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advice on small system wanted - inverters and controllers

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  • advice on small system wanted - inverters and controllers

    Hi all,

    I'm in the cloudy UK trying to set up a system for a cabin.

    My power requirements are to run a dehumidifier for a couple of hours a day to try and stop the place going mouldy while no one is there to light the burner. It uses about 220watts.

    I have bought 2 panels which are about 300w each approx 36v and 8A giving me a max of about 600watts in perfect conditions - which will never occure in Brittish winters so I don't know yet what realistic power I'll get.

    I have 4 sealed lead acid leisure batteries totalling 400ah.

    In my rush, I decided to get a pwm controller, as it was dirt cheap, and a 300w 12v inverter (that was also dirt cheap), thinking that it would do that job. However, upon reading the indtructions for the controller, and doing more research, I discovered that the pwm would give me hardly any charging power from my panels if I configured the batteries to be 12v. And if I configured them to be 24v, then my inverter is useless.

    So I have to decide to either get a new mppt controller and keep the 12v inverter or keep the pwm controller and get a 24v inverter.

    The trouble is, finding a 24v inverter around 300watts is not so easy (especially if I want it pure sine wave) - they generally start in the 1000w range and are quite expensive (and I don't want to pay silly money for something I'm not making full use of). On the other hand, I'm finding it hard to source a good but cheap mppt controller - they seem to range in price from £10 to £600 for something that claim will do the job but I don't trust that they're either a rip-off or just won't work and it's hard to find trustable reviews.

    The other concern I have, but don't really know about, is whether the batteries can handle the current that an mppt controller will give them, if I take it from 36v to 12v (which I think is about 50Amps?)

    So can anyone recommend whether I'd be better off getting an mppt controller or a 24v inverter and any makes that are cheap but not rubbish.