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John G-
Admiral

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793 Posts

Initially Posted - 07/13/2002 : 16:24:32

Do any of you have an inverter on your boat? I am in the happy situation of being able to spend 3-4 days a week on Peregrine, however I need to keep the cell phone topped off and I like to write. As many of you know I’m the C25/C250 Mainsheet editor so I’d like to have my laptop around.
So… What do I need to know? I have 2 batteries but am not sure of they’re power. I have an alternator on the outboard but am not sure how well it tops off the batteries. In other words I’m clueless.<img src=icon_smile_blush.gif border=0 align=middle>
Any and all info would be appreciated. Inverter types and sizes, battery sizes needed and how to monitor the batteries etc.
TIA

[url="http://www.peregrinefund.org/"]<img src="http://www.peregrinefund.org/images/intro_mid_image.GIF" border=0>[/url]
 John G- "PEREGRINE" C25-#4762 FK

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Leon Sisson
Master Marine Consultant

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USA
1893 Posts

Response Posted - 07/13/2002 : 19:44:05

John,<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>... have 2 batteries ... not sure of power ... alternator on outboard ... not sure ... In other words clueless ... Inverter types and sizes, battery sizes needed, how to monitor the batteries ...<hr height=1 noshade id=quote></BLOCKQUOTE id=quote>I suggest you begin by reading up on the idea of an on-board energy budget. It's very similar to the concept of a checking account. Using a spreadsheet helps, but isn't essential. A hand-held digital multi-meter however, probably is essential. If you don't have one, you need one anyway.

<img src="http://www.harborfreight.com/cpi/photos/37700-37799/37772.gif" border=0> [url="http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=37772"]Here's a link to a multimeter I recommend[/url]. The same vendor has several other meters. The feature you want to look for is the ability to measure 10 or 20 amps DC.

You start by determining the current draw, in amps, of every 12VDC accessory on board. Or at least the ones that you use. You can ignore seldom-used things like the bilge pumps. Then you estimate, give or take 10%, how much time you use each item in a day. Multply current by time for each item to get its amp-hour draw per day. Add up all those to get the total amp-hour draw per day. That's how much power you need to put back into your battery bank. Just like making deposits to cover your checks.

I think you'll find that although the outboard alternator is helpful, it's not going to be able to repay the entire energy debt in any reasonable amount of running time per day. Other sources of power to consider are: solar panels, shore power charger, portable gas-powered genset like a Honda EU1000 (I think that's the right model number). Each of these options has its advantages and disadvantages as you can probably see.

I highly recommend a big house battery bank and one or two solar panels as a good place to start. Also a separate cranking battery if you rely on electric start, as I do. If you end up with more than one battery bank, I you might look into using one or more battery combiners to share charging sources between banks without risking cross discharge.

If it looks like you're going to be relying on shore power charging (or solar charging) between trips to provide you electrical needs, you need to figure your entire amp-hour debt for the whole trip, double that, and the result is your minimum required battery bank capacity.

As for inverter types and sizes, check to see what the power requirements of your laptop are. Also ask the laptop manufacturer if it requires extremely sinusoidal AC power, or if it can get by on square wave, or semi-square wave (staircase waveform), or if there's a cigarette lighter adapter cord available for it. Shop for your inverter accordingly. When figuring power usage through an inverter, you need to multiply in a power loss coefficient that the inverter manufacturer should provide.

[url="http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=44164"]Here's a link to an example inverter.[/url] <img src="http://www.harborfreight.com/cpi/photos/44100-44199/44164.gif" border=0>

I don't presently use an inverter on my C-25, but I used to have one in a custom van. The most important thing I remember is that they will drain a battery down so fast you have to see it to believe it.

That should cause enough confusion for one post. And the [Preview] feature is screwing up again. Let us know if you have other questions.

-- Leon Sisson

Edited by - on

Sam Nelson
1st Mate

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USA
64 Posts

Response Posted - 07/14/2002 : 14:15:57

John, as an alternative consider running the laptop and cellphone charger right from the 12 volt system on the boat. Every cellphone has some form of 12 volt charger available, designed to plug into a cigarette lighter socket in a car. Also, take a look at your laptops charger. Quite often you will find that it's power output is in the vicinity of 12 volts DC, and your laptop will run just fine connected to the boat's battery bank. One thought, have a spare cellphone battery or two already charged up (from home) when you climb aboard.

