Powertech 2kW 24V Inverter Blew....

[MrPwr]

As I am new to this forum, please forgive me for any noob rules I have missed,

My system:
2x 285W Trina solar panels in series (~30V)
2x 12V 800cca car batteries (for now, I am still building my 18650 monster)
12V/24V 30A PWM Solar Charge Controller for lead acid and Lithium batteries (link below)
2000W 24VDC to 230VAC Pure Sine Wave inverter - Electrically Isolated (link below)
<400W load including any spikes from startup motor caps (when the problem occurred)

Currently my Inverter is quite oversized for the load and the source, but I chose this with expectations of expansion.

After several hours of operation (with very low load) from new, the inverter made a couple of very loud pops, and enough smoke to fill a small room (capacitors?)
however it continued to function as normal, even after I freaked out and flipped the breaker
(I have since received a replacement for this product under the warranty)
At the time, and for many hours prior to this event, the system was running between 24-28V and my guess is that the onboard over/under voltage protection circuit is what blew as the rest of the inverter continued to function (or it was just an unlucky insect)

I have yet to install the replacement unit, due to fear of blowing that one. can anyone see any compatibility issues in my system?
I would prefer to have it all connected to the same bus bar (charger, batteries, inverter) as I have seen in every wiring diagram I can find (even for my product!)

Thanks in advance to any who hears and responds to my plight

Products in question:

12V/24V 30A PWM Solar Charge Controller with LCD display for lead acid and Lithium batteries | Jaycar Electronics

Pulse Width Modulated (PWM) for efficiency and fast charging. Two Timer Programs Three Stage Charging External Temperature Probe

www.jaycar.com.au

2000W 24VDC to 230VAC Pure Sine Wave Inverter - Electrically Isolated | Jaycar Electronics

This pure sine wave inverter is capable of providing 2,000W continuously and a 4,000W surge.

www.jaycar.com.au

 

[gnubie]

It does sound like some electrolytic capacitors vented. The big ones can burst with quite a pop - note this is not exploding just the vent on the top rupturing. It's possible your charger went over their voltage rating. The battery's BMS may have disconnected without you noticing too. Unfortunately you can't check the capacitors without opening the unit and voiding your warranty. I'd be hesitant to connect the new inverter with the possibility of over-voltage still being an issue.

The inverter has high voltage shutdown at 30V so you might find the input capacitors are only good 35V. Electros have quite loose tolerances so that shouldn't have caused them to pop with a short term exposure to over voltage. Check your PWM charger to make sure it has the right voltages set up and equalisation is turned off or at least set to absorption voltage or lower.

Are you taking the inverter back to Jaycar physically? You might be able to get them to open it up so you can both see the state of the electros. If you can take some decent photos of the overall layout showing the damage and post here. That will tell us which, if any, capacitors vented and in turn if it was a DC input problem or something else.

 

[MrPwr]

It does sound like some electrolytic capacitors vented. The big ones can burst with quite a pop - note this is not exploding just the vent on the top rupturing. It's possible your charger went over their voltage rating. The battery's BMS may have disconnected without you noticing too. Unfortunately you can't check the capacitors without opening the unit and voiding your warranty. I'd be hesitant to connect the new inverter with the possibility of over-voltage still being an issue.

The inverter has high voltage shutdown at 30V so you might find the input capacitors are only good 35V. Electros have quite loose tolerances so that shouldn't have caused them to pop with a short term exposure to over voltage. Check your PWM charger to make sure it has the right voltages set up and equalisation is turned off or at least set to absorption voltage or lower.

Are you taking the inverter back to Jaycar physically? You might be able to get them to open it up so you can both see the state of the electros.

Thanks for your response!

I have already received a replacement model, they opened the faulty unit in front of me and couldn't see any visible damage, though more disassembly was required to get a better look, and the technician didn't seem too interested in further investigation.

"Check your PWM charger to make sure it has the right voltages set up and equalisation is turned off or at least set to absorption voltage or lower."

I am not sure my charger has these features, and I am not sure what they are either.
Furthermore, the unit I have appears to be missing some of the features demonstrated in the Manual.

Is MPPT better for these kinds of setups? I don't have any issues replacing that unit as it was quite cheap.

 

[gnubie]

Are you dealing with shading? If not the panels in series with a MPPT controller would be a better solution as it would give you more power out at the same sun exposure than the PWM controller would.

