What is the exact difference, electronically, between
a 6 volt power supply and a very basic 6 volt charger.

by basic I mean no timer, no meters, no peak detect, no program.

Is a charger fundementally just a power supply with control and detection circuits?

A power supply converts say... 110v AC to 12v DC. A charger doesn't.

A power supply is a constant VOLTAGE supply.
A charger is a constant CURRENT supply.

depends on the charger, lipo chargers are constant voltage supply

I know that a power supply typically
rectfies (converts AC to DC) and tranforms (converts 12v to 6v)
but at that point what is the difference for the way it outputs
5 amps at 6 volts and a charger 5 amps at 6 volts.

Are you saying the powersupply has a circuit that keeps (regulates) the volatge to remain a constant 6 volts ?

While the typical NIMH NICAD charger has a circuit that makes sure its ouput is 5 amps?

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Amoung other things, yes.

Unless we're talking about these cheap overnight wall-chargers....

The main difference is that a charger got a cut off device built in.

for NiCd's and NiMh's, the cut off can be determined by time, voltage drop or temperature.

Timed charging: Problem is, how much was left in the pack, and how much can it take over all? Since the charger dont really know, a pack charged this way is usually overcharged or undercharged. In, let's say, an electrical tooth brush, it dont matter much. But since we're stressing our NiCd's / NiMh in our cars, it makes a huge difference.

Temperature cutoff: This is a very effective cut off method, no false peaking and no over charged packs. However, it requires that the ambient temperature dont differ too much (or the charger shold compensate for that) and, especially, it requires that the user remember to mount the temperature sensing device....

So in moct cases, we use delta voltage sensing. When the pack is fully charged, the voltage will drop. So when the charger sees this, it stop the charging.

These three methods can be combined.

If you are thinking about the cheap "chargers" that come with the "Toygrade" rc cars, then most of them are nothing but small power supplys. Not even with control or detection circuits. They just charge slow enough so that the battery can, without damage, convert the extra charge into heat. I hesitate even to call them chargers.

However, real chargers most often need a 12 volt power supply and often have expensive components inside.