR drop in the motor become more important. This may mean that the motor may not have the speed or torque to turn over the engine and stall. When the motor stalls there is no longer any back EMF and all the current goes towards heating up the motor windings and that can damage the motor.
From what I've observed in real life, the lower the battery voltage swings during cranking, the more current is drawn, and more heat is produced by the starter, cables, and terminals. This would be caused by the resistance in the circuit and the increased current demands of the DC starter motor.
Yah, I'm dithering on buying a battery for the Rat. I drove it for a bit Monday. First time in 2 weeks. The engine starts very easily. The original starter rattled when I shook it. I took a gamble on a Chinese version that works just as well as the old one did but is much tighter. I couldn't buy the parts to rebuild the starter for what the starter cost. The much abused 4 yr old Value craft from Auto Zone rests at 12.4 volts. When I think of it, I charge it with a 1/2 amp trickle.
Mom's 1985 Maxima scorched numerous batteries to death. Sometimes I wonder if batteries that kept dying was what killed alternators, or if the alternators just couldn't handle the blazing underhood temperatures of that car.
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