Need help with unusual power needs

Roffensian · May 2018

Hi everyone, I'm sure everyone thinks their situation is unique - and I'm no different :-) However, I genuinely do have an unusual power need for my situation and need some advice as to the best kind of setup.

I have a dock around 650 feet from my home on the island of Roatan in the Caribbean. Running power from the house is a fairly significant cost so looking to put an off grid solar system on the dock. Lighting will be LED and quite possibly low voltage (12 or 24 volt) but would also want to run an inverter for regular power for occasional larger gatherings with higher power needs. Usage would be likely around 2 hours a day, 4 or 5 days a week with no need for too much reserve. Rainy season would reduce solar exposure obviously, but would also reduce the need - less likely to be sitting on the dock in a storm!

So far, so simple, but.....

I also need to power a boat lift. It will run on two 3/4HP motors and requires either 120v / 30A or 240v / 15A. I assume the additional amps are for start up surge. Usage would be no more than one down and one up cycle a day for a total of 5 to 6 minutes. I get that ordinarily I shouldn't be trying to put a 2000w converter on a 200 amp hour battery and a 200 watt panel, but what do I need for such high draw for very short periods? I'm assuming a 240v / 15A solution is better for the usual reasons, and am thinking a 24v battery system is the way to go, but beyond that I'm struggling to figure out how to meet my needs without overkill and while staying safe.

Any ideas greatly appreciated - even if it's only to suck up the cost of running house power!

Photowhit · May 2018

Okay, so you might not like my idea, but here it is;

Direct burial wire and one of these...

https://youtu.be/kNqOXul-GOQ

Roffensian · May 2018

Hey, no idea is a bad idea! Most of the cost of running from the house is actually product - labor is very cheap here, getting (quality) product is crazy expensive (shipping + duty + tax = US pricing + 40 - 50%). I'm thinking that may be the option though :-(

Roffensian · May 2018

I should add for clarity, I can get solar system exempt of duty / tax as an incentive for alternative energy. Quote for house power run to the dock was close to $5k.

Photowhit · May 2018

Yeah, a solar system would likely be as much or more, You would want a quality a large quality inverter and a good size battery bank, a large draw like that will create an issue trying to supply that much power at once. Solar and batteries do a much better job of providing small power over a long time.

So 1000 feet of 10/3 wire would be $1000 here;
https://www.wireandcableyourway.com/10-3-w-ground-uf-b-underground-feeder-wire-125-500-or-1000ft-coil.html

You would have about a 9% voltage drop, but i'd bet it would be within the limits of the motor at 220 volts;
http://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=3.277&voltage=240&phase=ac&noofconductor=1&distance=700&distanceunit=feet&amperes=15&x=56&y=21

Is the soil sand of shell/reef? down 10"? You might want to go more if you expect high erosion...

mcgivor · May 2018

Roffensian said:

Hey, no idea is a bad idea! Most of the cost of running from the house is actually product - labor is very cheap here, getting (quality) product is crazy expensive (shipping + duty + tax = US pricing + 40 - 50%). I'm thinking that may be the option though :-(

How many customs officials would need greasing along the way? Unless Honduras has stamped out corruption since I was last there, usually Utila.
Have you considered self contained solar street lights for lighting at least? An example not suggesting Ebay
https://www.ebay.com/itm/Commercial-Outdoor-Solar-Power-LED-Street-Light-IP65-Sensor-Post-Lamp-1-000LM-/323174463352

Roffensian · May 2018

Thanks for the suggestions guys. Erosion from run off is the biggest potential problem, island is the top of an underwater mountain range so hilly. That can be controlled to a degree with vegetation which we are doing, but no guarantees on the days you get a foot of rain! I would likely go 12 - 16: deep - with labor at 400 Lps ($17) per person, per day there's no reason not to. Soil is fairly sandy near the beach (well, duh), a little more solid closer to the house. Am waiting on another quote to run from the house, first was using 4 gauge copper THWN.

Customs still has options for creativity but hit and miss and usually easier for a large amount that is easier to 'lose' details of - I brought in half a container of building materials and was able to get a flat rate of duty based on them being 'used personal items' as long as I agreed with the customs official that it was actually a full container and not half! Not as easy as it used to be, and Roatan is harder than Utila or Guanaja - National Police check everything leaving the shipping dock and reconcile against paperwork.

Solar lighting for the dock is fairly easy - puck, post or similar lights, was also looking at underwater lights to pull in the fish - something like these - https://www.hodgesmarine.com/Bluefin-Led-Dl12-Industrial-Dock-Light-Cobalt-p/bfidl12i-sm-b128.htm. That's an ideal use for a solar setup of course, but if I'm going to have to run regular power for this boat lift I may as well use that for the underwater lights too.

Really appreciate the help!

