Does revving the engine help jump starting?
When jump starting a car, will revving the engine of the good car speed up the process, or does it make no diffference?
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Luke,
It should make little difference in todays modern cars with regulators that keep electrical output at constant levels of voltage in order to charge your battery with regulated current. (maybe 60amps)
But during start, your vehicle requires a massive amount of electrical current (hundreds of amps) for a very short time in order to turn the starter. It is the battery that is doing the work and not the alternator, which is why those jumper packs you can buy at the store are so effective, they are designed to put out the cold cranking amps. If you have to you can even jump another car with the jumping 'good' car not running at all.
That being said, we all do it since it makes us feel good.
Hope that helps,
Frank
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+ Ralph
My 2008 Honda does not start without jumping it. there is a new battery & alternator. The auto mechanic can not find anything. What's the next thing to try?
Mari Herrera my 2002 Honda cr v is doing the same thing did you ever figure it out???
@meephs try measuring the battery voltage DIRECTLY on the battery terminals, not the connectors, when you try to start it. If it remains high, you probably have corroded connectors.
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The method that I like is to turn on the dome light of the source vehicle and rev the engine just enough to keep the light from dimming.
Also if you let the primary vehicle charge the secondary vehicle battery then there will be more current available for starting.
Denis
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Umm...I started to pass this by, but had to put my 2 cents in.
The condition of the "good" battery, and its cables and posts, is important, when qualifying these previous answers.
The "terminal" or post voltage is what the battery delivers to the cables. If the "good" battery is weak, or the terminals are resistive (corroded), the alternator output (voltage) will help hold up the voltage being delivered to the jumped vehicle.
Whenever the battery is called upon to deliver current, its terminal voltage decreases, even when another car is not being jumped. If the drain is too high, the voltage decreases dramatically. Having the alternator deliver power will help hold up the "good" battery voltage, and compensate for the assumed lower voltage of the jumped vehicle.
My vote is to have the "good" vehicle delivering alternator current to aid the battery. I doubt revving the engine helps much, though.
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Which means, you don't understand it, Rugsmith? I am an electrical engineer with 45 years experience. It's a technically sound discussion, intended for those who like to understand what's going on. I believe that if you COULD understand it, you probably wouldn't be rude.
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You can start the bad car from a good battery. It needs the battery only. If that fails, you'll need to investigate further anyway.
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battery condition is important but the reason to keep the rpms up in the primary car is the output from the alternator at idle (usually less than 1000 rpm) is pretty low but at half throttle (3000 to 4000 rpm) is a considerable bit higher
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My latest hypothesis was that the continuous and unexplainable voltage drop coming from the after market amp installed to power the small subwoofer I had installed in my 2021 honda civic hatchback sport ?simple and easy solution to the issue was resolved by placing the a/c on high ! It's not even a question really I would have to wonder if you didn't have any ?you don't have to tell me that you are not going to believe that the fan speed would have much effect on the output of the alternator but with no rpm increase the volt meter reading on low was 8.5/9 and with the fan on hi the voltage produced was 13.9 to 14.5 most important conclusion of my journey to determine what is the cause and resolution to the random loss of voltage produced by the alternator ,(measurements taken directly from source )
The one and only true solution to the voltage fluctuation mystery resolved simply! No other option or way to avoid the loss is by turning the ac fan to high !! !! !! Have Not seen the first loss of voltage with the fan on high .
Wouldn't believe it myself ,if I didn't see the volt meter raise and lower consistently with the raising and lowering of the fan speed . From low at around 7.5/9 and high speed peaking around 14.9.
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