Battery Charging

Allan,
It is not only electrical concepts confused with weird ideas, I find the same with strange and impossible beliefs with mechanical items and concepts too. Not many people question and evaluate what they hear or check the truth of the concepts being unwisely believed.

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Neil, as alternators are rated at least 80 amps or more, I'm blowed (pun intended) if I know how their diodes could be harmed by a charger only capable of 10 amps or so.
Some people have great imagination.

Now, reverse connecting whilst jump-starting may be another matter.

Reverse connecting whilst jump starting!!!, just ask my daughter about that one!...


Big spark, battery fumes exploded, the old pag near ended up on Mars!.


Cheers Axle.

Axle.
For those who are not skilled in jump starting, the observance of big and small terminals and or colour or what is connected to the chassis or just the symbols on the gear being used is a definite advantage. Before connecting the last clamp ALL persons should be taught to “Test strike” the last clamp to see if there is a small current flow or a Pajero killing flow. Failure to observe at least a few vital concepts will endanger people and equipment.

I have repaired many alternators but the persons who charge a flat battery the wrong way so + is - and - is + does blow diodes in an alternator. I had to replace the diodes after the bunny did the frack to bunt charge and failed to carefully strike check any terminal when connecting.

G'day Explorers

Now we are all the wiser to the battery charging scenario which was asked about in the original post.

Now there's the 'Tim Flannery' and the belief structure thing?

I don't mind clever people having or giving an opinion on any subject if it's based on one simple thing, that being FACT.

Dr Tim Flannery is a likable bloke and with his mate John Doyle they had a very watchable television series as they wandered around Australia, then Dr Tim had a guest spot on a talk back radio show from ABC Perth.

Dr Tim Flannery had an opinion and gave the listeners his expert knowledge on the inland Pilbara and of the marvels and all things wonderful regarding the mining and shipping of Iron Ore.

He then 'shot himself' in the foot, by stating that Mount Newman had been mined and all it's Iron Ore deposits had been exported to China in Just 50 years ~ how bloody marvelous was that he said and how clever is modern man!

Unbelievable ~ says the talk back presenter 'just unbelievable'

Well, Joe here rings the radio station and gets to talk to the man himself, then I was cut off after I'd informed the man himself and who ever might have been tuned in to the broadcast that Mount Newman was there yesterday, but I'll just have a quick look again ~ Yep it's still there mate ~ as it still is to this very day.

Not sure if it will be there in 50 or so years time though.

Safe travels : Joe

The op referred to the issue around welding but is asking if a charger can be connected while still in use or remaining connected to a vehicle etc. Yes they can "cos they is smart. Even dumb ones can be too. Just can't leave the latter on for extended periods as charge voltages are often above the float voltage of the batteries being charged. Smart chargers cut off when voltage and or minimal amp flow is detected.

Yep , easy as to get off the original question when its 2 questions in 1 ... disconnect when welding ? I would especially if near a wet cell battery being charged at the same time ....Kaboom from the gas vapours is not unheard of ......As for disconnect battery for simple charging ? NO .....Two distinct processes that should be undertaken one at a time ......

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Simple Vince, positive-to-positive and negative-to-negative regardless of the vehicle earth polarity.
However, just do not let the bodies of the two vehicles come into contact at the same time or you will create a short circuit.

Allan,
I always wondered why we now have plastic bumpers, I suppose that insulation is necessary when starting old Austin’s and Morris vehicles. My Mum had a Morris Minor and it somehow suddenly changed to neg earth and a HD Oldhen alternator, wow, 35 amp output. Big difference from the Lucas, Prince of Darkness, C 39 genny.

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Yes, but then it no longer had self-dimming headlights. lol

Allan
Have I got this wright a neg earth car "can" jump start & positive earth car as long as the 2 do not connect

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.

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Yes Vince, you got it right.
Just keep the two bodies apart whilst the jumper leads are on.
Actually, that is good advice even for 'normal' jump starts.