Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 29-12-2009, 20:04   #1
Registered User
 
GeoPowers's Avatar

Join Date: Dec 2008
Location: Gulfport, MS
Boat: Beneteau 393
Posts: 947
Images: 27
Amp Hour Load Calculator - Did I Miss Anything?

Hi everyone,

I put together the attached spreadsheet to calculate my daily power consumption, and to a lessor degree as a tool to figure out possible house bank configurations. There are some loads on here I don't have onboard yet, but figured I'd plan for them now rather than later. I think I've covered all the major power draws, but any input as to any missing items or errors in the spreadsheet would be helpful!

I was especially surprised at the heater's power usage, which I got from a 6.5 amp draw from the Webasto 90S itself, and 2.5 amps for the 5 heater fans throughout the boat. I'm pretty sure this is right, but it is very high!

Necessity is the mother of all invention- this all came about after a 4-day weekend on the hook. Even before this, I suspected my 4-year old house bank (464 Ah) was very underpowered with the heater, and the cold weather meant the heater was in use pretty steadily. You can guess the rest of the story- a depleted house bank! On a side note, I also discovered that my starter battery wasn't isolated from the house bank in the manner I thought it was. AND, I also discovered it is a little over a mile to the nearest place to buy a new starter battery from the dinghy dock at Poulsbo, which doesn't have cabs or bus service on Sunday mornings... on the bright side, I got my exercise for 2010 already done!

Thanks, Frank
Attached Files
File Type: xls Power Consumption worksheet 2.xls (50.0 KB, 3288 views)
__________________

__________________
GeoPowers is online now   Reply With Quote
Old 29-12-2009, 22:26   #2
֍֎֍֎֍֎֍֎֍֎

Cruisers Forum Supporter

Join Date: Apr 2006
Posts: 13,056
Nice worksheet, Frank!

I think there's one error, the "gas valve" normally should only need power to stay open, when you are using the gas. I assume you mean it is a solenoid valve, and normally those will "failsafe" and shut when power is removed from them. So, that should not be using power 24 hours a day, but perhaps one or two hours a day, depending on how much you cook. I know some boats use a spring-loaded switch (the type sold for bathroom vent fans, or used in Europe for stairway lights) so that you can turn the switch up to 60 minutes--just like a kitchen timer--and if you forget to shut the solenoid power, it gets cut off when the switch runs out anyway. A matter of both safety and power consumption. Also not expensive.
__________________

__________________
hellosailor is offline   Reply With Quote
Old 30-12-2009, 00:14   #3
Registered User
 
cdennyb's Avatar

Join Date: Jun 2007
Location: Northern California
Boat: finally a catamaran dive boat...
Posts: 505
Send a message via MSN to cdennyb Send a message via Yahoo to cdennyb Send a message via Skype™ to cdennyb
I was thinking that the nav instruments excluding the radio and gps and/or radar plus the engine instruments would each take about .5 amps instead of .1 amps (did you include the nightly illumination lighting?). Correct me if I'm wrong.
Nice worksheet, may I use it for my own personal needs?
Thanks so much in advance.
__________________
the perfect dive boat is one you're on...
cdennyb is offline   Reply With Quote
Old 30-12-2009, 04:58   #4
Senior Cruiser

Cruisers Forum Supporter

Join Date: Jul 2006
Location: Chesapeake Region and Maine
Boat: 42' Bob Perry sloop
Posts: 4,038
Images: 4
Very nice job, Frank!

Two observations.

1. The daily power consumption is WAY high for a 40-footer. Yes, the Webasto will run it up when in use, but it would be prudent to look for ways to cut down on power consumption, since this is often much easier than trying to generate the power needed to replenish the batteries; and

2. Replacing 600AH per day ain't easy. And, if you're really going to go to a huge battery bank, you'll need a much beefier alternator. 80A just won't cut it, nor are the solar panels likely to do much to help...especially in the Pacific NW. This will entail some engineering, good planning, and a lot of $$$.

