I have an rs450/100 which is immune from this pv voltage on dc bus failure mode.
My understanding is that the 250/100s have a protective relay that operates to disconnect pv if it detects that type of failure.
However the failure seems possible on a 250/85
For my 250/85, what I am planning to use is a Midnite 600V 30A shunt trip breaker, which will be connected to a Midnite Hawkes Bay 90. The hawkes bay and Barcelona sccs have an independent monitoring circuit and will operate the shunt trip if it detects over 68V on the battery bus, this is what the design uses for isolation if the scc fails, normally this would be used in conjunction with the hawkes bay or Barcelona breaker boxes with one or two of those breakers however the sccs have three pairs of connectors for shunt trip breakers so I have two spare connections to use.
Unfortunately, seems that some users are not so lucky when mppt disconnect from battery, mine 100/50 survived once , at 25A load, but, maybe was just luckā¦
So, the trip release must be on PV side of the charger.
Unfortunately I donāt thatās about as detailed as Midnite has got about it. Be aware the shunt trip breaker is around $100 including shipping when purchased standalone.
Hereās how the shunt trip breaker connects to the hawkes bay scc:
Batteries are delicate and require proper attention, especially when off-grid. Think of your
batteries and solar equipment as a small nuclear power plant, hydro dam, or natural gas-fired
power plant. Just like any of those, your system needs DAILY attention to ensure it is performing
correctly and safely. We recommend the use of an independent battery monitor/alarm if you
have an expensive battery bank.
Well, in my case, already have DC MCB by Noark, I just add shunt trip release to mcb, when an Overvoltage occurs, the trip release mcb. The trip release are cheap, under 10ā¬.
I just have to use an external monitoring device, a BMV , which has an internal relay , or the multifunctional relay inside the Multiplus
This DC breaker will be between my PV panels and MPPT. A shunt trip release mechanically attached. In case of overvoltage detected, the trip bobbin energize and disconnect the panels. Needs manual intervention to reconnect.
Adding here - this just happened to me this weekend with a Smart Solar 100/50
After being in winter storage, I uncovered the van, reconnected everything, and got the batteries to full charge via shore power.
The next day I started hearing the fire alarm in the van going off, ran out. Van was full of smoke.
Hit the master off on the batteries, started looking.
Almost all the fuses were blown and I had 67v on the busbars.
The smart solar had shorted my panel voltage into the 12v circuit. Shorted almost everything attached and the fuses blew thereafter.
It killed the inverter, AC unit, multiple smart relays, and damaged the batteries (plus murdered a bunch of other random electronics)
Terminals on the MPPT were fine. This should not be able to dump panel voltage into the house circuit. If you buy one of these - make sure you have an over voltage disconnect!
I also have 2x smartsolar mppt 100/50. With 2x Canadian solar 440W in series on each mppt. Iām on 24V, so the maximum current to batteries is around 28A/mppt. On 12V you hit 50A. Last summer, in full sun, the charger was really hot. Then the paranoia began, I mounted a small fan to ventilate , itās under a polycarbonate roof, at the top. HA start/stop the fan over 25Ā°C and PV power greater than 1000W.
The smoke sensor is the next moveā¦ but then is already too late for the equipment. What was the source of the smoke in your van, anyway?
On 250/70 mppt (or close model) Victron implemented a latching relay, which short to the ground the PV input, in case of overvoltageā¦
MPPT Solar Charger Protection (PV Short Relay): SmartSolar MPPT 250/100 (VE.Can) units introduced in 2022 (Serial Number HQ2150 and newer) feature a built-in latching relay.
Function: If a short is detected between the PV input and battery output, this relay engages to short the PV input, protecting the system.
Reset: This protection requires a manual reset via VictronConnect, as it is a latching mechanism, not an auto-resetting fuse.
Long ago, the overvoltage protection on some SMPS, was made with a simple fuse and a thyristor with a zenner diode in gate. Effective , cheap and reliable.
Thinking deeper, when a short happen between PVinput and Battery+, shorting the PV to ground means shorting B+ to gnd. Thatās mean internal mppt fuse blow. The latching relay must be capable of lots of amps. And such a short must eat the contacts as well. Some kind of patch for a derrailing trainā¦
Current from mppt to battery will be 420W:14V= 30A. Mppt will run on full throttle at 15A. You can lose half of panel powerā¦ For your setup a 100/30 will be properā¦
