I think there’s some major overthinking going on for less that 300W of power haha
Solar 12 volt panels, is it better to wire two 100 watt panels in series or in parallel? (1 Viewer)
- Thread starter Fisher23
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Using an EFTE Solarpanel, helps a lot if your setup dont lead the panel directed to the sun.
Amazon product ASIN B07MT418PF
It runs keeps my battery full, while running compressor fridge at sunny weather, also if it is just 50W and pretty cheap!
Amazon product ASIN B07MT418PF
It runs keeps my battery full, while running compressor fridge at sunny weather, also if it is just 50W and pretty cheap!
- Thread starter
- #23
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So, I was wondering about this 13V you mentioned. You did not mention under what circumstances so I don't know when that was exactly, of course, but I am curious if it is possible that a typical MPPT controller would be far off the normal MPP point when the battery is fully-charged and it's running at low power. Perhaps because it no longer matters how efficient the process is at that point. So I went out and I checked mine when the controller was in float mode with the fully-charged battery kept at 13.8V and the controller only drawing 5W. But no, the panel (in direct sunlight) was still set to about 19V -so still right around nominal MPP- even with hardly any power drawn. So, at least in my case, it indeed appears to keep the panel around the MPP over a good range of powers. Of course, that is a function of the algorithm used by the controller and yours may be different.
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- #25
Yes, when I looked at the 13.x the battery was full. and in the sun. I'm going to check it in the morning.
The temp here has been in the 90's and the arb 63 fridge has been keeping between 27 and 29 degrees running only on the solar, including being opened and closed to get drinks and food out.
I mention the model as I had an arb 37 before and it ran on less juice.
The temp here has been in the 90's and the arb 63 fridge has been keeping between 27 and 29 degrees running only on the solar, including being opened and closed to get drinks and food out.
I mention the model as I had an arb 37 before and it ran on less juice.
well, if the fridge was going at the time, then the battery may have been full but it was still sucking power out of the panel so the controller was likely doing its thing, maybe hunting for the MPP. But I don't know how Renogy controllers work.
(Hopefully it's a true MPPT and not a disguised PWM cuz that could explain the low panel voltage... )
(Hopefully it's a true MPPT and not a disguised PWM cuz that could explain the low panel voltage...
)- Thread starter
- #27
It was this controller here, Renogy 30 amp with a blue tooth. I got the 30 amp so I could run a 300 watt portable panel in the future, and keep the LC in the shade.
Not at the list price obviously.
www.renogy.com
Not at the list price obviously.
Rover Li 30 Amp MPPT Solar Charge Controller
Your batteries will be protected from discharging and over-charging With its advanced MPPT charging technology. Limited time sale, 10% off: Renogy10off
www.renogy.com
I am planning to fit a solar panel on my 78 roof .
the idea is to put 2x 100 W panels , slim and flexible style .
hook it up to a Victron 75/15 controller , to feed 2 Yellow Optima 75 ah batteries .
the batteries are quite old , but they still do the job .
batteries are in parallel .
my question is :
is it better to put the SP in series or in Parallel ?
pro -con for each .
which has better performance in shading ?
thanks Renago
the idea is to put 2x 100 W panels , slim and flexible style .
hook it up to a Victron 75/15 controller , to feed 2 Yellow Optima 75 ah batteries .
the batteries are quite old , but they still do the job .
batteries are in parallel .
my question is :
is it better to put the SP in series or in Parallel ?
pro -con for each .
which has better performance in shading ?
thanks Renago
Tons of articles on the internet about plusses and minuses of each. But, know it will take a differential of 5v between the battery voltage and the panel output voltage to initiate current flow. I have two 175w 18v (nominal) panels atop our Escape trailer and originally had them in parallel but changed to series and like it better especially when the battery array (LFP) is sitting at 13-ish volts...
Shading is typically not an issue for us and where we travel. Except with full on shade from a canopy of tall trees then the series/parallel issue is trivial.
Shading is typically not an issue for us and where we travel. Except with full on shade from a canopy of tall trees then the series/parallel issue is trivial.
- Thread starter
- #30
Hooking the panels in series is better.
The reason for this is in low sunlight the voltage on each drops . In series you get the max voltage enabling it to charge. In parallel there may not be enough voltage to charge. Example if each panel was putting out 8 volts, parallel 8 volts in not enough to charge but in series 16 volts is.
I was looking at this last month.
