hello ,
As you know , the max solar panel OCV is about 150V, from the view of safety certification, the input of MPPT should keep galvanic isolation with the battery side, why didn't victron product design a isolation topology ?
asked
Why is 150V/70A MPPT not a Galvanic Isolation Converter?
Maybe you need to also explain why you think it should be galvanically isolated as well?
Some of the victron products are isolated. I would imagine that needing this feature is install related, so not necessary in every application.
I think id the mppt mosfets fail, they will fail short. In this situation, you send 150V down to your battery. The question is important. Maybe the galvanic isolation is not needed, but it is indeed really interesting what happens if the mosfets within the victron mppt fails.
Agree, interesting. I'm pretty sure there is an internal fuse, but by the time that blows has damage been done outside?
In all the failures I have seen (and heard) out in the field from various daft things people do and other unfotunate events I have yet to see any mppt fail and pass down dangerous voltages or current or any kind of anything for that matter.
If you run through the error codes on the mppts you will be able to check all the protections that are in place.
Battery over current, pv overcurrent, battery over voltage anything that you can think of that would cause an issue already has a mechanism in place to prevent major problems, some of them non reversing, but hey the price of less danger.
I do hear you in the mosfet failed open scenario (have seen some other brand inverters and other electronic items on fire from that). But on victron mppt even with lightning (and no other protection I may add - please dont be this stupid folks) the batteries in the system were ok.
Install them in the system as recommended, have your fusing and other safety equipment in place your system will be fine barring major calamity.
is there anybody to answer this question ?
We're just volunteers in the community, with occasional manufacturer input.
This is a design question for Victron.
It would be really interesting, if victron can reply here. What exactly happening if the mosfets within the mppt are shorted? Will the mppt send the 150V directly to the battery? Will the mosfets fail closed, and no voltage is available for the battery?
I do think this is REALLY an very interesting and important saftey issue. If anyone have further information, this would be just great! Thank you!
@Guy Stewart (Victron Community Manager)
Hi Guy, guess you haven't seen this. Any chance of a tecchy answering? Thanks
Keep in mind that IF the mosfets did short then it would cause the panels Voltage to be CLAMPED down to the current battery voltage - thus there Wattage output would be greatly reduced down to the battery voltage x MAX current that the series string can supply - so for a 51 volt battery and most strings are maxed out at 10 to 15 amps then thats 500 to 800 watts max output
so really it would only affect you when the batteries are very full - yes I agree its not a good outcome however its NOT as bad as it seems on the surface - Saying that it IS BAD when the batteries get to there max working voltage for sure.
This is only a comment and is no reflection on the above comments
So what happens at point of failure? At the very least you get a big voltage spike. Lead might abdorb, but not sure about all the other kit on the low voltage side.
I'd expect a company like Victron to have a fail safe design.
I do not think, a fail safe design exists. We just need to know, that this could happens. For example, some people have relays between mppt and battery. The relays could be cooked, if they cannot handle such a voltage spike. It is not the point, to blame victron for a bad design. but to know that a mostfet failure within the mppt is not harmless. But maybe a victron expert can tell us more!
