expanding solar installation ?

[LillyPotemkin]

Hi

 

I'.m sure someone can shed a little light on this ;

 

I currently have a 400 watt install (*4 panels) going into a 30 amp MPPT and charging a 625 Ah bank.All is fine and dandy

at the moment I'm using around 50aH a day and i'm at 100SOC by 9am every day.

 

But I came across this solar calculator http://re.jrc.ec.europa.eu/pvgis/apps4/pvest.php# and in Jan it estimates I'll be good for approx 30 AH a day.

 

My question is, would it be worth doubling up to 800 watt of solar to meet my requirements.Or will running the engine for an hour a day be OK, adding 30 amps into the bank.? Or a two hour jaunt every couple of days to the cafe

 

If it is the solar route can I add another MPPT in to my existing bank ? controlling the new 400 watt install.

 

Thanks in advance

[KJT]

I don't think you can ever have too much solar. It beats running an engine or genny. We started with four 100 watt panels and a 30 amp Tracer MPPT controller. Last year I added a 130 watt panel and an additional Tracer 10amp MPPT controller. Pity we don't have any room for any more panels otherwise I would have more.

 

Ken

[MtB]

 

My question is, would it be worth doubling up to 800 watt of solar to meet my requirements.Or will running the engine for an hour a day be OK, adding 30 amps into the bank.? Or a two hour jaunt every couple of days to the cafe

 

 

You need to sort out in your head the difference between Amp hours and Amps. Or was that just a typo?

 

Running the engine for an hour a day will not necessarily add 30AH of charge to your batteries, in fact if they are approaching a good state of charge I think it almost certainly won't.

 

As I understand it, getting a battery bank up to 100 SOC takes hours on end, whatever method of charging you are using. In summer the solar does this admirably due to the long hours of daylight, but in winter your batteries will need hours of generator or engine time. Either that or resign yourself to them getting abused for the winter months.

 

 

MtB

 

 

P.S. I have a related question. If one has more solar panel than one's Tracer MPPT is rated to handle (like the OP), does the Tracer just cap the solar panel output? Or does it throw a hissy fit and set fire to itself? Or something else?

Edited July 23, 2014 by Mike the Boilerman

[Paul C]

I believe from previous threads (but happy to be corrected) that it will cap the output. This doesn't sound as bad as it seems - because it could be sensible to size the controller to the required power you need, but oversize the solar panels. Of course, in the summer you're missing out on power (but are you? Because power requirements are lower, and the days are longer etc) but in the autumn and spring it allows you to 'stretch' the season where your solar input equals the demand for power, thus saving running the engine/genny. Of course in winter, unless you have about 3kw of panels you'll still need to do something else to generate power, and even then there will be some days with not enough becaue some days in winter are miserable for sunlight.

 

PS That's for situations where the solar panels are marginally more power than the controller stated capacity. Not sure what would happen if they were many times more capacity etc. Maybe the controller would go into an error mode and shut down, maybe something would overheat, maybe it would shorten the life of a component.

Edited July 23, 2014 by Paul C

[LillyPotemkin]

 

You need to sort out in your head the difference between Amp hours and Amps. Or was that just a typo?

 

Running the engine for an hour a day will not necessarily add 30AH of charge to your batteries, in fact if they are approaching a good state of charge I think it almost certainly won't.

 

As I understand it, getting a battery bank up to 100 SOC takes hours on end, whatever method of charging you are using. In summer the solar does this admirably due to the long hours of daylight, but in winter your batteries will need hours of generator or engine time. Either that or resign yourself to them getting abused for the winter months.

 

 

MtB

 

 

P.S. I have a related question. If one has more solar panel than one's Tracer MPPT is rated to handle (like the OP), does the Tracer just cap the solar panel output? Or does it throw a hissy fit and set fire to itself? Or something else?

Hi Mike,

 

30 Ah.I'm assuming that providing the batteries are sufficiently discharged that running a 70 A/h alternator for an hour will probably add a charge of 30Ah.

 

 

Yes I'm wondering about the MPPT, what would it do but in bleak winter I may be OK ?

[Paul C]

70 A/h???????????????????????!!!!!!?!?!?!?!?!?!?!?!?!?!?! (before anyone else does!)

[MtB]

70 A/h???????????????????????!!!!!!?!?!?!?!?!?!?!?!?!?!?! (before anyone else does!)

 

Agreed!

 

An alternator output is rated in Amps not Amps/hour. Amps per hour is a meaningless term.

 

If an alternator delivers 30 Amps for a period of one hour, it will have delivered 30 AH. If it supplies 15 A for two hours, that also is 30AH.

 

 

MtB

[LillyPotemkin]

ooer My thinking (misguided) was the alternator is rated at 70 amps and that running it for an hour would/could/might put back 30 amps into the bank?

