Solar/Ctek wiring

[Burnsy]

Hi all,

I will be ordering our new van with 2 x 100amp batteries and solar prewire and plan to install the Ctek D250s plus 2 x 120W solar panels. I have been searching for info on connecting 2 panels to the Ctek but can't find anything. I know by connecting the 2 panels in parallel the voltage from panels will be the same but what about amps? I can't find anything on max amp input but the Ctek has a max voltage input of 22V, I just want to make sure the Ctek is suitable for my application? Any thoughts?

Cheers
Burnsy.

 

[Tailor]

Hi Burnsy,

May not answer your question but you should find the following link interesting.

http://www.dynamicsolarsolutions.com.au/wiring_diagrams.htm

Cheers

John

 

[Burnsy]

Thanks John, I had a squiz at this one the other day. Still wondering about 2 panels but I spoke to a bloke on the phone and he said should be ok but I'd like to find out more!

 

[boots33]

hey Burnsy
two 120w panels in parallel will double the wattage to 240w thus doubling the amps available. Bear in mind that a panels output is usually ratted at around the 17v mark so your 120w panel should produce about 7amps or so in full midday sun (unless you are in the south pole!) the formula is simply watts divided by volts will give you amps. so your two panels combined will give you a max of around 14a. the ctec D250s can distribute up to 20a back to your batteries so should be fine with the two panels connected to it. Most companies are very helpful if you contact them so why don't you drop them a line and ask them just to make sure http://www.ctekbatterychargers.com.au/contact-us.html

 

[ROnEM]

Burnsy,

Thanks for asking the question as I was thinking the same!

Have you thought about adding just one bigger panel - say 200 Watt, rather than 2 panels. Might save on some weight and cost of solar panel mounts to the roof.

To

 

[ElectricGuru]

Hey Burnsy

First thing, do you have the specs on the panels please? Need to make sure that the panels are matched to the D250S.

Have a look at this thread where the question was raised about a single solar panel connection to a D250S... Solar-panel-voltage

Boots is right on with the Ohm's Law (Power = Volts x Amps) but the D250S will convert the 17 Vdc / 7 Amps to 14.4 Vdc / 8.1 Amps. This is due to it being an MPPT regulator that is able to convert the voltage to the correct battery charging level without much efficiency loss. Main thing is that you are not exceeding the two critical ratings on the D250S that is the input voltage (max 22 Vdc) and the current (max 20 Amps).

Another thing to ensure is that the panels each have blocking diodes in their connection box. Reason being if there are no diodes and one panel is slightly shaded, the full sun panel will start causing issues due to the higher voltage. It's like two engines bolted together on the drive shaft but not being throttled together, one will essentially drive the other instead of the load. Check out this thread with a picture of a solar panel connection box with the diodes (little black and silver things between the terminals) courtesy of Turtle...Solar-for-a-portable-panel

Also make sure the wiring between the panels and the D250S is correctly sized for the extra load. Need about 6mm2 cable minimum for all the wiring.

Let us know if you need more information.

Cheers

 

[Stone Stomper]

Hi Burnsy, I put two panels on the roof and wired both panels + to + and - to -, increases the amps but not the volts.

I have also just put the DC-DC Cteck in the car and it seems excellent so far.

Christian

 

[Mike7]

Hi, I was just about to order the D250S as I thought it would be perfect for my setup. Ive been following a thread on myswag that recons the D250S wont kick in until it sees about 4A of solar energy. Anything less and the unit will not charge the battery which seems a terrible waste as you can still get a significant charge in a few hours worth of say 3.5A on a cloudy day or early mornings etc.

Heres the link for what its worth. Im now rethinking my D250S purchase, bummer as it does a good lot of things that would suit me. Some more research before I commit.

http://myswag.org/forum/index.php?topic=9898.0

Cheers
Mike

 

[Burnsy]

Hi guys, sorry for the late reply, been a busy weekend. Thanks boots and ElectricGuru for the info, Guru i dont have any panels yet so no specs.
ROnEm i'm still thinking about which way to go, i see your point though. Hey Stone Stomper, i remember seeing your pics before in another thread, nice job and i'm glad your happy with the Cetek. Hey Mike, thanks for the info, the way i see it i'll only need 12V for lights, water pump, TV and maybe charging some things, however this can be done in the car if need be and i can also run the waeco off the dual batt in car. You would have to be unlucky not to get any charge over 2 or 3 days but i suppose it's something to think about and weigh up.

I was going to buy some 120W panels for about $300ea on ebay but when you talk to the solar experts they say the cheapies don't put out the rated amps when they get hot, they also recommend poly not mono panels so i'm really not sure which way to go or how much to spend. By the way has something happened to the "thanks" option on bottom of replies.

Cheers.

 

[ElectricGuru]

Hi, I was just about to order the D250S as I thought it would be perfect for my setup. Ive been following a thread on myswag that recons the D250S wont kick in until it sees about 4A of solar energy. Anything less and the unit will not charge the battery which seems a terrible waste as you can still get a significant charge in a few hours worth of say 3.5A on a cloudy day or early mornings etc.

Heres the link for what its worth. Im now rethinking my D250S purchase, bummer as it does a good lot of things that would suit me. Some more research before I commit.

http://myswag.org/forum/index.php?topic=9898.0

Cheers
Mike

Hey Mike

From what I can see in the thread, there is some conjecture between the contributors as to if there really is a problem with the unit (faulty) or if it mainly to do with the older version having a much higher power cut in. Either way there is no definitive answer apart from the approximate 40W cut in.

This is something that I will be looking at since I would like to get a D250S at some stage as well. The D250S has some advantages that shouldn't be overlooked like the dual supply ability and the MPPT solar reg plus the inbuilt starter battery cutout.

Will keep you posted as to what I can find out.

Cheers

 

[Mike7]

G'day electric guru,

I spoke to the supplier a couple of days ago and did get some confirmation on the cut in/out feature. It appears that the units dual battery cutout isolator circuit, which is set to disconnect the crank battery at 12.8V, is also used by the solar part of the D250S so the unit will not "activate" until the solar sees 12.8V from the panels. So unfortunately early morning/evening or cloudy days could see you missing out on some charge. Perhaps the MPPT will make up for any losses as the sun comes up.

I wander if this is really an issue in the real world or not, seems a pity to miss out on even a few amps of charge tho. I like the 6 stage charging of the D250 as well as it would look after the batteries health well. I was gonna use it's dc-dc function and the dual battery isolator function between the tug and van. Sure ticks a lot of boxes.

Anyhoo keep in touch with what you find out.

Cheers
Mike