Wouldnt a charger burn them out quicker? If a charger has enough juice to juice up a battery, then I would think it would be able to fry a glow plug faster. Just quick thinking, probably wrong
A GP is only a fraction of an Ohm resistance, so hooking a GP up directly to a battery is pretty close to the same thing as creating a dead short between the two terminals of the battery - for as long as the GP lasts.
Ever seen the sparks that fly when you get a wrench or something metal across the two terminals of a fully charged battery? That's because for all practical intents and purposes a battery will supply as much current as the conductor will take until the conductor burns up or the battery goes dead.
Think a battery charger will make the same kind of fireworks?
For example:
12v battery across .1 Ohms = 120 amps
12v battery across .2 Ohms = 60 amps
12v battery across .5 Ohms = 24 amps
12v battery across 1.0 Ohms = 12 amps
If you watch the YouTube video, that 12 amp charger is pegged the whole time - meaning if it could supply more juice the GP would take it...
So, unless the charger is capable of some pretty high amperage - and a 10-12 amp charger is about as big as most people are going to have unless they own a repair shop - the charger just isn't going to supply enough juice to be the same as a battery.
. That makes sense though 
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