Solar panel controllers
I've been looking at buying a solar panel for my van. Whilst doing some research I've noticed that the wiring diagrams for the solar panel controllers show 3 connections. Unsurprisingly there's a solar panel input, an output to the battery for charging but was surprised by the 3rd which on the diagrams shows lights or an inverter connected to it. I have no current plans to use an inverter and as my 12V lights are already connected to the battery I presume I'd just leave this connection free. Anybody out there got any knowledge on this? If, in the future, I did decide to connect an inverter I presume the battery supplies the power to the 3rd connection when the solar panels aren't able to, is that correct? The controller prices also vary considerably. Is it worth spending the extra money on a more expensive controller and which type would you recommend?
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Some come with what is typically called a pair of "load" connections. These are used where those "loads" placed on the battery are fed not directly from the battery but from the controller. In that role the solar controller can limit the current load that can be taken and probably will not allow any draining should the battery become depleted to a set amount. These are used where protection from battery abuse by over discharging is required.
I have it on both of mine but have never wired it up or been interested in that feature.
I can see with the real abuse an inverter could do to a battery it is a very useful feature to have. Note that here oversizing wires from those needed for just the solar duties are almost certainly required.
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For further reading the attached link is the manual of a quality Pulse Width Modulated [PWM] technology solar regulator, typical of those we would use:
Page 18 Clause 4.3 details the Load Control Information. Here it states it limits the “load” by disconnecting if the current gets too high, plus it protects the battery from the further drain of that load by also disconnecting should the battery voltage get too low.Page 23 gives the low voltage disconnect as 11.5 volts and then when the battery reaches 12.6 volts it reconnects the load.
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My solar controller has a third pair of "load" terminals which can be used to feed a lighting circuit.
The idea is that when the sunlight on the solar panel falls below a preset point then the controller switches on this lighting circuit. This "on" time duration can be set for various number of hours ranging from one to eight.
I can't think of any practical application on a touring van so mine remain unused.
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