SMA Sunny Island Restart question

[Salts]

So apparently, the SMA Sunny Island inverters, (mine are 2x 6048 units), have a quirk where, if you disconnect battery voltage from them and shut them off, you have to wait about 15 minutes per inverter (2 x 15= 30 minutes) before they will turn on again.
If you attempt to apply battery power before this time, they won't do a damn thing.. just sit there with a dark screen. Then you have to again as the proverbial clock is reset because the caps have been charged back up.

There must be some kind of latching circuit inside.

This waiting period IS mentioned in the manual. You have to wait for the capacitor bank inside them to bleed off their stored charge. Putting a meter on the DC input terminals, you can see the capacitors bleeding down, but damn, its like watching the grass grow.

I want to know if there's a way to speed this up. Sent email to SMA, they're not all that great with responding, will call them as well on Monday. But in the meantime, I'm wondering if anyone has encountered this and found a way to speed it up without damaging anything.

Wondering if a 50 or 100 ohm power resistor across the Pos and Neg terminals would do the job. Should be able to bleed them down at 0.5 to 1 amp, but don't want to try that with my expensive inverters without more information.

Interestingly, the BMS's precharge resistor fills them up this way. 66 ohms across the main positive terminal contactor before activating for about 10 seconds and the caps will charge to just shy of 50 volts.

[Salts]

UPDATE: I got it figured out.

My system utilizes an ABB Load Shedding contactor that is hooked up to the Sunny Island's aux programmable contacts. I noticed that after I de-energize the system, that contactor stays closed for about 5 seconds, and while its closed, the 48 VDC coil starts to discharge those capacitors.. but only down to about 26 volts.

So I figured if the contactor is allowed to drain the caps, why can't I do it? Right?

I jumpered a 25ohm power resistor between sys neg and sys pos and bled those capacitors in about 5 seconds.. System started right back up.

Good to know if the inverters ever need to be restarted right away.

[bob-n]

Salts,

What follows is random rambling and guesses.

With the limiting resistor, it sure sounds safe. Odds are that their discharger drops out because the voltage gets too low for the coil of the contactor. The contactor may double as a safety circuit that brings the terminals down from a relatively dangerous 48V to a safer 26V. But shorting those terminals at 26V is still enough to cause a good spark, so be careful that you don't connect the resistor wrong.

[Salts]

Salts,

What follows is random rambling and guesses.

With the limiting resistor, it sure sounds safe. Odds are that their discharger drops out because the voltage gets too low for the coil of the contactor. The contactor may double as a safety circuit that brings the terminals down from a relatively dangerous 48V to a safer 26V. But shorting those terminals at 26V is still enough to cause a good spark, so be careful that you don't connect the resistor wrong.

The Load Shedding contactor is something I installed to shut down the house before the Sunny Islands force a shutdown.

When connecting a 25 ohm resistor across 25 volts, you get 1 amp of current... or 2 amps across 50 volts. Ohms law ( voltage divided by resistance). And when I did it, there was no spark that I could see and the caps discharged quite nicely in just a few seconds. Even removing the connection mid-way through the discharge, did not produce any arcing.

I think I got it.. I was worried that something was really broken when those big heavy and expensive inverters wouldn't start up.. had to dig for a while through 200+ pages of the manual to figure out why.