Voc is 21 V , on a 100 W panel
^^ Fisher, there are indeed strong benefits to the series configuration as discussed earlier in the thread but as to your post #30 above it doesn't quite work like what you refer to, AFAIK. If you look at the IV curves for a solar cell, you'll see that as the insolation decreases, the current decreases significantly over most of the load range, but that the max power voltage doesn't. Even at low insolation the panels will still give fairly high voltage, but of course then only low current. And of course, with a good MPPT you will stay right at max power voltage. For example, just a couple of days ago, I was checking a nominal 20W panel, the sky was completely socked in and the panel was only putting out 2W, but the voltage was still plenty high, and the charger happily chugging along -if maybe a bit frustrated for not stretching its legs-. So your concern is not really that much of an issue in real life, I think.
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- Thread starter
- #33
I agree not exactly as I said as that was just a crude example. I run (2) Renology 100 watt panels and I can keep the fridge going with a single panel most of the time.
The voltage does drop in low light. Most of the time I look at the panel info it is putting out between 15.5 and 16.5 volts. It does not put out 21 volts as someone pointed out above.
This has been my experience from actually using the 100 watt panels.
VOC 21 , is obvious that it will not be an operating volts.
Maybe 18 V Aprox , at the controller .
Maybe 18 V Aprox , at the controller .
Resurrecting this thread since it seems there are many folks knowledgeable about solar and 12V on here. I am trying to put together a system of a combination of two panels, one fixed to the hood and one portable, to serve several purposes. I already have a 130W portable panel with an MPPT charge controller that has worked well for us while stationary, but was thinking that adding the hood panel would help keep my AGM single Group 31 battery happy while sitting and not having to plug it in so often to my NOCO charger. Our garage is too small for any vehicle especially a Cruiser, so with parking on the street it’s kind of a pain to plug it in.
Would a standard MPPT controller with say a 50W panel mounted to the hood serve my purpose of keeping the AGM happier? It probably depends on the internal programming of the charge controller and the voltages it uses I would imagine, so will continue to fully boost the battery at least once a month.
Apropos to the above discussion, is there a way to wire them in series and have one of the panels easily removable? I was thinking you could rig up something with a change over relay that would allow the hood panel to charge at all times then somehow trigger a relay with the power from the portable panel itself when plugged in that would then be wired in series, but I don’t know enough about 12V wiring to not light my Cruiser on fire trying something like that. Maybe the complexity isn’t worth it and I should just wire them in parallel for easy removal of the portable panel? Was just concerned about the MPPT 5V differential for charging and having the second hood mounted panel boost voltage to overcome that scenario if it arises.
Would a standard MPPT controller with say a 50W panel mounted to the hood serve my purpose of keeping the AGM happier? It probably depends on the internal programming of the charge controller and the voltages it uses I would imagine, so will continue to fully boost the battery at least once a month.
Apropos to the above discussion, is there a way to wire them in series and have one of the panels easily removable? I was thinking you could rig up something with a change over relay that would allow the hood panel to charge at all times then somehow trigger a relay with the power from the portable panel itself when plugged in that would then be wired in series, but I don’t know enough about 12V wiring to not light my Cruiser on fire trying something like that. Maybe the complexity isn’t worth it and I should just wire them in parallel for easy removal of the portable panel? Was just concerned about the MPPT 5V differential for charging and having the second hood mounted panel boost voltage to overcome that scenario if it arises.
I would use two Victron controllers, one for each panel, and create a "Smart Network" for charging when using fixed and portable panels.
Interesting, will look into that. My concern with the Victrons is they can’t be mounted under the hood due to their water rating being abysmal. That makes wiring a PITA. My charge controller (Epever Tracer that came with the Bugout) is IP68 rated.
50W should be plenty to keep the battery topped off from just sitting there if there is nothing abnormal going on. A good controller would also make a monthly boost unnecessary I think. You could use a waterproof box but it's probably easier to just draw some wires into the cabin and keep a non waterproof controller there.
If the panels are to be in series, you can manually interrupt the circuit and introduce or remove one easily enough with switches or connectors, I would not bother with relays. If in parallel, I think 2 different controllers won't have any issue, they will just see whatever the battery voltage is at that time and react according to their own logic.
What is your concern about the 5V? Normally it's not much of an issue in practice if you have a panel that is built for a 12V system.
If the panels are to be in series, you can manually interrupt the circuit and introduce or remove one easily enough with switches or connectors, I would not bother with relays. If in parallel, I think 2 different controllers won't have any issue, they will just see whatever the battery voltage is at that time and react according to their own logic.
What is your concern about the 5V? Normally it's not much of an issue in practice if you have a panel that is built for a 12V system.
No
Not based on any real world experience or issue, I just read that it’s a potential pitfall for MPPT controllers to be aware of. I’ll probably follow the KISS principle and wire them in parallel. Thanks for your feedback!
