12 volt solar panels

[lesrollins]

Can anyone tell me a good supplier for 12 v 250 watt panels and what size mppt controller would I need for 4 panels ( 1000 watts )

Thanks

[Alan de Enfield]

Various sizes (watts), kits complete with relevant MPPT if you want it.

 

http://www.bimblesolar.com/solar/individual/solar-fronteir-170w-cis

[Phil Ambrose]

Got all my solar kit from eBay

Phil

[Jambo]

I don't think you can get 12V panels with as much as 250W power output. As you're going for an MPPT controller you can connect pretty much any panel to it (making sure that the array open circuit voltage Voc stays within the MPPT's voltage limits) so look for domestic grid tie panels for best value for money.

 

Two good brands of MPPT are Morningstar and Outback but they're at the more expensive end of the spectrum.

 

At 12V you'll need an 80A controller to get the maximum out of 1000W of panels. Having panels greater than the power rating of an MPPT controller shouldn't be an issue as when it's bumping up against 80A of power you'll probably be getting way more electricity into your batteries than you can possibly hope to deal with.

[lesrollins]

Thanks Jambo I have been told by solar alliance energy that 12v 250 w panels don't exist. I was quoted £175 for a 250watt panel which was a Germany make and told to use a 80amp mppt controller but they only supply a Chinese version that came in at £450 plus the vat. But would rather go with morning star or outback

Thanks Jambo I have been told by solar alliance energy that 12v 250 w panels don't exist. I was quoted £175 for a 250watt panel which was a Germany make and told to use a 80amp mppt controller but they only supply a Chinese version that came in at £450 plus the vat. But would rather go with morning star or outback. Would it be best to connect poss to poss or poss to neg

Thanks

[Jambo]

You can probably find panels a bit cheaper than that but it's not an outrageous price, especially for European panels. You can get an Outback FM80 for about the same price so I'd steer clear of that Chinese MPPT if I were you.

 

I'd strongly recommend getting assistance from someone with experience. You don't want to mess around when you've got 1kW of PV panels to connect up or you'll kill your controller or worse, do yourself some damage.

 

You need to consider matters such as how you're going to connect your panels (series, parallel or a combination of the two), cable thickness, the fuse between the controller and battery, how you're going to secure the panels etc. There's lots of information about all of that on this forum but please don't go about this if you don't know what you're doing.

[Alan de Enfield]

I don't think you can get 12V panels with as much as 250W power output.

 

315w panels here :

 

http://www.bimblesolar.com/solar/individual/LG-315W-solar

[Jambo]

 

315w panels here :

 

http://www.bimblesolar.com/solar/individual/LG-315W-solar

 

Voc 40.6V

[Alan de Enfield]

 

Voc 40.6V

 

 

The Voc on my panels is 112v and they work OK with an MPPT (all sourced as a kit from the same supplier)

 

Why would 40v be a problem ?

 

[WotEver]

 

Why would 40v be a problem ?

 

It wouldn't. Jambo pointed out that you can't get 250W 12V panels. You posted to a 350W panel as a reply - he was pointing out that it wasn't a 12V panel.

 

Not that the OP wants 12V panels anyway - he simply doesn't understand how it works.

 

Tony

[Loafer]

Can anyone tell me a good supplier for 12 v 250 watt panels and what size mppt controller would I need for 4 panels ( 1000 watts )

Thanks

 

Whatever panels you go for, with a decent MPPT controller you can't really go wrong. The controller will have a maximum INPUT voltage, and a maximum OUTPUT current.

 

Your panels will add their stated Voc's together in series, but the short-circuit current remains the same as ONE of them.

 

In parallel, the Voc will be the same as ONE of them, but the currents add up and needs thicker cable.

 

You can also mix and match, e.g. 2X12V panels in series, paralleled with another pair in series.

 

Just be sure that your maximums don't exceed that of the controller.

[Alan de Enfield]

 

It wouldn't. Jambo pointed out that you can't get 250W 12V panels. You posted to a 350W panel as a reply - he was pointing out that it wasn't a 12V panel.

 

Not that the OP wants 12V panels anyway - he simply doesn't understand how it works.

