Hello and a question about Solar

[TaffyRon]

Any solar saves you money and wear n tear on the cut

[Groundhog]

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.

 

 

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

 

Thanks for all you're help. I've been looking at this the wrong way I think. I don't need to automatically connect shore power I just need to keep my eye on the batteries and get to know the system. Once I'm off shore power and using the system for its intended purpose then a device to automatically connect shore power that I don't have will completely useless.

 

What I need to do is use smart gauge to trigger an alarm when the batteries are getting low so I know I need to do something about it.

 

The reason I want to get the system installed now rather than when I need it is to shake down any faults and get used to the way it performs.

[Phil Ambrose]

I think you might find you don't need the alarm because checking the bat SOC will become second nature, it's one of the things you just do when you live on a boat.

Phil

[TaffyRon]

What should "soc" be on on float? Mines 60% thats rubbish isnt it

[nicknorman]

What should "soc" be on on float? Mines 60% thats rubbish isnt it

Should be 100%, but what is float voltage, and how are you measuring SoC?

[Loafer]

Should be 100%, but what is float voltage, and how are you measuring SoC?

 

Could be that his monitor hasn't been reset, or zeroed, occasionally. The SOC reading is only a calculated one, based on various curves and coefficients, and eventually can become useless information.

[rogeriko]

Setting the MPPT charger higher than the mains charger wont work because as soon as you start drawing current the battery voltage will drop and the mains charger cuts in even if your batteries are full. Therefore you are always drawing mains power only a little from the solar. In the morning your batteries will be charged by the mains, expensive, and then when they are full the solar will just keep them topped up. In a proper off grid system the charger only cuts in when the batteries drop to 50/60% but you must have good batteries, like forklift batteries, if you want them to last a long time.

[Loafer]

Setting the MPPT charger higher than the mains charger wont work because as soon as you start drawing current the battery voltage will drop and the mains charger cuts in even if your batteries are full. Therefore you are always drawing mains power only a little from the solar. In the morning your batteries will be charged by the mains, expensive, and then when they are full the solar will just keep them topped up. In a proper off grid system the charger only cuts in when the batteries drop to 50/60% but you must have good batteries, like forklift batteries, if you want them to last a long time.

 

I would beg to disagree with SOME of the above, but by no means ALL.

 

It IS possible to take advantage of the sun whilst plugged in. You could have the charger set to float, for example. About 13.4V.

 

Anytime the solar panels have enough energy to raise the batteries above that, then they will take over, with a setting of 14.3, say, to avoid gassing.

 

That'll probably quite soon in the summer, and happen all day if it remains sunny.

[nicknorman]

Setting the MPPT charger higher than the mains charger wont work because as soon as you start drawing current the battery voltage will drop and the mains charger cuts in even if your batteries are full. Therefore you are always drawing mains power only a little from the solar.

Won't work 100% but will work a fair bit. It depends on the voltage regulation "softness" of the MPPT and the charger, and whether there is sufficient solar to meet the drawn current. If there is enough solar, the voltage shouldn't drop much below the regulated voltage (depending on regulator softness) and so most, if not all, the drawn current will be provided by the solar.

[Loafer]

Setting the MPPT charger higher than the mains charger wont work because as soon as you start drawing current the battery voltage will drop and the mains charger cuts in even if your batteries are full. Therefore you are always drawing mains power only a little from the solar. In the morning your batteries will be charged by the mains, expensive, and then when they are full the solar will just keep them topped up. In a proper off grid system the charger only cuts in when the batteries drop to 50/60% but you must have good batteries, like forklift batteries, if you want them to last a long time.

 

The voltage won't necessarily drop noticeably when you draw current. EG, if my batteries were only drawing 1A to remain charged, and my solar panels could be providing 20A, then I will have 19A available instantaneously for use. No voltage drop when switched on!

Edited December 12, 2014 by Loafer

[rogeriko]

It takes quite a few amps to maintain a battery at 14.6 volts as soon as you start drawing power the voltage will drop. Obviously if you have 1kw of solar charging at about 600w and you turn on the lights the voltage wont drop but when a cloud comes over the mains charger will kick in.

[Loafer]

It takes quite a few amps to maintain a battery at 14.6 volts as soon as you start drawing power the voltage will drop. Obviously if you have 1kw of solar charging at about 600w and you turn on the lights the voltage wont drop but when a cloud comes over the mains charger will kick in.

 

That's true. But I was quoting an example where my batteries were only taking a small current to maintain whatever voltage I'd set on the charger. Therefore as soon as solar is available, all but 1A of it will be available.

 

Of course, when the sun disappears then the charger will take over. That's the plan, innit?

[Jambo]

Thanks for all you're help. I've been looking at this the wrong way I think. I don't need to automatically connect shore power I just need to keep my eye on the batteries and get to know the system. Once I'm off shore power and using the system for its intended purpose then a device to automatically connect shore power that I don't have will completely useless.

 

What I need to do is use smart gauge to trigger an alarm when the batteries are getting low so I know I need to do something about it.

 

The reason I want to get the system installed now rather than when I need it is to shake down any faults and get used to the way it performs.

