Hi, all.
Some time back at Yelgun there was a general discussion about solar power and a fellow drinker asked me how many solar panels we had. The bus has 2@135w and 140w on the roof and a 140w folder, with a 30amp controller and 4*120amp Fullriver AGMs. After installing the second pair of AGMs last October we’ve only needed to fire up the $400 genet once, about three weeks ago.
Turns out the bloke was an independent solar installer. “ Aha! What you need now is an MPPT controller, and I can fit one for you for only $900! Today!“ Seems this would increase my charging voltage by half a volt! Thinks - for $900 you can buy 2 more AGMs, a large solar panel and a slab or two. Hmmm. We’re still thinking about it.
Gottahavit! Gottahavit!
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Re: Gottahavit! Gottahavit!
You may have read my thoughts on MPPT controllers and their viability as solar controllers for recharging 12v batteries
in a nutshell, designed for those who have too many dollars and not enough sense
they all rely on theory using numbers that are theoretical rather than real life factual to show gains in percentages. None will give a guaranteed improvement in Ah per day, even though you can tell them what solar you have, let’s face it, that battery is in Ag and only more Ah in is going to get the state of charge higher. Talking in watts is great for a theoretical argument, but unless they can convert that back to how many more Ah you will get at the end of the day, they aren’t actually telling you anything.



A person may fail many times, they only become a failure when they blame someone else John Burrows
Those who struggle to become a leader, rarely know a clear direction forward for anyone but themselves
Those who struggle to become a leader, rarely know a clear direction forward for anyone but themselves
Re: Gottahavit! Gottahavit!
Terry mate and don't get cranky with me . How come ALL house grid connect solar has MPPT controllers?
Bernie.
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Re: Gottahavit! Gottahavit!
Can't wait for the answer! 

Steve Williams
http://stevew1945blog.com/
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Re: Gottahavit! Gottahavit!
Well this topic is for LOW VOLTAGE...... so all you high powered wannabees better hop on over to the high power thread...... !!
12V DC against 240V AC ......... Into batteries & into grid too.
I dunno..........
I got enough to worry about. lol

12V DC against 240V AC ......... Into batteries & into grid too.
I dunno..........
I got enough to worry about. lol


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BruceS
Mannum, SA
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BruceS
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Re: Gottahavit! Gottahavit!
HI, all.
T.I.Terry - methinks this is the same sort of bloke who would sell and install a you beaut battery monitor for $600 when all you need is an on-off switch to your solar controller's input.
T.I.Terry - methinks this is the same sort of bloke who would sell and install a you beaut battery monitor for $600 when all you need is an on-off switch to your solar controller's input.
See you on the back roads,
shonky et al.
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Re: Gottahavit! Gottahavit!
MPPT into the grid is into a set voltage, 255vac I think they aim for so there is enough voltage differential for any current produced to flow back into the grid. Sort of like water flow needs a down hill slope. As the voltage stays within a very close range, the panels can be linked in series to build a very high voltage to allow for Vmp drop as the panel temp rises.
Vmp is the Voltage maximum power point, the point where the voltage line and current line meet, so the panel will produce it's max output at this point. Solar panels are designed to be face as close as possible to where the sun will have max impact, this also the same point max heat is absorbed, well over 70*C in an Aust summer. Basically, the inverter has a reasonably fixed voltage to achieve and a bottom less pit to pour and current into.
MPPT for battery charging has a voltage range from 10.5v to 15v to match with a supply voltage between 15.5v (an average 12v nom. panel @ the same 70*C) or a series string voltage of between 22v (CTek max) and 150v (OutbackMX80 and Midnite Solar) The 15.5v is very close to 15v, so there isn't much room for impedance match to gain any magic improvement, yet the circuitry in an MPPT controller must still be powered, nothing works without burning energy and this is wasted energy you can never recover.
That leaves series string connection. This is even more inefficient as a very high voltage must be converted to a low voltage and higher current, there is a lot of heat generated during this process, that is why MPPT controllers have very big heat sinks and often a fan as well. All that heat and power to run the fan is wasted energy you can't get back.
What is the difference between grid tie and battery charging MPPT, everything, only the letters and the theory are the same, worlds apart in practice. It’s bit like saying Whirlpool make good washing machines so their cars must be good because they are both white.
Vmp is the Voltage maximum power point, the point where the voltage line and current line meet, so the panel will produce it's max output at this point. Solar panels are designed to be face as close as possible to where the sun will have max impact, this also the same point max heat is absorbed, well over 70*C in an Aust summer. Basically, the inverter has a reasonably fixed voltage to achieve and a bottom less pit to pour and current into.
MPPT for battery charging has a voltage range from 10.5v to 15v to match with a supply voltage between 15.5v (an average 12v nom. panel @ the same 70*C) or a series string voltage of between 22v (CTek max) and 150v (OutbackMX80 and Midnite Solar) The 15.5v is very close to 15v, so there isn't much room for impedance match to gain any magic improvement, yet the circuitry in an MPPT controller must still be powered, nothing works without burning energy and this is wasted energy you can never recover.
That leaves series string connection. This is even more inefficient as a very high voltage must be converted to a low voltage and higher current, there is a lot of heat generated during this process, that is why MPPT controllers have very big heat sinks and often a fan as well. All that heat and power to run the fan is wasted energy you can't get back.
What is the difference between grid tie and battery charging MPPT, everything, only the letters and the theory are the same, worlds apart in practice. It’s bit like saying Whirlpool make good washing machines so their cars must be good because they are both white.
A person may fail many times, they only become a failure when they blame someone else John Burrows
Those who struggle to become a leader, rarely know a clear direction forward for anyone but themselves
Those who struggle to become a leader, rarely know a clear direction forward for anyone but themselves