Quote:
Originally Posted by HarryM1BYT
That is an absolutely ridiculous statement to make, batteries are nothing like buckets in their behavior, they need an excess of voltage to make the current flow. As said, even a good fully charged batteries voltage is only around 12.7v. Have you ever come across a battery charger which only outputs 12.7v? The answer to which is no and the reason being that at 12.7v no charge current can possibly flow.
Try this simple experiment....
Connect one flat and one fully charged battery together, via an ammeter. You will get a small initial current flow as the voltage on the two batteries equalise, then there will be no further flow at all, nothing at all, zilch. The reason being that their is no voltage differential between the batteries to make the current flow from one to the other.
If you have a bank of batteries connected in parallel, standard practice is to do what is called an equalising charge occasionally. The batteries are left on charge for an extended period, to ensure all of the batteries are brought up to a fully charged state. The reason for that equalising charge is that the low batteries cannot be charged from the fully charged batteries, because they lack the voltage to transfer their charge.
Once again - batteries are not buckets, nor do they behave like buckets! The public are being fooled by the sellers of these items and if you doubt that you only need read the many reviews which confirm they do not work.
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There is a direct correlation between the voltage measured and the charge of the battery. Two batteries of the same type and the same condition, yet one charged and one not, would display two different voltages.
If you would care to go and verify that from any graph depicting charge vs voltage, you could perhaps go and look at the link in the previous post?
It is perfectly sensible to expect two batteries connected together to equalize their charges, and that is indeed what happens.
What would be unreasonable, is to expect the one battery to charge the other fully, and I have never claimed that. What I
have claimed, and what is indeed true, is that if you connect another battery, that is charged to your discharged car battery, that a flow will go from the charged battery into the uncharged battery and that will persist, until the voltage difference is nil.
So the case is, in this story, it
will help to connect any other battery with a higher charge to your car battery.