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Old 06-13-2018, 06:02 PM   #21
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How come three panels can not be wired in parallel? I just have some harbor freight panels on temporary, but plan to buy some this summer, and had not heard three panels are trouble. So any info as to why would be great . Thanks

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Old 06-13-2018, 09:00 PM   #22
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My bus is 99% 12V except the fridge which runs off a power inverter. The inverter I have has 3 outlets. One for the fridge, one for the power strip, and one for a spare.

I cn charge a laptop if needed, but most of my internet browsing is done with my tablet or phone which will charge from a USB outlet (have 5 in my bus) or a charger in a 12v outlet (have 4 in my bus) so I am good to go. If I need to charge a laptop, then the power inverter will do the job.
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Old 06-14-2018, 05:49 AM   #23
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Quote:
Originally Posted by Ronnie View Post
How come three panels can not be wired in parallel? I just have some harbor freight panels on temporary, but plan to buy some this summer, and had not heard three panels are trouble. So any info as to why would be great . Thanks
You can absolutely run an odd number of panels in parallel, you just can't do it when you're doing both parallel and series sets.

If you have 3 100W 12v panels there won't be any problems running them in parallel for a 300w 12v input. What you can't do is wire them in differently sized banks, like a 2+1 configuration, trying to get 24v.

I have 4x 100w panels in parallel and recently I've been adding a 5th panel as it still give me a useful increase of power over 4 panels throughout the day even with a 30A controller.
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Old 06-14-2018, 06:14 AM   #24
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Ok, this makes sense. Thanks. For my energy loads 3 or 4 100 watt panels should be plenty, and will be 12 volt, and was planning parallel wiring.
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Old 06-14-2018, 10:47 AM   #25
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I always thought the number of watts from the panel/panels hat to be equal to the amount of watts of the appliance with the highest wattage. From reading here on the forum and researching, i take it the charge time will depend on the number of watts from the panels? So one can have a single panel but charging the batteries will take longer?
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Old 06-14-2018, 11:39 AM   #26
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There are a few formulas but ultimately it comes down to three things:

. The watt/hours you consume
. The watt/hours you can store
. The watt/hours you can produce.

You're not so much powering your devices from your panels, you're charging your batteries from them. Consider that your devices are being powered by your batteries, and you need to generate enough power to keep them full.
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Old 06-14-2018, 08:00 PM   #27
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Makes sense. Anyone know the highest wattage a single panel has?
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Old 06-16-2018, 05:06 PM   #28
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Originally Posted by Iceni John View Post
You mentioned possibly getting three panels. Odd numbers of panels can be problematic. The only way they can be connected is in series, then their combined voltage is much too high for a PWM charge controller (you'll end up wasting more power than you use), and unnecessarily high even for a MPPT controller (the greater the voltage stepdown, the more heat it makes and the lower its overall efficiency). If you have an even number of panels you can wire them in parallel, and this will avoid the problems I mentioned, plus it makes the array less affected by shade on just panel - if one panel is shaded, a series array produces very little power, but a parallel array produces all the power except that from the shaded panel. Parallel makes more sense on a bus or boat where the panels are probably not ideally orientated to the sun most of the time. The advantages of series panels are irrelevant with a bus or boat.

As others have said, first calculate your loads, then determine how much battery capacity is needed to support them, then how much solar power is needed to correctly charge the batteries.

John
Why can't odd quantities of panels be connected in parallel?
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Old 06-16-2018, 06:50 PM   #29
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I'm in the middle of a skoolie build and here are the products i bought:

Inverter, AIMS Power 2000 Watt 24 VDC Pure Sine Inverter Charger w/ 6000W Surge Amazon link https://amzn.to/2ynOlW2

Canadian solar panels CS6U-335P 335 watt, Poly solar panel I bought 6 of these panels, I'm putting 4 on the bus roof and the other 2 on my enclosed trailer roof (folks that's over 2000 total watts) (No Link)

SLR155 12 Volt 155Ah AGM Deep Cycle Hi Performance Battery (I bought 6 of these and plan on wiring them in series and parallel, so i'll have 3, 24 volt batteries with a total of 465 ah(NO Link)

I haven't had a chance to install this yet but it could be a life saver (WirthCo 20092 Battery Doctor 125 Amp/150 Amp Battery Isolator) it's battery isolater that also has an emergency jump start button that lets you pull power from your house/coach batteries to help start your rig (the emergency jump start on engages for only 30 seconds) then it goes back into normal, here's an amazon link https://amzn.to/2My2L97

I hope this helps some one
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Old 06-16-2018, 07:23 PM   #30
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eBay 310 watt panels. Outbackpower.com
They have great advice and wonderful plug and play systems. Remember pay bananas get monkeys. I’ve lived off grid for 12 yrs- 8 freezers and two houses. Outback power has a great help line. More panels are better, they are cheap now, used panels 50 cents a watt. Charge controller , inverter, and battery bank to store the power.
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Old 06-16-2018, 08:05 PM   #31
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what’s the rule of thumb on venting golf cart batteries that are not maintenance free, ie, not sealed batteries? can harmful gas enter the bus?
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Old 06-16-2018, 08:50 PM   #32
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what’s the rule of thumb on venting golf cart batteries that are not maintenance free, ie, not sealed batteries? can harmful gas enter the bus?
My old class c RV had a two piece plastic box with a duct that ran to an outside vent.

I imagine you could either use some of those hefty black plastic storage boxes with the yellow lids from HD and run a vent duct from the lid or you could enclose them in a wood box, seal the seams and run a vent duct from there.

