advice on small 12V system?? - SailNet Community

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Old 03-20-2007
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advice on small 12V system??

I am planning on doing some weekend - 1 week coastal cruising (close to shore) on my 23 ' sailboat. I currently have a very simple 12V system, set up by the previous owner, with 1 fairly new marine battery (not sure if it is a deep cell or not - will have to check brand, etc), and a couple of very small solar chargers. I used the radio, GPS and depth sounder last summer without having them die/ lose power, but would like to use my laptop and chart software this year, with an inverter.
As this may exceed my battery reserves, when I need it the most, I would like to see how to best improve the system, for a modest price (ie a few hundred bucks)
The boat has a 20 year old, 7.5 HP Honda 4 stroke outboard, not set up with an altenator.

Should I add a second battery - if so would it have to be the same kind, deep cell or regular?

What about carrying a cheap 950W gas generator, that puts out 8Watts DC, to charge the battery/ies for a half-hour or so, if they get too low. I currently do not even have a panel /meter, to see what the charge level is!

Thoughts?
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I would get a DC-to-DC power supply for the laptop, since it would be much more efficient than using an inverter and the AC power supply.

You don't say what the power requirements of your laptop are. If you have a very efficient 10" LCD sub-notebook, then your requirements will be very different than if you have a 19" widescreen notebook with DVD and dual-core processor.

I would add a deep-cycle (not deep-cell) battery, since it will tolerate what kind of use you are going to put it through far better than a car battery.

A bigger solar panel, like this one, might be able to extend the battery life long enough for you to get back, and put the battery on a real charger.

A small generator is also an option, but they tend to be noisy, use fuel, and can be a carbon monoxide hazard, especially on a boat the size of yours.
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SD - Thanks for the reply. My laptop is a panasonic toughbook - not sure of the acual power consumption, but googled it quickly, and it claims to be 70% more efiicient than a regular LCD.
I will check into a DC power supply. I would not be using the DVD, etc.

Thanks for the correction. Can I combine a new deep-cycle battery with my existing marine/ car battery type?

Not knowing any better, I only used the solar trickle charger last year, as the boat is on a mooring, and I didn't unhook the battery to bring it home, for a full charge.

I though of the small generator, as I see them on sale for $199. I called teh company, and was told taht I would be OK charging batteries, if I keep an eye on them, as their is no overcharge protection / regulator( not sure if they are the correct terms). It would only be for occassional use, however, the model I looked at, states not to use in the rain, wet conditions, etc. That would not be much help if the weather turns bad, and my battery runs low!
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Solar panels aren't so great in the rain and cloudy conditions...

You should be able to combine a car-type battery and a deep-cycle battery, since they are both 12V wet-cell batteries without too much of a problem. However, it isn't ideal.

The power requirements of your laptop should be one the bottom... how many watts and the DC voltage. If it doesn't say there, it should say what the output of the power supply is on the transformer itself... something like 5 amps @ 16VDC...

Does the generator provide AC voltage... if so, it might be better to get an intelligent AC three-stage charger and use that to charge the batteries. I couldn't say without knowing what the specs were..
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You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
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Last edited by sailingdog; 03-20-2007 at 09:40 PM.
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Targus makes a 12 volt plug with numerous attachments for the different plugs that different brands of computers.
pigslo
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The Targus one isn't ideal for use on boats... the Hama DC-to-DC power supply is better since it has a wider input voltage acceptance range IIRC.

Also, from my experience with the Targus, when I used to send them out with journalists... they're not that durable in normal use, and I doubt that improves in a marine situation.
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You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
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—Cpt. Mal Reynolds, Serenity (edited)

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SD - you are correct - laptop is 15.6V, 5A.

If a generator proves to be a decent addition, for occasional use, I am open to brands, but don't want the costs to spiral out of control. My next boat will have an inboard, alternator, etc. However, currently, I would like to keep the investmnet down, due to the size of the boat.

The inexpensive generator, that I looked at, did have an AC plug 120V, 6.8A AC output, and a 12 V plug 8.3A DC output.
http://www.kingcanada.com/Products.htm?ID=11889

I do realize that you generally get what you pay for. But in this case, I thought something along that line may work, for my occasional surplus power needs.

What size / price range of deep-cycle batteries would you recommend.
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Damn... not a bad guess... I was just winging it... LOL...

Honda has a pretty decent little gas-fueled generator. The EU1000i.

I hear that these are very good, but I haven't dealt with them personally.

As for batteries... I'd go with the Group 27... but it may be a bit heavy for you.. at about 53 lbs.. but gives you almost double the power of the Group 24 battery which weighs 35 lbs. Price is about $85.
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You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
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—Cpt. Mal Reynolds, Serenity (edited)

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Having done what you are doing ... tough call. I was grateful to have the little 1000 watt honda generator I bought before I left. It wasn't that I wouldn't have preferred to have a solar panel or wind generator instead, which I could have at the cost of the quiet honda ... it's that the honda had one feature that the other methods of generating power didn't have - it worked NOW, when I absolutely needed it. That said, I'd much rather have a good capacity battery bank, wind generator, solar panels, etc, and rely on that instead, but at the time I went out I didn't have the resources (mostly time) to install all of that. If you get a generator, be prepared to wait, it takes a long time to fully recharge a deep cycle battery with a little honda generator. Oh, and I would not invest in anything less than the quiet honda, because it really does make a difference to be able to recharge batteries without annoying every neighbor you have.
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One other thing.. you should get a battery box and mount the battery very securely.
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You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

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