12 vs 24v solar charge controller ??

**Mick-Kelly** · 25th December 2011, 11:16 AM

So i have gone and spent some hard earned on a solar charge controller to run off a 60w solar panel into a 120A deep cycle for the camper trailer. Problem is i missread the labelling and i have ended up with a 24v controller (its a 15amp model). Will this work at all for a basic setup like this or do i have to repeat the process and make sure i get a 12v controller? Any help from the electrically minded people greatly appreciated.

**bee utey** · 25th December 2011, 04:05 PM

I suspect you will have to get another. Google search the controller you have to find out its specs. There exist some multi volt controllers but they are usually at the high price end.

**Warb** · 27th December 2011, 02:23 PM

You need to give more information...

However assuming it is purely a charger for 24V batteries, then it is no good to you.

Also note that for a 60W panel you don't need anywhere near a 15amp unit. 60W at 12V is 5amp......

Also note that you need to know the output voltage of the panel and get a controller to suit. The charge controller needs to be able to cope with the voltage from the panel, which could be anything up 50V. Some charge controllers are designed to work with "12V" panels (mpp of perhaps 18V), others will work with higher voltages. Then there's MPPT controllers which give you better usage of the panel when the battery is flat - they allow the panel to keep producing it's maximum voltage, where a cheap controller will drag the voltage down, and therefore reduce the power output of the panel.

**harlie** · 1st January 2012, 08:24 AM

24v controller is for 24v battery banks. Some of the better (more$) are switchable between 12 and 24, some are auto sensing. All the MPPT units I’ve looked at can handle panel ‘string’ voltage from 12 (really 18-22) to 96v (really 160 short circuit) or even more, but most of these still specify the battery bank that they will charge (12, 24 or 48). As mentioned, if funds allow go for a MPPT controller, when the battery is really down their output can be 30% higher than the cheaper PWM regulators.

60W panel will be 12v (somewhere from 18 to 21v short circuit).

**Warb** · 1st January 2012, 10:47 AM

Originally Posted by harlie

60W panel will be 12v (somewhere from 18 to 21v short circuit).

It is likely that a 60W panel is nominally 12V, especially if sold for battery charging, and most current production 60W panels are 12V. However there are 60W panels available in 24V, and even 48V (higher voltage and lower current reduces cable losses). They are not common, because there is no real need for them when most grid connect panels are now much bigger (250W typical), but that doesn't mean it's not worth checking! Since the demise of the feed in tariff in NSW, companies have been dumping stock at cheap prices and sometimes those "bargains" are not really the best solution, nor do the companies always give full details of the product especially if they're trying to sell less desirable items!

Mind you, some of the eBay sellers have gained a reputation for shipping products entirely different to those advertised.

Also note that the maximum voltage from a solar panel is open circuit, not short circuit. A short circuit produces maximum current, minimum voltage.

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