Friday, Oct 04, 2019 at 13:21
G'day Vince
A jump start is really only a connection of two batteries in PARALLEL, + to + and - to -, as Alan mentioned, so YES any vehicle can start any vehicle.
ONLY if one is Positive to chassis, (an OLD English idea of the generator era) and the other negative to chassis, means a DEAD short of the batteries is created IF the frames or any bracketry touches the other vehicle.
Almost anything with an alternator as original equipment is negative to earth/frame though.
So you definitely have it right and correctly understood!
Many times, the jumper leads can be connected correctly to ANY vehicle and the engine of the live one then started and operated a bit above idle so the charge from the alt is dumped into the flatter
battery. Run like this for a few minutes will, most times, see the flatter
battery recharged enough to start it. So switch off the good system and try a start of the sus system. No need to use the good system
battery as a jump starter as it is being used as a recharger and not jump starting. less problems that way. Just make sure ALL systems are stopped when disconnecting the jump leads.
Any dangerous voltage spikes are caused by suddenness of jump leads being applied or taken off under heavy current flow between the two batteries..
The above recharge method eliminates any spike problems because the voltage difference between the two batteries is very small and current flow isn't happening at that moment.
There are other safety precautions which can be easily done to avoid spikes if jumpers leads HAVE TO BE removed while engine/s are running. More explanation is needed for that.
FollowupID:
902260