The Solar Portion of my Boat Dock Project

o2bnMaine

Questions:
(1) How many batteries should I get? 
(2) Can I get too many Amp Hours for my solar configuration?
(3) Battery Box venting/insulation?
(4) Fuses/Circuit Breakers?
(5) Inverter choice?

The other thread I started ended up focusing on Power of Ethernet as a power source for the majority of my power needs. Thank you for all your comments! I do still have an aspect of the boat dock that will be powered by solar though. I am close to moving forward... hopefully you will help make sure I'm on the right track. I hope to avoid any issues since I don't want to burn my dock down with an exploding battery or something!

I have not ordered anything yet, so please feel free to steer me in a different direction. 

The hoist motor is 11.6 amps @ 110 volts = 1,276 watts. Normally, the boat hoist motor will run for just a few minutes at a time less than 10 times a day (5 times down, 5 times up). It'll probably run less than 5 times a day, but I want to be conservative in my estimate. I plan on connecting in two 6w or 9w lights as well. And, if we find there's room in the system, maybe a low-powered ceiling fan to move air. 

I'm opting for a 4-panel configuration/kit (4x128=512 watts). http://www.soldonsun.com/Pr/Solar/Off-Grid/512W-Battery-Charger-1224v.html

I like the uni-solar panels because they fit in a metal roof tracks/ribs. (My dock has a metal roof.) This solution means I won't have to drill any holes in the roof and I won't be advertising to people that there are expensive electronics to steal under the eaves... all I have to do is peel and stick the panels to the roof. On Friday when I get home, I'll be measuring to be sure the roof is at least 18 feet long on its western side -- the eastern side is less than 7 feet long. If that's the case, it will fit these oddly shaped panels. 15-inch x 216-inch. If not, back to the drawing board! 

I am trying to decide whether I should set up a 2x2 (4 12v battery configuration to get to 24v) or a 2x3 configuration. There are two different lead acid batteries I'm looking at... 90Ah or 105Ah. Do I need to worry that the 4x128w panels won't be able to charge a 630Ah (105Ah x 6 batteries) battery bank fast enough? The above charge controller in the kit is 24v 45a. I've read that in Florida, I should use a ~6 hour charge day for December. With the panels on the western side of the roof, this seems like a reasonable estimate.

I have been looking at getting a 3kw inverter, which should be way above the maximum watts I'll be demanding. The hoist won't break 1.5Kw (11.6a x 110v), right? Would I be better served with a 2kw inverter? At some later date, I may want to add more to the system.

http://www.aimscorp.net/3000-Watt-Pure-Sine-Wave-24-Volt-Inverter.html <== I'm putting this down as the inverter mainly because it has a very high (175-degree) shutdown temperature. Being that my whole set up will be under a hot tin roof (with a piece of foam insulation to help mitigate the heat impact), I figure it can't hurt to be sure the inverter can handle the heat.

I am going to build a walled shelf for the battery bank up in the rafters of the boat dock. I plan on putting each battery in its own marine housing for redundancy. This means I'll end up with a 12" 2 gauge wire between each battery in series. Using 24v wiring diagrams for 12v batteries, this means I'll end up with 7 12" wires connecting the batteries. I'll have two longer runs to the charge controller and to the AC inverter. I will keep these as short as practically possible. The charge controller will be mounted on a joist a few feet from the battery bank. The AC inverter will be mounted on a joist on the other side of (and a few feet from) the battery bank. This should keep the electronics away from the batteries.

The structure will be an open pavilion style structure. No walls. Nothing to impede air flow. I could probably find a way to get some fans to help move air around without cannibalizing on my power too much.

Estragon

Can you get a DC motor for the lift?.

The big inverter to run the motor could use 30ah/day at 24v just being on. Using a DC motor would change a lot of numbers.

6x100ah@12v batteries wired for 24v is 3 parallel strings of 2 batteries. 3x100ah=300ah@24v.

