I don't know if this has always been a problem and I just discovered it. Or perhaps it's a new problem with firmware v508. Or maybe it's Operator Error?
I have a Multiplus I, 24/3000/70-50 120V. 
It is plugged into the grid via a timer.
For 21 hours a day, the Multiplus is connected to the grid. It passes grid to a refrigerator/freezer, and charges up some batteries.
For 3 hours a day (from 16:00 to 19:00) on weekdays, the timer disconnects the Multiplus from the grid and the Multiplus powers the refrigerator/freezer (UPS Mode) using the batteries.
It has worked perfectly for two or three years now.
But during the past two weeks, the Mulitplus sometimes (but not always) fails to reconnect AC Line after 19:00. (I tried to add a photo. But am seeing the dreaded "No link in upload response" message. So I'll try to add these in an add-on comment later.)
And so, without grid power to pass to the refrigerator/freezer, the batteries eventually discharge to their internal low voltage cutoff and everything shuts down.
This has happened three times now in two weeks.
At first I thought that the cheap (Chinese) timer might be failing to reconnect grip. (It uses a mechanical relay.) But tonight I caught the problem and there is proper grid voltage going to the Multiplus. (Photo.)
The Multiplus LED's were showing "Inverting." But not showing "Mains On."
What changed in the past weeks?
1) I updated the firmware in the Multiplus to v508.
2) I raised the Low Voltage disconnect voltage. (From the default 105 VAC to 109 VAC.)
3) I lowered the High Voltage disconnect voltage to 130 VAC.
(Nominal grid voltage here is 122 VAC. I can't imagine that our grid voltage ever spikes to 130 VAC. (There haven't been any thunderstorms (or EMPs) in the area.))
Before catching the problmem in real time tonight, I had swapped in a second Multiplus for days ago. (Same model.) But as I said, the problem happened again tonight.
So it's not an electrical failure in the Multiplus, per se.
But I also flashed the firmware in my second Multiplus to v508 before I swapped it in. So I can't say if this problem, if new to the new firmware, follows the firmware.
So tonight I plugged the USB dongle into my laptap to see what the Mulitplus said was the problem.
At first, VictronConnect didn't see the Multiplus. Uh oh.
But after a few minutes of retrying, it finally connected.
The Home page said "Grid disconnect reason: High AC voltage." (Photo.)
But as you can see in that photo and the photo with my DVM, the grid voltage was 124-125 VAC.
Shouldn't the Multiplus have reconnected?
Interestingly, when I unplugged the timer and waited for a minute and plugged the timer back in, the Multiplus reconnected.
So it's an intermittent problem. Is the over voltage firmware too quick to act? Am I setting something incorrectly? Other?
