On Tue, Jun 06, 2017 at 01:12:19AM +1200, RussellMc wrote:
> I recommen.
>=20
> Do NOT be afraid of an inductor based circuit. With off the shelf and off
> the net circuits and advice from here you should have no excessibely majo=
r
> [tm] problems with the converter.

I'm going to throw down the gauntlet on this Russell. I'll start a separate
thread.

>=20
> Do not even think about thinking about a manual voltage limiting system.
> MUST be automated.
>=20
> A very cheap monitor can be made based on a TL431 and a few resistors.
> These can be designed to be reliable and to have an utterly minimal chanc=
e
> of having any hidden gotchas.
> Two cost hardly more than one.
> Two such can independently provide reliable reducndant cinverter shut diw=
n.

These are the kinds of ideas that I was looking for. Thanks. I was actually
thinking about three semi-independent circuits:

1. The typical controller such as 12F1840 or 16F1825 using either the ADC
or the internal comparitor with the fixed voltage reference. The controller
is programmed to cut the charger off with the standard 4.1V/cell "full
charge" of 49.2V.  The output would drive an SSR which is the input=20
switch for the charger.

2. A 555 timer setup as a separate driver with the same pushbutton start
trigger as the controller. The 555 independently monitors the battery
terminal voltage with a slightly higher cutoff than the controller, say
49.6V. The output of the 555 would pull down the SSR giving it an override
over the controller if for some reason it doesn't perform its standard
cutoff function at the lower voltage.

3. Finally have a completely separate TL431 based crowbar circuit set for
50V. While it will not turn off the SSR, the fuse between the charger
output and the battery would force a disconnect between the two.

While there are no absolutes, with minimal interaction between the three
circuits, the likelihood that all would fail at exactly the same time would
be minimal.

BAJ
--=20
Byron A. Jeff
Associate Professor: Department of Computer Science and Information Technol=
ogy
College of Information and Mathematical Sciences
Clayton State University
http://faculty.clayton.edu/bjeff
--=20
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