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Hello and a question about Solar

Groundhog

By Groundhog
in Boat Equipment

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Groundhog Engager

Groundhog

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Seems like I know you all already after a few years of on and off lurking. You've helped me buy two boats, sell one and provided masses of maintenance information. I'm going to be a full time live aboard in the not too distant future when my divorce is finalised and I've got a question about solar that there isn't an answer to already!

 

I'm going to be mostly marina based with a shoreline at least for the first year or so but I still want to use solar as much as possible. I'm not sure of the best way to go about it. My plan at present is to install 1kw of solar panels using an MPPT controller and I'm clear on how this works. What I'm less clear on is how I can keep a shoreline connected but only use it if and when the batteries fall below a specified state of charge. I've read on here about smartgauges and how they can be used to auto start generators. Would it be possible to do the same with a relay that connects the shore power to a charger/inverter?

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Sierra2 Collaborator

Sierra2

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I have no answer to the question but I am interested in the answer. Chaz


Thinking about it, if you are running everything on 12v (lights, pumps, fridge, usb chargers ect) then you only need a relay on the battery charger, not the whole consumer unit/inverter ?

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Groundhog Engager

Groundhog

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I've got a combined inverter/charger so I thought it would be easiest to have the relay connect the 240v supply to everything rather than getting a separate charger. I'd like an alarm trigger as well so when there is no shoreline for the relay to connect I know it's time to start the engine.

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Boredrider Collaborator

Boredrider

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If you look at page 20 of the Smartgauge manual, you will see that alarms can be set based on voltage of the domestic bank (not SOC, but near enough for your purpose). The alarm output terminals could be used to switch a 12v relay which controls the 240V live to your charger/inverter, or indeed the 240V supply to everything on the boat. I've no idea what sort of fuse/safety arrangements you'd have to incorporate though, perhaps one of the experts will be along in a minute!

 

On a slightly different tack, have you done some sort of cost/benefit analysis? At about £1 per watt plus a good controller, the cost of your solar installation would pay for a lot of mains electricity, especially at the lowish costs that (some?) marinas charge. Or maybe you are taking the philanthropic approach...........

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Loafer Veteran

Loafer

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Posted (edited)

Seems like I know you all already after a few years of on and off lurking. You've helped me buy two boats, sell one and provided masses of maintenance information. I'm going to be a full time live aboard in the not too distant future when my divorce is finalised and I've got a question about solar that there isn't an answer to already!

 

I'm going to be mostly marina based with a shoreline at least for the first year or so but I still want to use solar as much as possible. I'm not sure of the best way to go about it. My plan at present is to install 1kw of solar panels using an MPPT controller and I'm clear on how this works. What I'm less clear on is how I can keep a shoreline connected but only use it if and when the batteries fall below a specified state of charge. I've read on here about smartgauges and how they can be used to auto start generators. Would it be possible to do the same with a relay that connects the shore power to a charger/inverter?

 

 

Are you able to change the charging voltage of your charger?

 

If so, set that to 14.4V max, which is safe for anything, then adjust your solar panel controller to provide 14.5.

 

Then as soon as the sun gets up, your battery voltage will exceed the charger's programmed limit and it will stop charging, because the solar controller will have taken over and keep your charger from charging. Your charger thinks it's job is done.

 

When the sun goes away, your battery voltage will drop immediately, thus waking up your charger.

 

I guess not all chargers can do this, but I'm sure you can override it at the solar controller.

 

ETA: Those figures could possibly use a 1V reduction across the board, whilst you're in the marina and probably at 'float' charge levels in your batteries.

 

Experts needed here!

Edited by Loafer
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TaffyRon Collaborator

TaffyRon

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Are you able to change the charging voltage of your charger?

 

If so, set that to 14.4V max, which is safe for anything, then adjust your solar panel controller to provide 14.5.

 

Then as soon as the sun gets up, your battery voltage will exceed the charger's programmed limit and it will stop charging, because the solar controller will have taken over and keep your charger from charging. Your charger thinks it's job is done.

 

When the sun goes away, your battery voltage will drop immediately, thus waking up your charger.

 

I guess not all chargers can do this, but I'm sure you can override it at the solar controller.