If the PWM controller is working correctly it shouldn't have gone over voltage so that might not be the problem.

 

[MrPwr]

Are you dealing with shading? If not the panels in series with a MPPT controller would be a better solution as it would give you more power out at the same sun exposure than the PWM controller would.

If the PWM controller is working correctly it shouldn't have gone over voltage so that might not be the problem.

Definitely no shading
I did read that MPPT are better in those circumstances for higher yield, not well versed enough to diagnose however.

Well it seems to just pump out whatever voltage it is given, is that abnormal operation?
I was testing across all it's terminals (no oscilloscope, just a multimeter) and they are all within 1V of the solar input

 

[gnubie]

PWM controllers output a bit above battery voltage. They work by, effectively, connecting the panels to the battery and letting the load of the battery pull them down to near battery voltage. You say your panels in series are about Vmp 30, that's a pretty low Vmp per panel so please post a link to the particular model panel and I'll confirm that. I have seen cheap blue ebay PWM charges lose the plot and go over voltage when there is rapid sun light fluctuations. I'm guessing the control routine couldn't vary the PWM fast enough to keep a lid on the battery voltage.

30 Vmp at 285W is about 9.5A. With a PWM controller the voltage is pulled down to near the battery voltage. Let's say that under charge that is 25V. Your wattage is now 25 x 9.5, 237. Quite a drop. The actual wattage will go higher as the battery climbs in voltage.

With a MPPT controller you deal with a percentage loss. It varies a bit as the amps and volts on either side changes but you can find it is up around 95% efficient so 270W out with 285W in.

The catch is MPPT needs a bit of headroom to work with. 30Vmp is low for charging a 24V battery with a MPPT controller, so post the panel specs or exact model or link to web page so I can check.

 

[MrPwr]

PWM controllers output a bit above battery voltage. They work by, effectively, connecting the panels to the battery and letting the load of the battery pull them down to near battery voltage. You say your panels in series are about Vmp 30, that's a pretty low Vmp per panel so please post a link to the particular model panel and I'll confirm that. I have seen cheap blue ebay PWM charges lose the plot and go over voltage when there is rapid sun light fluctuations. I'm guessing the control routine couldn't vary the PWM fast enough to keep a lid on the battery voltage.

30 Vmp at 285W is about 9.5A. With a PWM controller the voltage is pulled down to near the battery voltage. Let's say that under charge that is 25V. Your wattage is now 25 x 9.5, 237. Quite a drop. The actual wattage will go higher as the battery climbs in voltage.

With a MPPT controller you deal with a percentage loss. It varies a bit as the amps and volts on either side changes but you can find it is up around 95% efficient so 270W out with 285W in.

The catch is MPPT needs a bit of headroom to work with. 30Vmp is low for charging a 24V battery with a MPPT controller, so post the panel specs or exact model or link to web page so I can check.

Wow thanks for all of that! you know your stuff, I can see I am going to like it here

I have uploaded the datasheet for my panels

 

[gnubie]

OK, they have Vmp of around 30V. You are good to put two of them in series if you want to use a MPPT controller. Both panels would give you around 23A to the battery full tilt, if they ever get there, so a 30A MPPT controller would cover you if you weren't going to add more panels down the track. Even if you did add more panels, the controller would be able to use up to around 750W before it starts to limit power (30A x 24V, about 750W).

Most controllers are rated at 100V on their solar input in this sort of amp range so you have a good selection. Epever, Renogy at the lower end of pricing, but not cheap junk, while at the higher end of pricing Victron etc. If you want to look around for a MPPT charger, post a link to what you like and someone will check it to make sure it will work OK for your panels and battery.

I'm hoping that in your opening post where you said the panels are in series you really meant parallel. In series (~ 60Vmp) with a PWM controller and 24V battery you are throwing away a bucket of power and potentially even pushing the PWM controller to the point where it does lose control of the battery voltage... and that would explain why your last inverter went pop.

Car batteries (cranking batteries) aren't going to last you long when used for running an inverter. They are designed to produce very high current in short bursts to start the engine. They have a fairly porous plate structure that gives heaps of surface area to get that high burst current but it becomes sulphated very easily.

