Solar Power Regulators

As an example of a good solar power regulator let's look at the Plasmatronics PL20, which is rated at 20 amps supply.

This regulator consists of two logical parts in a single unit. 1) solar regulation, and 2) the ability to supply a load. The load is usually your fridge, lights, etc.

The solar regulation part – which is the input to the battery so that they get charged – uses a system called pulse width modulation (PWM) which is a fancy way of saying it acts as a very fast switch. It is therefore is not troubled by excess current from the solar array in the same way a normal non-PWM (series) regulator would be. Even though it is rated as 20 amps, it actually has no trouble at all handling 40 amps of solar array power input, as the extra current does not dissipate much extra heat.

The PL20 also allows current to flow from the battery to a load. The reason the regulator is involved in that process (which has nothing to do with charging the battery), is simply so it can continuously measure the actual current consumed and thus give you a reading of power in and power out of your system.

A device called a "current shunt" (supplied as an option from the regulator manufacturer) allows you to increase the ability of the regulator to supply very large loads. For example a 400 watt sine wave inverter can draw around 50 amps at full load, so here you would be obliged to use a shunt.

It is easy to get a shunt to allow the inexpensive PL20 to monitor loads up to 200 amps being drawn from my batteries while simultaneously providing regulation of +20 amps solar input to the batteries from the solar array.

Hopefully you follow the point, which is that PWM solar regulators are really not stressed at all by high current input from the solar array. Don't confuse the ability of the 'regulator' to supply load current with it's regulation ability for charging the battery array.

They are different functions and a simple shunt is all that is needed to fix the load problem.