Solar Assistant unit blew up

[vladkgb]

I have 2 EG4 6500ex in split phase, and a 6x EG4 Lifepower4 battery bank. And I currently have 3.5kw (400 voc) of solar into PV1 MPPT on my 2p1 inverter. This setup is only supplying AC out to my shed which is powering a small load of about 500W.

I recently received my SA unit and connected the included DC to USB-C cable to my current connected bus bars. It was connected to my 2p1 inverter using the DB9 to RJ45 that came with the inverter and a DB9 to USB adapter from Amazon. It was running just fine for about a week. Before the incident, we had 2 cloudy days, then when we finally had a sunny day, i went to check on the system, and the batteries were showing low SOC, and alarm was blinking on all, and my 2p1 had the solar icon blinking, but not charging. The 2p1 was also showing 60 warning code, which according to the manual is "batteries can't discharge or charge". I restarted all batteries, and both inverters, and the warning went away and solar began to charge.

I decided to check my SA unit to try to see what happened to cause the inverter to go into this state only to find that it was dead. No green light. Checked the DC to USB-C cable, the inline fuse was fine, and I was able to plug my phone into it to get it to charge. The bus bars were supplying 53v at the time. I looked inside the SA unit and found that the chip near the USB-C plug labeled "AXP805" had damage on it.

SA support says that this was most likely caused by a spike in voltage to over 59v and to use an AC power cable instead. This could explain why the batteries were refusing to charge or discharge, perhaps the BMS was protecting them? Does anyone know what could cause a spike in voltage like on the battery connection from the EG4 6500ex inverters?

 

[zanydroid]

Sorry this happened to you :-(

I don’t have solar specific info on this, but this incident is an example of needing to understand whether DC power supplies are isolated. For AC to DC they always are unless you got something extremely weird.

For DC to DC I believe it’s normal to assume they are not (this is a common way to kill things in the Power over Ethernet hacking community). And if they are not, if there is any kind of wire going into the device that might be grounded/be a path to a fixed voltage point, you could be in for a rude surprise. For PoE case, this means that stuff like access points and ethernet switches are fine (the latter have isolation transformers on the ethernet ports) but cable modems are high risk, HDMI is a risk, USB is a risk.

 

[zanydroid]

Your issue indicates that the RJ45 connection has a possibility of breaking anything connected to it.

 

[trig2]

I just recently set one up with the DC-DC supply and I could swear it said on the adaptor it was rated up to 70 something volts, weird.

Edit: it's actually 11-60v

 

[zanydroid]

I just recently set one up with the DC-DC supply and I could swear it said on the adaptor it was rated up to 70 something volts, weird.

If a DC DC converter is rated up to 1000V but not isolated you could fry whatever is on the output of the supply if it does weird things like reference off +Vin pole of the supply. Then whatever is on the output gets 995V on -Vout and 1000V on +Vout

 

[MizzouMookie]

I had the same thing happen, I was in the room when it failed. The eg4 6500 was powering loads like normal just lights at the time. Then the inverter faulted f12 I believe, dc-dc over current. Pv was disconnected at the time actually because we were supposed to be having some extreme high winds in the middle of the night, I usually disconnect pv just in ease the panels go flying or something it doesn’t kill the mppt. But anyway pv disconnect, fault code, and dead SA. Mine had a smoked smell and visible arc / burn damage to the usb port on the SA. No grid connected and other inverter is fine. Both were connected to SA but just the 2p1 inverter faulted and only that usb port was fried. Other inverter and usb ports all fine. So this was the last straw with these eg4 inverters, I ordered a sol-ark 15.

 

[vladkgb]

I believe I figured out what caused the voltage spike.

A few days after the SA unit blew up, I found my batteries in a similar state, with red lights blinking on all but the top battery, but SOC was at 50% this time, and MPPT refusing to charge even though it was nice and sunny outside. It showed over 300 volts but no amps. Restarting the batteries cleared the fault, but as soon as the MPPT kicked on, the bottom batteries flashed red again and charging stopped on the inverter again. There were no fault codes.

Assuming it was over voltage protection, I put my multimeter on the DC connection going to my batteries to try to catch the voltage spike. Disconnected the PV connection, reset batteries, reconnected PV, sure enough, there was a momentary spike in voltage to over 60v before MPPT shut down and batteries had red light on again.

After some research I realized I was hitting the low temp charging disconnect of the BMS, which is set to 32F, because it was below 30F in the room. This also explains why the top battery in the rack wasn't getting disconnected because heat rises.

My battery rack is in a shed with no heating. I solved the problem by adding two seed mats to each side of the rack which are controlled.by an ink bird temperature controller to turn on below 35F and turn off above 40F. Also covered the rack with a moving blanket for insulation.

TLDR; It appears that when the inverter is attempting to charge and the batteries' BMS disconnects due to low temperature, there's a momentary spike in voltage on the DC battery connection. Be careful when directly wiring DC components.