Re: Gauge Number from eBay ---- Wiring question, about 24 volt and "bridges" -- update for today

Jove Lachman-Curl

Good info guys,
here is a good diagram from another ebay meter I came across. (nice URL link feature John will like that)
I think Cal should be able to use voltage as a good proxy for how much capacity he has left. He may want to throttle off, and measure pack voltage, that is one area where the steady voltage decline of lead acids is realy helpful vs lithium ion which don't seem to have much voltage sag over the central 90 of their capacity so voltage doesn't tell you much unless you're FUL or very empty. This should negate the need for a "reserve tank"... second image. C rate on the right side of the curve is full battery discharge per hour. so C=1 is discharged in one hour. C/3 =3hours. The article is an interesting read.

On Mon, Aug 31, 2020 at 6:02 PM johnacord <jcacord@...> wrote:
If you are running 80A, a 100A shunt is fine.  If you run a bit more than 100A it will just heat a little and that's OK for short periods.

I like to keep a shunt and meter around for testing and setting things up.  A meter made for panel mount is generally not so practical, generally needs voltage too, so I just use a shunt and my digital voltmeter.  The photo attached is a 50A 50mv shunt:  each mv read across the shunt is an amp.  I just wire it into whatever circuit I want to measure.

I don't know why 75mv shunts seem prevalent.  ?? Makes the reading an odd factor of amps, ie 75mv = 100A.  So how many amps is 32mv.........??

Remember, a shunt is just a precision resistor.  If you want to measure small currents just go buy a 1% resistor of the appropriate value from the electronic supply house and use the same way as in the photo.

John A

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