Voltage from pv array dropping

[Coach jhawk]

Help please! I have a classic 250. Yesterday my cc ran fine with the following setup:

2 strings in parallel of 3x 320 watt 40v in series
The cc was consistently reading inputs of 110 volts and 55amps on a partly sunny day and charging my 12 volt lithium battery bank just fine.

Today I switched locations and pv array to now be:1 string of 4 of the same panels in series and when I connect the pv leads into the cc terminals I get a reading of 11 volts. I pulled the pv leads off of the cc terminals and got 160 volts. But the moment I wire into the cc the voltage drops to 11V and obviously won’t charge the battery bank.

What could have happened to cause this? Any help is appreciated!

[mike90045]

160V is above spec for a 150V rated controller
   If you are very lucky, it went into safety shutdown and when PV voltage is below 150V things will resume

Otherwise, you may have fried the controller with overvoltage.

Running +80V of PV to charge a 12V battery is costly in voltage conversion losses.  It works, but generates a lot of heat.  Only do it if you have very long distances to run the PV cables from the PV array to the controller.

Did you use the controller sizer chart to validate the array size ?

http://www.midnitesolar.com/sizingTool/index.php

[Vic]

Hello Coach..,   Welcome to the Forum.

So,  it kind of sounds like you may have this system setup in an RV,  or similar.   Your Classic 250 should be able to handle 160 Voc,  or Vmp,  fine.

It also sounds like this setup might have NO circuit breakers between the PV and the Classic 250,  and perhaps none between the Classic and the battery,  guessing.

What is the battery voltage?   Many MPPT Charge Controllers (CC)  will show around 2/3 (+/-- a bit) of battery voltage as Vin,  when the PVs are not connected or when they are producing no power.

You may have some wiring issue on the PV side of things,  as this sounds like a bit of an experimental setup.

TWO THINGS:  160 VDC  can be LETHAL.   Any DC voltage above about 50 VDC  can hurt/kill you.   SO,  if you are connecting the PV cables into the CC with their voltage present at that time,   STOP IT!

Do NOT ever short the PV + &  -- terminals of the CC together,   ever,  with the battery voltage present on the CC.

As usual  we always really need a lot more info.

More later,   Vic

[boB]

Hi Coach...

Question, 

When you see input of 11 volts, is the Classic "Resting" or did it wake up when you connected it and THEN come down to 11 volts from 160V ?

Also, do you see any sparking or arcing when you re-connect the PV array  and voltage comes down to 11V ?

Monday morning, you might want to call us and talk to tech support if you don't figure it out right away.

[Coach jhawk]

I’ll call later this morning. The display read the same even during the night and I’ve taken a picture. I have breakers in between the pv array and cc and between the cc and batteries. When I turn the breaker on between the cc and batteries the cc turns on, runs through its boot-up and immediately goes to the display I’ve taken a picture of.....11 volts and “resting.” Thanks for your fast replies and desire to help! Also, I’ve seen no sparking and or arcing.

[boB]

I’ll call later this morning. The display read the same even during the night and I’ve taken a picture. I have breakers in between the pv array and cc and between the cc and batteries. When I turn the breaker on between the cc and batteries the cc turns on, runs through its boot-up and immediately goes to the display I’ve taken a picture of.....11 volts and “resting.” Thanks for your fast replies and desire to help! Also, I’ve seen no sparking and or arcing.

Interesting...

Is that a 12V battery bank ?   I notice the Classic says 15.2V which might be a wee bit high for a 12V battery without an active charger..
But you might have another charger in the system besides the Classic ?

Hope our tech support gave you some advice and am wondering what they said.