solar

peter_s · Veteran Member

solar

PeterD · Guru

It is usable but you need an MPPT (Maximum power point tracking) controller. The PWM controllers for 12 V bateries need panels with a Vmp of around 17 V, yours has a Vmp of 36 V.

Tony Bev · Guru

Hello Peter S

I have recently been doing some research on a solar panel set up, but I must say that as I am not an expert, the following is only my opinion through my own observations

What Peter D has said is correct

To add to his advice, I have a CTEC D250S DUAL which is a DC to DC battery charger, plus a MPPT solar controller or regulator. The specifications on my devise clearly say that the maximum input voltage is only 23 volts.
Although your panel has a Voltage (VMP) of 36 volts, it also has an Open Circuit Voltage (VOC) of 44.2 volts, which your panel could achieve at a worst case scenario.

I would therefore advise that any solar controller you obtain, is capable of regulating your highest voltage of 44.2 volt panel down to your battery voltage.
If my opinion is wrong, then I hope that more knowledgeable people will come along and correct this post.

My grandson personally knows an aquaintence who used a household solar panel to charge a 12 volt AGM battery, using a cheap Ebay regulator, and fried his battery

ps
I hope that the date is correct Feb 2016

PeterD · Guru

Tony, the D250S is the only MPPT regulator that has such a low maximum input voltage. There have been reports from others asking what when wrong when their D250S was zapped when they used a higher voltage panel (they did not read the specifications and/or understand them.) All the other MPPT controllers will handle higher voltage arrays, it's just a matter of reading the specifications seeing what is the maximum open circuit array they will handle.

Tony Bev · Guru

Hello Peter S

I will stand corrected, and say that any other controller other than the CTEK will do the job, as Peter D has advised.
I hope that I am not hijacking this thread, and I thank you in advance for allowing me to reply to Peter D, on your post.

To Peter D
Thank you for that information Peter, it was appreciated, and I have taken it on board. It was something which in all honesty, I had not picked up on.

I choose that particular devise as it seemed to meet my below requirements of just bolting it down and forgetting about it.

I am under the impression, (by reading the fine print) that this controller will automatically :-
Isolate the engine battery, from the house battery, when the engine is not running - under 12.8 volts and starts to operate when the engine voltage is 13.1 volt
Switch the solar input to charge the engine battery, when house battery is full
Choose the best, or both of solar and engine combined, to charge the house battery

My setup will be

1. 300 watt mono solar panel --- 22.5 open circuit volts, 18 volt (Pmax) --- 17.58 amp short circuit current, 16.67 amp current (Pmax) --- paid for and on the way
2. 2 off 120 AH AGM Deep Cycle house batteries, to be purchased locally after solar fitted, to replace existing 100 AH GEL battery of unknown age, which is no longer holding its full charge
3. CTEK D250S Dual, specifications of --- maximum input voltage of 23 V --- battery capacity of 40 / 300 AH --- already bolted down in the battery bay

If there is any reason why the above three items will not match up to each other, then I would certainly appreciate and take your knowledge on board.

PeterD · Guru

Tony, that would work. However I consider that something with an output of only 20 A is not big enough for quick charging of a 240 Ah battery bank. I would be more inclined to use one of the Redarc 40 A models for quicker battery recovery.

Tony Bev · Guru

Hello Peter D and appologies to Peter S if I have hijacked this thread, as I have yet to learn how to fully navigate this very informative site

Thanks for that information Peter, it has been appreciated, and certainly taken on board
Later on down the track your recomendation will be on my shopping list

I did actually look at a lot of controllers, at the time of purchase.
I assumed that my original 100 AH battery would be good enough for my requirements.
That wrong assumption was probably made, because I am just a little grubby, greasy hand, retired Fitter, with between little and no electrical knowledge

Jaahn · Guru

Hi Tony,

Just a point about the panel. It has been said that very large panels may be suffer from cracking of the glass when used on mobile applications. You might take that into account and mount the panel securely. Perhaps also some support in the middle of the panel underneath.

Jaahn

Tony Bev · Guru

Hello Jaahn

Thank you for that information, it is appreciated, and once again in all honesty, it was something that I had just not picked up on

As my vehicle is a 2006 Jayco Conquest, which has a roof made in a very economical manner, I had already made and fitted a frame from 40x40x6 aluminium angle, for the solar panel to sit upon/inside the long edge, to protect the roof.

I shall now purchase some whatever depth is required x lighter 3mm thick aluminium angle to support the centre of the panel, which turned up today slightly bent, so another one will soon be on the way, without any drama from a happy customer

Without your advice I would have just fitted the panel, and only been wiser after the event (broken glass) had happened.

I picked a single panel to use, instead of two smaller panels so that with the vehicle rear facing north, there will be no shade over the panel. If I had used two smaller panels, one of them would have always been partly shaded by the air-con, unless I had kept manoeuvring the vehicle in a semi circle.