The basics on power while cruising - SailNet Community
 
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post #1 of 9 Old 05-01-2010 Thread Starter
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The basics on power while cruising

I've begun looking for my first boat, and my knowledge of marine electronics is virtually nil. Probably the best way to start would be from the goal and then ask for help working backward to what I need to be shopping for.

I'm looking at 25-28' boats for Great Lakes cruising. First choice would be an inboard motor, but I'm not ruling out an outboard. When cruising for a week or two, there's a good chance I'll need to work on my laptop for a few hours a day. I'm looking at worst case here. Most likely, if this happens, it'd probably be prudent to head to a marina to stay for a couple days.

So my two questions are about Internet access and power.

1. For Internet access when away from marinas, I'm wondering if my land-based system will work. On land, I tether my laptop to my cell phone and use Sprint's data network. It's not fast, but it's good in a pinch. Is cell phone coverage something I can generally count on near the shores of Lake Michigan? Is it spotty?

2. To power a laptop for a few hours a day, how much will I drain my batteries? And as they drain, how much might I need to run my inboard to recharge that amount?

2a. Same power issues, but with an outboard. I'm assuming that, even with an electric start outboard, it isn't really going to charge marine batteries to any degree. So should I start looking at solar panels? Perhaps my need to use a computer might be the thing that forces the out/inboard issue.

Thanks!

ETA: I just looked at my laptop's power rating. 3.65A at 16.5Vdc.

Last edited by SirRealism; 05-01-2010 at 03:08 PM.
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post #2 of 9 Old 05-01-2010
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I used to cruise the North Channel in a Niagara 26 with a Honda outboard to charge the batteries. We got by because we used very little power. I would carry a small kerosene hurricane lamp that I hung from the backstay for as an anchor light for instance.

One small advantage to an outboard is you do not need battery power to start it. That being said I definitely prefer a nice dependable diesel inboard. Very much easier on fuel is a major advantage so fewer trips to a fuel dock.

No idea what cell coverage is like on Michigan, I am on the nicer lake immediately to the right.
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post #3 of 9 Old 05-01-2010 Thread Starter
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Quote:
Originally Posted by Gary M View Post
I used to cruise the North Channel in a Niagara 26 with a Honda outboard to charge the batteries. We got by because we used very little power. I would carry a small kerosene hurricane lamp that I hung from the backstay for as an anchor light for instance.

One small advantage to an outboard is you do not need battery power to start it. That being said I definitely prefer a nice dependable diesel inboard. Very much easier on fuel is a major advantage so fewer trips to a fuel dock.

No idea what cell coverage is like on Michigan, I am on the nicer lake immediately to the right.
Gary, I've heard rumors that there was a quaint little body of water to the east. Is it still there? Actually, a couple folks have been pointing me in your direction. (Recommendations for Lake Michigan cruiser) I live in Indianapolis, so I'll be driving a few hours, regardless. Toledo is ~ 1 hr farther from me than Hammond, IN. I might be making a road trip to Detroit and/or Toledo in the near future to see check out what's available for sale in those areas.

Last edited by SirRealism; 05-01-2010 at 03:18 PM.
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post #4 of 9 Old 05-01-2010
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A couple of hours a day shouldn't be a big drain on your batteries. Best to get the 12 volt adaptor for your laptop. If only a couple of hours a dasy you could use the laptop on its internal battery and charge it when plugged in even. '
As far as coverage check with your cell provider or other sailors in the area you will be cruising.
An outboard won't do much in the way of battery charging.

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post #5 of 9 Old 05-04-2010
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A few hours a day with a 60 Watt laptop is going to take about 5.5 amps at 12 VDC, assuming some conversion losses going with a DC power supply. If using an inverter, it'll be worse. that's 22 amp hours or so.

How big is your house bank. If you have a single Group 31 battery, which is about 130 amp-hours, three-days use without any other electrical loads will bring down your bank to 50% or so.

You really will want have some sort of passive recharging.

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post #6 of 9 Old 05-05-2010
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Cell coverage for the Verizon network is actually pretty good along Lake Michigan's eastern shore. I've found very few voids from Grand Haven to Charlevoix. You'll also find that many of the ports/marinas have WiFi service available, either for free or a fee.

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post #7 of 9 Old 05-05-2010 Thread Starter
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Thanks for the answers. That's a couple more items down on my pre-purchase checklist. I'm getting closer.

Last edited by SirRealism; 05-05-2010 at 05:50 PM.
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post #8 of 9 Old 05-05-2010
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We have found the laptop/cellphone option very dependable everywhere we've gone. MUCH more reliable coverage than an air card from the same provider. Verizon had good coverage in Lake Michigan, ATT better in Chesapeake, so you really have to check your provider network.

A laptop with a large bright screen is quite the power-eater, as S'dog points out. I use a netbook with flash memory (smaller screen, and no spinning hard drive both big power savers) for writing and other "slow" computer jobs, or wait till I'm plugged in. Otherwise, we power our lives with 2 65-watt solar panels.
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post #9 of 9 Old 05-17-2010
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For the laptop I'd recommend a DC 12V to DC16.5V power converter. It's more efficient than changing from 12VDC to 115VAC then back to 16.5VDC. An example is here on newegg. I bought one and use it on my boat but for 12V to 12V with my netbook that I use as a chartplotter. When plugged in to shore power the adapter does get hot though. for low voltage it's cool running.
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