Dave Angelini · May 2018

Fond memories of the years in the Cays of Honduras. The port captains and duty for the customs people was not cheap. With the right amount you could get deliveries on a Sunday and a new visa on a Saturday night.

The Bay islands are perfectly located for getting a boat out of the hurricane zone quickly.

Sometimes if you get a quote for THHN they will give you a dual rated wire for much less. Home Depot does this all the time and you get the submersible rating of of THWN for a lower price. Probably not down in the Caribbean...

BB. · May 2018

One person here suggested simply using the boat's battery bank/power system for the dock lift (I forgot who made this suggestion).

The problem with a dock lift can be -- The high current for a short term still needs a very large battery bank for lead acid batteries... But the bank does not need to be large for the amount of energy needed (a few minutes per day)... For example. C/8 (8 hour discharge rate) is a "nominal" flooded cell deep cycle battery load... C/5 can be used for shorter times. And C/2.5 hour rate for maximum surge current:

30 amps * 120 volts * 1/0.85 AC inverter eff = 4,235 Watts from battery b

If you are are using a 12 volt bank (or your boat has a 12 volt bank), and use C/5 discharge rate:

4,235 Watts / 12 volts * 5 hour discharge rate = 1,765 AH @ 12 volt "nominal" flooded cell battery bank.
4,235 Watts / 18.5 volt battery cutoff voltage = 403 Amps @ 12 volts

As you can see, this is a large battery bank with very heavy wiring requirements.

If you use good quality AGM batteries (or even possibly some sort of Li Ion bank), you could perhaps get to a C/1 hour discharge rate and your battery bank could be:

4,235 Watts / 12 volts * 1 hour discharge rate = 353 AH battery bank at 12 volts

At least this is getting more reasonable. And if you can run at 24 volts, that would be better too (1/2 the current for the DC bus wiring).

The size of battery bank needed to run the power requirements is not large because of the short time the motor(s) run. For example, if you plan for 2 days of "no sun" and 50% maximum battery discharge, it would suggest a minimum battery bank of:

4,235 Watt load (DC bus) * 1/12 volts * 0.10 hours per day (6 minutes) use * 2 days storage * 1/0.50 maximum discharge = 141 AH @ 12 volt battery bank

Sizing the solar array--Suggest rate of charge minimum of 5% (10%-13% is typical sizing for full time off grid system):

1,765 AH battery bank (flooded cell)* 14.5 volts charging * 1/0.77 panel+controller deratings * 0.05 rate of charge = 1,662 Watt array minimum (large flooded cell bank)
353 AH battery bank (AGM) * 14.5 volts charging * 1/0.77 panel+controller deratings * 0.05 rate of charge = 332 Watt array minimum (smaller AGM/Li Ion bank)

Sizing the array based on loading (something like 4 hours of sun per day in tropical marine environment):

4,235 Watts * 0.10 hours per day usage * 1/0.61 DC off grid system eff * 1/4.0 hours of sun minimum per day = 174 Watt solar array minimum (based on loads)

If you have other power needs (want to float the battery bank on the boat, use 120/240 VAC tools to work on boat, have a nice of lighting for dock and beach area, etc... Then the solar power system does not look so 'unbalanced" (other loads besides the large dock lift motors).

If the boat is large enough to justify a larger battery bank (flooded cell or AGM), then using the boat itself to run the lift and a local solar array to recharge/keep the boat batteries floating may be interesting.

Or, use a (probably cheaper) ~5 kWatt (minimum) AC genset to run the AC motors (or power the lift directly) and use a 1/4 liter of fuel (or less) every lift cycle (roughly 1 gallon or 4 liter per hour genset, 6 minutes a cycle).

Then there is the AC run from home option....

If you can find a more efficient dock lift (1.5 HP of motors to lift a boat out of the water in 3 minutes sounds like a lot of power--If you can find a system that uses less wattage, that will save you money on either a solar system or running AC wiring from the home).

Marine environments are hard on everything (especially salt water)--Keeping costs down for system installation (solar, run from home, local genset, dock mechanism, etc.) will save money on maintenance down the road.

-Bill

Roffensian · May 2018

Wow, thanks so much everyone for such thorough responses. I did consider a generator - would need to have a way to secure it as well or it would grow legs on a dark night. Not sure the boat is the best power supply as I suspect I'll successfully get a boat into the water that may not start! Incidentally, it isn't 3 minutes up and 3 down, more like 4 up and 2 down to get to the minutes, weight helping on the lowering part obviously. It also only lifts around 6 feet.

