Need help choosing solar gear

[DeanS]

Many thanks to all. I've learnt an amazing amount in this thread.

[smileypete]

BTW one thing to remember in going from 12V to 24V batts, is that it can double the power handling of the MPPT.

 

Say a 30A PWM 'costs' 4p/watt at 24V and 30A MPPT costs 15p/watt at 24V, it still may be a close run thing depending on panel and cabling costs.

 

For EQing batts at higher charge voltages, if one or more can be isolated from the others then a DC CC converter should do it quite nicely.

 

cheers, Pete.

~smpt~

Edited April 27, 2013 by smileypete

[DeanS]

Excuse me guys.

 

Would THIS Mppt controller be able to accommodate 4 x 230Watt Navitron panels ?

[DeanS]

or alternatively....going for low voltage panels and PW controllers.

 

10 of these 80Watt monocrystaline panels = £630 They are low voltage panels (so PW controllers should do)

 

Then, I would divide my battery banks into 2 sets. One for the 12V appliances, and one for the invertor supply.

I'd feed one small bank with 2 solar panels through a 20Amp PW . Cost £20.

I'd feed the invertor battery bank with 8 panels through a 60Amp PW . Cost £75

 

Total cost = £725

Wattage = 800Watts

Benefit = 2 controllers, seperated battery banks, and the 60Amp controller would have space for more panels if needed.

 

This is a completely different solution, to the one earlier which was high voltage panels, with step down mppt controllers.

The output amps of 80W panels is about 4amps each which is a total max of 40amps, which would be 240amphour over 6 hours.

 

Although I understand why you would have mppt on high voltage panels, if I get these low voltage panels, it would seem from all the discussions that PW would be ok?

 

Comments?

[Paul C]

Woah, slow down! Where did this bonkers suggestion of splitting the battery bank in two come from?

[Justme]

Excuse me guys.

 

Would THIS Mppt controller be able to accommodate 4 x 230Watt Navitron panels ?

 

 

That looks ok.

 

Woah, slow down! Where did this bonkers suggestion of splitting the battery bank in two come from?

 

Ditto. Split banks are not a good idea unless you are running life / mission critical equipment.

[blodger]

There is much to be said for keeping things simple and standard but without really planning it, I started out with a three x 110ah battery bank & starter. It became clear that being no longer on shore power those batts were inadequate and pretty knackered. I replaced with 4 x 110 ah batts and set up the old bank elsewhere as a separate bank. Pretty soon they were replaced with three new ones and when the boat is in use via their isolators they are operated as one bank. I discovered when I had to replace a calorifier that I could squeeze another 3 x 110ah in and it just so happened I acquired three for nowt that someone could not be bothered desulphating and equalising.

Dean said he may add another(or more) batts and there is no harm doing them in two or three banks with isolators which in effect make them one bank for peukert. I would not separate off the services to differnt banks as Dean is thinking of however. There is the advantage of being able to do battery maintenance when not on line with multiple banks and as has been suggested to equalise from one bank to another using a sufficient capacity buck boost converter, etc

 

ETA

I also have three old batts boxed on the fore deck I use as a sort of solar dump but am able to run all but the inverter off them much of the time surprisingly

Edited April 27, 2013 by blodger

[DeanS]

ok then. forget the bonkers idea of splitting banks

 

My question is then....

 

Option 1

 

 

10 of these 80Watt monocrystaline panels = £630 They are low voltage panels (so PW controllers should do)

2 controllers :

20Amp PW . Cost £20.

60Amp PW . Cost £75

Total cost £725 for 800W

ORRRRRRRRRRRRRRR

Option 2

Would THIS Mppt controller be able to accommodate 4 x 230Watt Navitron panels

Total cost £717 for 920W

WHICH IS THE BEST?

WOULD EITHER OPTION DELIVER SIMILAR?

Edited April 27, 2013 by DeanS

[blodger]

You need to think about and allow for the cost of wiring and connections as purist style is pretty expensive.

