On Apr 21, 4:49 am, "marcus" wrote:
Has anyone come across a circuit for a manually-adjustable, or even
automatic regulator circuit
to control a 24V car alternator?
Application is deep-cycle solar battery charging using 3-5HP small petrol
motor coupled to 24V alternator.
Need to tweak the voltage up to about 29-30V to equalise the batteries.
Solar batteries like a 3-stage charging regime - boost, bulk & float. These
voltages are all diff. and also depend on battery type (chemistry), so the
field needs to have these adjustable set-points.
Would be nice to be able to sense battery voltage and feedback into
alternator field voltage, to make a set-and-forget circuit.

Here's some background (12V, and no feedback) :http://www.homepower.com/files/mark8.pdf

Thanks to everyone in aus.electronics who had a look at this.

Jim Thompson : I notice from your web pages that you have designed some car
alternator regulation projects - wondering if you have any thoughts?

Thanks all

Marcus in outback Oz


I agree with Jim about going analog. I've built more than one voltage
regulator for old vehicles I've owned. Building a simple analog
voltage regulator and getting it to work is relatively easy.
I got the basic idea from this website:
http://homepage.sunrise.ch/mysunrise...ot/voltreg.htm
The voltage regulator on that web page is for a grounded field
alternator. If you want to use the kind of alternator Jim suggested,
flip the diagram upside down and reverse the polarities. GM (Delco)
alternators for example have the kind of field Jim is talking about.
Field is tied to the high end, and you do the switching at ground.
The guy that designed the voltage regulator on the website suggests
jumpers (you could use switches) across diodes in the string to set
the voltage. If you want finer resolution in the voltage setpoint you
could put a shottky in the series.
Or you could work it out a little differently with a potentiometer/
voltage divider scenario, for continuous voltage adjustment.
I used a mosfet instead of the darlington in the diagram. The
hysteresis in Joerg's circuit minimizes heat in the switching element
by making it switch on and off in a narrow band around the setpoint
instead of going into linear operation.

Final note. A great website for RE stuff is
www.fieldlines.com