Re: Can a low battery cause poor idle and rough running? (73-454)
 

Does this jerk ":U 73-454" do nothing but leave negitive comments and try to make himself feel good. He should be band from the forum :yesnod:

Re: Can a low battery cause poor idle and rough running? (SLICKMAN)
 

I must commend Fevre on his class and self constraint

Re: Can a low battery cause poor idle and rough running? (Fevre)
 

To answer the original question, yes it can affect the operation of the ignition if combined with a bad alternator. One possibility is a bad alternator that doesn't put out enough power to recharge the battery or to run the ignition properly. Eventually the battery become too weak to supply the ignition but, in that scenario, it probably wouldn't start the car either. Another possibility is a bad alternator and a bad battery. The battery will charge but only at a fraction of what it should and won't hold that charge for long. Most of the power it had was consumed by running the fans and starting the car, leaving it with not enough power to adequately operate the ignition. I've intentionally used the term "bad" alternator because an alternator can be "bad" in several ways but still not have failed completely (as can a battery). In some cases, it becomes incapable of recharging the battery at idle or low rpm but will charge at higher rpm. In another case, with an internally regulated alternator, a bad diode prevents it from converting it's AC current to DC. It still puts out the proper voltage when measured but the car's electical system is DC. The battery won't accept the charge and the rest of the electrical system won't run on AC either. If your headlights dim at idle but brighten up at higher rpm, the ignition is likely getting the same power fluctuation also.

73-454, "It always amazies me on how manay stupid Bubbas on the board". Well, you've managed to prove that there is at least one :). The idea that the draw from an alternator would dramatically affect the idle quality is ludicrous. Most any car on the road is capable of idling just fine with every electrical accessory running and it's alternator working at full tilt. The only exception I can think of is if the engine were putting out so few horspower that it couldn't spare a few more. Perhaps a Yugo on 3 cylinders? I've owned dozens of cars and all of them have idled just fine on a cold, dark, rainy, night sitting at idle with headlights, wipers, stereo, heater blower, brake lights, etc. forcing the alternator into max duty. In some low powered cars, you may be able to notice the difference when the alternator engages but it's a very weak engine that would have a problem.

Re: Can a low battery cause poor idle and rough running? (Fevre)
 

Great discussion. Weird how some topics take off. Learned some interesting info.

Re: Can a low battery cause poor idle and rough running? (Fevre)
 

Ok, here is another explanation using the popular water analogy.
https://iotech.no/corvette/technical/images/battery.gif
Pump=alternator (deliver a water flow (current) up to it's max capacity, ex. 100gal/hr (=100amp).
Pressure regulator=voltage regulator, controls the output pressure (voltage) of the pump, ex. 14.4psi (=14.4volt)
Storage tank=battery, pressure at the bottom when full 14.4psi (14.4volt)
Consumer= fans, lights etc, a restricted opening to free air (ground), (resistance in ohm)
Leak=battery self discharge


[Modified by Ingar, Norway, 9:38 AM 6/24/2002]