Connecting a solar panel

[Lusty Wench]

As a newbie I can't be sure that this isn't answered elsewhere, but I have had a search and not found out.

I have an Eclectic Energy D400 wind generator. It is connected to a regulator, and if voltage in the house bank gets too high, will dump power to to large coils that will soak up any excess.

I currently have 2 very tired flexible solar panels that I am considering replacing with 2x100W panels. I am in Turkey, so there could actually be sufficent sun to generate quite a bit of power (for the flexible panels, the fact that the fridge and freezer are always on takes care of excess - even if we are on shore power - which is rare).

I am thinking of connecting the new solar panels to the output lead from the wind generator, thus making use of an existing regulator. Does anyone know if this would damage either the wind generator (on a sunny day - or reading one of the other threads - on a very bright moonlit night) or the solar panels on a windy day? I have emailed the manufacturers of the wind gen, but so far no response

 

[vyv_cox]

Considering that the cost of a good solar panel regulator will be about a tenth of what you will pay for the panels, I would fit the correct item. You only need to boil the batteries, short-circuit the panels or the wind generator or start a fire to wipe out the small saving that you will make by trying to combine the services.

 

[GrahamM376]

I don't know your wind genny but, certainly Aerogen limit the amount of solar power which can be input to the regulator, in parallel with the genny. Unless the solar panels have a blocking diode, you would need to fit one.

I would fit a separate regulator (or two if you are feeding more than one battery bank) for the panels.

 

[vyv_cox]

I would fit a separate regulator (or two if you are feeding more than one battery bank) for the panels.

Or one that will charge two banks. Mine is a Sunworks DB1C

 

[gonad]

solar

fit separate regulators unless you want to burn the batteries like i did

 

[OldBawley]

Volts

Just noticed having 14,4 Volt on the system. Have to shut down one of the panels. It is me, not you with the two freezers that needs the regulator.
The desert with ice cream was fantastic do. Thanks again.

 

[tarik]

Solar regulator

I don't know your wind genny but, certainly Aerogen limit the amount of solar power which can be input to the regulator, in parallel with the genny. Unless the solar panels have a blocking diode, you would need to fit one.

I would fit a separate regulator (or two if you are feeding more than one battery bank) for the panels.

I have bought a 60watt Solar panel and a solar regulator which I hope to fit next week. I have two heavy duty12v batteries linked together and use a 1-2-both switch Do I need to fit 2 regulators or will one be sufficient?

Thank you for al replies.

David

 

[vyv_cox]

I have had a dual bank regulator for many years now. My first one was a Sunware, old technology with mechanical relays. This worked fine for more than five years, when it seemed that one of the relays was a bit sticky and sometimes didn't seem to connect the panels. I replaced that with the Sunware one referenced above, which is solid state. That has been in for about five years and has performed faultlessly.

The advantage of a dual regulator is that it charges the domestic bank preferentially. I'm not sure how two regulators could do this.

I have 3 x 110 Ah domestic batteries and 1 x 30 Ah starter battery.

However, if you only have a single regulator but want to charge either battery I suggest you wire it to the output connection of the 1-2-both switch. The panel will then charge whichever battery is being used, but of course it won't charge on leaving the boat if the switch is off.

gonad - fit separate regulators unless you want to burn the batteries like i did

Batteries can boil for a number of reasons but I'm not sure why a dual bank controller should be one of them.

 

[GrahamM376]

The advantage of a dual regulator is that it charges the domestic bank preferentially. I'm not sure how two regulators could do this.

I have 2 - 15 amp regulators which work OK, one to each domestic bank. The lowest voltage bank draws the most current. I don't bother solar charging the engine battery directly but can if necessary, via the battery switches.

Fitted diodes in the supply line from the panels after I found the regs would back feed at night, equalising the batteries. Diodes in the line before the regs (around 21 volts) don't have much effect whereas if they were between regs and batteries they would drop the charge rate.

 

[Lusty Wench]

Thanks to you all for the help

Thank you all for the contributions. I have decided on the advice of the suppliers of the wind generator, to fit to the single regulator. The solar panels have a blocking diode, so power from the wind gen will not harm them.