Bill
__________________
btrayfors is offline   Reply With Quote
Old 30-12-2009, 06:43   #5
Registered User
 
Jentine's Avatar

Join Date: May 2004
Location: Cruising on the hook
Boat: Beneteau 393, "Blackthorn"
Posts: 744
Images: 5
Frank,

The most glaring error I can see is that you expect to use all of the equipment on board each and every day. Do you really make 36 gallons of water per day? Do you have the radar and other navigation equipment and lights on at anchor. Your chart is wonderful, but your assessment is skewed. We currently live aboard in a similarly equipped boat but the main difference is that we are currently in the Florida Keys. My daily consumption is generally replenished by the sun (only minimally, one sunny day in five), the wind (most generously) and when all else fails, by the Honda 2000 generator that sits quite nicely on the swim platform.
We have found that relying on the sun and the wind and the engine will not provide the necessary power when there is no sun and no wind and who, but a fool, would run a main engine for battery charging. We have, only once, after sitting in an anchorage for two weeks with little sun or wind, depleted the batteries to the point where it was necessary to start the engine.
I have 460w. of solar, a KISS wind generator, the standard Hitachi alternator with a Balmar MC-612 regulator (you really need this type of regulator), 660 ah of battery capacity (880 if the starting pair is included), and of course, the Honda generator. We lack no power for any usages aboard, nor do we live like we are camping but power management is a prime concern daily.
I think you have the right equipment but need to work on your conservation techniques. All the power generation in the world is worthless if conservation is not part of the equation.
Should you have any specific questions, PM me.
__________________
Jim

We are what we repeatedly do.
Excellence, therefore, is not an act but a habit."
--Aristotle
Jentine is offline   Reply With Quote
Old 30-12-2009, 08:31   #6
Nearly an old salt
 
goboatingnow's Avatar

Cruisers Forum Supporter

Join Date: Jun 2009
Posts: 13,649
Images: 3
Theres an old saying that " logic is a way of going wrong with confidence". Your chart is undoutably comprehensive, but very very misleading,

Questions, Chartplotter for 24 hours , why, given the autopilot is being used for 5?, (

Chartplotter looks way too low ( ok for a pure GPS model).

Autopilot is way too low, looks like a steady state figure, in my experience on long distances this is the biggest power draw after reeffers.

For example 8 hours of TV, ( is this at anchor or underway?). If at anchor why autopilot comsumption ( or chartplotter for that matter). DO you need all that VHF or hours heater hours?.


WHat you need to work out is underway comsumption and at anchor comsumption, bring any conservation figures to bear, also look at typical comsumption versus worse case comsumption. There little point in trying to generate X amp/hs as a worse case when all you really need is x/3 amphs usually.

And good look generating 600ah per day.??,
__________________
goboatingnow is offline   Reply With Quote
Old 30-12-2009, 08:34   #7
CF Adviser
Moderator Emeritus
 
Hud3's Avatar

Cruisers Forum Supporter

Join Date: Sep 2007
Location: Virginia
Boat: Island Packet 380, now sold
Posts: 8,929
Images: 49
Pretty spiffy spreadsheet!

I would come up with an energy budget for offshore sailing and one for cruising amongst the islands. Sailing 24/7, you'd have your running lights on all night, and be using the radar from time to time, but much of the other stuff wouldn't be used at all. Cruising and anchoring for the night would have an entirely different energy use profile.

460 AH/day does seem awfully high. In the Caribbean, we used about 150 AH/day on our 38-footer, and the bulk of that was the Frigoboat reefer/freezer. We had 600 AH of AGMs for the house, and could generally charge them in an hour or less with the diesel and the 210 A alternator.
__________________
Hud
Hud3 is offline   Reply With Quote
Old 30-12-2009, 09:29   #8
Commercial Member
 
CharlieJ's Avatar

Cruisers Forum Supporter

Join Date: Dec 2008
Location: St. Petersburg, FL
Boat: Gulfstar Long Range Trawler; 53'; BearBoat
Posts: 837
As noted by other posters, your estimate of 460 amp-hr/day is very high.

Key to battery bank design is to make it big enough so that you rarely, if ever, dip below the 50% DOD (depth of discharge), but not so large that your charging sources cannot bring it back to 100% SOC (state of charge) on a regular basis without having to run a lightly loaded diesel excessively.

