Ok, this is a question that is not so battery-charger specific, but is obviously related.
So here's a circuit fragment:
18V +----+--------__^------/\/\/-----------+ | 2n3055| 0R5 | | | 5W / | | \ 5R10W | | / |_______|> \ | |_ 2n2906 | | | | | | | | | | +------__^ 2n2222 | | | / | 1M \ | / | \ | | | | | \ SW | \ | | | 5V +-----------+ | | GND +-----------+-------------------------+So this circuit shows ~38mA going in to the base of the 2n3055, and ~13.9V across the 5 ohm resistor. It gets warm quickly.
If I change the 2n3055 for a TIP147 (PNP, beta 1k) and make the obvious changes to the 2n2906 to make it work, there is ~80mA current at the base of the TIP147, and ~14.1V across the 10W resistor.
WTF, over?
Needless to say I am happy that my $14.00 DVM has a transistor tester, because with 10k feeding the 2n2222 the 2n2906 doesn't last very long with a TIP147 in-circuit. Of course, in that configuration the base of a 2n3055 still shows 38mA. These results suggest that the base-emitter current of the 2n3055 cannot go any higher without a larger power supply, but that is supposition that the 2n3055 somehow limits the base current to some proportionate ratio to the collector- emitter current available to it. Is that in any way a reasonable explanation for what is occurring here?
Regards,
Uncle Steve