 

I used flexible earth wire (the thick one, I think its 5mm2) I Ebayed and collected for about 50p/metre. I used household pattresses to house perspex with two bolts in to connect the ring crimped wires.

 

Personally, though I have a mix of 100w, 60w, 50w, and 30w panels if I had a widebeam I would go for at least 100/120w panels to reduce number to connect up whilst having them still manageable and not an expensive disaster when one gets broken, etc

[DeanS]

If Option 2's controller is adequate for the 4 Navitron panels, I would prefer to go for that.....similar price...one controller...new panels...good wattage......less wiring.

So is the Option 2's controller definately enough for the 4 Navitron 230W panels. The controller says 24V/1020 .....but the navi panels are 30V .......or am I reading things wrong?

[smileypete]

 

Would THIS Mppt controller be able to accommodate 4 x 230Watt Navitron panels

 

For 930W of solar to charge 12V batts you need 68A or more of MPPT capability, though you may be able to scrape by OK with 60A if the panels are usually flat.

 

You MAY be able to use 2 identical MPPTs of 30A, each handling 2 panels, but it means running 2 pairs of cabling between panels and controllers. Probably worth asking the MPPT supplier if it's poss though I can't see why not.

 

Also try to buy the MPPT from a EU based seller instead of one from Asia, or you may have to pay custom duties that can wipe out any saving.

 

cheers, Pete.

~smpt~

Edited April 27, 2013 by smileypete

[Justme]

The input voltage to that controller is 100v.

 

So you can have all 4 panels in series (but do watch out when wiring it up as dc over 50v can bite).

 

The extra amps that the panels can make but the controller cant use are not an issue. Also in real use you wont see peak output that often unless the array is installed in ideal conditions & the panels are cool.

 

My own controller is 80amps yet my array is 1200watts with a bat voltage of 12v. I loose the top end but I get a steeper charge curve building up to the max rate.

 

Bimble sells those controllers too.

Edited April 27, 2013 by Justme

[DeanS]

Thank you all for your patience. ;-)

 

SO I could get 4 x 230Watt Navitron panels , and use ONE of these from Bimble (60A MPPT) and wire the 4 panels in series. If the controller isnt big enough, I could downgrade the Navitron panels to 2 x 230W and 2 x 180W if it would help things.

 

If this is a yes answer, then this will be the ones I get

Edited April 27, 2013 by DeanS

[George94]

Thank you all for your patience. ;-)

 

SO I could get 4 x 230Watt Navitron panels , and use ONE of these from Bimble (60A MPPT) and wire the 4 panels in series. If the controller isnt big enough, I could downgrade the Navitron panels to 2 x 230W and 2 x 180W if it would help things.

 

If this is a yes answer, then this will be the ones I get

 

I am worried by Bimble's statement that there could be a "small" customs charge of around £15-30.

 

This is highly optimistic.

 

If you get clobbered for duty, you will also get clobbered for VAT, and the total you will have to pay will be nearer £50.00 than £15.00.

[Justme]

Thank you all for your patience. ;-)

 

1, SO I could get 4 x 230Watt Navitron panels , and use ONE of these from Bimble (60A MPPT) and wire the 4 panels in series.

 

2, If the controller isnt big enough, I could downgrade the Navitron panels to 2 x 230W and 2 x 180W if it would help things.

 

If this is a yes answer, then this will be the ones I get

 

 

1, Yes

 

2, You could but then you open another can oh worms re the peak power voltage & peak power & making sure that all the panels are the same (which they cant be). As you would still want them in series the 2 x 230 watt panels would only give the same wattage as the 2 x 180 watt ones as the total current flow (amps) is limited by the lowest rating. So you would in effect have 4 x 180 watt panels.