As a data point, when we cruised the Caribbean in our trawler, we had a new household reefer that accounted for 80% of our amp-hr usage. We consumed 500 amp-hrs per day from our bank of 12 series-parallel T105 batteries for a total house bank of 1,320 amp-hrs. The bank was replenished in about 5 hours with a Balmar unit comprised of a 6.5 hp Kubota diesel directly coupled to a 190 amp large case Balmar alternator.
__________________
Charlie Johnson
JTB Marine Corporation
"The Devil is in the details and so is salvation."
CharlieJ is offline   Reply With Quote
Old 30-12-2009, 09:52   #9
֍֎֍֎֍֎֍֎֍֎

Cruisers Forum Supporter

Join Date: Apr 2006
Posts: 13,056
denny-
Instrument loads can be deceptive. The first time I measured a LORAN I found out it drew 440mA. And then, if the LED lighting on the panel was shut, the LORAN itself only drew 40mA! A tenfold difference between what the instrument needed, and what the lighting (night use only and we were daysailing) needed.
With autopilots, even identical autopilots, one user may have a well-balanced boat, well-trimmed, in light winds, while the next guy has an autopilot constantly thrashing about trying to fight the helm. Again, very different loads versus the "rated" power draw. And with radios, of course the question is how much are you transmitting versus receiving? Odds are the rx rating is the one you'd put in the daily spreadsheet, most of us wouldn't be transmitting a whole lot.

Electric heat has GOT to be a killer, but I'll bet it feels good in the morning.
__________________
hellosailor is offline   Reply With Quote
Old 30-12-2009, 11:06   #10
Registered User
 
GeoPowers's Avatar

Join Date: Dec 2008
Location: Gulfport, MS
Boat: Beneteau 393
Posts: 947
Images: 27
Thanks for everyoneís input! I agree that 460 Ah per day is really high. I put the toggles in the spreadsheet to see what my consumption was during various scenarios. Hereís what Iím thinking I use-

During summer, at anchor only: 180-200 Ah
During summer, sailing and at anchor same day: 225 Ah
During winter, at anchor: 300-315 Ah
During winter, sailing and at anchor same day: 340-350 Ah

These #ís donít take the radar or water-maker into account, as we donít have them now. Realistically, we only have use for a radar for the next few years, as we will always be close to good shore water. Right now we coastal cruise. We also donít have the solar or wind, so for now we are stuck recharging using the 80A alternator. Iím looking at both right now, but thatís another topicÖ


I revised my sheet so the heater and heater fans are in separate lines to account for the different run times and use of ďfreeĒ heat when the engine was running. Still, that heater is an energy hog, especially when you consider it is a ďdiesel heaterĒ! Iím just not sure Iím figuring this right. I still get a little over 100 Ah per day during the winter from it, based on 14hrs on the heater and 6hrs on the blowers. So really this means a 200 Ah increase in the size of my house bank? If so, we obviously need to move south for the winter!


Thanks for the input on the values, which was my main concern. To answer your specific questions:

hellosailor, it is a gas sensor and valve control, but youíre probably right on the rating being a little high. I got the number off of the manual, which I assume is its max consumption.

cdennyb, Nav instruments for me is my tridata and wind display. I got the values from the power consumption off the raymarine website, which are 45 and 65 mA. I thought this was low, too, is this an accurate way to est. the power usage? And of course you can use the sheet, glad you like it.

goboatingnow, I also got the power consumption for the chartplotter/GPS from the specs on the raymarine site. Does this work? The raymarine site shows 2.75-6 amps for the autopilot as you say, so I picked 5 amps. Am I missing any components here? I leave the chartplotter on at anchorage for the anchor alarm, unless it is a place Iím comfortable with. I fixed the TV hours, that helped!

The biggest danger I see in the sheet is verifying run times for the big draw things like the fridge and heater, and the amperage ratings for continuous use things.

