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Old 06-19-2017, 06:29 AM   #21
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If it was my install and they weren't high enough to get under, they would be hinged on one side and pinned on the other.

Even better, they would be pinned on both sides for easy removal and have leg supports to possibly be tilted for better sun angle.
Haven't seen a lot of installs but almost all have been with very little space under the panels.

Your suggestion sounds good but it seems like most of the mount designers are completely clueless. Have you seen mounts like that from a vendor? IMHO, the mounts have always been the weakest like in solar on boats.
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Old 06-19-2017, 07:01 AM   #22
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Usually vender stuff is at best, half way to a good design.

Not always, but on boats, often.

Plus, most solar is for land based stuff so I wouldn't have even bothered because of additional adaptation or materials.
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Old 07-07-2017, 06:34 AM   #23
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I had to have my attachment clips fabricated so that the 260W panel was raised above the vents on the coach roof. It is high enough that I will be able to clean under it.
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Old 07-07-2017, 07:37 AM   #24
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Do you have a photo of them in use? Looks like a quality piece.
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Old 07-07-2017, 06:01 PM   #25
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I'll take one this weekend. They cost me $90 to have the guy design and make them. Which is a lot of money for a few brackets, but not so much when you think of the process and the custom design. And I got to visit their totally cool facility, where upstairs they are working on space sat stuff. The fabrication work is a side hustle because they have these hi-tech cad-cam computers and other big techy machines of which I know naught. When I saw what they do I wanted to go back in time and have a career doing that kind of thing!
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Old 07-07-2017, 07:11 PM   #26
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Electricity is my weak point when it comes to boat systems. So I'll throw this one out there to you guys. Just looking for a rough or SWAG figure.

Say I had room on the flybridge hardtop for ~100 sq feet of solar panels. And the panels/chargers are today's state of the art units.

Say it's a mostly sunny day in the summer time.

Without getting into nuances like latitude and other details, how long do I have to run my 20kw generator to equal the amount of electricity generated by my hypothetical panels?
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Old 07-07-2017, 07:26 PM   #27
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This is a serious SWAG, but let's say yo can fit 1kw of panels, and get 5hrs of full sun equivalent output. That's 5kwh per day. That's 15 minutes of gen run time at full output.

Now if you are wondering how much gen run time the panels will save, it's actually better than that because your chargers are very unlikely to consume the full 20kw of your gen. You might have 3-6kw of charger capacity, so you are looking at more like a full hour of run time.
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Old 07-07-2017, 07:36 PM   #28
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how long do I have to run my 20kw generator to equal the amount of electricity generated by my hypothetical panels?
If the use case is charging batteries on the hook long-term, with that much genny all solar will do for you is

greatly reduce genny runtime

triple the life of your bank, making it worthwhile spending more on quality

If you're already burning dino juice 5+ hours most days, then probably solar is not worth it.
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Old 07-07-2017, 07:58 PM   #29
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I find with solar, keeping the batts up all day, you dont need to run the genny till you lose too much energy from the batts.

Lets the batts get low, and it takes hours for the genset to charge them up...but kerp the charge up all day long, it takes little or no charging from the genset.
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Old 07-07-2017, 07:59 PM   #30
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This is a serious SWAG, but let's say yo can fit 1kw of panels, and get 5hrs of full sun equivalent output. That's 5kwh per day. That's 15 minutes of gen run time at full output.

Now if you are wondering how much gen run time the panels will save, it's actually better than that because your chargers are very unlikely to consume the full 20kw of your gen. You might have 3-6kw of charger capacity, so you are looking at more like a full hour of run time.

Twisted's numbers look OK without running the math. There are things though that are simplified. For example, assume only a 3KW charger charging a 12 V bank. The battery bank would need to accept is 3000/12 or more realistically 3000/14 = 214 amps. Of course, there are losses to contend with which I have neglected.

This is a very large charger and you will need a huge battery bank to accept the charge. Your generator is not as good as one would like for charging batteries. You will have to run your genny for hours depending again on the charger along with how large the bank is.

Now consider solar and Twisted's assumptions...1KW in panels and an MPPT controller (high nineties for efficiency) charging currents will be about 1000/14= 71 amps for 5 hours or 355 amp hours returned to your battery bank. And when the batteries are fully charged the controller will enter float mode with very little current being supplied to the bank. IMHO-- SOLAR is the way to go and on top of that, it is silent!
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Old 07-07-2017, 09:06 PM   #31
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Say you have a 1000AH bank, that's big enough for a small A/C unit, huge by most mobile standards. If that's lead 500AH usable for longevity, and say that's how much needs restoring.