 

[MrPwr]

I do plan to get a few more panels, I will try to get the same models as I have heard you can have issues with unmatched panels (from a mate, haven't verified that yet) and the car batteries are only a temporary solution as I am still building my 18650 rig (xmas present to myself).

Whoops yes I meant to say the panels are parallel! Astute observation
I have the wiring in place for another two panels which would be added to this parallel configuration.
My parallel connectors

PV Style Self Locking Branch Connectors - Pair | Jaycar Electronics

MC4 Style Self Locking Branch Connectors - Pair

www.jaycar.com.au

What do you think of this model for mppt? or should I post this in another area?

50 AMP MPPT Solar Charge Controller | Jaycar Electronics

Intelligent charge controller

www.jaycar.com.au

Once again, thanks so much for your help!

 

[MrPwr]

Pdf for the above 50A MPPT charger:

 

[gnubie]

Jaycar says that one is discontinued but it goes up to 95V on the solar input so that's OK and 50A so covered on the battery output side too.

Rover Li 30 Amp MPPT Solar Charge Controller

Renogy Rover Li 30A MPPT Solar Charge Controller making it great for RVs, caravans, and boats. With its advanced MPPT charging technology, your batteries will be protected from discharging and over-charging.

au.renogy.com

Only basic options available via the front panel. More detailed programming needs the bluetooth dongle for the mobile app access, or a Windows PC (the software is pretty bad) or the remote panel.

AU EPEVER 40A 30A 20A MPPT Solar Charge Regulator LCD 12V/24V Negative Ground | eBay

Find many great new & used options and get the best deals for AU EPEVER 40A 30A 20A MPPT Solar Charge Regulator LCD 12V/24V Negative Ground at the best online prices at eBay!

www.ebay.com.au

Recommend getting the MT50 as again only basic setup available via the front panel.

 

[MrPwr]

Jaycar says that one is discontinued but it goes up to 95V on the solar input so that's OK and 50A so covered on the battery output side too.

Rover Li 30 Amp MPPT Solar Charge Controller

Renogy Rover Li 30A MPPT Solar Charge Controller making it great for RVs, caravans, and boats. With its advanced MPPT charging technology, your batteries will be protected from discharging and over-charging.

au.renogy.com

Only basic options available via the front panel. More detailed programming needs the bluetooth dongle for the mobile app access, or a Windows PC (the software is pretty bad) or the remote panel.

AU EPEVER 40A 30A 20A MPPT Solar Charge Regulator LCD 12V/24V Negative Ground | eBay

Find many great new & used options and get the best deals for AU EPEVER 40A 30A 20A MPPT Solar Charge Regulator LCD 12V/24V Negative Ground at the best online prices at eBay!

www.ebay.com.au

Recommend getting the MT50 as again only basic setup available via the front panel.

There are a few units available near me that I can get of the newer model that replaces the discontinued model:

12V/24V/36V/48V 50A MPPT Solar Charge Controller with LCD display for lead acid and Lithium batteries | Jaycar Electronics

SOLAR CHG CONTLR MPPT 12-48V 50A W/LCD

www.jaycar.com.au

it is the same manufacturer as the model I currently have but this unit has many more features and capacity, I'll also have a chat to the guys instore when I go there.

I'll post back here with the outcome, thanks again for your help

 

[MrPwr]

Jaycar says that one is discontinued but it goes up to 95V on the solar input so that's OK and 50A so covered on the battery output side too.

Rover Li 30 Amp MPPT Solar Charge Controller

Renogy Rover Li 30A MPPT Solar Charge Controller making it great for RVs, caravans, and boats. With its advanced MPPT charging technology, your batteries will be protected from discharging and over-charging.

au.renogy.com

Only basic options available via the front panel. More detailed programming needs the bluetooth dongle for the mobile app access, or a Windows PC (the software is pretty bad) or the remote panel.

AU EPEVER 40A 30A 20A MPPT Solar Charge Regulator LCD 12V/24V Negative Ground | eBay

Find many great new & used options and get the best deals for AU EPEVER 40A 30A 20A MPPT Solar Charge Regulator LCD 12V/24V Negative Ground at the best online prices at eBay!

www.ebay.com.au

Recommend getting the MT50 as again only basic setup available via the front panel.

G'day mate, thanks for your help last week!
So the new setup has been operating without any issues for almost a week now! I got the 50A MPPT and now I have capacity for more panels and* more batteries

Once again thankyou for your help!