 

Tony

 

Thanks

I didn't realise that the OP meant panels with 12v output rather than panels with higher voltages controlled down to 12v by the controller,

 

For the OP

 

Watts are 'fixed'

Amps and volts are 'variable'

 

To work out any one of them use the formula W=A x V

 

12v output panels would be useless - they would never charge your batteries.

 

The purpose of the MPPT controller is to take the panel output voltage and current and convert it to something your batteries can use

Edited May 16, 2016 by Alan de Enfield

[Loafer]

A brief note on solar panel maxima:

 

All solar panels have a maximum deliverable current, e.g. 6A (short circuit) and an 'open circuit voltage'.

 

To get maximum power from a 100W panel, this cannot be achieved by using a cheap controller that simply turns them on or off. This latter type holds the panel voltage at the battery voltage, averaging about 13V say. 13V times max current =13X6, which =78 Watts.

 

To get the maximum power out of them, the panels need to be held at the voltage which will give max POWER. In the case of our 100W panel, this voltage is Max Watts divided by 6A (max current) so in this case it would be 100/6, which gives 16.6V.

 

An MPPT (Max Power Point Tracking) will force the panels to remain at their BEST voltage, not the battery voltage. The result CAN be equivalent to 1/3 of an extra panel!

 

There is more to it than this, but the above probably serves as a rough intro.

[Jambo]

 

Thanks

I didn't realise that the OP meant panels with 12v output rather than panels with higher voltages controlled down to 12v by the controller,

 

 

It was excessive precision on my part At first I thought they were looking for 12V panels but then realised that they weren't.

 

I seriously think that the OP should either spend a considerable amount of time researching how 12V electrics and solar PV works (it's very feasible to teach yourself this but it does take time) or just get an expert to do it. Without a good working knowledge of the ins and outs of both there's a real risk of equipment damage or injury.

[RufusR]

I have a Chinese MPPT controller and it works fine and has been faultless ever since the last owner ( known to me ) installed it 2 years ago , You will probably find most western brand MPPT controller are actually made in China any how .. pretty much everything electrical is made in in China , Turkey or India these days . If the installer is willing to put his name and warrenty to it then he must have faith in aint gonna pack up tomorrow .. remember I phones and I pads are all made in China .. nought wrong with them

[Jambo]

You're absolutely right but I'd personally go for a known brand over an unknown brand if they were the same price. If it doesn't perform as expected then it should be easier to get it sorted.

[lesrollins]

What size cable would I require from the panel to the mppt and then from the mppt to the batteries. And what size fuse do I need from the mppt to the battery. There will be a total of 1000w of panels. They will be wired in sequence

Sorry I meant to put wired in parallel

[WotEver]

What size cable would I require from the panel to the mppt and then from the mppt to the batteries. And what size fuse do I need from the mppt to the battery. There will be a total of 1000w of panels. They will be wired in sequence

Sorry I meant to put wired in parallel

Which panels? What voltage and what wattage?

[WotEver]

 

You'll potentially have 80A going into the batteries so you'll need some fat cables from the controller.

[lesrollins]

Sanyo 240w panels I have found 4 at a good price. It's the last 4 they have. I think panasonic have now taken them over

[WotEver]

4mm² or even 2.5mm² will be fine for the panels (<6A flow) and ideally 50mm² for controller to batts (<80A).

 

Tony

100A fuse would be fine at the battery end of the charging cables.

Edited August 13, 2016 by WotEver

[lesrollins]

Am I restricted to what cable lengths I can use between panels and controller and between the controller and batteries. I was looking at probably using the victron 150/85 mppt but I see the terminal size is only 35mm2/AWG2 so I wouldn't be able to fit the 50mm2 cable

Edited August 13, 2016 by lesrollins

[WotEver]

Am I restricted to what cable lengths I can use between panels and controller and between the controller and batteries. I was looking at probably using the victron 150/85 mppt but I see the terminal size is only 35mm2/AWG2 so I wouldn't be able to fit the 50mm2 cable

The closer you can get the controller to the battery the better. 35mm² would be okay, and with a short run wouldn't drop much.

[lesrollins]

How close would I need to get the controller to the batteries to be able to use the 35mm2 cable

[WotEver]

3m would be great. It'd only drop around 0.2V @ 80A.

5m would drop closer to 0.4V @ 80A which would probably work out just fine in the real world where you're unlikely to see full output very often (you'd need full sunshine and very flat batteries).

 

Tony