Jim Wilkins wrote:
On Feb 16, 3:18 am, "PrecisionmachinisT"
wrote:
wrote in message
...
Refer to Clue above. I suspect that the charging circuit is
heavily current - limited and would not supply sufficient
current into the very low impedance of a properly sized battery
to cause harm.

DC circuits have zero impedance
....

DC circuits eventually settle to voltage and current values determined
by resistance, regardless of their reactance which can be
considerable. Impedance is the combination of resistance and
reactance, as Rich wrote.

Right, but this isn't a 'pure' DC circuit.

By mentioning 'impedance' instead of just ESR, I hoped to remind us
that the current waveform into the battery is dependent on
it's Equivalent Series Resistance *as well as* how it 'looks'
to the pulses of D.C. from the rectifier, in the frequency domain.

See for example, Table 1 of:
http://www.telepower.com.au/INT95b.PDF

Here is a gross example to show the effect.

If you load the following circuit into LTSpice, you can vary
the inductance of L1 to change the inductive reactance seen by
the generator winding. (The circuit shows the output of the
'battery charge' winding in series with a rectifier, a 1.0 mH
inductor and a battery that has an ESR set to 1.2 milliohm.
The generator is running at 3600 RPM).

Note that I am *not* saying that the inductive reactance of
any healthy battery is *anywhere* near as high as shown in
this circuit. I'm just showing that pulsed D.C. faces more
'opposition to flow' than that posed by simple resistance.

Even with the D.C. resistance of the inductor fixed at zero, the
peak current into the battery will be inversely proportional to
the inductance of L1 (in addition to the ESR of the battery and
the effect of the forward drop of the rectifier).


Version 4
SHEET 1 1276 680
WIRE 32 144 -64 144
WIRE 224 144 96 144
WIRE 336 144 304 144
WIRE 336 192 336 144
WIRE -64 256 -64 144
WIRE 336 304 336 272
WIRE -64 368 -64 336
FLAG 336 304 0
FLAG -64 368 0
SYMBOL voltage -64 240 R0
WINDOW 3 13 107 Left 0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR Value SINE(0 22.6 60 0 0 0 5)
SYMATTR InstName V1
SYMBOL voltage 336 176 R0
WINDOW 123 0 0 Left 0
WINDOW 39 24 132 Left 0
SYMATTR InstName V2
SYMATTR Value 12
SYMATTR SpiceLine Rser=1.2m
SYMBOL ind 208 160 R270
WINDOW 0 32 56 VTop 0
WINDOW 3 5 56 VBottom 0
SYMATTR InstName L1
SYMATTR Value 1m
SYMATTR SpiceLine Rser=0
SYMBOL diode 32 160 R270
WINDOW 0 32 32 VTop 0
WINDOW 3 0 32 VBottom 0
SYMATTR InstName D1
TEXT -80 416 Left 0 !.tran 0 .1 0

--Winston 'Z is the word is the word is the word..'