I agree with that, my mppt takes up to 14.5 but charger does 14.7, clever bits of kit

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Arthur Brown Influencer

Arthur Brown

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IMO real life electricity generation costs more than mains electricity, so use the shoreline.

 

Remember that one Kw at 12v is something in the order of 80 amps so you need to work with fat cable and well chosen connectors.

 

Galvanic corrosion happens when the ground potential at the boat is different from the ground potential where the earth wire is actually grounded, which can change over time with faults at other places.

Usually a galvanic isolator is fitted. Some people go for an isolating transformer and take two wires(L&N) from the mains as input, and get L and N from the out of the transformer and ground the N wire to the hull only.

 

Wherever you get the power from remember to use a clever charger, and use it well. Hopefully your batteries should be full to 100% SOC for a lot of the time, but holding them at over 14.4 causes them to lose water and over a year they will suffer, best that batteries are charged to something like 14.4v then held at a float voltage as recommended by the maker or possibly in the region of 12.8 - 13.2v

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Loafer Veteran

Loafer

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my mppt cuts the solar at 14.5 but the shoreline is still going, no? Hope so, been going since may!

 

I'm feeling a bit 'thick' here, but I'm suggesting that your solar stuff should override the shore stuff, while it's able to, thereby reducing your marina electricity bill.

 

Have I misunderstood you?

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TaffyRon Collaborator

TaffyRon

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I'm feeling a bit 'thick' here, but I'm suggesting that your solar stuff should override the shore stuff, while it's able to, thereby reducing your marina electricity bill.

 

Have I misunderstood you?

I dont know, last marina I was in charged 1.50 a day flat rate!

No, your right, figures wrong way, the victron will charge quicker than solar though unless sunny day

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Loafer Veteran

Loafer

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Been a while since ive looked but it all does as it should, but I agree with the op, would be nice to have something that kicks the shoreline in if the solar isnt man enough one day, but then being on shoreline all the time isnt good is it not?

 

It's good for your batteries, which (if the charger is good enough) will be kept at float voltage and unused, which adds loads to their longevity.

 

But it can introduce other problems. See other posts on here about galvanic corrosion.

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Phil Ambrose Veteran II

Phil Ambrose

Posted
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Are you able to change the charging voltage of your charger?

 

If so, set that to 14.4V max, which is safe for anything, then adjust your solar panel controller to provide 14.5.

 

Then as soon as the sun gets up, your battery voltage will exceed the charger's programmed limit and it will stop charging, because the solar controller will have taken over and keep your charger from charging. Your charger thinks it's job is done.

 

When the sun goes away, your battery voltage will drop immediately, thus waking up your charger.

 

I guess not all chargers can do this, but I'm sure you can override it at the solar controller.

 

ETA: Those figures could possibly use a 1V reduction across the board, whilst you're in the marina and probably at 'float' charge levels in your batteries.

 

Experts needed here!

This is exactly what I do, seems to work for me.

 

Phil

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nicknorman Veteran II

nicknormanDonate to Canal World

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If you intend to remain on shore power for a while, then eventually leave the marina, why bother to install solar now? Surely better to wait until you leave shore power.

 

Although your solar might mean a reduction in marina leccy bills, it will take a long time to repay the capital cost. And don't forget that when plugged into marina power, your batteries are permanently on float, whereas when on solar they charge by day and discharge by night - ie they are cycling and this impacts their life thus incurring a replacement cost.

 

If you do want to install the solar now, why not just fit a time switch for the shore power, set to come on around sunset and off around sunrise. That way the boat is (mostly, in winter) powered by solar during the day, and by shore power over night. If there is a shortfall in solar during the day, the shore power will recharge the batteries over night as well as meeting the boat's current power needs.

 

Alternatively you could set the MPPT controller's regulated voltage to be 0.25v or so above the Sterlings so that when the sun is working, it takes priority, and when the sun is not working you will effectively be on shore power, but that means that either the inverter or the solar is not set to the optimum voltage for the batteries.

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Loafer Veteran

Loafer

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I don't see how I could make that work with a combi but even if I could I'd prefer to not use the mains at all in the summer unless the state of charge drops to 50%. At night I'll be running just off batteries with the solar recharging them during the day

You can always just do it manually, plugging in your shore power when required. Or turning off your charger.

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