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Date Posted |
Forum
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RE: Which is better: Higher or lower volt solar panels?
Hi,
The efficiency of the controller is lower when the input voltage is at 48 volts compared to 24 volts. It is a tiny difference, but the watts in solar are pretty tiny too.
Price is no use in looking at the technology in the panels--recently the unisolar PVR 138 panels were being sold for well under $2 per watt.
If I were the OP and did not wish to expand the system I'd go with the Rogue controller and two panels in parallel.
If I were the Op and wished to allow for future expansion to a third panel I'd go with the Tristar 60 amp mppt unit and wire the panels in parallel.
I'd choose a wire size from the panels to a combiner box on the roof based on 170 watts @ 24 volts (7 amps), and from the combiner box to the controller based on 510 watts @ 24 volts (21 amps). I'd use #8 wire from the panels to the combiner box, and #6 wire from the combiner box to the controller.
Because both the Rogue and Tristar units have voltage sense lines, I'd probably use #6 from the controller to the battery bank.
I would use an automatic circuit breaker of 50 amps as close to the battery buss as possible. (assuming balanced wiring for the six six volt batteries)
I would have a switch on the output side of the controller so that I could be certain to be able to have a situation where I know the power is off.
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pianotuna
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02/08/12 04:43am |
Tech Issues
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RE: Battery Cutoff
Hi,
Inverters of any size (and 130 amps indicates a large unit) are most often wired directly to the battery bank--the cut off switch does not disconnect the inverter.
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pianotuna
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02/07/12 10:09pm |
Tech Issues
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RE: Spoon down the toilet
Hi,
Boil the spoon for five minutes. No need to trash it.
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pianotuna
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02/07/12 09:46pm |
Hybrid Travel Trailers
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RE: Which is better: Higher or lower volt solar panels?
Hi Mr. Wizard,
Then how do you explain Renoman's poor results--he has modern panels.
It still behooves the end user to test series vs parallel and make the decision from that point.
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pianotuna
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02/07/12 09:32pm |
Tech Issues
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RE: Which is better: Higher or lower volt solar panels?
Hi smk,
Losses depend on panel design and how many diodes there are. No harm to the panel if shaded so far as I know.
Perhaps 2oldman can chime in--his system is totally series.
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pianotuna
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02/07/12 08:27pm |
Tech Issues
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RE: Which is better: Higher or lower volt solar panels?
Hi,
If you do not wish to expand I'd go with the Rogue controller.
If you wish to expand I'd consider the Tristar 60 amp mppt because it is more fully featured than the 45 amp tristar.
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pianotuna
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02/07/12 08:07pm |
Tech Issues
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RE: Which is better: Higher or lower volt solar panels?
Hi Mr. Wizard,
I agree. Shade tolerant panels are superior to non shade tolerant--but it is about #24 down the list of reasons to purchase panels.
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pianotuna
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02/07/12 08:05pm |
Tech Issues
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RE: Time left from battery
Hi
BFL13 is our resident expert on external chargers. I'd ask him in your shoes.
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pianotuna
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02/07/12 07:45pm |
Tech Issues
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RE: Which is better: Higher or lower volt solar panels?
Hi,
that one has very bad reviews--and actually consumes more energy than it outputs. BAD CHOICE imo.
Fixed Install. I have seen some MPPT controllers that are pretty cheap but am not sure about how well they will do: LIKE THIS ONE. It is a 25 amp controller and will handle two panels if I stay that route.
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pianotuna
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02/07/12 07:40pm |
Tech Issues
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RE: Time left from battery
Here is a chart:
http://www.bestconverter.com/assets/images/charge_wiz_curve.gif
"The chart above shows the amount of time it took a PD9155 (55-amp) converter set to three different output voltages to recharge a 125 AH (Amp Hour) battery after it was fully discharged to 10.5-volts.
14.4-VOLTS (Boost Mode) – Returned the battery to 90% of full charge in approximately 3-hours. The battery reached full charge in approximately 11 hours.
13.6-VOLTS (Normal Mode) – Required 40-hours to return the battery to 90% of full charge and 78-hours to reach full charge.
13.2-VOLTS (Storage Mode) – Required 60-hours to return the battery to 90% of full charge and 100-hours to reach full charge."
Hi,
I suspect the OP has never fully charged the battery bank. It may take some doing to get back that lost capacity (corrected post).
OP here. So what do you mean I probably never fully charged the battery bank? And all the questions that go with that one.
Thanks
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pianotuna
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02/07/12 07:29pm |
Tech Issues
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RE: Which is better: Higher or lower volt solar panels?
Hi,
fixed or tilt install?
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pianotuna
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02/07/12 07:09pm |
Tech Issues
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RE: Which is better: Higher or lower volt solar panels?
Hi,
And how many of those lovely 24 volt 170 watt panels are in your hot little hands?
At 24 volts I'd encourage MPPT technology.
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pianotuna
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02/07/12 06:51pm |
Tech Issues
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RE: Which is better: Higher or lower volt solar panels?
Hi Mr. Wizard,
It depends on the panels. Renoman had major losses for series.
Unisolar are among the best for shade tolerance. I did test mine and shading one cell did not "shut it down", and even shading 1/2 the panel (both sides of the cells) did not cause much drop. Finally I shaded one entire panel and I still got power from the other series wired panel. But that is with Unisolar. Other panels may not be so tolerant.
My system is series/parallel for those who may not know that.
So the advice to go parallel is valid, at least unless the owner does a bread board set up first to test out the results.
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pianotuna
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02/07/12 06:27pm |
Tech Issues
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RE: wiring in my inverter
Hi fltioga89,
8 feet and 120 amps when the inverter is running flat out. This is a bad idea. Here is why.
Solution:
1 conductor(s) per phase utilizing a 1/0 kcmil Copper conductor will limit the voltage drop to 1.98% or less when supplying 120 amps for 8 feet on a 12.6 volt system.
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pianotuna
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02/07/12 05:31pm |
Do It Yourself Modifications and Upgrades (DIY)
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RE: Which is better: Higher or lower volt solar panels?
Hi,
What panels did you choose and what controller?
The advantage of parallel is shade tolerance. If the panels are in series output drops dramatically from the entire array if just one cell is shaded.
Since this is a new install I would favor parallel with good sized wire. Wire size is more important if an MPPT controller is to be used.
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pianotuna
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02/07/12 04:56pm |
Tech Issues
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RE: kill-a-watt that sends information?
.
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pianotuna
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02/07/12 11:21am |
Tech Issues
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RE: kill-a-watt that sends information?
Hi Go Blue,
I fail to see how your reply pertains to data logging?
And such surge protection is essentially useless to me. A case of the emperor's new clothes. I doubt there is an autoformer in my future either. For the cost of those I could at least double my solar harvest abilities.
I may have to start my generator for more than exercise on my next trip--but we shall see. If so, it will be the first time since 2008 in the fall.
Worthless unless you are going to watch it on a 24/7 basis...
Money well spent would be towards getting yourself a multi-function surge protector or autoformer...
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pianotuna
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02/07/12 11:14am |
Tech Issues
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kill-a-watt that sends information?
Hi all,
I bumped into this today:
tweetawatt
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pianotuna
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02/07/12 10:31am |
Tech Issues
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RE: add electric to gas water heater
Hi kneal44,
zero items found.
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pianotuna
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02/07/12 09:56am |
Tech Issues
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RE: Battery Charging
Hi Ken,
Yes, one bad cell (as in shorted) will draw down the other two batteries, but it usually happens FAST.
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pianotuna
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02/07/12 09:53am |
Class A Motorhomes
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