Edited April 27, 2013 by Justme

[DeanS]

1, Yes

 

2, You could but then you open another can oh worms re the peak power voltage & peak power & making sure that all the panels are the same (which they cant be). As you would still want them in series the 2 x 230 watt panels would only give the same wattage as the 2 x 180 watt ones as the total current flow (amps) is limited by the lowest rating. So you would in effect have 4 x 180 watt panels.

 

 

The Bimble 60A MPPT controller is well priced compared to the (expensive) alternatives out there. (even with extra custom duty and VAT), so I'll go for that one. I'm aware that if I wanted to get more panels, the controller would then be too small, and I would need to hook new panels to a new additional controller. So is it then possible to connect 2 controllers to a battery bank (they dont clash with each other do they?)

 

I'll get the 4 x 230Watt Navitron panels. which are new ones.

 

I suspect we are getting to a resolution, or am I being optimistic

 

and lastly...wiring panels in series....the last panels I bought 2yrs back came with a little black box on the back, and the cables already connected in. I guess I would need to start another thread called "How do you wire Navitron panels in series

Edited April 27, 2013 by DeanS

[George94]

Thank you all for your patience. ;-)

 

SO I could get 4 x 230Watt Navitron panels , and use ONE of these from Bimble (60A MPPT) and wire the 4 panels in series. If the controller isnt big enough, I could downgrade the Navitron panels to 2 x 230W and 2 x 180W if it would help things.

 

If this is a yes answer, then this will be the ones I get

 

4 x 230 = 920 watts. At 12 volts, that is 77 amps. So it is a bit more than the 60 amps of the controller. Swapping 2 of the 230s for 2 180s would still leave you over 60 amps. 4 x 180 would be exactly right. And 720 watts is still a lot of power. Most of the time it might be all you need, with a little care. And you could always run the engine occasionally, or buy a cheap petrol genny for those grey days..

[DeanS]

If I have it correctly..

The MPPT controller will ignore any amps above 60A....so if the panels are all producing at full power, I wont get 77Amps, but I'll still get up to 60Amps. If the sun shines for 5 hrs, thats 300amphour in a day, which is enough. If however most days are gloomy, and the panels all give 80%...they will fall under the 60A and the controller will be fine with it.

 

Am I right?

I know I should get an 80A controller, but I think they're probably expensive.

[George94]

If I have it correctly..

The MPPT controller will ignore any amps above 60A....so if the panels are all producing at full power, I wont get 77Amps, but I'll still get up to 60Amps. If the sun shines for 5 hrs, thats 300amphour in a day, which is enough. If however most days are gloomy, and the panels all give 80%...they will fall under the 60A and the controller will be fine with it.

 

Am I right?

I know I should get an 80A controller, but I think they're probably expensive.

 

The manual says "Don't overload the charger".

 

The manual is here: http://www.e-sun.ro/upload/MPP_Solar/charge_controllers/MPPT/PCM4048_6048_user_manual.pdf

[DeanS]

hmm...

 

Could I clarify something.?

If I connected 4 x 180W panels (720W) , and used a 60A controller, does this mean I'll get 60amps flowing from the controller in good sun.

 

If so, 60A x 5hrs of good sunlight per day is 300A per day, which is enough for me.

 

If the panels were operating at 75% efficiency, it would be 225A (75% of 60A x 5hours of sun)

 

Is my understanding correct?

If so, I'll get 4 x180W and the 60A controller.

[DeanS]

If the 4 x 230W panels are 920Watts..and the panels are wired in series.....24V each....would be 96V.....would the input current to the controller not be severely reduced?

 

I'm trying to connect all the dots in this thread.

 

One person has 1200W on an 80A controller.

so I should be able to do 920 on a 60A

however yes, I dont want to stress the controller out....but is putting them in series the answer.

 

I think I'm going to HAVE to get the Bimbles 60A controller.....just need to know what is realistically possible using Navitron panels...how many can I connect to that controller. ...George says 4x180W is the max. Is that the max?

