PJ 5KW v8 sounds like bacon frying

[Nilao]

Afternoon all,

 

I have a PJ 5KW V8 LF inverter. I ordered new boards, and mosfets as it quit working and none of the green LED's were lighting up except the mos boards. The only parts I didn't replace was the main board, transformer and charging board. 

All the LEDs are on now but upon powering up it says it's overloading and shuts off the power. While it's still running it puts out 110 volts according to my multimeter but it sounds like frying bacon in the transformer. 

Any ideas on where to go from here?

[Sid Genetry Solar]

Oh dear, that's not a comforting sound...nor a safe one I would say.  What is the input DC amps when it's trying to run? 

What caused the inverter to blow up the first time?  (Might have a major clue!)

"Frying bacon in the transformer"...are you sure there are not little metal scraps in the vicinity/inside the transformer core and/or the tranny isn't in contact with the chassis sides/lid?

 

[Nilao]

Hi Sid, I had it for exactly 5 days and it quit using a 1kw microwave. It had a burnt electrical smell afterwards. No visually blown fets. I contacted the seller who offered to send the parts bit after back and forth for several months I was informed PJ had no parts to send me as they were all being used in production.

I have not checked input amps. I'll need to find my amp clamp. Just replaced all the boards and fets which got all the LEDs working and the lady telling me 70% load, 100% load overload if I'm hearing her correctly lol gentry sent the fets for an 8kw unit which is bigger than my mounting holes on the 5kw so I de-soldered them and put them into my 5kw mos boards if that matters.

 

There's nothing inside the transformer and it's cover has been removed so it's not touching. 

 

Edited April 16, 2021 by Nilao
Spelling correction

[Sid Genetry Solar]

20 minutes ago, Nilao said:

gentry sent the fets for an 8kw unit which is bigger than my mounting holes on the 5kw so I de-soldered them and put them into my 5kw mos boards if that matters.

I'm confused here.  PJ has 3 MOS board sizes...the very smallest which they only use in the 1500W inverter (I believe).  And the very largest they don't use much anymore (used to be 9K / 15K).  That leaves just one size MOS board--so I'm not sure what's going on here.  They did change from a plate behind the FETs to simply bending the FETs to reach the heatsink...but...

It potentially could...it only takes one little solder mistake (or ruined through-hole) to cause issues.  Care to provide a photo or two of the MOS boards?  (Random crackling does not sound very encouraging...or safe.)

BUT...that being said, while a problem with the MOS boards could be a very solid cause for the crackling sounds, it does not explain why the inverter believes it is overloaded.  I am assuming this inverter does not have an LCD?

 

[Nilao]

Well my mos boards say 3kw/5kw and they ones I received say 5kw/8kw so I'm not sure. 

The lcd says how many hours in use, kw used and watts output. Even in overload display say 0 watts.

I'm not home so cant send current pics.

Edited April 16, 2021 by Nilao

[Nilao]

I think what I ordered was for a power jack and what I received was for a power tank inverter. 

[Sid Genetry Solar]

Just now, Nilao said:

I think what I ordered was for a power jack and what I received was for a power tank inverter. 

Same difference.  Power Tank is a different label on a Power Jack.  Same with U-Power...except they double-rate the exact same inverter.

 

Guess I only have "3K v2.2" MOS boards, and then the "8K v2.2" big FET boards.  Will await a photo or 2.

[Nilao]

I have attached the pictures. Now that I pulled it out of the shed it's now saying output has problems and list all the boards I have already replaced.

 

Pulls .74 amps.

 

I ordered 5kw mos boards and recieved 8k boards but the boards in it say 3kw....

[Nilao]

Ok, operator error.  Forgot to put a board back on.

Now it comes on and is pulling 60 amps.

I hope you can hear the transformer making it's buzzing sound like it's trying to make max power.

 

The positive side mosfets are reading 1.8 volt gate to ground, the negative side is 1.1 volts. They all measure the same across all mosfets per side.

[Sid Genetry Solar]

Ah, video makes a LOT more sense.

Low battery voltage alarm is probably due to voltage drop in the wires to the inverter--which are probably saving your FETs.

It sounds like the AC feedback is not working in the inverter; it's running to 200% throttle (pretty much a perfect square wave) overflowing and running 0-200% throttle again...trying to find the desired regulation voltage.  I notice that the connectors on the "resistor boards" are extremely dirty.  As the PJ feedback design uses an infinitesimally small signal for feedback, I wonder if cleaning these dirty spots up might restore it to functionality?

You might also try swapping those 2 little boards.  I notice the nuts on the screws are missing, have you replaced these?

The sound isn't quite "bacon frying" in my book--no snapping/crackling, just a very oversaturated 60Hz buzz.  Normal operation if the feedback circuitry isn't working.

Photos showing the FET boards you received...those are the BIG FET boards used in the older 9K and 15K units.  (PJ doesn't use them much anymore.)  Really weird that you received those...

[Nilao]

Yes, but I did find the FET's on the negative side were fried. Not violently failed but failed none the less. I found the FET's were the same number so I just de-soldered them and moved them over to the smaller boards.

 

I will try reversing those boards and cleaning up the contacts. Being in Florida humidity gets into everything if it just sits. 

[Sid Genetry Solar]

Assuming you've replaced the LF Driver board?

[Nilao]

Yessir, I ordered the whole setup but never recieved the charge board, possibly it didn't come with it but I thought it did.

