Originally Posted by john61ct
Yes I just meant "if it could" be improved
or a new device developed by Victron
to act as such, not be so limited
that "would be nice".
I see. Yes, that would be nice.
But certainly as is, I think this is still a great improvement,
more suitable than before as part of a DIY LFP
for those with separate charge and load busses.
...and with (small) loads guaranteed to be lower than the rating (which itself is underspecified... "peak" for how long?).
FET arrays tend to fail quietly and infuriatingly: they cascade short and turn into wires.
Contactors have a distinct advantage here. For a given nominal rating, good ones can handle substantial overcurrent transients for periods well into seconds, and at the same time their primary failure mode (contact arc
welding) occurs during breaking events
rather than in normal use.
Put another way, if your Battery Protect is "on" in a system running normally, and you inadvertently apply something north of the peak transient current
for 20ms, you may well now have a BP that won't P! (That peak is marketed as 2.5x the rated continuous, by the way.)
On the other hand, if your contactor is closed "on" in a system running normally, inadvertent transient currents well in excess of 10x the rated continuous are unlikely to do a thing. The device won't melt, and the contactor doesn't have a gap to arc
over. It will still happily break a nominal current, later, in a shutdown event.
In large systems, substantial transients can be created as inverters with big buffers are switched into the system. (Ask me how I know!)
I'll stop there, and just summarize: don't use Battery Protects as pack disconnects in high-power lithium systems. They look cool on paper, but they're not robust enough for the job.
They're probably fine for small systems with light, unidirectional loads. Make sure you understand their drawbacks before proceeding.