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Old 05-28-2012, 05:32 AM   #1
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Default Electrical load analysis

Hey guys,

As mentioned about 10 days ago I finally bought a yacht, the SV Kepelina which is a Hartley Queenslander pilothouse sloop. Haven't been up to Sydney yet to see it, but one thing I do know is that it needs a lot of electrical stuff installed, and being an electronics tech I've had a think about what is required as a minimum to make her usable around Sydney Harbour as a live-aboard.

Already present is an 80W solar panel and 100AH battery, mast light, running lights, and a Raymarine Autohelm 2000 (which needs fitting). But my needs are a bit higher than this, so here's a quick list together with estimated usage.

240V power - via 1000W inverter ($34 from eBay!)

240 volt items Rating Est. daily usage (Watt Hours) Notes


Soldering iron - 40W - 3
Cabin Lights - 60W - 240 - Compact flouros
Printer - 60W - 5 - Nav charts
Power Tools - 1kW - 80
Television - 40W - 120

12 volt items Rating Estimated daily usage (Watt Hours)

Radios (standby) - 10W - 60
Radios (xmit) - 50W - 25
Chargers - 20W - 60 - phone, battery drill
Notebook (Nav) - 40W - 40
Water pumps - 12W - 1 - solar collector to tank
Autohelm - 10W - 80
12v lights - 30W - 360 - mast and running lights
Engine starter - 1200W - 40

Input

2 x 80W solar panels - 1280W (est. 8H sunshine per day average)

Battery

12V 100AH = 1200W available


The total power usage and capacity of the battery (and solar panels) matches pretty well, although a second battery would be advisable for redundancy when out on the ocean. Around the harbour this setup should be adequate.

Desirable items which have been omitted are:

1kW microwave @ 3min/day = 50W.H usage
Fridge (heavy usage)
Bread maker (heavy usage)

The last two items would require a much heavier battery, and running the engine for several hours a day, which is an expense I'd rather avoid right now.

I have already bought the inverter, charger cables for various battery-powered gadgets like phone and notebook PC, and also found some navigation software that runs on the notebook for $130 including licenced maps for Australia / New Zealand down to 1500:1 resolution. Most of the other stuff I already owned.

I have probably been a bit optimistic on how much power the Autohelm will use, and also on how much will be collected by the solar panels. Comments, experiences, and suggestions for any forgotten items will be much appreciated.

Cheers,

Rob
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Old 05-28-2012, 09:55 AM   #2
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I wonder if your inverter is a pure sine one or not ... if not it will blow phone chargers at the very least and prob the TV too as happened to a mate not long ago.

The rest looks good in theory but unfortunately practice is sometimes different ... I would double up on the battery storage capacity at the very least.

I am a live aboard and sail regularly. I have 270 watts of panels and 450 amp hours of storage in batteries and on cloudy days need to run the gen set. I have a 60 watt TV and my computer uses30 watts a couple of LED lights and thats about it for the evening, Oh, I also have a fridge freezer that uses 30 watts per hour but that is hard wired into the system and doesn't go through the inverter.

A 600 watt microwave won't run well on a 1000 watt inverter... dunno why but thats the way it seems to be, I have tried several. The bread maker I have no clue about. I have a Honda 1000 watt generator to take care of the short fall and a 25 amp charger.

Hope this helps,

Lex
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Old 05-28-2012, 11:12 AM   #3
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Hey Lexx,

Pure sinewave converters are about 5x the price so I'll try these first. The TV is actually a USB stick in my notebook computer at present, and this will be run off 12v. If I get a dedicated TV I'll buy one of the 12v ones, thanks for the warning.

Chargers and stuff are already working fine via a cheap 150W cigarette lighter inverter in the van, so I don't expect any dramas there.

I was surprised you still have to run the genny with 270W of panels, so maybe I should look at adding another 80W panel or a wind generator. Do you use the common $10 Chinese solar panel controllers off eBay? Running straight from the panels into the battery would be one way to cause the troubles you've outlined.

I do also have a battery charger available but don't expect to be attached to shore power very often. The outboard can charge batteries in a pinch anyhow. Thanks for your comments mate, might see you when I get up that far!

Rob

p.s. the fridge you have is quite efficient, but at 30WH represents a load of 720W a day, more than half my power budget. That's why I'll be avoiding it for now. I'll also be doing a comparison of CFs vs LEDs soon for cabin lighting.
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Old 05-28-2012, 11:34 AM   #4
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Hi Rob,

The fridge is an 80 litre Engel. Its max draw down is 30 watts. Once cool and cycling as it should the draw is more like 12 to 14 watts.

