Solar Panel Disconnected from SUN

Get a controller rated for 30 amps minimum. Especially if going BlueSky.

It has been recommended to allow at least 20% of head room. Don't forget, current creates a lot of heat, so you need to oversize your controller considerably. I went with a 30 amper for my pair of 140w/8.15a Isc panels. I wouldn't go with anything less than a 50a controller with your panels, especially being in a cooler climate such as yours.

And make sure you wire accordingly, to avoid excessive volt drop.

Mr Wiz said his Blue Sky 2000 (25 amp with 20 amp recommended max) clips any excess amps so it will not overheat and damage the controller.

It is the US NEC that wants the 20% margin for controller amps rating with controllers that do not clip their amps. Regular PWM controllers just pass through whatever amps they get and overheat if that is too many amps for them for too long a time.

So if your "expected amps" is 25 amps then NEC wants you to have a 30 amp controller for that 20% margin. Panels sometimes put out more than their rated amps, such as when they are cold or at high altitude, etc. The brief burst of high amps from edge of cloud effect doesn't matter AFAIK since that only lasts a few minutes at a time with those pretty white clouds going by the sun every so often.

So what is your "expected amps" anyway? If the Isc of your 140 is only 7.5a I suspect it is a mono panel with corresponding higher Voc too, since a 140w poly's Isc would be near 8.8a. If yours is poly maybe that 7.5 is Imp? (Imp does not apply to PWM)

But isn't the Blue Sky 3000 an MPPT controller? So now you have a complicated sort of "expected amps" depending on whatever watts you are getting and whatever the battery voltage is at the time, which is always changing.

So let's say your four 140s are mono with Isc of 7.5a as stated, and your expected amps will be at least as good as what PWM would get.

4 x 7.5s = 30. That's with panels aimed at high sun. Flat on roof will be less than that. It could be close with the sun overhead in summer in the south part of the USA mainland.

Your MPPT controller should clip the amps as required so no need to fuss with input if the controller is mounted properly with good ventilation cooling.

If I had four 140s I would make two pairs and get an eBay 20a PWM controller for each pair and parallel those two controllers on my battery bank. Save a bundle on controller costs and get approx the same amps.

Are those Kyocera 140watt panels?
They are excellent panels and can easily output more than their specs

I have four of them (actually 2 - 135w and 2 - 140w) for 550 watts
I see 40amps under good solar conditions

Your controller might be a bit small - zero headroom
Might want to consider a 45amp or 60amp controller in the future

I agree 100% with installing Breakers/Switches/fuses (your choice) both before and after the controller

If you only have a 24AMP solar controller that is all it will draw from the available 30AMP Capacity being produced by the solar panels. What is left over is being wasted if not used. This does not harm the solar panels at all if you do not use the available VOLTAGE being generated by the sun. It is just available for you to use when in high sun. This is why you have batteries connected. The available power being generated has to be stored in the batteries so it will be available to use after dark. No sense wasting the available power. Add more batteries to store it in...

The switches and circuit breakers in the solar line is only really needed to protect the wiring in case of battery system overload or short circuits. Smaller wiring will not like to have 30AMPS DC being drawn from the solar panels. MrWIZARD had a short circuit mishap just a couple of days ago...

Your system is looking almost like the my upcoming solar system using two each 120WATT panels on one end and hopefully a single 240WATT panel on the other end on top of my OFF-ROAD POPUP setup...

Hoping big time to have 14.4VDC@30AMPs capacity coming from solar controller for 6-7 hours during the day to play with charging up my battery bank. Game plan for me is to cut back on my generator run time each day.

Roy Ken

CT_WANDERER wrote:
The controller(Blue Sky 3000I) I want to use has ISC rate of 24A, however they say it will work up to 30A. So would my panels only reach this 30A on ideal conditions? Or will I be pushing the 30A limit a lot? If I could hit more than my 30a limit could I just shut off on breaker?

According to my calcs, you'll be hitting it a lot.

You need a bigger controller. Your plan is a lot of work, and, you're throwing away power. Are you going to be sitting around the rig watching your controller and throwing breakers?