 

1kW should give you way more than you need from about April/May to September/October (and possibly even further). We have 1kW and only fired up a generator to run the washing machine a few times for the whole of that period. After a while I stopped checking the battery SOC because it never dropped below about 80% (although this will depend on your battery capacity and usage).

[Dinz]

Basics of what you are doing seem right.

As you say if sorted out now then ready for the cut.

With a bit of messing with voltage settings on my Victron I got mine set so that my EU20 can run 'ticking over' on a sunny day with the batteries charging from say 60%.

As soon as a cloud comes you can visually see the panels darken.

The EU picks up on revs to compensate to get charge rate back up.

Quite fun to watch and had a few savvy walkers fascinated as they could actually witness the Solar working in a sort of audio / visual way.

Tells me that sun = less fuel=saving.

Am just shy of a kilowatt of panels and don't need to run engine for power from april-octoberish.

Also fitted cheap inverter to Mppt that has a relay when batteries full [morning star] This is wired to immersion which is the same as a dump load.

Water doesn't get much hotter but seems to maintain temp. for longer.

Still messing about with wind turbine for winter days but very hit and miss unless in certain locations.

 

Good luck with it!

[Ssscrudddy]

I wanted what the OP has asked. I wanted Solar for whilst out & about, & then seeing as I have solar I want it to use all the available solar 1st before using shore power whilst I'm in the marina connected to shore power.
I could not find an answer on how to do this. The closest I got was something I read that seemed to suggest it would just be down to luck
I too thought about programming the mppt controllers & my charger to various levels, but I still got nowhere.

Now to the real world, I recently got solar & had it wired up, only had it for winter so far. It seems to use all available solar 1st without me programming anything.

I have taken (inaccurate) readings (before getting solar). When on float charge via shore power my batteries seem to sit at 13.3V. If I disconnect shore power & then reconnect it straight away, my charger seems to think my batteries are not fully charged, it has 5 LEDs & the bottom 2 will be lit, it then gets to float charge fairly quickly.

Using the same equipment to take readings, my 12V fridge seems to use 6 amps. My 12V TV seems to use 2 amps. Each circuit of 12V LED lights seem to use 1 amp. No idea what my water pump uses or what my shower waste pump uses. This equipment only shows whole amps.

Then I got solar. Using the equipment that came with the MPPT controllers, it shows my batteries to be 0.3V higher than what the other equipment shows.

It is winter, I have 660W of solar panels. On a dull grey rainy day I get practically nothing out of solar, as would be expected. On a bright sunny day, with no clouds, I am getting around 1A (steady) with my solar panels flat, according to the equipment that came with the mppt controller. With my panels tilted on the same sunny cloudless day I can get just above 7A, it fluctuates, I imagine it is fluctuating with the fridge going on & off. I havent seen it go as high as 8A. I have seen the voltage of the solar panels change. Flat they are at a pretty low voltage (around 15V), tilted they are at almost maximum voltage a lot of the time.(on a cloudless sunny winter day like today)

This suggests to me that all of the solar is being used 1st for my 12V needs, & that it can keep up with my fridge, but not quite my fridge & TV.

It cannot contribute to my 240V needs. My charger is a Mastervolt Inverter/Charger. If it is connected to shore power then it passes through the 240V shore power to my 240V system. My 240V system is just plug sockets = washing machine, microwave, desktop computer, & whatever else I happen to plug in.

I did try running once (on a cloudless winter day) from the inverter with shore power disconnected but it did very slowly lose power, which ties in with me thinking it can keep up with my 12V fridge, but not fridge & TV, & therefore not the extra power required by the inverter as well. I also tried it with the fridge turned off & my batteries stayed fully topped up (I didnt use washing machine or microwave or desktop computer)

[TaffyRon]

In summer I get 15amps and that reads 100% soc when its dark the mppt reads 60% thats right isnt it?

[bottle]

Sorry Ron

 

Cannot quite get my head round what you are 'asking' but

 

15 amps is the maximum you can get from your solar array.

 

what is telling you 100% SOC

 

Does your MPPT have a display that gives you SOC readings.

 

Some gauges for example the Smarrtgauge can be inaccurate when batteries are being charged but will then give a true reading when no charging is taking place ( when its dark for example)

Edited December 13, 2014 by bottle

[TaffyRon]

Sorry Ron

 

Cannot quite get my head round what you are 'asking' but

 

15 amps is the maximum you can get from your solar array.

 

what is telling you 100% SOC

 

Does your MPPT have a display that gives you SOC readings.

 

Some gauges for example the Smarrtgauge can be inaccurate when batteries are being charged but will then give a true reading when no charging is taking place ( when its dark for example)

yes, ive got an extra bit of kit that plugs in to the mppt from bimble, maybe it isnt right, who knows

100% when good sun, 60% soc when dark (I know its not charging) but does that take into account the charge in the batts?

[bottle]

Bimble will or should.

[TaffyRon]

I have 265watts at 37volts, best ive had out of it is 16amps

[bottle]

Sounds about right and I suggest at that reading the batteries were at a low SOC.