Blown Outback Charge Controller

solarquestion2011

Alright Experts I need some help.

I have two trailers with identical systems.

System

30 Trina PA05-225W Modules in 3 modules x 5 strings per charge controller
2 FM 60 Charge Controllers
2 Outback 3648 in a Flexpower 2 FP-29 Package

per trailer.

For some reason one of the FM60s keeps blowing.

I have had service calls twice to replace this same charge controller over the last 6 months.

I have checked groundfaults, breakers, grounding on the DC and AC sides to no avail. I have also changed the gfdi breaker on this unit and added a second breaker between the gfdi and the battery to act as a load break switch.

I am totally baffled why this may be occuring.

The other trailer's system has had no problems.

Any advice would be most appreciated

mike95490

Re: Blown Outback Charge Controller

re array, whats the :
Voc cold ____
Voc hot ____

solarquestion2011

Re: Blown Outback Charge Controller

Voc: 36.8V @ STC , 110.95V String
Voc: 40.66 @ -15C , 121V String

First Time it Blew Voc of each string was about 108VDC
This Time the tech checked and the string was 98VDC.

150V max is the input voltage for the fm60 i think.

Cariboocoot

Re: Blown Outback Charge Controller

If all else is equal and only the one controller in the same location is dying I would suspect a wiring fault to that location. Likely as not it is an intermittent problem - the hardest to find. Since the input and output should both have circuit protection, it might be something is shorting on the "wrong side" of that; hot touching ground on the output would be favourite.

Difficult to diagnose by remote. Not so easy in person either, eh?

solarquestion2011

Re: Blown Outback Charge Controller

Its possible that this could be the cause as there is over-current protection at the combiner on the strings and the gfdi with breakers between the battery and the charge controllers. If this was the case wouldn't the gfdi open if the short was in the enclosure. The first time it blew I was looking at it. I did not see any arcing at the charge controller just the sound of popping inside. There was arching in the gfdi breakers also. It was strange, I had cycled the system several times then one time it just blew.

For Note: The GFDI is the Outback Unit with the twin 80A Breakers ganged with a .5A gfdi breaker.
I originally feared that the GFDI was not clearing properly and replaced the unit after the first failure along with the charge controller.

Cariboocoot

Re: Blown Outback Charge Controller

I have to confess to not being a fan of DC GFCI. What I'd do is probably illegal; remove the GFCI stuff.
But it still isn't likely to be the problem as all the systems are the same and only one FM is frying.
I can't imagine a situation that would cause that one controller to somehow become connected to both arrays in series (negative from one array being interrupted and at the same time shorting to positive of the other; controllers have shared negatives) but that would fry it too.

waynefromnscanada

Re: Blown Outback Charge Controller

Arcing in the gfdi breakers? Now that's scary!

solarquestion2011

Re: Blown Outback Charge Controller

It was strange. The gfdi breaker appeared to try to trip, but got stuck half way. I manually opened the breaker as it was arcing and popping. Strange thing was that the CC continued to blow even after opening the gfdi and the ganged breakers between the battery and the CC. At first I thought maybe the gfdi breaker was not able to break under load. I checked with Outback and Tech Support said that I was rated for load break operation. I didn't see if the arcing in the breaker was in the gfdi or the CC breakers attached (I was quickly walking down the step ladder. ha)

The whole episode began after I cycled the breakers a couple of times.
- PV circuit was closed to the CC
- Inverter was on but not pulling a load.
- Breaker was cycled several times with no problems.

Cariboocoot

Re: Blown Outback Charge Controller

Should I bother to mention they're not supposed to do that?

They are supposed to trip if something goes wrong - load or no.

solarquestion2011

Re: Blown Outback Charge Controller

I do know that.

That's why I replaced all the breakers after the first incident along with the CC.
I assumed that the breakers weren't clearing properly.

BB.

Re: Blown Outback Charge Controller

I personally do not like DC GFI setups...

However, one way to debug the GFI is to use a filament light bulb.

Pick a 40 watt or so 120 VAC appliance light and place it across your 48 volt battery bus--it should light... If not, you may have to take 4x 12 volt car bulbs (brake lights or similar) in series... Anyway, something that lights on 48 volts.

Place the filament light bulb across Battery Return and Trailer Frame/Earth Ground...

Start moving wire and equipment and see if you can trip the GFI breaker and/or get the test lamp to light. The lamp will show + to earth ground short circuits---but limit the current to something less spectacular (just enough to light the lamp).

You could also hard bond your battery bank return to trailer frame (bypass the GFI breaker)--You might find the short that way too (trip a branch circuit breaker)... But it may be bit more eventful.

-Bill

niel

Re: Blown Outback Charge Controller

i don't think i'm quite following this as you keep saying the fm60 is blown. define blown. i can't figure how any short or any other condition with your said equipment in the system would blow an fm60 unless somehow ac power got caught up in the mix. is the inverter output somehow feeding into that controller? this is crazy. there obviously is a difference between the trailers or one wouldn't be failing. do try bb's light bulb idea and keep looking as it has to be there even though it isn't obvious to you.

solarquestion2011

Re: Blown Outback Charge Controller

by blown I mean the CC is dead. The CC smells of burned electrical equipment and the room had a little smoke in it. The CC that i had previously replaced in the system in the same location sounded like popcorn popping when it blew. There appears to be a nothing between the pv input terminals and the CC output terminals. The PV input terminals are now reading the 48V battery voltage not the pv array voltage normally measured.

To make it stranger the other CC is still running and the inverters are fine like nothing happened.

niel

Re: Blown Outback Charge Controller

if i read that rightly you are not seeing the pv volts at the input to the cc. if so disconnect the pvs from the cc and see if proper pv voltages are still there. there isn't that much to this so please recheck everything step by step. is the anyway you can verify proper operation on the inverter in the trailer in question in addition to polarities being properly observed?

solarquestion2011

Re: Blown Outback Charge Controller

When pulled from the CC the pv voltages were correct and polarities checked (~100V).

Checked the voltages and polarities at blown CC
At PV input 48V
At CC output 48V

Checked the voltages and polarities at the other CC to compare
At PV input 100V
At CC output 48V

Afterwards the PV for that CC was disconnected at the combiner, b/c i was afraid of the batteries backfeeding the array at night.

The Inverter and other CC are running normally.

niel

Re: Blown Outback Charge Controller

this is a baffler and if you find the cause, do let us know please.