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Old 05-08-2018, 07:22 PM   #1
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Higher Amperage or Higher Wattage for charging Via Solar

I have 4 panels. For charging batteries, would it be better to up the amperage by running two pairs of panels in series or should I run them all in parallel?

The panels are these: 350 watt panels x 4
https://www.solar-electric.com/silfa...RoCUVEQAvD_BwE

The guys at NAWS confirm that my equipment can handle running two pairs in series.

I will be charging 4 Renogy AGM 12volt 200ah batteries wired in parallel using a MPPT Midnite Classic 200.

I'll be a over the country with this rig and I'll have a generator at some point and shore power when available (which probably won't be often)

So, in your opinions, which is better:

Four 350 watt panels in parallel

Or

Four 350 watt panels with 2 pairs run in series?

Thank you in advance.
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Old 05-08-2018, 08:35 PM   #2
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at 38.9 volt per panel i would run them in parallel. That will make you less sensitive to partial shading .

good luck
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Old 05-08-2018, 09:02 PM   #3
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at 38.9 volt per panel i would run them in parallel. That will make you less sensitive to partial shading .

good luck
later J
Thank you Joe. That's what I had planned to do previously. The guy at NAWS had mentioned that series was possible so I thought I would come ask here.
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Old 05-08-2018, 10:09 PM   #4
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With a 12volt battery bank and mppt controller, you'll be charging the bank very shortly after the sun comes up.
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Old 05-08-2018, 10:38 PM   #5
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Getting a say 50% depleted lead bank back to 100% Full takes 4-6 hours no matter how many potential watts& amps you have.

Just the last 5% can take well over 90min.

Make sure with an expensive bank your SC is adjustable enough to overcome the usual dropping to Float before reaching Full as per endAmps.

Faoling to regularly get to that 100% point will early murder a bank nearly as fast as discharging too low.
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Old 05-08-2018, 10:46 PM   #6
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Getting a say 50% depleted lead bank back to 100% Full takes 4-6 hours no matter how many potential watts& amps you have.

Just the last 5% can take well over 90min.

Make sure with an expensive bank your SC is adjustable enough to overcome the usual dropping to Float before reaching Full as per endAmps.

Faoling to regularly get to that 100% point will early murder a bank nearly as fast as discharging too low.
This ^^^ One hundred times this.

It's a stunning sad indictment on the entire RV industry that many makers, complete with their fancy RVIA stickers, are still fitting lead/acid batteries and charger/converters that top out at 14.4 volts.

It should be criminal, and they know it.

One thing they do not do is fit Trojan batteries and honor the 5-year warranty those items carry, because they know the equipment they are fitting will wreck them.
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Old 05-08-2018, 11:37 PM   #7
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This is from the manual of my controller. I will be able to set the voltage points for each stage. I thank you John and Twigg for the input.
Screenshot_20180509-003430.jpeg
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Old 05-08-2018, 11:50 PM   #8
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I think my question should have been higher amps or higher voltage as the Watts will stay the same?
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Old 05-08-2018, 11:51 PM   #9
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But I think that parallel is the way to go?
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Old 05-08-2018, 11:53 PM   #10
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So if I run in parallel I would need a 40 amp breaker in the combiner box?
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Old 05-09-2018, 08:25 AM   #11
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If voltage is high enough to get good MPPT efficiency from your SC, parallel will help deal with partial shading.

No CP is needed between panels and SC.

Unless you want a switch anyway, or the vendor specs it.
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Old 05-09-2018, 09:16 AM   #12
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JohnCt, I would disagree with "No CP is needed between panels and SC". With 4 panels in parallel and one set of wiring shortcuts that sets of wire could take the remaining short current of the other panels.
Potentially a fire hazard.

Also in the case of SC failure and 3 panels disconnected and one shorted the SC to battery fuse might be heavier then the individual solar panel wire can handle.

I suggest breaker or fuse each panel as close to the SC as possible and then tie them parallel to the SC.

