Hi,
I’m using the Multiplus 2 with ESS for emergency power for the fridge….
It Multiplus 2 works really great.
But if something happens with the battery (if it's only the fuse) or the Multiplus is damaged also the grid power over the Multiplus is away.
Or is there any possibility?
I think this can happened more often than a longer grid power failure.
I can Bypass the Multiplus, but if I'm away the emergency power for the fridge will fail.
With an mppt and some solar, the victron can self recover without grid.
Why would a fuse blow? Usually that indicates a much larger problem. A fuse blowing is not normal in a well built system. In fact I have not ever experienced it.
With online monitoring it is easy to keep an eye in things from anywhere.
If you are running out of battery in an overnight power outage with just a fridge that is weird, most only use 1 to 2 kwh a 24 hour day (normal nore modern home fridges). Most of the time 1x 5.0kwh battery can handle that for a 24hour period with no solar.
Surge protection devices can help with protection from grid/lightning problems that may cause faliures. With a well sized solar array, having grid does not matter.
It is all in the design.
I was thinking the other way.
If grid is ok. And something other get damaged. The Emergency Power is away.
Maybe the fuse was a bad sample. But if the BMS or the Multiplus is damaged, over the years (maybe only the power supply …)
My emergency power is away, although grid is good.
After maybe ten years it can happen every day that something gets faulty, and on worst case in holiday…
It would be great if the passthrough is applied, also on some minor troubles.
That is what regular maintenance and checks are for?
A backup system has to be recommissioned usually at least once every 3 years.
And the same as RCDs are check once a month, inverter and back up function should be checked as regularly.
There is no such thing as fit and forget.
Victron has a 5 year warranty (extended to 10 if installed correctly suppplier willing as well). And lifepo4 batteries usually have 10 years. Most supported victron lifpo4 batteries do let the system into passthrough when there are issues.
I have seen systens running more than 5 years on with no issues. What kinds of problems would you be expecting?
I think the Victron will work a long time. But you can’t say when it fails. (So preventive exchange would only help a little bit and would be expensive)
If only one capacitor in the Victron or the BMS fails, the hole system can fail. Not only the backup function doesn’t work. The output can/will fail with grid present.
And I have to bypass the Victron. With a stable grid this can happen more often than grid failures.
Maybe something like an automatic bypass can help?
I had more power failures on the output of the Victron then on the grid. It was every time my fault (update, switch the battery of…) but it can happen with a hardware fault to.
You could use one of these contactors. Connect the coil to the AC-Out1 of the Multi, and the load (fridge) to the AC-Out1 via the n/o contacts and directly to the grid via the n/c contacts and a suitable fuse or breaker.
Then if the Multi is working you will have the protection of the ESS but if it fails you will have the grid supply - unless you are unlucky and both are down.
This is my next planned upgrade!
The Idea with the Contactor is very good and makes what I want.
But I don’t think it’s allowed. Because if the Contactor fails AC-In is connected to AC-Out.
In normal operation the Multiplus 2 has for this the double relay that this can’t happen.
And it can also be a problem if higher loads switching with different phases….
Is there an other possibility?
I would be great if the Multiplus 2 could do this internal.
Generally speaking these contactors are designed so it is almost impossible for the n/o and n//c contacts to be closed at the same time.
The most likely failure mode would be the n/o contacts becoming welded, depending on how it is designed this might automatically prevent the n/c contacts from closing so no problem, I would have to take a contactor apart to be sure.
Unless you have a big inductive load (large motor, welding set...) I don't think it is a serious risk. If you are really concerned you could fit two contactors - made by two different manufacturers - in series to be extra safe.