Happy to look at AGM battery options, Li Ion is likely overkill for the need, especially given the marine environment - figure I'll have to replace due to corrosion way before normal EOL. No real ability to do beach lighting as dock is 140 feet long (very shallow drop off) and boat isn't big - 22 foot runabout for fishing and to get to snorkeling / diving spots. I've looked at other boat lift options, most are similar / same power requirements. There are a couple of direct DC motor lifts with solar panels but the lifts themselves are way more expensive - I can get a 10,000 / 12,000 lb lift for $8,000 installed with an AC motor, the DC solar ones would be nearer $15,000 installed. There are also some retro fit DC motors available for the now obsolete hand wheel boat lifts. None of those here that I know of and local boats are built solid (read heavy). I also have limitations to the boat lifts I can put in because I only have 29" of depth at low tide.

I have no issue with a 24 volt battery / 240 VAC system if that makes more sense, but the more I learn the more I'm thinking shore power is the best option. I can always look at putting a whole home solar system in down the road to remove reliance on the local electric company (which is an 'interesting' organization).

Dave Angelini · May 2018

As Bill said about boat batteries! I would add using a large DC motor on 12V boat batteries is probably the fastest way to need new batteries. A large DC motor windlass on a boat is guaranteed income for battery companies unless it is designed and installed perfectly!

mcgivor · May 2018

@Roffensian
What is the actual purpose of lifting the boat daily? Out of curiosity, my experience in the Bay Islands most/all boats remained in the water 24/7.

Roffensian · May 2018

mcgivor said:

@Roffensian
What is the actual purpose of lifting the boat daily? Out of curiosity, my experience in the Bay Islands most/all boats remained in the water 24/7.

Virtually all smaller boats are lifted from the water - minimizes the effects of salt water, reducing the need for cleaning and making the process easier and provides an added level of security. The only boats that are regularly in the water here are either the ones where a boat lift is impractical because of size / boat type (keeled hull) or visiting vessels.

Dave Angelini · May 2018

Visiting vessels or as we called ourselves, cruising boats. You remember my boat Astraea in the mid 90's? She loved Roatan Guanaja and Utila! I have got to get back there again...

mcgivor · May 2018

So if a lift is essential, I would think a counterweight system would minimize the energy required, only powering the difference in weight between the boat and the counterweight. Thinking outside the box, Google wasn't very helpful, thought someone must have thought of this for a pleasure craft, but it seems there are no commercial lifts with energy savings in mind, that I could find, at least. Air bag lifts are available commercially, but don't offer much in the way of security. Without attempting to be facetious ,is the value of the boat, including depreciation, worth the cost of the lift and the infrastructure needed to power it, over replacement say every 5 years, selling the used craft to offset a new purchase, bearing mind the lift itself would need maintenance especially if solar powered, batteries are not cheap with limited life expectancy. Not trying to be an ass, just offering a different perspective.

Roffensian · May 2018

Not taken as facetious at all, it's a legitimate question. It comes to more than simply money - hassle for sure, but also logistics of buying / selling. This isn't the US, if you want to buy a boat you either commission one from one of the two builders and wait 3 - 6 months or you find out who is selling one that kinda sorta meets your needs - it may well have been out of the water for several years, it may not have been looked after, etc. When it comes to selling - well, be prepared to wait - not everyone wants what you ar selling, especially if it's been sitting in the water and only looked after occasionally.

There's also the deterrent aspect. The people here are wonderful, but it's a sad fact that no matter how much we expats try to become part of the community there is a gulf in living standards that can cause temptations. It's opportunistic but a boat in the water presents such an opportunity, a boat on a lift requires much more effort and time - easier to move on to something else.

All that said, this is an island of innovation and I may look at some kind of solution that involves strengthening the beams of my dock 'boathouse' roof and combining with slings and chain hoists / come alongs. Combine those with some large padlocks and I may have a secure and workable solution that also provides some exercise

mcgivor · May 2018

Totally understand the gulf in living standards, I spent 10 years in Guatemala, visiting Honduras to go diving, loved the people but never felt safe, now in Thailand, the gulf still exists but the people are different in some way, despite modest living I'm still a Farang or Gringo, can't shake the stigma. Getting back to the boat lift, have you considered a counterweight system? Just seems logical, wether manual or electrical, a concrete block, some chain, pulleys, cable, couple of sprockets, a 100 to 1 gear reduction, simple brake mechanism and finally an electric motor or elbow grease.

Roffensian · May 2018

Hadn't thought too much about a counterweight until you mentioned it, but am now. I'll have to figure out how best to engineer it but it might make life easier - especially if my arms become the motor!!

Estragon · May 2018

Elevators for people use counterweights and pulleys, I don't see why it wouldn't work well in a boat lift.

Dave Angelini · June 2018

Add on to an elevator thought with just doing what the boat yards do, a marine railway...
Might as well just get a travelift and make some money

I like the no smoking sign!

.

Image: https://us.v-cdn.net/6024911/uploads/editor/jp/ct47mocx9qff.png

Roffensian · June 2018

LOL. I think I have an option similar to a marine railway - I call it a trailer :-)

Need help with unusual power needs

Comments

Categories