The advantages are:
1 any excess voltage will be diverted to a dump - whatever source it is from
2 the system will then charge any battery that is low
3 saving of space - particularly inside near the panels, where I am fast running out of mounting space

The regulator is rated at 60 amps so it should cope.

 

[bateau57]

Something to consider

Most solar panels put out about 17V when in full sun (and I mean full sun). When a back stay or whatever casts a shadow over the panel it may (often does) drop below the charging voltage of around 14.4V rendering the solar panel null and void. If you have two panels wired in parallel and one gets shade you get only the output of one panel, a common problem and not very efficient. The solution I use has a MPPT solar regulator. It can make solar charging at least 10% more efficient and often more (80% if you get partial shade on one panel).

Most common regulators take the output voltage of the panel and throw away the charge above what is required by the batteries at that time. Say the battery in its present state of charge needs 14.4V and the solar panel is putting out 17.1V then a fair chunk of charge is just discarded to deliver 14.4V. An MPPT regulator differs by converting the output wattage of the source to what is required by the battery loosing only a small amount in the conversion. Not to make it too technical but AMPS X VOLTS = WATTS so if a panel produces 5A x 17V = 85W. A normal regulator will sink 5A x 14.4V = 72W into the battery. An MPPT regulator will adjust the voltage to 14.4V but retain the watts output so it sinks 5.9A x 14.4V = 85W into the battery.

The advantage is much greater with multiple solar panels as you can wire the panels in series (reduce the size of cables used as well). Like (5A x 17V) + (5A x 17V) = 170W or said another way 5A x 34V. When charging it converts that to 14.4V @ 11.8A which is 170W sunk into the batteries. This was not trying to teach you how to suck eggs but the biggest advantage for a cruiser is if one panel gets full sun and one has a backstay shadow so in theory the output was something like (5A x 17V) + (5A * 10.8V) as the shadow takes out 2 rows of PV's. With an MPPT regulator you get 139W still which it converts to 9.6A @ 14.4V. A standard regulator will sink 5A x 14.4V = 72W because one panel is below the 14.4V charge threshold so it cant use it.

This is an overly simplified view of this but if you are like me, you are scratching for every bit of juice and are extra carful how you spend it on lights, fridges and computers. Every bit counts, reduce you weight aloft with less panels, reduce you cable costs because you can wire in series. Hope that helps and hasn't overly complicated matters. Now watch all the boffins correct my simplistic explanation of how it all works. By the way, I did not take the small amount of power loss you get with an MPPt regulator into my facts. I know about it but I wanted to keep it simple.

We have tested this by the way and my MPPT regulator cost me about £160. Many sceptics in the yard with electronic backgrounds were sceptical at first but a multimeter answers all questions on this.

Regards
Graham
SV Charlotte

 

[idpnd]

I am planning a solar install soon-ish, but I have two battery banks - 12V and 24V. Both power a couple of systems and get similar usage when off-grid.

Is anyone aware of dual (different voltage) output MPTT regulators? What would your preferred solution be?

Thanks for your time!

 

[noelex]

Thank you all for the contributions. I have decided on the advice of the suppliers of the wind generator, to fit to the single regulator. The solar panels have a blocking diode, so power from the wind gen will not harm them.

The advantages are:
1 any excess voltage will be diverted to a dump - whatever source it is from
2 the system will then charge any battery that is low
3 saving of space - particularly inside near the panels, where I am fast running out of mounting space

The regulator is rated at 60 amps so it should cope.

Are you planning to do something with the dumped power? If not I don’t understand 1 and 2.
3 I understand.

 

[noelex]

This was not trying to teach you how to suck eggs but the biggest advantage for a cruiser is if one panel gets full sun and one has a backstay shadow so in theory the output was something like (5A x 17V) + (5A * 10.8V) as the shadow takes out 2 rows of PV's. With an MPPT regulator you get 139W still which it converts to 9.6A @ 14.4V. A standard regulator will sink 5A x 14.4V = 72W because one panel is below the 14.4V charge threshold so it cant use it.

