We use shunt in renewable energy as a meter shunt to determine the amount of power generated by a PV panel or the total current used to charge a battery bank. A meter shunt is all the time used with a DC meter to extend the range value of the current passing through  the DC meter and to cover the pick values which are exceeding the maximum range of that device. In the same time is a way to divert the excess load and to protect. When charging the current flowing into the batteries should never be more than 10% of the battery capacity  e.g. a 100Ah battery should not be charged with more than a 10 Amp current or it may be damaged and/or overheat.  We can achieve that by paralleling an additional resistance with the inherent DC resistance of the meter itself. (See figure).

In the same time overheating the meter shunt will permanent corrupt the results. When we choose a shunt we have to follow some very few rules: The formula to determine the shunt resistance is:

R shunt = R meter / (n - 1)

Where R shunt is our meter shunt resistance, R meter is the inherent meter resistance and "n" is the multiplier. If we want to extend a meter range value  from 0.1mA DC  to 5A DC  the multiplier "n" is 5A divided by 1mA or 5 / 0.001 which of course equals 5000. So (n - 1) must be 5,000 - 1 = 4,999.  As a rule of thumb 5A range value extension for a 0.1mA meter request a 100 m ohms shunt with a drop voltage of 100mV.

For loads up to 70A for battery bank systems we will use shunts connected to meters in the range 100A with 100mV voltage drop.  Everything else can be covered by a 500A with 500mV voltage drop shunt.

The wire we use to connect to our meters must be chosen using following formula:

Length (in feet) = R shunt / [R wire / 1000]

Bogart Engineering provides a  22 Gauge 4 Wire Twisted Pair Cable Kit, 50ft length Trimetric monitor system or a 18 Gauge 4 Wire Twisted Pair Cable Kit, 50ft length.