Solar Controller for Low Voltage Panels? Not Victron!

[hpeer]

Originally Posted by CarinaPDX

Thanks for the clarification; I hadn't made the distinction. This is definitely "bang-bang" as the on/off cycle is quiet long and with a wind gen quite noticeable. IIRC it was recommended by the wind gen manufacturer (early AirMarine unit).

Greg

I think there is a way to set it up so that in the “off” cycle it diverts to a load resistor, which could he a hot water heater. But you need an external relay?

[noelex 77]

Originally Posted by hpeer

I think there is a way to set it up so that in the “off” cycle it diverts to a load resistor, which could he a hot water heater. But you need an external relay?

This can be done with some solar controllers including the NC25A-12. Wind generators usually require this type of controller. If this is not present when there is no load, the wind generator will speed up, risking damage. It is not not necessary with solar panels, but it can make use of energy that would be otherwise be wasted.

However, even if this is done the bang/bang or on/off nature of this type of controller means it generally does not charge a lead acid battery correctly, or at least takes a very long time to achieve 100% SOC. The progressive charging nature of PWM or MPPT controllers is much better.

[Msailor]

Thanks for continuing the discussion. The NC25A-12 has me a little curious. Is the heat from a resistor going to work on an insulated tank of say, 6 gallons? What do the battery manufacturers think about "on-off" chargers (and where did the "bang-bang" label come from)?

In actual use my Victron MPPT rarely keeps battery voltage constant in either bulk or absorption phases. It get's down to the float level at times. Is the NC25A-12 likely to be better at maintaining a single constant voltage? Either may or may not be good for charging and battery health. Lifeline does recommend 3 stage charging for AGMs, but does that apply to the variable nature of solar power? I'm going to try to get their view.