My panels were bought from JayCar and so were the panel regulators. I fried a power pac for a lap top and a phone charger, took a day or three but sure wrecked them hence I bought the pure sine inverter and haven't had a problem since and that was a couple of years ago. A friend on his boat just bought a TV and fried it with a cheap inverter. I am just giving you my experiences and you got to decide what you are happy with.

Remember as well that although a battery may be rated at 100 amp hours, you get nowhere near that out of it.

I don't have a wind generator and am about to add another 120 watt panel and replace the batteries with 5 x 100 amp hour ones.

I live aboard so its not the occasional weekend thing and maybe my power usage is a little higher than yours would be... I never worry about it and just turn on the gen set if I am getting low.

I am sure you will sort it all out no worries.

Lexx
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Old 05-28-2012, 11:43 AM   #5
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Hey Lex,

Yeah, I've heard nothing but good stuff about the Engel fridges, but geez they're expensive!!

I've decided to go with LEDs throughout after reading this:

Compare: LED Lights vs CFL vs Incandescent Lighting Chart

One of the 80W panels came with the yacht, previous owner paid $280 for it. The new one I bought cost $139 delivered. Progress! Bigger battery - yes. I think he only sized this one to run the mandatory lights while he was away.

Rob
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Old 05-29-2012, 04:45 AM   #6
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Hi Lexx and Haiqu

A lot of enthusiam there in your discussion and that is good. But now a quick shower of rain on the parade to temper the heat. Though I do not want to "rain on the parade" do consider this:

Drawing down a small battery capacity to near-zero is folly. Best bang for the buck as far as battery life is concerned is usually 40-60% discharge, even for the deep cycle types.

The spec'd solar output is under optimal conditions. With cloud, fog, bad incident angle but especially with partial shading, output drops dramatically. Even the "shade tolerant" panels are no panacea.

A good generator as adjunct is almost an essential for a 24/7 fridge set-up and may need to run two or three times daily in summer.

My boat has 260w in two panels and 6 of 6v deep-cycle batteries as house bank, but also wind and water gen, plus diesel genset. A regular engine alternator does NOT give enough amperage at 1000rpm to charge at 40-50amp.

Some solar living and alt. engine sites will give you a whole lot more caveats and the details I do not have time to go into here. Suffice to say I have an off grid home on full solar and find you need to budget and plan for overkill, or you may be dissappointed with your results.

Happy calculating and go easy on pumps, coffee-makers and fridges... real energy hogs. With only LEDs, GPS, radio and nav-lights etc a minimalist set-up will work quite well though. Fog and cloud can reduce your solar intake to 10% for days, so factor that in too!

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Old 05-29-2012, 06:46 AM   #7
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Hey Ivo,

- Pumps: one 12W fishtank water pump to top up the shower header daily (or less) from the solar collectors. Total use 5 minutes, or 1 watt-hour.
- Coffee maker: are you serious? I have a gas stove for that.
- Fridges: see above, problem already recognized. I've been living without one for 12 months and it hasn't killed me yet.

I agree that pulling the battery down to zero would be a Bad Thing (tm). However, daytime usage is about 35% of the total and (under ideal conditions) the regulator will supply that directly while charging the batteries. Worst case is therefore 65% discharge on the figures in my initial post.

Lex already pointed out the need for a bigger battery and I concur entirely.

The analysis shows that external lights are the biggest energy hog in fact - and they are unfortunately mandatory - closely followed by internal lighting. I may even put all the lights on a dedicated circuit with their own controller, for safety.

Cheers,

Rob
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Old 05-29-2012, 08:24 AM   #8
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Interesting thread. Hubby has just been doing lots of work on our own electrical system. Mainly we'd put off wiring/installing the 12V DC lighting throughout the boat. We've been using compact fluorescent lights since they generally are more energy efficient that the LED lights you can purchase. Recently, we ordered a bunch of LED, the drivers and wired up several to refit into our Perko fixtures. Those are both cheaper up front and they're more efficient than the LEDs we can purchase ready made. Our Perko fixtures have a good diffusing lens which helps alot.

Hubby just posted something on our blog today about a mathmatica program he ran to check how we could use solar here with the local weather and I thought I'd copy the important part from his blog post...it is about solar not being all it's cracked up to be. If you're living in a harbor, with easy access to fuel for a generator, you may find that it is less expensive to charge using your generator than solar.

He says: "On a classic yacht, it is hard to implement wind or solar power without it looking all wrong; but I decided to take another look at those technologies. It’s amazing what data is available out there, so to evaluate cost-benefit, I wrote a program that calculated the power I could obtain from a 135W solar panel. I used data from the nearby airport (less than 1 mile away) and imported cloud cover and visibility data. I used that to calculate the distribution of direct solar radiation and the diffuse radiation hitting the solar panel for every hour of every day for the last two years. The depressing result is that solar panels suck. More than batteries suck.