Does this a can of worms smiley

[Paul C]

You're thinking is about right but the units you used (A/h) is technically incorrect. An amp is a flowrate - of current. Thusly, amps PER hour is a change of flowrate - an acceleration of current, if you like, which is in this context meaningless. Don't worry about it, I was being pedantic partly to prevent someone even more so, and partly to encourage you to think of what is actually happening when a battery charges or discharges, to gain a deeper understanding.

[Ex- Member]

Hi

 

I'.m sure someone can shed a little light on this ;

 

I currently have a 400 watt install (*4 panels) going into a 30 amp MPPT and charging a 625 Ah bank.All is fine and dandy

at the moment I'm using around 50aH a day and i'm at 100SOC by 9am every day.

 

But I came across this solar calculator http://re.jrc.ec.europa.eu/pvgis/apps4/pvest.php# and in Jan it estimates I'll be good for approx 30 AH a day.

 

My question is, would it be worth doubling up to 800 watt of solar to meet my requirements.Or will running the engine for an hour a day be OK, adding 30 amps into the bank.? Or a two hour jaunt every couple of days to the cafe

 

If it is the solar route can I add another MPPT in to my existing bank ? controlling the new 400 watt install.

 

Thanks in advance

 

Hi Lilly

 

To help energy input through the winter we're planning to add 2 x 200 to 300w of flexy solar panels. These weigh just 2.8KG each and we plan to attach to the boat side panels to glean energy from the low winter sun. We've sourced some 50mm pot magnets which will be fitted to the flexi panels, and we can move them appropriately to glean winter sun each time we moor.

 

Like you we have ample energy from March to October from our 740w of solar panels. Last year we ran the engine for an hour every morning to bulk charge the batteries. Quite often most days we would also run the small generator for an hour sometimes more. We're hoping the additional panels will reduce the use of both boat engine and generator. We'll add the additional panels in October until March when they'll be put away for next winter. We'll need another charge controller too at 20/30a This can remain fitted when the panels are decommissioned.

 

If you don't add panels, we found that running the engine in the morning gave us hot water and bulk charged the B/B the solar panels would further top up the batteries through the day if there was good light. This regime seemed to keep the batteries at a good SOC 50% +

[neilsro]

Hi,

 

I have a couple of questions here-

How many additional controllers do you require while adding more panels? I mean is there a proportional equation for that?

Also I want to know what is best heating or solar PV heating system I can have for my boat?

FYI

Boat - Bayliner 660 HP

Panels - 2 - 400 + 300 w

 

Thanks

Edited July 24, 2014 by neilsro

[Ex- Member]

Hi,

 

I have a couple of questions here-

How many additional controllers do you require while adding more panels? I mean is there a proportional equation for that?

Also I want to know what is best heating or solar PV hot water or heating system I can have for my boat?

FYI

Boat - Bayliner 660 HP

Panels - 2 - 400 + 300 w

 

Thanks

 

If your current controller cant accommodate any additional solar panels, you'll need to add another controller at an appropriate size to cope.

 

I don't think that running 2 different charge controllers is a problem or conflict, I've asked this question on this and another related thread just in case there is, but non of the boffins have given any definitive answer.

 

There is a thread with regard to heating water using excess energy from solar panels using a 12v or even 240v elements in a calorifier to heat hater with solar energy, this is known as dump load or more correctly diversion load. Good quality charge controllers seem to have a function for doing this, you just need to fit an appropriate relay.

 

The thread is here. http://www.canalworld.net/forums/index.php?showtopic=66982&hl=

[Grace and Favour]

Hi,

 

I have a couple of questions here-

How many additional controllers do you require while adding more panels? I mean is there a proportional equation for that?

Also I want to know what is best heating or solar PV heating system I can have for my boat?

FYI

Boat - Bayliner 660 HP

Panels - 2 - 400 + 300 w

 

Thanks

There's no effective solar PV heating system - - unless you're in a country where there's sufficient sun (and the UK's excluded)

 

Where's your boat normally moored - do you have access to regular supplies of solid fuel? (if not, you'll need to heat by diesel I suspect)

[smileypete]

But I came across this solar calculator http://re.jrc.ec.europa.eu/pvgis/apps4/pvest.php# and in Jan it estimates I'll be good for approx 30 AH a day.

 

That's an average though, in reality it'll vary by a wide multiple! eg:

 

http://www.bristowfamily.co.uk/solar/

 

Why not cross that bridge when you come to it, most off gridders with solar seem to get by OK with some engine/genny running in deep winter. Don't know of anyone who does it exclusively on solar.

 

cheers, Pete.

~smpt~

Edited July 25, 2014 by smileypete