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Solar vs Generator


Nick D

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I have been thinking about installing solar, but a friend in the same position is thinking of getting a generator instead. Benefits are that it is initially cheaper and can be used during the winter months when solar is not so effective.  Downsides are the ongoing costs of fuel, storage, noise etc.  Any thoughts?

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Just now, Nick D said:

To clarify we are not liveaboards but cruise off grid for 3/4 weeks a time

That may put a slightly different complexion on the problem.

If it's not sunny when you're on the boat how are you going to charge the batteries?

Solar is out

Generator?

Engine? - If that's out 'cos it's noisy then generator

           If it's not how about putting a larger alternator in to charge your batteries a bit quicker

           If it is then a genny is an alternative, but not a petrol one - get a proper inboard water cooled piece of kit instead. Expensive

 

That'll get the conversation going...  

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11 minutes ago, Nick D said:

To clarify we are not liveaboards but cruise off grid for 3/4 weeks a time

If your on the move more than not (like every 3 or 4th day) when cruising then you don’t need a generator (although you may want to look at your current charging to see if it’s performimg well).  Solar is only really beneficial if you don’t have shore power at your home mooring as it will keep the batteries topped up when your not using the boat,  it it will also extend the days in summer that you don’t need to run the engine if your not moving.

Edited by Robbo
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7 minutes ago, Nick D said:

When we're on the cut we tend to cruise for about 4 hours a day. This doesn't give us enough charge for our needs so we run the engine for another three hours on average.

You cruise everyday?   If so and your not getting fully charged in 4 hours then that’s an issue and should be looked into.    What are your power requirements? Are you using any kind of battery monitoring?

Edited by Robbo
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8 minutes ago, Nick D said:

When we're on the cut we tend to cruise for about 4 hours a day. This doesn't give us enough charge for our needs so we run the engine for another three hours on average.

if you can't charge your batteries after 4 hours' cruising then solar won't make a lot of difference.

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You have asked an impossible to answer question because you don’t say what your current battery/ charging setup is or what your energy needs are. On our last boat we found four hours cruising with a domestic bank of three batteries mostly providing power to 12 volt appliances, TV, radio, shower and lights and a 240 volt hairdryer via an  invertor was sufficient for our needs.

Edited by Stewart Kirby
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4 minutes ago, Stewart Kirby said:

You have asked an impossible to answer question because you don’t say what your current battery/ charging setup is or what your energy needs are. On our last boat we found four hours cruising with a domestic bank of three batteries mostly providing power to 12 volt appliances, TV, radio, shower and lights and a 240 volt hairdryer via an  invertor was sufficient for our needs.

Our use is similar to yours, 12v fridge/freezer and led lights, inverter for tv, wi-if router charging phones/radio. No hairdryer or microwave. On 4 x 110ah batteries, should four hours engine running be sufficient?

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1 hour ago, Nick D said:

  Downsides are the ongoing costs of fuel, storage, noise etc.  Any thoughts?

Proprietary inbuilt 'diesel' generators - cost of aquisition

Portable petrol powered generator - you have to run it off the boat to stay safe, you need to run it downwind of your boat and any nearby boats, they produce deadly amounts of CO even 6-10m away from the exhaust pipe, then there's petrol stowage, petrol safety, strict refuelling regime - ashore, not on the boat.

There are upsides, but you know those. So if you go down the portable generator route. Respect your neighbours, respect yourself, look after your genny properly. https://www.boatsafetyscheme.org/stay-safe/generator-safety/ 

Edited by Rob@BSSOffice
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12 minutes ago, Stewart Kirby said:

Get the alternator checked at once before you ruin the batteries. I have been in exactly the same situation.

It was checked prior to the new batteries being fitted and was fine. I think I might need a more accurate, digital volt meter reader as I am currently relying on an analogue one.  So based on my usage, you would say that 4 hours engine running should be sufficient?  

6 minutes ago, Rob@BSSOffice said:

Proprietary inbuilt 'diesel' generators - cost of aquisition

Portable petrol powered generator - you have to run it off the boat to stay safe, you need to run it downwind of your boat and any nearby boats, they produce deadly amounts of CO even 6-10m away from the exhaust pipe, then there's petrol stowage, petrol safety, strict refuelling regime - ashore, not on the boat.

There are upsides, but you know those. So if you go down the portable generator route. Respect your neighbours, respect yourself, look after your genny properly. https://www.boatsafetyscheme.org/stay-safe/generator-safety/ 

Good points, thanks.

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1 hour ago, Nick D said:

based on my usage, you would say that 4 hours engine running should be sufficient?  

Impossible to answer because you haven’t given us your usage. Only a list of stuff that you have. You also haven’t said what power your alternator is. A power audit will tell us what you use and then, if you also tell us the size of your alternator, we can have a stab at estimating how long you might have to take to charge. 

 

As a general rule no, 4 hours isn’t enough. 6 to 8 hours is more like it. 

 

Edited by WotEver
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1 minute ago, WotEver said:

 

 

As a general rule no, 4 hours isn’t enough. 6 to 8 hours is more like it. 

 

That's what I thought, hence my initial question about whether solar or a generator would be better on balance to make up the shortfall rather than running the engine whilst stationary 

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Just now, Nick D said:

That's what I thought, hence my initial question about whether solar or a generator would be better on balance to make up the shortfall rather than running the engine whilst stationary 

I’ve got 1000w of solar and my batteries are fully charged by 12pm I run a washer fridge tv freezer. You could get a decent setup for around £400 - £600 if you look at that website I posted. 

 

You’re not beating solar as it pays for itself at one point then it’s all free power

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2 minutes ago, Nick D said:

That's what I thought, hence my initial question about whether solar or a generator would be better on balance to make up the shortfall rather than running the engine whilst stationary 

In winter solar is useless. In summer if you have lots its good. We cruise everyday so our batteries are topped up every day without solar. My bog standard engine alternator whacks far more in to the batteries than my solar ever did in say a two hour period but solar is good to maintain batteries or indeed run a boat if you live like Fred and Wilma?  How much lectric do you use?

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2 minutes ago, Nick D said:

That's what I thought, hence my initial question about whether solar or a generator would be better on balance to make up the shortfall rather than running the engine whilst stationary 

I think you’ve had all the pros and cons for that decision. If you cruise early in the day then I’d plump for a modest Solar installation as the alternator has done the heavy lifting leaving the Solar to gently top the Batteries up through the rest of the day. 

 

Unless it’s grey and overcast...

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1 hour ago, Nick D said:

It was checked prior to the new batteries being fitted and was fine. I think I might need a more accurate, digital volt meter reader as I am currently relying on an analogue one.  So based on my usage, you would say that 4 hours engine running should be sufficient?  

Good points, thanks.

And how many times have we heard that. How was it checked and when? To check aNan alternator on the boat you need to check the4 amp[s delivered when the batteries are fairly flat or a load at or greater than the alternator output is running so that often means first thing in the morning.

 

Then you need to check the voltage last just before you stop charging after several hours engine running when the alternator is delivering less than 10 amps so a  long timeafter the current test.

 

I bet the only test done was voltage and that is inconclusive without current readings.

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2 minutes ago, leeco said:

I’ve got 1000w of solar and my batteries are fully charged by 12pm I run a washer fridge tv freezer. You could get a decent setup for around £400 - £600 if you look at that website I posted. 

 

You’re not beating solar as it pays for itself at one point then it’s all free power

So on a rainy January day you run a fridge, freezer and washing machine via solar? Do your panels keep batteries fully charged through the winter then?

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