If I connect the jumpstart to the car battery and leave it connected, well the power from the jumpstart transfer into the car battery?
Therefore if the power is drained from the jumpstart into the car battery, would that mean the car battery would now transfer the power back into the flat jumpstart?
Maruice Cole (hotspot) gurgled happily, sounding much like they were saying :
A bit, yes.
But the batteries in jumpboxes aren't that big at all. Your best bet is to use it as intended - start the car, then let the alternator charge the car's battery.
My (£20) jumpbox has a car charger lead, to allow it be charged from the ciggy cable. It takes forever and a week compared to charging it from the mains.
Mine never seems to need charging, even after a few starts. Yet on the label it says charge for 12 hrs after each use. When not using it for a while the charge needle never seems to drop below 100%. I charged it for a couple of hours once from the mains after using it a bit, but the battery was starting to gurgle and needle was quite a bit over
100% and remained their. Would of thought a full 12hrs on charge might cook a little battery like that? Have had about a year and hardly ever charged it, Most only use a tiny amount of power to get the car going again, as car battery just a bit weak rather than totally flat I think.What is the minimum voltage reading a car battery would start a standard old 1.6 car?
Yes - if the car battery has a lower voltage than the 'jumpstart', obviously.
Only if the engine is running and the alternator working. Otherwise they'll reach an equilibrium.
Impossible to say without knowing the current being drawn. You would be better off asking what SG of acid in the battery.
However, at 18degC you would want at least 12.2V (about 25% charged) to have a good chance at starting a car, and for a 1.6 petrol I'd suggest you want that voltage on a battery giving at least 300CCA
Of course. The voltage of two chargeable cells connected in parallel will equalise over time just as the level in two water tanks connected together will equalise over time. The equilibrium voltage will depend on the relative capacity of the two cells.
-- Dave Baker
It only takes a small amount out of the jumppack to start an engine in good nick apart from the flat battery, and if you don't whip the leads off too quickly the alternator will put back in what you took out. I very rarely charge mine either.
Steve
Depends on what you mean by a "Jumpstart" - you'd need to see if the particular unit in mind incorporates a battery charger.
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