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Old 22-03-2014, 19:13   #1
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What Generator?

I'm planning on taking my 30 trailerable sailboat to mexico next. On the boat I plan to have an outboard that doesn't have a charging system. So I'm considering a generator to charge my batteries. I'm wonder how big of a generator and what kind of battery charger I will need. My boat is fairly power friendly. No refrigeration. Only cabin light (one), running lights, depth sounder, VHF radio, AIS, and autopilot. What I wonder do I need a generator and battery charger. Or can one solar panel do? If I need a generator how often might I need to run it and how long? Also how many watts does it need to put out, or amps? Also currently I only have a single battery, I'm considering going with just one, or should I have two?
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Old 22-03-2014, 20:09   #2
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Re: What Generator?

You need to figure out an energy budget before you try and work out what will provide that much power. Add up the energy drain of all your usage items multiply by the number of hours a day they will be on. Once you have that it's just a numbers game to figure out what will provide that much power.
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Old 22-03-2014, 20:19   #3
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Re: What Generator?

Most of the items you mention will use low to moderate amounts of power but you mention autopilot. If the autopilot runs off electric power then it will likely use a a lot of power.

How many batteries depends on how big the batteries. The correct question is how many amp hours of battery power you need.
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Old 22-03-2014, 20:40   #4
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Re: What Generator?

solar, solar, solar. i have a 51' boat with very little power draw--no refrigeration, no AC, no watermaker, etc-- and the 2 Kyocera 130 solar panels I have top up my 450AH battery bank by 1100 each morning, even when it's overcast. my autopilot is mechanical rotary but only uses 8 amps when working REALLY hard and then just momentarily.

in fact, i just ditched (sold) my Northern Lights 5kw generator yesterday because of la ck of use.

save lots of bucks, lots of fuel, lots of noise, lots of weight, lots of oil changes, etc and get a small solar panel!







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Old 24-04-2014, 12:25   #5
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Re: What Generator?

Here's a chart that outlines the different running lengths, watt generation, etc. of different generators that could be helpful when making the decision.
Generator Comparison Chart (sortable) | Best Portable Generators 2014
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Old 24-04-2014, 13:30   #6
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Re: What Generator?

I don't now who created that chart, but it doesn't include the Honda 2000 or 3000, easily the quietest, most popular portable generators on the market.

To the op: I'd recommend doing a power survey to determine how much power you'll need per day, then plan on 1.5x that for safety margin. I'd swap over to LED lights for all lights on board. Depending on what you budget is, you might want to get 2 or 3 AGM batteries, or maybe get the LiFePO4 batteries, they're much smaller, lighter and more powerful and not much more expensive than the best AGM batteries.

I love solar power, if you can manage the room to mount a couple instead of a bimini or dodger or flexible ones on top of the bimini, that would be great.

I believe everyone should have a backup source of power, and the Honda 2000 is a great generator. Quiet, reliable, compact. If you want used, craigslist is a good source, if you want new, wisesales.com is a good place, in addition to a couple others who escape me right now.
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Old 24-04-2014, 13:48   #7
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Re: What Generator?

Your autopilot will be the biggest draw- 3-4 amps while in use, say 6 hours so 24 AH.

Other instruments, maybe 1 amp so 6 AH

Anchor light for 10 hours at 1 amp, so 10 AH\

Cabin lights and misc, 10 AH.


40 AH for 24 hours. One Group 27 battery has a capacity of 80 AH. Since you don't want to discharge more than 50% you will need to completely recharge every day. This isn't easy to do. I would use a minimum of 2 batteries and plan to cycle their 160 AH of capacity from 50 to 85% or 56 AH. So you still need to recharge daily, but maybe not as long if by genset.

A 200 watt solar panel will put out 65 AH on a sunny day. That might solve your needs, but if it is cloudy for 3-4 days your batteries will be flat.

Another rule of thumb is to never charge flooded cell batteries at more than 25% of their amphour capacity in amps. So you are limited to a 40 amp charger. Chargers of this size typically draw 7-8 amps AC at 120V.

A 1000 watt generator like the Honda 1000 EU may just squeak by. Its continuous output is 7.5 amps.


So, two choices: 200 watts of solar panels and live with cloudy days. Or a 40 amp charger and a 1000 watt generator. The best would be both. But it will be costly: 300-400 for the charger, $7-800 for the little Honda, $250 for the solar panel and $150 or so for the MPPT controller (or two 100 watt panels and a much cheaper PWM controller), two batteries-$200, wiring and installation-???.

David
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Old 24-04-2014, 14:31   #8
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Re: What Generator?

from what i've gleaned from the discussion so far, heres my take -

you need at least two batteries.

if you can arrange a good mounting place, solar is number one. once installed it pretty much takes care of itself. put up as much solar as is practical on a 30 foot boat.

if you need a standby generator, get a honda 1000. buy a smart automotive
charger (under $100) and plug it in to the honda - don't use the 12v dc output plug on the honda, it's too small (8amp). i use a honda 1000 and plug in a 35 amp smart automotive charger. the honda 1000 will probably support a 45 amp charger if you think you need that much, but i don't think you do.

anyway, the above is pretty much what i've been doing the past ten years....
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Old 24-04-2014, 14:34   #9
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Re: What Generator?

Quote:
Originally Posted by obelisk View Post
solar, solar, solar. i have a 51' boat with very little power draw--no refrigeration, no AC, no watermaker, etc-- and the 2 Kyocera 130 solar panels I have top up my 450AH battery bank by 1100 each morning, even when it's overcast. my autopilot is mechanical rotary but only uses 8 amps when working REALLY hard and then just momentarily.

in fact, i just ditched (sold) my Northern Lights 5kw generator yesterday because of la ck of use.

save lots of bucks, lots of fuel, lots of noise, lots of weight, lots of oil changes, etc and get a small solar panel!

again.
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Old 24-04-2014, 14:48   #10
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Re: What Generator?

+1 on using a battery charger, not the generator's charger output, to recharge the battery bank.

The battery chemistry is important in selecting the correct charger.

Using AGM batteries is a good choice because they want to be charged much faster than flooded cell batteries. The AGM battery wants to be charged between 0.2C to 5C (20A to 500A on a 100Ah battery). A flooded cell battery wants to be charged at C/10 (10A on a 100Ah battery).

So, using AGM combined w/ an appropriately-sized larger charger will permit recharging the battery bank quickly, using less gasoline.
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Old 24-04-2014, 16:14   #11
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Re: What Generator?

Make sure you have enough solar with controller to top up the battery each day and give the battery a long life. Run it low frequently and it won't last long.
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