VitaminJ said:
No. The voltage will be lower. Go do it yourself. The text I quoted states exactly the same. E=IR, there are three variables. If resistance is higher then current or voltage, or both, will be lower. Based on the text I quoted, both current and voltage will be lower in low temperatures and that is common knowledge about lead acid batteries you have it plain backwards sorry to say.
I'm sorry Vitaminj, but I'm going to have to call you out on this one. Either we're not talking about the same thing or you really don't know very much about electricity and batteries.
I'm talking about a discharged lead acid battery on a Leaf being charged via jumper cables off of a running ICE car.
If you're talking about the same thing you don't make any sense. I don't need a voltmeter to know what's supposed to be going on. For one, because I've charged lead acid batteries and used voltmeters on them a countless number of times. And two, because of the math.
You can take a completely dead lead acid battery that's at 0V, hook it up to a 14V charger, and it will have 14V instantly across its terminals. It's not going to go slowly up from 0V, to 1V, to 2V... etc. Hell! You could throw a 24V charger on there and you'd instantly have 24V.
Vitaminj said:
If your voltmeter was halfway accurate and it measured exactly 12v with the car off, guess what bub the lead acid battery is a gonner.
Let's say it was 12V when I was jumping it. The ICE charges at 14V. If the ICE is at 14V, and I have jumper cables totaling 0.006 ohms (4AWG at 10 foot twice) them the current through those cables would be 333A. But of course the maximum current draw of the alternator is 105A putting the voltage differential between the two batteries not more than 0.6V (Leaf 12V, ICE 12.6V. Ok?)
Now I highly doubt that the voltage was 12V and that the car wouldn't start at that. Normally an ICE won't start off of less than 9V. I'd imagine the Leaf to be at least 10V. So at 10V, that would be less than the 1,000CA battery on the Golf. At 10V the amperage would be close to that 333A without the alternator. Put the alternator back into the equation and if what you say is true, the charging voltage of the Leaf battery is still going to be around 10V, too low to start the Leaf, we're looking at a charging current of around 400A.
400A feeding what? What device on the Leaf would draw the charging voltage down that much? It's utterly preposterous, illogical, makes no sense whatsoever.
The references you are using talk about a single battery system by itself, not a bad battery and a good battery connected together or a battery being charged from an external source. Therefore they aren't very relevant and furthermore I don't see and reference to voltage. Which really wouldn't matter if it did since we are talking about hooking up three different voltage sources together at the same time, not just one by itself.
GerryAZ said:
The Hall Effect current sensor at the negative terminal of the 12-volt battery has nothing to do with this. A loose connection somewhere would cause the failure to start regardless of the battery voltage. It is possible that the connection at the current sensor was loose, in which case the car would start if the booster battery negative cable was connected to chassis ground.
Now this makes the most sense. A bad connection somewhere, even if it were a bad jumper cable connection and a dead Leaf battery.
I might test the lead acid battery capacity myself if I get the time. But I'm still leaning towards a bad connection somewhere. Maybe I got it when I cleaned up the battery terminals. I'll definitely try that negative ground cable at the frame, as well as the DC converter connections.