Charge Controller failed…inverter magic smoke missing

H2SO4_guy

4 Evergreen 210 watt panels wired in series for a combined voc of about 89 volts into a Midnite 20 amp breaker to a Trace C-40 charge controller. I happened to be in the electrical room when it happened. The Exeltech XP-1100 shut down probably due to too high of voltage. The Trace charge controller was charging a single 48 volt string of Lucent 115 AH batteries that run lights and some other loads. They are AGM’s and just turned 13 years old. The set point was 57.2 volts and it was over 60 volts so I readjusted the C-40 to get the voltage back down. The inverter went off then 2 loud pops inside of the inverter and magic smoke appeared. The room had gone dark and I immediately killed the panel breakers, and went for the inverter breaker, but it had already tripped.

Once the lights were put on a different inverter I checked the voltage at the charge controller and it was 89 volts. Not much voltage regulation going on there! Everything was on Midnite breakers so even if I wasn’t there I believe it would have been safe from a fire, but the batteries would have been charged with too much voltage, but they were scrap when I bought them 7 years ago, so every AH I get out of them is a bonus.

Don’t know what would have prevented that from happening, but it was exciting for a moment

Skip

Cariboocoot

Re: Charge Controller failed…inverter magic smoke missing

89 Voc isn't relevant. The Vmp of the four in series would be 70, just right for a 48 Volt system. A 48 Volt Exceltech will take about 62 Volts max, so it sort of sounds like the actually batteries 'disconnected' from the inverter/charge controller allowing the V at the inverter input to climb. Even without the charge controller the batteries should have been able to 'clamp' the panel Voltage down to 70 Vmp in full sun. Check that out first. If you're reading Voc out of the controller there's no "load" (batteries) connected to the panels.

Exeltech inverters are tough, and their customer service is great. You shouldn't have any trouble getting it back in working order.

H2SO4_guy

Re: Charge Controller failed…inverter magic smoke missing

The Midnite 63 amp breaker had tripped from the batteries to the bus bar as well as the inverter to bus bar breaker too. The charge controller to breaker did not trip nor did the breaker from the string of panels. There was typically 300 watts or less load on the inverter for general purpose lighting, so I don't overload the battery breaker, it seems that something in the inverter is causing a dead short. Just for grins, I hooked attempted to turn the inverter on and it tripped the breaker immediately.

Thanks for your input Coot, I enjoy your posts very much and often get additional insight.

Skip

Cariboocoot

Re: Charge Controller failed…inverter magic smoke missing

Skip, maybe we're looking at this from the wrong end. It'd just possible the inverter went first, and generated the other symptoms.

The controller's breaker is only likely to trip if something goes wrong with the controller and the batteries feed it too much current. That panel string is only capable of the Isc for maximum current, and that's <15 on those I think. No way can they mangle a C40.

But if the resistance went high between the batteries and everything else, than the Voltage on the other side of that resistance (where the inverter input is) can go high as the panels' output wouldn't have as much load on it to pull it down. Current doesn't matter at that point; one moment of too high Voltage on the Exeltech and something inside fries instantly, creating a short that draws the current and trips the breakers.

Maybe. Can't say for certain of course. "Black boxing" via remote is more art than science.

waynefromnscanada

Re: Charge Controller failed…inverter magic smoke missing

Hopefully the batteries didn't go dry, and thus more or less open circuit, allowing the voltage to skyrocket

H2SO4_guy

Re: Charge Controller failed…inverter magic smoke missing

The resting voltage of the AGM pack is 51.3 volts with no charge or load for 24 hours. They were pretty charged when this happened and this is a typical charged voltage for them. The breaker to the charge controller did not trip, only the battery pack to bus and the inverter to bus both tripped.

Skip

niel

Re: Charge Controller failed…inverter magic smoke missing

the problem is using a c40. at some times the voltage will be allowed to swing high and low before it settles on the proper setting. this is not good for charging agm batteries with, but while connected to the inverter and it is on during one of these voltage excursions it could pop electrolytic caps inside the inverter. i have a c40 with a 12v pv and i have seen swings up as high as just below 16v in spite of my 14.3v setting and the swings usually occur when a great deal of solar power is introduced all of a sudden. this power introduction can be manually turning on a switch or breaker to the cc during bright sun or the sudden clearing after a well defined front has gone by.

i know you are using 48v, but i'm quite sure the voltage spikes would appear at whatever battery voltage is chosen. i do not recommend using the c line for agm batteries as this excursion in voltage can pop the vents. if it did pop some caps in the inverter, this could've physically damaged other nearby parts too.

H2SO4_guy

Re: Charge Controller failed…inverter magic smoke missing

Thanks Niel for the insight. I will be using a Morningstar TS-60 from NAWS and it just needs to be wired in to the pack. This should resolve the charging issue. Soon I'll probably buy one for that pack so I don't have to change settings on the controller, just juggle the amount of panels going to which charge controller. I want to get another Midnite Classic, but it is the cost of 3 of Morningstar TS-60's. Always interesting when the power company is at fault.....and it is you!

Skip