500w pv might give 350-400w in your coastal climate or about 400/28v charging=~14a. For a system in daily use, this is pretty low. Also, facing west isn't ideal, so 6 hours sun equivalent in Dec may not be realistic. If you know the roof slope you can get a more accurate number (google pvwatts - I'd post link but haven't figured out how on phone).

I understand the reluctance to put holes in the roof, but my understanding is flexible panels don't tend to last as long, so you may want to find out what's involved in unsticking them when they need replacing?

If possible, I'd be tempted to consider making a couple of vented buried vault for batteries and electronics. The ground would moderate the temps better than being under a metal roof, and may be more secure from theft.

o2bnMaine

I do have the option to switch out the motor if I so choose. I started looking for an appropriate DC motor but gave up due to time constraints. The dock builder has already installed his standard motor. I'll spend time looking for a 1HP DC motor though to see if I can get one that will work. I've never liked having to connect an inverter to operate the hoist.

I plan on turning the AC inverter off while not in use, so I don't expect any battery drain throughout the day. We will turn it on whenever we want to use the boat or turn on the brightest lights on the dock. Everything else out there will be low voltage.

I feel like I trying to force a solution at this point. So, I'm going to slow things down and continue (with your help?) doing research and learning more.

In the meantime, I will buy two 12v deep cycle batteries that will live in a wheel barrel. I'll configure them as 24v to power the inverter. I can disconnect the batteries and charge them over at the house. This will do a few things. (a) I'll learn more about how much power the hoist really uses. (b) I'll be able to take more time learning about solar!

I might find that all I need is 200Ah of battery, and therefore scale back the whole 4 or 6 battery configuration I have outlined. 

I have done some research into trying to use Power over Ethernet to power a battery charger, but I am fairly confident I can't get high enough amperage over the wires for that to be useful. I would need upwards of 13A to be successful. I can run a battery maintainer that way, though, again, I'm not sure that's entirely useful for this situation.

I could go really crazy and create a water cooling solution using a submerged pump to cool the battery bank. I could set up a radiator and a fan. ;-) I have a feeling the town wouldn't allow me to bury batteries that close to the lake. I haven't checked, though. Where I'm from in Maine, you aren't allowed to break ground within 100 feet of shore! Here's a FL picture for context. The walkway out is around 50 feet long.

Estragon

Looking at the pic, it looks like burying isn't viable even if it was allowed. The ground under the walkway looks like it gets submerged periodically, and 50+' is a long way to run big dc wiring.

Hauling a couple of batteries around initially to get a better handle on loads sounds like a good plan. Having that info makes it much more likely that the system design will be right later. You might want to consider using anderson connectors or similar to make hooking up batteries repeatedly easier, faster, and safer.

dennis461

Make a set of enclosed steps,  which look like they are used for getting into a tall boat.  Put two 12 volt batteries inside.
(My brother keeps cleaning supplies in his steps). Or enclose one of the benches.

If the winch is used as little as you've said, and the inverter gets switched off, then you do not need a large battery array, or solar array.  The parts you've been discussing seems to be a workable solution.  Big rig trucks run 24 volts, so a small fan is easily found.  (We've never needed fans on or around our boats in NJ, maybe Florida has no sea breeze?

One more thing, how deep is the water there, I may have to sail down and check it out!

o2bnMaine

Thanks guys. I figured the picture would help with context. 

When the water is this low we have between 5-8 feet of depth at the end of the dock. 

I didn't know what those connectors were actually called. I'll end up doing something like that after the first couple of weeks, I figure. 

Eventually, I'm asking my electrician to help me run a conduit underground that houses the few ethernet cables that power and provide access to the webcams. I'm going to have to be sure it is water tight considering the water can come up to the dock's frame. And with a hurricane, it could come up higher. When a hurricane is approaching, I'll have this set up turned off though. 

o2bnMaine

So! I am STILL waiting for the roofing contractor to put the metal sheets on the roof. I measured the roof at 18' 2", which is 2 inches longer than I need for the type of solar panels I'm looking at. They fit in between the ribbing of a metal roof and use adhesive to stick. That's option 1. I have found a more traditional approach will work too as there's a product that will allow me to attach solar panels to a metal roof without putting holes in the metal. So, I have a fallback. I like the idea of having solar panels that don't stand out (above the roof profile).

