"T i m" wrote in message
...
On Thu, 21 Sep 2017 23:52:05 +0100, "Dave W"
wrote:


"T i m" wrote in message
. ..
On Thu, 21 Sep 2017 21:23:26 +0100, "Dave W"
wrote:

snip

should be driven so that when the
battery voltage is below 10V the meter is still on its zero mark, and
full scale for 15V. You are driving it from the Arduino so it can be
any old range e.g. 10mA fsd.

In this case I was going to make a straight analogue meter Dave, both
amps and volts mounted in a suitable box and to be (optionally)
plugged in series with the load. If the voltage drop at max current
affects the voltage too much I'll run a separate cable back to the
battery directly.

I don't understand.

Because there are times when a straight 'old fashioned' analogue panel
meter can show (in a human sense) things better than a digital display
(and why few car speedos are digital today AFAIK) I intend, as a
parallel project, making a two panel meter box with an in-line plug a
socket to match the outboard to battery connectors so that I can just
put it in series with anything I'm playing with to give me a
quick_n_dirty display of volts and amps. ;-)

The current can be read anywhere in the system but if there is any
significant resistance in the lead between the battery and where I
have this box, I can 'remote' the voltage mater supply / sense wires
directly to the battery terminals to remove the influence of the
voltage drop over the cables that will range from 0 at no current to
maximum (that should still be pretty low in ideal circumstances) at
full current.

Cheers, T i m

OK understood. You could use the voltage between the two ends of the
current-carrying wire from the battery as input to your Arduino current
sensing arrangement. The resistance of the lead is the current shunt.

Cheers, Dave