Leon is correct in his statement that inverters use a lot of power, because they are inefficient. If you do elect to go with an inverter, look for one with an efficiency rating of over 80%. And turn it off when it's not in use, don't just turn off the device plugged into the inverter.

Sam Nelson
C25 "Stratos" #3811

Edited by - on

Mike Vaccaro
1st Mate

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77 Posts

Response Posted - 07/15/2002 : 03:38:44

John,

We have a 600 watt inverter on board. It's powered by our house batteries, two group 24's underneath the starboard setee. We also have a 10w "smart charger" system. To install the inverter and charger close to the battery bank, we cut a hole in the back of the starboard setee. This is similar to a mod a lot of folks make to add storage space. We then expoxied a varnished piece of marine plywood to the inside of the hull. This serves as a mounting "breadboard" for all of the electrical components. Mounting electrical components in this area in this area has two advantages: 1. Very short wire runs to the batter compartement (which is desirable), and 2. The components are mounted relatively high above the bilge (if they get wet this high, I've got a much more serious problem than worring about getting an inverter wet!).

We have two AC circuits on-board, one that runs off the shore power and one that runs off the inverter. To keep things simple, the port side of the boat runs off shore power, and the starboard side runs off the inverter.

Having both AC and DC power available at all times is darn convineint, but not necessary. Most electronics and even some appliances (blenders, etc.) are available in 12v models as well. You also need to understand that there are two types of inverters available, one type produces what is called a "pure sign wave" and the other type is a "pseudo sign wave." The latter are the more inxepensive, smaller output units. The only disadvantage to the later is that it produces some electrical "noise" that could interfer with some types of electronics. But we've had no problems running laptops, cell phones or blenders on our system!

There are several different ways to measure battery charge, with voltage being the simplest. Multi-meters work great for this as well as meters that you can wire into your system. This acts as a "fuel guage" for your battery bank. If you're willing to spend more money, you can by a system that will actually measure amp-hours used and display hours remaining. These are great units, but cost several hundred dollars.

One last thing to consider is that most pure sign wave inverters can be had as a combination unit with a built-in "smart" battery charging system. These are the best marine inverters you can buy, but you'll need to spend nearly a grand (if not more) to obtain one. You can buy a combination of a smart charger and inverter for less than 500 dollars. To figure out your AC power budget, take a look on the back of the appliances you intend to run, there should be a sticker that shows power draw. Be aware that AC systems may initially draw a high amount of current before settling down to their rated draw (a perfect example is when you turn on your air conditioner--it may initially draw a couple thousand watts before it settles at rated power, this is why the lights may flicker momentarily). Your inverter needs to be large enough to handle these initial power requirements. For most electronics, this will never be a factor; but may be for small appliances.

If you have access to a West Marine catalog, you may want to take a look at that as there is a good discussion of electrical systems in there. I believe that material is also available on the web at www.westmarine.com .

Best of Luck,

Mike Vaccaro on the "Swoose"
84TR/SK #4707

Edited by - on

coldducks
Captain

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USA
342 Posts

Response Posted - 07/15/2002 : 07:11:37

we just had shore power and inverter installed on our boat along with some outlets and a battery charger. we just spent two weeks on the boat and several nights on the water. it was great to be able to run the tv, hair dryer and coffee pot in the morning. the captain is not home at the moment, so i cant give you all the specifics. but the inverter is 1750 watts. we told the installer what we wanted to be able run and he supplied the correct inverter. he also installed another battery and depth finder. when we come back to the slip, we plug the boat in and switch on the battery charger and charge both batteries. it works great. all the comforts of home!!!

COLDDUCKS
FANTASY #409 C250WK

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tapinkham
1st Mate

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USA
36 Posts

Response Posted - 07/15/2002 : 15:48:34

I have owned three inverters from these guys: http://www.statpower.com/home.htm
I have had great luck with the company from a customer
support perspective.
Good luck!

Tim

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