solar panels

No.

Panels designed to charge 12 volt batteries have an open-circuit voltage of 21 volts in bright sunlight.

You don't need a regulator to charge a 12 volt or 6 volt battery or a 2 volt battery from a "12" volt solar panel - a 100 watt panel will put about 5 amps into all of them when connected directly.

A Regulator is used to stop the current flow when the battery is fully charged

Not absolutely correct Alloy. Most solar regulators don't change the voltage. They simply stop excessive voltage reaching the battery by disconnecting the panel from the battery when the battery voltage is at a safe maximum. As Peter says below, an MPPT (maximum power point tracking) solar panel controller WILL change the voltage to suit the 12V battery. This improves the efficiency of the system, as a panel intended for charging a 12V battery actually has its peak power output at about 17-18 volts. The 24V panel will have its maximim power output at about 36V. A suitable MPPT controller will allow the panel to operate at its optimum voltage and will convert the voltage to suit the battery. Only recently have they become available at sensible prices.

John

Peter's answer below is the most correct answer -

"as a temporary measure you can hook up your 24V panel to the 12V system - you'll lose half its output power though"

thanks for that john and val as iam still learning about all this iam glad that i have joined exploroz all the members have been helpfull in every thing i have asked.

cheers mick

John ,twas only giving a short answer , ,, as for your statement that a 12v panel has a peak output at about 17-18 v that is not absolutly correct either , open circuit voltage can be upto 27.5 v from a 120w Kycera .

Mick,

You may find our blog Electricity for Camping useful. There are also other very informative articles on this site relating to solar panels and electrical setups generally. Look behind the "Articles" tab at the top of the screen.

Cheers

John

Alloy - Yes the peak power point does vary a bit, but is usually around 17-18 volts. The unloaded (open circuit) voltage may be considerable higher than this as you say, but then the power drops to zero when open circuit!!!

Cheers

John

thanks for that peter do u sell them or were can i buy 1 what cost are the y around about

thanks mick

no worries Mick,

sorry, we don't stock these, but other business members might.

You can google around a bit, you should find them under "MPPT controller".
But I have to warn you, just for the one panel, it'll be uneconomical because last time I checked, I didn't find them particularly cheap.
They're mainly for a complete array of panels, to get maximum solar power out of them.
You can select the output voltage on the MPPT (12, 24, 48), completely independetly from the solar array input voltage configuration.

Someone with more solar experience may be able to help finding what your want.

What's the application? Why this mismatch between panel voltage and rest of system?

Best regards, Peter

thanks peter even if i buy a mppt for around say 700 it will still be cheaper than a 130 watt system at around 1300 i think it will work out about 900 all up and it will be a 175 watt system
thanks mick

Mick,

Your numbers are a bit worrying! Just what sort of system and what sized panels are you considering? The MPPT controller will help you get closer to 100% of the panel power into your battery instead of under 70% with a simple controller. It won't turn a 120W panel into a 170W one.

Cheers

John

hi allan it is just 1 panel a suntec 175 watt 1.5x880x35 mm 24 volt


thanks mick

that is the link looked up to post the Sunsaver MPPT
will be ideal for your 175w panel

the postage at $US19 for the ebay one makes it super cheap

here is an Aus dollar listing for the same item

suggest buy the meter at same time

thanks for that ed very helpful is a lot more cheaper thatn local


cheers mick