I would like to get my AC-coupled system into "Passthru" mode on sunny days so the MP-IIs don't waste energy on (dis-)charging the battery packs when there's no need to.
This seems to have somewhat worked:
However, as you can see above and below, one battery pack is still allowed to get a small charge of ~0,4A:
What's a good way of figuring out why the Multiplus-IIs still allow the system to charge? And why doesn't setting the maximum charge current to "0" force actual passthru?
It is interesting how it is only one pack 'taking a charge' and not the other two.
Why the conclusion it is the Victrons fault? If it was all three taking a small charge, I would be more inclined to agree with the conclusion in your post. Potentially here the one pack needs to catch up to the rest in voltage and balance (or maybe it has a resistance difference), that is a more likely reason - the battery.
It's not about anybody's fault - it's trying to understand why a setting like DVCC max charge current isn't honored. If there's a current available to the battery pack, it may or may not take it. But if I use a physical switch to turn off all current, the battery wouldn't be able to consume anything either. So the question is: Why is the MP-II delivering any current to the battery when the setting is "0"? Why doesn't it behave like a software switch (until/unless any situation appears where this may be considered harmful/damaging etc.)?
Why do I see "Passthru" as the mode (which is what I see when communication is severed as well, when there's actually 0A going through the wire) but it's actually charging at the same time?
There might be a good reason for this, all I'm trying to do is find the log/reason so I can understand it better. So much of the internal implementation details are a black box. Where's the debug log? ;)
The system is battery lead, you’re trying to force a behaviour by setting the inverter limit to 0 and the charge current to 0. Hence the status codes 6 and 7.
It is not intended for that purpose.
Batteries will always be lent on, physics prohibits a zero value not to mention measurement inaccuracies at low levels.
If you want 0 usage, fit a bypass switch.
> It is not intended for that purpose.
What is the purpose of being able to set a 0 value for (dis-)charge if it isn't setting (dis-)charge to 0A?
> physics prohibits a zero value
Turning off the charger would lead to a zero value. Why would you think that that's impossible?
> If you want 0 usage, fit a bypass switch.
Like I mentioned, I can do this manually and it works well. As outlined above, I'm trying to understand what the purpose of ESS #6 (User configured a charge limit of zero) and #7 (User configured a discharge limit of zero) would be if not to make it zero.
There isn’t a separate charger and inverter, its one device that changes between the two modes, likely why there is a charger or inverter only switch.
It will not behave the way you are expecting.
I'm sure there are a lot of variables, which is exactly the reason for asking here. However, look at my initial screenshot: there's plenty of power available from the pv inverter, and there is no need to charge the battery since it's obviously not below any critical threshold. So why is it beside the point to expect the setting to be honored under these exact circumstances?
I'm sure there'll be a ton of failsaves to consider. In a stable system however, I would like to understand what made the charger deliver a charge instead. Is that really so far off?
Setting a limit, and a 0 limit are not the same thing. It simply cannot honour 0A.
Why is this an issue?
Is your voltage increasing? (usually only seen on undersized packs)
While the system will favour grid, this is a battery-centric architecture and it will always have small amounts of energy moving, sometimes larger amounts, depending on load/generation variances.
As already stated. a low measurement is unlikely to be accurate anyway.