Edited April 27, 2013 by DeanS

[blodger]

To get current to flow into the batts the controller has to supply at a higher voltae so the sum you do for ampage from the solar has a higher divisor than the batt voltage. I would use 15 to allow for some inefficiency. So

720 /15 = 48

:920/15 = 61ixh

Edited April 27, 2013 by blodger

[peterboat]

Hi have been down both routes can assure you that 30 v panels are the cheapest and to be effective you have to have mppt otherwise your pwm controller might overheat and catch fire I am talking from experience here!! As others have stated shop around and you will find good priced mppt controllers on the internet. I have 2 x 45 amp controllers for just over 1 kw of panels. both the same brand they dont seem to work against each other. I bought my panels new for very little money from the solar panel supplier 100 yards up the road from memory they cost £100 pounds each 5 in total. Hope this helps

 

 

 

Peter

[DeanS]

All is good.

 

I'll order the following then

 

 

4 x 230W from Navi...

1 x 60A MPPT from Bimble

 

;-)

 

 

 

 

Thank you to EVERYONE who has contributed in this thread. It's quite a bit of cash to outlay, and left to my own devices, I wouldnt have had a clue.

[Justme]

4 x 230 = 920 watts. At 12 volts, that is 77 amps. So it is a bit more than the 60 amps of the controller. Swapping 2 of the 230s for 2 180s would still leave you over 60 amps. 4 x 180 would be exactly right. And 720 watts is still a lot of power. Most of the time it might be all you need, with a little care. And you could always run the engine occasionally, or buy a cheap petrol genny for those grey days..

 

 

Sorry George but the fact that you dont understand that 2 x 230 + 2 x 180 (into the same controller with a single input) = the same a 4 x 180 really does mean you should not give advice about stuff you dont understand.

 

920 watts will almost never = 77 amps.

 

Your battery should never be at 12v.

 

Even after heavy usage by the time the sun gets to full power the voltage of the bank will be well over 12v. Real world usage will mean that a more likely peak of 65 amps (14v).

 

Also you dont seem to understand that controllers do not burst into flames when you have more potential energy available then their capacity. The excess energy is just not collected. Controllers dont like over voltage.

 

For example today my 1200 watt array peaked at 1260 watts.

My 80 amp controller peaked at 86.6 amps x 14.54 volts.

(it would not have stayed at that level for long as its system would have derated itself)

Just for info the peak array voltage was 106v

 

hmm...

 

Could I clarify something.?

If I connected 4 x 180W panels (720W) , and used a 60A controller, does this mean I'll get 60amps flowing from the controller in good sun.

 

If so, 60A x 5hrs of good sunlight per day is 300A per day, which is enough for me.

 

If the panels were operating at 75% efficiency, it would be 225A (75% of 60A x 5hours of sun)

 

Is my understanding correct?

If so, I'll get 4 x180W and the 60A controller.

 

 

The larger the array the more time you will be above you requirement.

 

A good rule of thumb is that in winter you will be lucky to get 1 x the arrays rated amount. In summer you will get 6 to 8 times its rated value.

 

The trouble with just meeting your daily needs is what will you do if you have a day with little or no solar? The day after will never be able to catch up as you have no spare capacity.

 

My summer needs are around 2.5kWh yet I have had peaks of 8kWh when I have had a few bad solar days followed by a good solar day.

 

In winter my needs are nearer 3.5kWh.

 

If I sized my array for my summer usage (200ah so need 250ah to recharge) I would only have 440 watts.

 

It could only meet my needs on the few good sunny days. It would never catch up after bad days & would only work in May June July & August.

 

As it is I have 1200 watts & it copes with most of the year bad the real winter months & periods of over 5 days in a row of bad weather.

 

Oh bog.

 

Just realised I made a mistake with the 4 x 230 watt panels & that controller.

 

You wont be able to have one string.

 

The OCV is 30v for each panel. Thats 120v when the max is 100v.

(I was thinking about my controller that takes 150v)

 

You would have to wire it in two strings of two panels.