Later J
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Old 05-09-2018, 01:51 PM   #13
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The vendor recommends a breaker between panels and SC. After playing with the sizing tool on the Midnite site, it recommends 2 pairs of series for the controller. I do appreciate all the comments and advise and feel.more educated from this discussion.

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Old 05-11-2018, 02:45 PM   #14
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Always put a breaker between the panels and the charge controller. Add another breaker between the charge controller and the batteries. You might have to use a fuse block terminal on the battery for your inverter ... in my case it was pretty tough to find a 200 amp DC breaker. Not only do all of these breakers safeguard your equipment but it's really nice to be able to flip a switch and shut off power for maintenance. I bought a small RV breaker panel and wired it all nice and neat. I might suggest you do the same. Keep in mind also that depending on the size of your solar array, running in parallel might not be the way to go ... especially if you're using stock wires from a kit. Most of them are designed to be run in series as you'll need a thicker gauge wire to carry more current if you plan on going parallel. With a good MPPT charge controller (like a Morningstar), series will work just fine. Although, that being said, running a combined parallel/series type system does protect against shade. My bus is never really shaded so it's a non issue. If I need power I park in the sun.

EDIT: Just saw your reply. Midnite is a good brand too. Good luck with your build.
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Old 05-11-2018, 03:16 PM   #15
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Many small builds are just fine with no CP between panels and SC.

How you disconnect panels from SC is a separate matter, convenience of a breaker also providing that functionality may tip the balance but does not demand that particular solution.

Best for shade handling is one SC per panel, getting a panels whose specs maximize use of the SC helps keep costs down.

e.g. Victron 75/15 MPPT for under $100@, paired with a 220-250W panel, even up to 300W if you find a great bargain, and Voc rated between ~40 and 65V.

If you're trying to maximize watts capacity, completely fill every inch of rooftop with panels then of course the physical sizing geometry and cell efficiency rating become important.
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Old 05-12-2018, 05:45 AM   #16
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Thank you for the information Warewolff and John.

I believe I've finalized my solar equipment. I will run two pairs of panels in series. These will go to a combiner box where each pair will run to it's own 15 amp/150 volt breaker. This will then run to the Midnite Classic 200. After that it will go to a 80 amp breaker and then on the batteries. I will use the spec sheets that come with the equipment to use the largest size wire Incan to make the runs. I'll also place my SC as close the battery bank as possible.

One more question for everyone, if I'm going to add a battery monitor, does the SC need to have the negative run to the shunt or is it only needed on the negative side of the 120v/12v output from the batteries?
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Old 05-12-2018, 06:25 AM   #17
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One more question for everyone, if I'm going to add a battery monitor, does the SC need to have the negative run to the shunt or is it only needed on the negative side of the 120v/12v output from the batteries?
The shunt should be wired so that all power (negative) passes thru the it. One side goes to the battery bank negative and everything else goes to the other side.
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Old 05-12-2018, 06:57 AM   #18
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In and out of the battery bank?
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The shunt should be wired so that all power (negative) passes thru the it. One side goes to the battery bank negative and everything else goes to the other side.
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Old 05-12-2018, 09:10 AM   #19
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The shunt should have one wire that goes from it to the neg battery post. Everything else that you would normally put on the negative battery post, now connects to the other post on the shunt. So imagine if you will all of the negative leads go to the shunt and funnel down to the one negative lead that goes from the shunt to the wire.

If you start running out of space on the shunt stud, I'm pretty sure you can use a negative junction stud for a little more stud real estate and run a wire from that to the shunt.

You want to keep track of every amp going in or out of the battery. If you bypass the shunt, your appliance would still work, but you and more importantly, your battery monitor, wouldn't be able to keep track of how much is actually being drawn from the bank.
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Old 05-12-2018, 09:12 AM   #20
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So imagine if you will all of the negative leads go to the shunt and funnel down to the one negative lead that goes from the shunt to the wire.
Sorry, that should have read "So imagine if you will all of the negative leads go to the shunt and funnel down to the one negative lead that goes from the shunt to the battery."
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