by Collyn Rivers
Solar Regulators with Current Shunts
If connected incorrectly, solar regulators with current shunts can register twice your true solar input. This article explains why. Moreover, how you can fix it.
Some years ago a magazine article outlined a solution to a non-existent problem. The article claimed that Australia’s sun may produce excess output. Furthermore that it can overheat solar regulators. It quoted a Plasmatronics 20 amps regulator as indicating 36 amps. The solar array, however, was only 18 amps.
The article misrepresented that happening. It wrongly assumed 36 amps output was feasible. It also advised adding a fan to cool the regulator. In reality, that system’s actual 16-18 amps were registered twice. Once as it flowed through the solar regulator. Then again. It flowed through a current shunt. That shunt’s output also, was to that regulator.
Solar in areas close to a large expanse of water or sand may produce freak high voltages. This happens if direct irradiation is reflected back to light scattered clouds. Then down again. Solar voltage may thus briefly escalate. Their output current, however, is limited automatically.
Solar regulators likewise block excess current. That is necessary for small capacity lead-acid batteries. AGM and lithium batteries, however, accept high currents without harm.
RB Books advises you to use a cooling fan for a solar regulator in tropical areas where airflow is also limited. You do not need one otherwise.
Battery return connection
For solar regulators with inbuilt monitoring, battery positive and negative returns must be direct to that battery. If you include a current shunt, your battery return must bypass that shunt. Unless you do, the solar current is recorded twice. Details vary between regulators.
It is not feasible to show how to do this in article form. Full details, however, are in Solar That Really Works! (for cabins and RVs). Also in Solar Success (for home and property systems). Furthermore, in Caravan & Motorhome Electrics.