Unfortunately solar panels and MPPT regulators cannot do this. A shaded cell develops very high impedance effectively preventing any current flowing. Solar cells have bypass diodes that allow these shaded areas to be areas to be bypassed, but only in multiples of the output voltage.
The effect of this is a shaded panel will not produce high current at low voltage. It can only produce reduced current at the same voltage
A major drawback for MPPT regulators on boats is there is a lot of shadowing. This gives each panel, or series of panels, a different MPPT point (IF one MPPT regulator is used)

 

[idpnd]

A major drawback for MPPT regulators on boats is there is a lot of shadowing. This gives each panel, or series of panels, a different MPPT point (IF one MPPT regulator is used)

What implications does this have for series vs parallel linkup? Thanks

 

[noelex]

What implications does this have for series vs parallel linkup? Thanks

Series or parallel is always a difficult question for MPPT controllers. The manufactures recommend having a solar panel voltage well above the battery voltage which means at least wiring up in series 2X12v panels for a 12v system.
Unfortunately all there recommendations are based on domestic systems where it is easy to arrange that the panels in a string to see the same light and shade conditions.
On a boat different panels will often have different conditions due to shade from rigging etc.
No one seems to have done any testing to discover which is best in the conditions we find on a boat. Until they do I think the question cannot be answered.
My best guess is 2X12v panels rig them in series. With 4 X12v panels rig 2 in series and use 2 MPPT controllers.

 

[Lusty Wench]

Thanks to you all for the help

Especially the info about mppt regulators - thanks Graham.

Noelex. My biggest worry was frying the batteries. The reason for this is that we have no facility to stop the wind gen, which has a potential 400W output. It was installed with a comprehensive regulator system by a professional. It will charge both battery banks - house preferred, and should it ever manage to get all batteries to 14v (I can dream) it has a safety dump facility, to prevent over-cooking. We never have managed to get to that voltage except when on shore power - very rare.

We are selling the boat, but as these things can take time, and we would like to keep the engine hours low (currently 1500) to keep that attractive to potential buyers. In fitting the solar panels we wanted to use those charging facilities, rather than duplicate. In short, we are not planning anything with the dumped power, except to save the batteries from boiling.

Thanks again
Tim and Sam
Lusty Wench

 

[noelex]

ham.

Noelex. My biggest worry was frying the batteries.

That would not happen if you had a separate solar regulator either. A properly set up solar regulator will turn the solar panel down or off to prevent overcharging.
More batteries die overall from undercharging than overcharging.14.0v as a maximum is a bit low you might like to revise the settings.

 

[dmmbruce]

I have two solar panels going to an MPPT controller from Midsummerenergy.

They told me about the problem mentioned by Noelex in post16 and advised me to use semi-flexible panels as they are more tolerant of shade and to wire them in parallel. This apparently avoids Noelex's problem.

This setup has worked excellently for me even in the limited sunshine in England.

Not mentioned in the explanation of the working of MPPT controllers above, is the additional benefit that when the generated voltage falls below 14.4 (?) for charging, eg morning and eveneing or just cloudy. The controller will set up the voltage to 14.4 though obviously reducing the amperage at the same time.

I suggest you talk to the techies at the suppliers. They are familiar with these things.

Mike

 

[noelex]

Not mentioned in the explanation of the working of MPPT controllers above, is the additional benefit that when the generated voltage falls below 14.4 (?) for charging, eg morning and eveneing or just cloudy. The controller will set up the voltage to 14.4 though obviously reducing the amperage at the same time.

Mike

This is a common myth. MPPT regulators use buck converters (95% of them anyway) and cannot boost the voltage from the solar panel.
You can wire solar panels in series to boost the solar panel voltage, but this only works well if there are no shadows, which is rare on a boat.

Edit
I just had a look at midsumerenergy website and they sell the Empo-ni SOL-1 regulator which is one of the very few regulators with a boost converter so it will increase solar panel voltage.
Very interesting regulator.
I have not seen one and the handbook is a bit vague on the battery management side. If this is the regulator you have Dmmbruce can you confirm how it regulates is it a single voltage point only, or does it have boost, absorption and float stages? are the voltage points for these adjustable?