Thanks again for your input- Frank
__________________
GeoPowers is online now   Reply With Quote
Old 30-12-2009, 11:23   #11
CF Adviser
Moderator Emeritus
 
Hud3's Avatar

Cruisers Forum Supporter

Join Date: Sep 2007
Location: Virginia
Boat: Island Packet 380, now sold
Posts: 8,929
Images: 49
If you install a battery energy monitor like the Link 10, you can find out how many amps each piece of equipment draws by turning them on, one at a time. The ones that cycle rapidly, like the autopilot, will require a little interpolating by eyeball.
__________________
Hud
Hud3 is offline   Reply With Quote
Old 30-12-2009, 12:23   #12
Registered User
 
Bright Eyes's Avatar

Join Date: Dec 2009
Location: Nassau, Bahamas
Boat: 1985 Seidelmann 37 - s/v Bright Eyes
Posts: 94
Great spreadsheet, I got excited when I saw it as I have been trying to decide the best way to keep track of this stuff.

One fun item I purchased was a watt meter, which you just plug things into it and it tells you the voltage, wattage, ampage, time, and keeps a running total.

Amazon.com: P3 International P4460 Kill A Watt EZ Electricity Usage Monitor: Electronics
__________________
s/v Bright Eyes
http://www.sailblogs.com/member/joeynchristine/
Bright Eyes is offline   Reply With Quote
Old 30-12-2009, 12:23   #13
֍֎֍֎֍֎֍֎֍֎

Cruisers Forum Supporter

Join Date: Apr 2006
Posts: 13,056
Short of buying a Link10...you can also buy any $20-25 multimeter that has a 10-amp (rather than 2-amp) maximum DC-amp range on it, loosen one wire or pull the fuse behind any instrument, and insert the multimeter in line to directly measure the current. If you exceed the rating of the meter, expect to blow an obscure fuse that is IN the meter, so also try to find spares.

There are also clamp-on ammeters, which used to cost a fortune but even Sears has a model well under $100 bucks now. They'll do alright for higher loads (i.e. 1-100 amps) but for measuring little loads like instruments or the chartplotter--I'd stick to the multimeter. Odds are that most of the stuff will come close to the spec in the manual in "typical" use.

I'm not surprised by the low numbers for the wind and tridata. LCD displays often run on flea power these days, as do the electronics behind them. The lighting is more likely to draw more power.
__________________
hellosailor is offline   Reply With Quote
Old 30-12-2009, 13:28   #14
Registered User
 
Stillraining's Avatar

Join Date: Oct 2008
Location: Puget Sound
Boat: Irwin 41 CC Ketch
Posts: 2,876
Scratch 100..
Attached Thumbnails
Click image for larger version

Name:	Wood Stove-3.jpg
Views:	370
Size:	29.5 KB
ID:	12265  
__________________
"Go simple, go large!".

Relationships are everything to me...everything else in life is just a tool to enhance them.
Stillraining is offline   Reply With Quote
Old 30-12-2009, 13:37   #15
Moderator
 
Paul Elliott's Avatar

Cruisers Forum Supporter

Join Date: Sep 2006
Posts: 3,888
Images: 4
Regarding the use of clamp-on DC ammeters, for measuring smaller values of current I have a ten-turn coil of wire in my kit. You have to disconnect one end of the wire whose current you are measuring (or bridge across an opened breaker or pulled fuse), but the ten turns through the clamp gives you a 10x multiplication factor, so (for example) 0.1A reads as 1A.



It's no more convenient, and probably less accurate than using the 10A range on your DVM, but this trick can still come in handy.

For what it's worth, on VALIS we consume about 200Ah/day when sailing, and significantly less when anchored. Of course we are anchored in the tropics, so don't need to run the heater, and we don't have a TV, but the refrigerator is running at close to a 50% duty-cycle (5A when running).
__________________

__________________
Paul Elliott, S/V VALIS - Pacific Seacraft 44 #16 - Friday Harbor, WA
www.sailvalis.com
Paul Elliott is offline   Reply With Quote
Reply

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Engine Starting Video / Real World Amp Load Data Maine Sail Electrical: Batteries, Generators & Solar 21 20-11-2010 14:17
What Do You Miss ? JusDreaming Liveaboard's Forum 60 14-09-2010 04:43
What Do You Miss the Most? What Do You Like the Most? sww914 Liveaboard's Forum 21 22-12-2009 10:43
Electrical Calculator GordMay Electrical: Batteries, Generators & Solar 0 17-04-2007 03:02
Wire size calculator Alan Wheeler Electrical: Batteries, Generators & Solar 0 21-09-2004 14:42



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 14:24.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.