Solar Charge Controller 'Load' Output Voltage

[lpdsn]

I'm looking at what is feasible with the cheap solar controllers such as the one in the link below, or similar.

http://www.banggood.com/12V24V-20A-Solar-Charging-Controller-Switch-Panels-p-975745.html

They have two outputs, for battery charging and a load. Has anyone measured the voltage across the load terminals? Is it a regulated nominal 12V or full solar panel output voltage?

Just trying to short cut having to get one and do my own measurements.

 

[RAI]

The load terminals are connected to the battery terminals via a relay that disconnects the load when the battery voltage sinks below a set voltage, typically 11.8 volts.

 

[lpdsn]

The load terminals are connected to the battery terminals via a relay that disconnects the load when the battery voltage sinks below a set voltage, typically 11.8 volts.

I'm surprised by that behaviour. I understood the 'load' to be a dump when it stops putting current into the battery. How did you find out about that behaviour?

 

[VicS]

I'm surprised by that behaviour. I understood the 'load' to be a dump when it stops putting current into the battery. How did you find out about that behaviour?

What RAI says.

You can use the load terminals to supply something such as a fridge which is normally on all the time but which without some form of protection circuit could run the battery unacceptably low.

The specification indicates that it will disconnect the load when the volts falls below 10.8 and will reconnect it when the battery has recharged to 12.3 volts.

There is also over voltage protection of the "load circuit" which will disconnect it if the volts rises above 16.5 volts, reconnecting again when the volts have fallen to 15 volts.

Solar chargers do not normally dump the excess power like a some/most wind charger controllers do. It is not necessary. It can be electronically controlled.

If you do not need this load control facility you would improve your solar to battery charging by using a "pulse width modulated" (PWM) regulator or, if you are really in the 20 amp charging regime and want the most out of your solar panels, a "maximum power point tracking" (MPPT) regulator

 

[ghostlymoron]

For an extra couple of quid, I went for a PWM type also from Banggood. It still has a load output (which I don't use). I couldn't justify upgrading to a MPPT one.

 

[lpdsn]

What RAI says.

You can use the load terminals to supply something such as a fridge which is normally on all the time but which without some form of protection circuit could run the battery unacceptably low.

The specification indicates that it will disconnect the load when the volts falls below 10.8 and will reconnect it when the battery has recharged to 12.3 volts.

There is also over voltage protection of the "load circuit" which will disconnect it if the volts rises above 16.5 volts, reconnecting again when the volts have fallen to 15 volts.

Solar chargers do not normally dump the excess power like a some/most wind charger controllers do. It is not necessary. It can be electronically controlled.

If you do not need this load control facility you would improve your solar to battery charging by using a "pulse width modulated" (PWM) regulator or, if you are really in the 20 amp charging regime and want the most out of your solar panels, a "maximum power point tracking" (MPPT) regulator

Thanks all. Sounds like I don't need the load output. Just looking for a cheap charger to go with a small panel for trickle charging.

 

[RAI]

Thanks all. Sounds like I don't need the load output. Just looking for a cheap charger to go with a small panel for trickle charging.

If your panel is small compared to your battery, you don't need a controller at all (if the panel has diodes to prevent reverse flow).

 

[VicS]

Thanks all. Sounds like I don't need the load output. Just looking for a cheap charger to go with a small panel for trickle charging.

If its only a small panel maybe you don't need a controller at all.

the usual rule of thumb is that you don't need a controller if the solar panel is less that 1 watt per 10Ah of battery capacity, although it is usually recommended that solar panels over 10 watts have a controller irrespective of the battery capacity.

 

[lpdsn]

If its only a small panel maybe you don't need a controller at all.

the usual rule of thumb is that you don't need a controller if the solar panel is less that 1 watt per 10Ah of battery capacity, although it is usually recommended that solar panels over 10 watts have a controller irrespective of the battery capacity.

At the prices involved, I may as well fit one.

It's basically because the marina I over-wintered in last winter had a quite high daily charge for shorepower, so I went down about once a week and plugged in for a day, hence thinking of a cheap panel and a cheap controller for trickle charging to do away for the need for regular visits.