Compared to what we pay for electricity at the dock, a $500 solar panel will save us a puny $8.50 a year in electricity. That equates to roughly a 59 year payback if one ignores the cost of capital. Hardly a wise investment especially since we would require many panels to meet our full electrical requirement, so we still require a genset. Remember here that we are professionally engaged and thus work aboard our boat; we can’t conserve our usage down to nearly nothing. Using the higher cost of electricity from a genset (both fuel and depreciation of the genset) as a cost basis helps, but even then, the payback is over 11 years. Solar data in San Diego, a more southern latitude, yielded a little faster payback as should be expected, but anywhere on the US West coast, the only way to make solar have a reasonable payback is to use reflectors. Think: big parabolic monstrosities. On a 1931 schooner, the need for reflectors is a deal breaker.

Although we are in San Francisco which is notorious for the wind, the wind turbine analysis was only slightly better–28 years payback based on market rate electricity at the dock and 5 years 3.5 months for genset electricity. If we were planning to spend most of our time at anchor, a wind turbine might be viable. But, similar to solar power, a wind turbine will not meet our full demand, so we will still require a genset. It really sucks having a MBA married to an EE–between the cost analysis and performance analysis, we’re dead in the water every time. Yes, one way or another, a lot of things suck."


When actually cruising, solar is great--since you're not going to have access to fuel everywhere. In harbor/close to harbor, that's not necessarily the case.

Energy use--not trying to conserve at all and working (on computer) from the boat, we find that we're using between 100 kWhr and 300 kWhr per month. Quite a bit of energy use. When traveling, we're using more like 100 kWhr per month.
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Old 05-29-2012, 09:23 AM   #9
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Let me start by saying I don't do the maths to work things out. I am more of a try it and see kind of person.

For thee past year 2 of us have been living on my yacht full time. I have 270 watts of solar panels, (have an additional 120 watt panel I am about to add). I also have a 1000 watt Gen Set and 25 amp smart charger. My battery bank is 450 amp hours.

I run an 80 litre fridge freezer 24/7, it uses about 15 watts per hour at normal cycling, 30 watts drawing the temp down.

I use a computer for 6 or 7 hours a day, it uses about 30 watts per hour.

TV is on most evenings for 4 to 5 hours, it uses about 60 watts.

I use 2 x 20 led light fittings most evenings, not sure how much they draw.

Oh I also have an electric toilet and an electric fresh water supply pump, no idea how much they use.

Probably some stuff I forgot, like stereo and VHF etc.

Living on my mooring in sunny Port Douglas, North Queensland, I use my genet about 4 or 5 hours every 3 days to top the batteries off, uses 1 litre of petrol for that. I put in a litre and fire it up, letting it go till it runs out.

If its full cloud cover like it is during the wet season here, I use the genet for about 3 or 4 hours a day.

When I cruise I generally coast hop doing daily runs of 40 to 60 miles and my power situation stays about the same as the above.

Like I say I have never done the maths and came about the above by doing and seeing and it has worked well for the past year. Once I add the extra panel I should be able to lighten the load on the genet a bit and I am shortly going to replace my deep cycle batteries for new ones and the new house bank will have 500 amp hours.

So where am I ... I reckon I use somewhere between 1000 and 1400 watts per 24 hour day so for arguments sake lets call it 1200 watts per day or 100 amp hours.

I put in about 1500 watts from the gen set every 3 days, so ... the solar panels are giving me 2100 watts every 3 days or 700 watts per day = 60 amps. I reckon I can live with that pretty okay. The system seems to work.

Looking at the above will give others some ideas I am sure.

Got a sore head now so time for a beer me thinks ...

Lexx
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Old 05-30-2012, 01:42 AM   #10
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Lexx, Rob, Bopsie ( poetic licentiousness, ok? )

Further thought is the 25A charger will be too wimpy to equalize the new 500aH battery set-up. Rather go for a 50-60A unit that will match that 1kw genset and loaf along after the initial bulk charging. The higher amperage will save you a little initial generator run-time, the solar can then do the lower amperage float charge.

As to coffemakers, for many it's a must-have and would not look out of place next to the watts-chewing bread-baker. Same league really!

As to hooking up the extra batteries, be sure to have "equal resistance connections" between all the +ve and -ve terminals. Bolt the output leads at OPPOSITE ends of the combined + and - terminals. Too often the outputs are bolted across a single battery, the rest simply hooked up any old how in a chain. With no load or draw this measures out OK but at +50A there are very small resistive drops which load each battery differently. The result is overloading one, undercharging others... but you knew that as EE's and techs already, correct?

