| Solar Charge Controller Question [message #155877] |
Sun, 08 January 2012 00:05  |
RadioActiveGMC
Messages: 1020
Registered: November 2010
Location: Hot AZ desert
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Maybe someone can tell me if I'm correct. I'd like to buy a MPPT Controller for my solar panels. I'll currently have (4) 100 w panels (12v/24v using them at 12v of course). I'm guessing I need to buy a 40 amp controller for them if I want to use all of them on the same controller. Am I correct?
***"Gettin There"-1973 23' Sequoia-
Michael, Onans smell, "Go solar/wind power!"
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| Re: [GMCnet] Solar Charge Controller Question [message #155903 is a reply to message #155877] |
Sun, 08 January 2012 09:36  |
Kudzu
Messages: 377
Registered: November 2011
Location: Marshville, NC
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Correct. It wouldn't allow you to add another 100W panel, however.
Dan in NC
Caregiver to a 1976 Eleganza II
On 1/8/2012 1:05 AM, Michael wrote:
>
> Maybe someone can tell me if I'm correct. I'd like to buy a MPPT Controller for my solar panels. I'll currently have (4) 100 w panels (12v/24v using them at 12v of course). I'm guessing I need to buy a 40 amp controller for them if I want to use all of them on the same controller. Am I correct?
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1976 Eleganza II
1996 Chevy Impala SS
1999 Kawasaki Vulcan Nomad
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| Re: [GMCnet] Solar Charge Controller Question [message #155979 is a reply to message #155907] |
Sun, 08 January 2012 17:46 |
Douglas Norton
Messages: 191
Registered: April 2008
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I do not think a 40 amp controller is necessary.
Before you get a 40 amp, check with a knowledgeable installer or reputable dealer. I suggest that you check because I do not trust my math and limited knowledge base. But I think a 30 amp controller would more than suffice. To get 400 watts out of 4 panels, the voltage has to be at it's maximum power point: 17 volts or so. At that voltage you would only put out 400 watts divided by 17 volts or about 23 amps. At 13.3 volts (the lowest charging voltage you reasonably expect), the math would get to 400 watts if you were ABLE to put out 30 amps (30 X 13.3 = 400). However, since your panels can not put out maximum power at that 13.3 volts, you will not be able to generate anywhere near 30 amps. The most to expect would be way below 30 amps.
It is a different story if you use a MPPT (Maximum Power Point Tracking) controller. Potentially you could get more (a bit under 40 amps) as the controller keeps the input voltage near 17 volts and adjusts output voltage down and output amperage up. MPPT controlers only work their best magic (maximum watts from panels) if the conditions are right - and they rarely are (sun at 90 degrees to the panels and batteries well discharged so they can accept a large charge).
Someone else more knowledgeable than I may have some contrary comments; I welcome any critiques as I do not wish to allow my ignorance to burn me or my solar system again. I fried a 7 amp controller with 115 watts of panels, but it took a couple of summers; they rarely charged the batteries at as much as 5 amps. I forgot the controller shunted extra amps to ground.thus heat, smoke and flames rewarded my incomplete understanding.
________________________________
From: Michael <radioactive626@msn.com>
To: gmclist@temp.gmcnet.org
Sent: Sunday, January 8, 2012 8:18 AM
Subject: Re: [GMCnet] Solar Charge Controller Question
Its crazy how fast the prices of the controllers go up however after 30 amps.
--
***"Gettin There"-1973 23' Sequoia-
Michael, Casa Grande, AZ
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| Re: Solar Charge Controller Question [message #156016 is a reply to message #155877] |
Sun, 08 January 2012 20:29 |
RadioActiveGMC
Messages: 1020
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Location: Hot AZ desert
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I think I may just go with a 60 amp MPPT. I'd like a little wiggle room to add more panels or a wind turbine. I usually am aiming the panels at the sun, and living in AZ we get a lot of direct sun. I thought 30 amps would work and I think it will to. Its like the bare minimum after I did the math, after loss and everything. But I like overkill so adding a 60 amp maybe how I'm going to go. I've been reading a lot about MPPT controllers and they seem to be the best way to go. But I'm still researching.
***"Gettin There"-1973 23' Sequoia-
Michael, Onans smell, "Go solar/wind power!"
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| Re: [GMCnet] Solar Charge Controller Question [message #156028 is a reply to message #155979] |
Sun, 08 January 2012 23:29 |
Kudzu
Messages: 377
Registered: November 2011
Location: Marshville, NC
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I think you're asking for trouble if you try and "right size" it too
closely. Plus, he'd have to buy a second controller for any growth. JMO...
Dan in NC
Caregiver to a 1976 Eleganza II
On 1/8/2012 6:46 PM, Douglas Norton wrote:
> I do not think a 40 amp controller is necessary.