If it's old-school FLA, from 50% SoC to say 80% will take 2+ hours, since around 150A is the maximum current the chemistry will accept, so forget about your KW charger.

After the Absorb voltage setpoint is passed, the resistance rises, current accepted declines, that last 80-100% -which you DO need to get to for bank longevity - will likely take at least 4-5 hours, very quickly current amps dropping to low two-digits, finally down to the defined-full point below 10A.

That's where it would be stupid to devote dino juice to just charging, and exactly where you get more than your money's worth out of solar.

With a smaller bank you easily may never need to run a motor unless you want to for other reasons.

With a higher CAR lead chemistry like quality AGM, you get past .5C rates, if your charger/alts can put out 500A, in theory you get that early stage done in half the time, but the long tail will take nearly as long.

LiFePO4 is even faster acceptance, and **never** needs to get to 100%, so that buys a lot more flexibility, no need for solar if you don't like it.

But at seven+ times the cost plus specialized charge sources required, call it an extra $2K on top.

For liveaboards and others on the hook away from shore long periods, solar is a no-brainer.
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Old 07-08-2017, 08:18 AM   #32
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And when the batteries are fully charged the controller will enter float mode with very little current being supplied to the bank. IMHO-- SOLAR is the way to go and on top of that, it is silent!
In haste I misstated "are fully charged" where I should have stated " ended absorption"


John's above post is EXCELLENT and provides a better explanation than mine. Keep it up John!!
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Old 07-08-2017, 09:08 AM   #33
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A small solar panel is a great addition to make sure that your batteries always get recharged to 100% and stay charged if you are on a mooring like us.

We have 220 AH of house capacity plus a NextGen 3.5KW genset. If we are anchored out for a few days, running the genset for a half hour morning and night brings the batteries back to 85%. Then when we get back to our mooring the solar panel brings the batteries up to 100% within a day or so.

I have a 100 watt panel with an inexpensive Morningstar PWM controller. It cost about $200 for materials to install.

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Old 07-08-2017, 09:26 AM   #34
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In haste I misstated "are fully charged" where I should have stated " ended absorption"


John's above post is EXCELLENT and provides a better explanation than mine. Keep it up John!!
why thank you kind sir

Note that was no error.

Many (most) automatic charge sources end the Absorb cycle **way** too early.

Float should only happen when the bank is 100% Full. Think of it as "standby mode" ready to carry any loads coming online so the bank stays full. And for long-term storage when there are no loads.

LFP should not be floated at all.
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Old 07-09-2017, 04:11 PM   #35
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Do you have a photo of them in use? Looks like a quality piece.
As promised: (shims required because of the crowning of the roof. Well caulked around the bases. Note how I needed some height because of the vent covers).
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Old 07-12-2017, 07:35 PM   #36
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Now consider solar and Twisted's assumptions...1KW in panels and an MPPT controller (high nineties for efficiency) charging currents will be about 1000/14= 71 amps for 5 hours or 355 amp hours returned to your battery bank. And when the batteries are fully charged the controller will enter float mode with very little current being supplied to the bank. IMHO-- SOLAR is the way to go and on top of that, it is silent!

But it's even more than that. Even if the output is too low to charge the panels, you get a contribution on the realtime loads so the demands on the batteries are lessened. That is the case early and later in the day, or on overcast and rainy days.

We have found that our 24 hour demand is about 200-250 amp-hours. We have 435 watts of panels. We used to run the genny for 1.5 hours in the morning and another 1.5 hours in the evening and there was always a deficit of at least 5%. Now, on a sunny day, our bank is fully charged by 3-4:00pm and the loads are carried on until 8-9:00 pm before we run into the negative. We rarely find a deficit in the morning that exceeds 80 amp hours on our 1125 amp hour bank, and we always get our bank fully charged each day, with a combination of running, etc. The genny is used exclusively for washing and to offset the demands of the Webasto hydronic system.

I made my own mounting brackets out of 1.5" aluminum angle (1/4" thickness). Less than $20. I just drilled holes before cutting it with a mitre saw. They are assembled to form a "U" and I glued them down on the PH roof with 4200, no holes or screws. They are rock solid but may have to be reglued in a couple of years.

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Old 07-13-2017, 09:02 AM   #37
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Excellent job on your brackets!!! And by keeping your battery bank from depletion, you should get many years of use from it!!!
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