I bought AGM batteries and will still be adding some ventilation, just in case. I'll also be painting all the surfaces with fire resistant paint from Sherwin Williams
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Old 06-17-2018, 12:03 AM   #33
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Venting batteries is really important- I’ve heard of boats having explosions from the hydrogen gas from the batteries meeting with a spark. My battery box has a fan venting the box. Even small 12v fans can be powered with the solar panels. Mine is tied into the generator so when I’m equalizing my battery the fan evacuates the gas. It’s a easy thing to do and worth it.
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Old 06-17-2018, 01:27 AM   #34
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Why can't odd quantities of panels be connected in parallel?
Short answer is that parallel circuits will have equal voltages, therefore (lets say you had four panels in one string and three in another) the maximum voltage would be limited by the shorter string.
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Old 06-17-2018, 07:36 AM   #35
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Short answer is that parallel circuits will have equal voltages, therefore (lets say you had four panels in one string and three in another) the maximum voltage would be limited by the shorter string.
But that only matters if you're doing banks of serial + parallel. If you're just doing parallel panels (like I do), then the only real negative is you hit your amp limits faster.
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Old 06-17-2018, 09:42 AM   #36
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Backwoods Solar from Idaho is a great company to work with. Very knowledgeable and willing to educate. My dealings with them have been top notch.
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Old 06-20-2018, 10:58 AM   #37
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I've had successful dealings with these people- but note that it's all high-end quality stuff ($$$$): https://www.solar-electric.com/ Everything they sell is built to last.

For cheap stuff, I've had good luck with the Harbor Freight inverters and PWM charge-controllers. This guy has run those inverters in setups for a long time, and IIRC they lasted 7 years: https://thefieldlab.blogspot.com/
I've used their PWM charge-controller stuff as a quick-deploy system to charge/maintain my starting batteries while parked for extended times: https://www.harborfreight.com/7-amp-...tor-96728.html

There's a ton of articles out there about solar sizing; I can try to summarize them:

1) inverter - you need to size this to easily power your largest load (plus startup spike) (this is probably your AC). Inverter prices go up quickly as capacity needs increase, to the point that I would seriously question your need for inverter-powered AC. For my personal uses, I instead use a swamp cooler @ 1/10 the watts, and have a small generator that gets deployed to power a portable 8.5KW AC (I do a good amount of off-grid desert camping- if you go places with hookups this completely changes your use model) (I like the modularity and backup factors that come with running multiple small inverters versus one big one)

2) panels - unique to a bus kind of situation is the mounting and panel selection. The bigger the panel, the more difficult it is to mount it in a way that can sustain the bumps and such of vehicle life. Additionally, the panel itself and the connections you make need to be made to survive those kinds of shocks. Re how to hook them up, your bus is mobile, so the "partial shading of one panel in a string" shouldn't be an issue if you simply park in the right place.

3) charge controller - I think most would say "MPPT" here (and this will be absolutely needed if you're connecting panels in series) but there's enough of a price difference that I could argue depending on use. Remember again that you're mobile, and getting a place in the full sun is more important than anything else, and that extra $$$ can be used to get another panel or more battery etc

4) batteries - the solar model is that everything runs off the batteries, and the panels are there to charge the batteries. As such, the batteries need to be sized accordingly to provide the power you need for as long as you need it. I personally see splitting my battery bank between "house" and "starting" as just a waste of battery capacity and money. There are long-term optimal battery-use models ("don't discharge below 70%" etc) but I view them more as suited for long-term home/backup situations, and to adhere to them you need to spend a lot of money on a huge batter bank. My model here is "as many cheap new-with-warranty deep-cycle batteries as will fit" and simply expect to replace them all every few years. Nowadays most places sell batteries with a non-prorated simple 3y replacement warranty, which is great for the battery-abusers among us.

5) generator - If you do anything remote at all, I've found that having a small (think EU2000) generator completely changes what you expect out of your solar system, and adds flexibility while reducing costs. If you're no longer worried about draining your starting batteries and getting stuck in a no-sun or component-failure situation, you can tie them in to your house batteries and expand your capacity by that amount. Your whole system can be sized much smaller (cheaper) if you can cover occasional large loads with your generator.

6) have fun - having a solar setup and getting all your energy "free" right from the sun feels magical, because it kinda is. Plus, the liberation felt by being able to generate energy anywhere as needed adds a temporary feeling of disconnectedness-from-society that for me adds greatly to the natural camping experience
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Old 06-22-2018, 02:12 PM   #38
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I have used RVsolarelectric.com on three different projects. I have been very satisfied on the products and their warranty. They have been around for a long time. My first project was in 1986.

My second project in 1999 the inverter failed right out of the box. It would not work with the remote. Made a phone call. Found a serial number mismatch , FedEx had a new circuit card in my hand the next day. And the address was way out in the boonies.

The Magnum inverters are US made. 2 were used in my third project last year. It was a very detailed complicated installation. I spent a lot of time on the phone with Doug designing the installation. We got all the bugs worked out on paper and actual install went well.

Getting ready to do my forth project. I'll only use them

Oh btw. All three projects are still working with out a hick up.
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Old 07-05-2018, 03:22 PM   #39
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where would I even start to figure this out?
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Old 07-05-2018, 04:02 PM   #40
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First- add up all the watts and amps you will be requiring. Each appliance has a rating listed on a tag. Add everything up and math it.
First of all call OUTBACKPOWER.com and tell them what you want to do. Ask for their recommendations. They are a top drawer organization and sell great products quality and customer service.
Then size your battery bank based upon your load (wattage and amps). Then run the pv panels on the bus and using the charge controller and the necessary inverter you will get clean sinewave power! Suitable for sensitive computer ops too.
You are on the right path.
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