>
>
> Before you get a 40 amp, check with a knowledgeable installer or reputable dealer. I suggest that you check because I do not trust my math and limited knowledge base. But I think a 30 amp controller would more than suffice. To get 400 watts out of 4 panels, the voltage has to be at it's maximum power point: 17 volts or so. At that voltage you would only put out 400 watts divided by 17 volts or about 23 amps. At 13.3 volts (the lowest charging voltage you reasonably expect), the math would get to 400 watts if you were ABLE to put out 30 amps (30 X 13.3 = 400). However, since your panels can not put out maximum power at that 13.3 volts, you will not be able to generate anywhere near 30 amps. The most to expect would be way below 30 amps.
>
>
> It is a different story if you use a MPPT (Maximum Power Point Tracking) controller. Potentially you could get more (a bit under 40 amps) as the controller keeps the input voltage near 17 volts and adjusts output voltage down and output amperage up. MPPT controlers only work their best magic (maximum watts from panels) if the conditions are right - and they rarely are (sun at 90 degrees to the panels and batteries well discharged so they can accept a large charge).
>
>
> Someone else more knowledgeable than I may have some contrary comments; I welcome any critiques as I do not wish to allow my ignorance to burn me or my solar system again. I fried a 7 amp controller with 115 watts of panels, but it took a couple of summers; they rarely charged the batteries at as much as 5 amps. I forgot the controller shunted extra amps to ground.thus heat, smoke and flames rewarded my incomplete understanding.
>
>
>
> ________________________________
> From: Michael<radioactive626@msn.com>
> To: gmclist@temp.gmcnet.org
> Sent: Sunday, January 8, 2012 8:18 AM
> Subject: Re: [GMCnet] Solar Charge Controller Question
>
>
>
> Its crazy how fast the prices of the controllers go up however after 30 amps.
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1976 Eleganza II
1996 Chevy Impala SS
1999 Kawasaki Vulcan Nomad
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| Re: [GMCnet] Solar Charge Controller Question [message #156032 is a reply to message #156028] |
Mon, 09 January 2012 00:19 |
Douglas Norton
Messages: 191
Registered: April 2008
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Dan, I concur with your opinion. I did not realize he would be using a MPPT controller. Even if it only hit 40 amps a small percent of the time, that could be enough to overheat a 40 amp controller, especially since new panels often exceed their rated output. Also, there are some conditions when reflections such as from cloud edges will cause a panel to exceed it's rated output. If he is tracking the sun, 40 amps is too close for comfort.
________________________________
From: Daniel Jarvis <TheJarvis@carolina.rr.com>
To: gmclist@temp.gmcnet.org
Sent: Sunday, January 8, 2012 9:29 PM
Subject: Re: [GMCnet] Solar Charge Controller Question
I think you're asking for trouble if you try and "right size" it too
closely. Plus, he'd have to buy a second controller for any growth. JMO...
Dan in NC
Caregiver to a 1976 Eleganza II
On 1/8/2012 6:46 PM, Douglas Norton wrote:
.... The most to expect would be way below 30 amps. .... It is a different story if you use a MPPT (Maximum Power Point Tracking) controller. Potentially you could get more (a bit under 40 amps) as the controller keeps the input voltage near 17 volts and adjusts output voltage down and output amperage up.
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| Re: [GMCnet] Solar Charge Controller Question [message #156060 is a reply to message #156032] |
Mon, 09 January 2012 11:30 |
Marc Hogenboom[2]
Messages: 70
Registered: March 2011
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There is one other thing: the edge of cloud effect. In some weird way when
the sun comes from behind a cloud the output of the panels goes way up and
amperage can go over 40 for a short time.
Marc Hogenboom
'73 Painted desert Diesel
Madrid NM
-----Oorspronkelijk bericht-----
From: Douglas Norton
Sent: Sunday, January 08, 2012 11:19 PM
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] Solar Charge Controller Question
Dan, I concur with your opinion. I did not realize he would be using a MPPT
controller. Even if it only hit 40 amps a small percent of the time, that
could be enough to overheat a 40 amp controller, especially since new panels
often exceed their rated output. Also, there are some conditions when
reflections such as from cloud edges will cause a panel to exceed it's rated
output. If he is tracking the sun, 40 amps is too close for comfort.
________________________________
From: Daniel Jarvis <TheJarvis@carolina.rr.com>
To: gmclist@temp.gmcnet.org
Sent: Sunday, January 8, 2012 9:29 PM
Subject: Re: [GMCnet] Solar Charge Controller Question
I think you're asking for trouble if you try and "right size" it too
closely. Plus, he'd have to buy a second controller for any growth. JMO...
Dan in NC
Caregiver to a 1976 Eleganza II
On 1/8/2012 6:46 PM, Douglas Norton wrote:
.... The most to expect would be way below 30 amps. .... It is a different
story if you use a MPPT (Maximum Power Point Tracking) controller.
Potentially you could get more (a bit under 40 amps) as the controller keeps
the input voltage near 17 volts and adjusts output voltage down and output
amperage up.
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