This past weekend, I lugged two 75-pound, 105Ah batteries over to the dock and connected a 3KW 24v AC inverter to the batteries and hoist. Everything worked great! I used the hoist approximately 10 times over the course of three days. The batteries drained down to 75%, which seemed in line with my hopes/expectations. I was able to get the batteries fully charged using a traditional battery charger back at the house within 6 hours. I am very encouraged with the results.

Since it is very close to when we close up the house in Florida and head to Maine for the summer, I think I'll hold off on buying solar panels and MPPT. I'll start back up on this in Fall.

I have ordered a heavy duty, vented battery box to install in the rafters. This weekend it was 90+ degrees with no wind. Under the dock's roof it was noticably cooler, so I'm not worried about the battery getting too hot. I'll install a battery temp sensor regardless.

mike95490

o2bnMaine said:.....That's option 1. I have found a more traditional approach will work too as there's a product that will allow me to attach solar panels to a metal roof without putting holes in the metal. So, I have a fallback. I like the idea of having solar panels that don't stand out (above the roof profile)......

That's a mistake, in my opinion.  Like putting a 5 gal bucket size resonator on a honda civic.  All looks,   But with PV panels, without some air circulation under them, heat buildup with lower their output and shorten their lifetime.

littleharbor2

o2bnMaine said:

So! I am STILL waiting for the roofing contractor to put the metal sheets on the roof. I measured the roof at 18' 2", which is 2 inches longer than I need for the type of solar panels I'm looking at. They fit in between the ribbing of a metal roof and use adhesive to stick. That's option 1. I have found a more traditional approach will work too as there's a product that will allow me to attach solar panels to a metal roof without putting holes in the metal. So, I have a fallback. I like the idea of having solar panels that don't stand out (above the roof profile).

Are these what you have found S 5!, S-5-u mini clamps
  http://www.roofthings.com/s-5-u-mini-universal-clamp-rooftop-solar-mounting-system.html

o2bnMaine

littleharbor2 said:

Are these what you have found S 5!, S-5-u mini clamps
  http://www.roofthings.com/s-5-u-mini-universal-clamp-rooftop-solar-mounting-system.html

Yes. Those look like them. The ones I found were rated to hurricane force winds, so that should suffice in FL. I'll hope.

o2bnMaine

mike95490 said:

That's a mistake, in my opinion.  Like putting a 5 gal bucket size resonator on a honda civic.  All looks,   But with PV panels, without some air circulation under them, heat buildup with lower their output and shorten their lifetime.

Here's what I found... the type that lays flat on the metal roofing. The company has gone out of business, but it doesn't seem that quality/performance was the reason from what I can find.

https://smile.amazon.com/dp/B004TIX862/_encoding=UTF8?coliid=I5JHST3WCKYYY&colid=GJGZE6AIS5AS

Anawa

The S-5 clamps you are looking at requires a standing seam metal roof. They will not work on the conventional corrugated type.

jonr

I never had a problem with running the hoist motor from the boat battery.   On the other hand, there were times when I wished a had a little bit of solar panel to keep the boat battery fully charged.

littleharbor2

o2bnMaine said:

mike95490 said:

That's a mistake, in my opinion.  Like putting a 5 gal bucket size resonator on a honda civic.  All looks,   But with PV panels, without some air circulation under them, heat buildup with lower their output and shorten their lifetime.

Here's what I found... the type that lays flat on the metal roofing. The company has gone out of business, but it doesn't seem that quality/performance was the reason from what I can find.

https://smile.amazon.com/dp/B004TIX862/_encoding=UTF8?coliid=I5JHST3WCKYYY&colid=GJGZE6AIS5AS

Keep in mind, those are 18 feet long.  They are also thin film technology which are half as efficient an crystalline panels but do have their place in certain situations.