Brian Gaff (Sofa 2) wrote

I'd imagine one could design a circuit with a two colour led, where its
red one way and green the other and use an op amp and a low value resistor
as a shunt and measure the polarity with the amp. Crude, but should work,
but might need to be set up.

Makes more sense to use an OBD2 device with a fully
configurable display of the charge and discharge current
and even an intelligent app that keeps track of what
should be happening with the other engine and time
since starting detail so you don’t have to keep track
of that mentally.

"Chris Green" wrote in message
...
wrote:
Hi All,

Back in the dark ages (60s,70s, 80s) cars had little bulbs that would
come
on to tell you your battery was no longer charging.

There have been a few people on the Peugeot'007 self
Help FB group I'm on whose alternators have died, but their car's not
charging
light hasn't illuminated (despite its passing its POST before the
problem
and after its been rectified (see what I did there).

Got me to thinking, how were these bulbs driven in the past (i.e, what
electrics / electronics / circuit lit them when charging stopped)?

Most alternators (and also dynamos as were used in 60s and before) had
a specific terminal to drive the 'charging' lamp. It monitored the
voltage between the alternator/dynamo output and the battery.


And how are they supposed to work in "modern" Cars?

On the '007, I believe it's an LED and I SUSPECT it's fed from the ECU??

On modern 'all electronic' cars it needs to do exactly the same job
but is presumably down to the designer exactly how it's driven.

--
Chris Green
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