I was testing it on a small battery so it would drop the voltage before cooking anything.

Got it running on my main bank now, 4 agm batteries, and it runs without shutting down but something is definitely off... pictures should help explain it. 

Pulling 82 amps but shows no output amperage. That usage time includes the time it was sitting in my driveway maintaining the batteries in my semi. Only pulled 4kw from it before it toasted....and that was a 1kw microwave that cooked it lol. 

[Sid Genetry Solar]

This is sounding a smidge more like bad FETs / blown LF driver.  82A @ no load is definitely really wrong!

1 hour ago, Nilao said:

Yes, but I did find the FET's on the negative side were fried. Not violently failed but failed none the less.

When was this?  After the initial failure, or after replacing boards?

[Nilao]

Initial failure. I'd be more than happy to order a whole new board assembly from power jack.com. Show to be 85 bucks for the whole setup. 

[Nilao]

Do you think my FET's are good being one set shows 1.889 volts and the other set shows 1.187 from gate to back plate?

 

Is it possible the driver board is just driving them as hard as it can regardless of what the cpu is asking it to do and I just need a new driver?

Also the only be mosboard I see listed is for a 24v inverter. Are they the same no matter the voltage or are they voltage specific? I'm thinking they're interchangable as the FET's are rated at 40v.

[Nilao]

What is the function of the signal board?

[Waterman]

11 hours ago, Nilao said:

 Being in Florida humidity gets into everything if it just sits. 

Everything and anything. People don't understand that we also get Sahara dust along with that humidity and the two can kill electronics. And there is also salt in the air which adds to the problem.

[Sid Genetry Solar]

16 hours ago, Nilao said:

Do you think my FET's are good being one set shows 1.889 volts and the other set shows 1.187 from gate to back plate?

Slightly concerning...that's a pretty significant difference for boards that should be completely identical.  Depends if the LED is present (and working), number of FETs (and required gate resistors too), etc.

 

16 hours ago, Nilao said:

Is it possible the driver board is just driving them as hard as it can regardless of what the cpu is asking it to do and I just need a new driver?

Technically, the driver board simply converts the 5v 0.02mA (max) SPWM signals from the CPU to ~10-15v 2.5A gate drive signals.  Not any smarts there 😉.  Unlikely that it's at fault, unless it was connected to FETs that blew--in a PJ inverter, this usually damages the driver board.

 

16 hours ago, Nilao said:

Also the only be mosboard I see listed is for a 24v inverter. Are they the same no matter the voltage or are they voltage specific? I'm thinking they're interchangable as the FET's are rated at 40v.

Voltage specific for 48v anyway--those use 100v FETs.  40v will be fine for 12 / 24v use--not like the amperage is significantly better on the FETs they use for lower voltage anyhow.

 

16 hours ago, Nilao said:

What is the function of the signal board?

The little resistor boards that I pointed out?

[Nilao]

2 hours ago, Sid Genetry Solar said:

The little resistor boards that I pointed out?

No sir, the board that sits to the left of the driver board. If your looking at it from the side the transformer good to the main board. 

[Sid Genetry Solar]

That board is indeed the "signal board"...it's what converts and scales output voltage (+ charge input, if equipped) and output current to the CPU.  If it's not working right, you'd also get a similar result.  Output of the "resistor boards" go to this "signal board", and then to the CPU.

[Sid Genetry Solar]

The board that's mounted standing upright...has one purpose: to short the SPWM outputs of the CPU out if they feel the need.  Not like the CPU has a fault shutdown input that can do exactly the same function...!

[dochubert]

Hope no one minds my 2 cents thrown in here;

I would take all the boards including the mainboard out and thoroughly wash and dry them.  Lots of soap and water.  Then put it back together and see what happens.  I see in your pics signs of moisture/dirt getting into several spots, which means its in several spots you can't see as well.  As Sid said, by now you may have a damaged lf driver board, even if you have already replaced it once.

[Waterman]

13 hours ago, dochubert said:

Hope no one minds my 2 cents thrown in here;

I would take all the boards including the mainboard out and thoroughly wash and dry them.  Lots of soap and water.  Then put it back together and see what happens.  I see in your pics signs of moisture/dirt getting into several spots, which means its in several spots you can't see as well.  As Sid said, by now you may have a damaged lf driver board, even if you have already replaced it once.

I might disagree on the soap but washing them with distilled water could help.And then making sure they are well dried afterwards. I have been using a boost converter to go from solar panels rated at 18 Volts to get to charging Voltage on the 24V system. I can count on replacing one every 6 months because of the salt, dust, and humidity all attacking the units.

[dochubert]

6 hours ago, Waterman said:

I might disagree on the soap

Dish soap won't hurt electronics but you must rinse it off thoroughly.  I have put large electonic boards in the automatic dishwasher and run it thru a cycle with excellent results.  In this case the powerjack parts are small and wouldn't remain in place so the dishwasher wouldn't be a great idea.  Hand washing with dish soap and a toothbrush probably best.  Lots of rinsing and make very sure parts are completely dry before using.

 

6 hours ago, Waterman said:

I can count on replacing one every 6 months because of the salt, dust, and humidity all attacking the units.

Wow!  Glad I live in Idaho!  I bought two powerjacks a few years ago from a guy in Georgia that were badly corroded and with visible rust on the mosboard connections and other places.  Had to thoroghly clean them before I could use them, but since being cleaned, have not "re-corroded" here.