Cut and try is OK but some calcs may save you some grief later. Solar will not replace a genset, rather see it as a part of a triad or a quad: solar, genset, wind/water gen and battery storage. In a pinch ( bad karma ) you may need to rely on your batteries only and having skimped there could be a poor choice. SSB, VHF, deck lights and BILGE PUMPS depend 100% on your battery state. Skimping on them is at your peril!

Smooth seas and happy amp-hours

Ivo
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Old 05-30-2012, 11:11 AM   #11
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Umm the solar that I have provides most of my power needs and the genet backs it up through my rather expensive C TEK 25 amp charger that I have no intention of replacing. I have 450 amp hours of batteries now so adding 50 amp hours with the new batteries isn't a great deal of difference... just like adding an extra 120 watt panel won't make much difference but will mean the genet runs for less time. As a back up I also have a hight output engine driven alternator if I really need it.

I currently have a separate engine starting battery and a separate 100 amp hour battery for my nav lights VHF etc ... I can also switch in the start battery into this or the house bank into either.

Oh I have 3 electric bilge pumps and 2 manual ones. My house batteries still work but the upgrade is a part of my regular maintenance schedule I swap out the batteries every 4 years whether they need it or not, I also get balanced batteries, the same kind and ratings. The extra panels actually to help with charging as I intend to add a 40 litre freezer in the near future.. an Engel of course.. can't beat them for low power consumption.

I kinda feel I have things covered pretty well with my way of doing things. Not everyone will agree and I don't expect them to... it works for me and I am a happy lil sailor, have been for the past 40 years of sailing.

Lexx
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Old 05-30-2012, 03:46 PM   #12
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Fine Lexx, good on the Armstrong bilge pumps too. The idea of separating battery systems is very sound as it is too easy to have a failure in one take down the whole system. I'd almost add more battery capacity at this point as you can generate amps at will but not battery capacity. Of course, it's a space and choice issue and no single shoe fits all.

From my experience, having 6x of 6V T105 types aboard for the house bank have served me well and I've never had routine issues with low power... barring hard faults of course.

If you replace batteries every 4 years it may not matter but where do you get the equalizing charge ampacity from? Run the hi-output engine alternator? I'd expect you'd need more than 25A even with your current set-up.

With 40 years sailing I'm sure you've figured it out. For me the whole issue is more empirical, as I'm also running my home off solar. ( 16 panels and batteries, about 1.5kW max solar output ) That has been enough to run it, albeit with judicious power use during cloudy days. Fridge is on 24/7 and is a regular 120V one, and nothing energy-fancy at all.


Only the lights are fancy... they gather up darkness.

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Old 05-30-2012, 04:18 PM   #13
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Hi guys,

Well, this stirred up a hornet's nest. For me, using a genset in Sydney Harbour is out of the question. The basic rule at NSW Maritime is that one is not permitted to live at the swing mooring for more than 21 days a year. I intend to be there a helluva lot more than that, no point painting a target on myself.

300kW in a live-aboard? Holy crap!! If I use more than 50kW/month I'll be very surprised, but then I'm a confirmed bachelor and have simple needs. Gas is more efficient for cooking, including coffee and bread-making.

I've now investigated wind power and find the hardware is exhorbitant, so I won't be going that way. Solar panels are down to $1.50/watt so that suits me in a country with tons of sunshine. I may need to burn more fuel in colder and less salubrious climes, of course, but in that case I'll be mobile and can top up the batteries while running the engines for other uses.

Rob
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Old 05-30-2012, 05:03 PM   #14
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Rob

with a below-deck genset there is not that much noise, only the water splashing out of the wet exhaust. Some of the newer gas on-deck ones are also extremely quiet. But I hear you... high fences make for good neighbors and it only takes one a......e and everyone has got one.

You seem to have access to really good solar pricing. My searches in CA still show $2-3/w ( USD ) but then again you may have access to chinese panels dumped below cost. The local Mfr. Solyndra went BK here recently but it may have been the usual gummint corruption and graft involved too, not just competition.

Your main point, the 300kwh/mth is very high for a venerable old boat. Then again, lil BeBop and hubby are kinda working off it, so consider that too. ( all those POSTS, you'd need a full nuclear power station just for that, ya tink? )

At my mountain home I rarely even use 8-9kw/day but then again I'm also very skinflint and frugal with power. Actually I'm just in training for the day they start taxing sunshine here in CA, along with air and rainfall. Ain't a tax they don't like! A-tax-on-tax next.

Ivo
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