Testing Panels: maybe a bad panel??

inthejungle

Wondering if anyone can help me,


I am living in the middle of the Jungle in Liberia


I have three Canadian Solar panels 245 watts sitting on the roof wired in series, model csp-245p, Vmp 30.0v,ImP 8.17, Voc 37.1v, Isc 8.74, around a total of 735 in theory I understand that you don't get everything.

I have these three panels wired into my FM80, when I look at the FM80 stats screen in the middle of dry season which we are currently in, it is saying that my max watts seen is 556.

The panels are facing SW at around 10-15 degrees on the roof. I normally will see my best solar output around 11-12 in the day.


I am just very curious is maybe a panel is bad and even how to check and see what might be going on.

Any thoughts?


Thanks for anyone's help and thoughts

ITJ

BB.

Re: Testing Panels: maybe a bad panel??

Using my "typical" solar maximum output formula, I would expect a typical warmer time of year to have a rough maximum wattage of:

3*245 watt panels * 0.77 panel+controller derating = 566 watts

You are seeing 556 Watts--Well within the guesstimate of the typical warm season output of the array (filling a battery bank that needs charging).

Keep track of the Vmp-array as reported by your FM 80--More or less, the Vmp-array should be proportional to the temperature of the solar cells (hot weather, lower Vmp-array; cold weather, higher Vmp-array).

The Imp-array is proportional to the amount of sun light--So is more difficult to eyeball (not all clear days are 'equal').

Both values are really only accurate/useful for checking the Solar Array when the controller is in MPPT/Bulk charging mode... Once the batteries are getting near full (and you do not have much in the way of day time loads), the MPPT charge controller will start dialing back on the current from the array (and Vmp--array will rise some).

In general, if your array wattage is over ~1/2 of its rated output--Things are probably OK. If you see a dramatic drop in the array voltage and/or output current (when the MPPT controller should be outputting maximum power), then you should worry.

Lastly, it is not unusual for a charge controller to be off by 5% or more for its readings... They are just not that accurate (different brands/models can have higher or lower accuracy). IN general, with solar panels, if your readings are within 10% of what you expect--That is pretty much dead on with a typical DMM and no reference cell (to measure actual sunlight levels).

-Bill

vtmaps

Re: Testing Panels: maybe a bad panel??

inthejungle wrote: »

I am just very curious is maybe a panel is bad and even how to check and see what might be going on.

Any thoughts?

I agree with Bill... there is probably nothing wrong.
My next thought is 'Please put your system details in your signature'. The reason is that the advice I offer depends on your system voltage. If you have a 12 volt system you could reconfigure your panels in parallel with a combiner box and three breakers. Then it becomes simple to troubleshoot... just turn on one breaker at a time and see what you get.

--vtMaps

inthejungle

Re: Testing Panels: maybe a bad panel??

BB and vtMaps,


Thanks for confirming what I thought was true, vtMaps thanks for the advice and I will get my signature line setup.

If I did switch everything over to parallel, the original reason I did not do this was making the MC4 connections- most of my buddies here cut the MC4 connectors and use wire nuts, I didn't want to do this and void the warranty.

What is the easiest way to make MC4 connections? Currently I have #10 wire up there, if I did go parallel would #10 work for 20 or so feet?

Then I would bring the wires into the house and put them in a combiner box, any suggestions on a good one to use?

Based on the panels it would seem that the breaker needed for each panel would be around 30a does this sound right?

The other issue with going in this direction is my lightening protection, currently the + and - lines coming in are put on a little fuse like this

http://www.littelfuse.com/products/varistors/industrial-high-energy/ba/v131ba60.aspx

What would be the thoughts to provide lightening protection for each panel in a parallel approach?

ITJ

vtmaps

Re: Testing Panels: maybe a bad panel??

inthejungle wrote: »

If I did switch everything over to parallel, the original reason I did not do this was making the MC4 connections- most of my buddies here cut the MC4 connectors and use wire nuts, I didn't want to do this and void the warranty.

What is the easiest way to make MC4 connections? Currently I have #10 wire up there, if I did go parallel would #10 work for 20 or so feet?

Buy an MC4 extension cord and cut it in half. Attach the connector ends to you panels and take the cut ends and combine them. You should use a combiner box with a circuit breaker for each panel. Your voltage drop with 20 ft of #10 wire will be too high. #8 wire will give you an acceptable voltage drop of 2.24%.

inthejungle wrote: »

Then I would bring the wires into the house and put them in a combiner box, any suggestions on a good one to use?
<snip>
What would be the thoughts to provide lightening protection for each panel in a parallel approach?

No! put the combiner near the panels and put a lightning arrester on the combiner box. Don't bring lightning into your house! Midnite makes great combiner boxes and you can even get them with circuit breakers, lightning arrester, AND built-in MC4 connectors (special order).

inthejungle wrote: »

Based on the panels it would seem that the breaker needed for each panel would be around 30a does this sound right?

I think a 12 amp circuit breaker for each panel is correct for those panels.

-- vtMaps

inthejungle

Re: Testing Panels: maybe a bad panel??

vtMaps,

Thanks for your thoughts- I originally used MC4 extensions cables to make my connections so I am quite familiar with them. What I am wondering is there a way (without breaking the bank) get a field kit to make mc4 connectors? When you live this far out, sometimes you need to make your own connections and don't have the ability to buy something.

I hear what you are saying about the combiner box, but where we are living while it sounds like theft would not be a problem we have a problem with it. We are one of a kind in a small town and that makes us stick out. When we mount things to our roof it is noticed and maybe messed with. What would be your thoughts on theft and a combiner box?

I don't really want to mount the combiner on the side of the house or on the side on the panel mounts because it is just inviting people.

Thanks
ITJ

vtmaps

Re: Testing Panels: maybe a bad panel??

inthejungle wrote: »

vtMaps,
What I am wondering is there a way (without breaking the bank) get a field kit to make mc4 connectors? When you live this far out, sometimes you need to make your own connections and don't have the ability to buy something.

What would be your thoughts on theft and a combiner box?

You need a special MC4 crimper tool. There are several threads about it. I don't own one so I can't really say much about them.

As far as theft and combiners.... I'm not sure my world view about this is relevant in your jungle. I think your panels are more valuable than a combiner, so if the panels don't invite theft, why would the combiner?

--vtMaps

SolInvictus

Re: Testing Panels: maybe a bad panel??

Canadian Solar csp-245p PV panel specifications

Series fuse rating: 15 A