Feature request MultiPlus

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jbakuwel asked Oct 8, '18

Feature request MultiPlus

Hi there,

Currently, an off grid MultiPlus with an AC coupled inverter is not able to automatically recover from a LVD: once the MultiPlus decides it needs to LVD, the "grid" goes down and takes the PV inverter with it.

So at this stage an additional charge controller with it's own set of panels is required to allow the system to automatically recover from a LVD.

It would be great if the PV assistant on the MultiPlus (I assume this is where this functionality would likely be implemented or possibly it could be in VenusOS too if VenusOS would be able to get the required level of control of the MP) would have a feature called "Recovery" or something along those lines that can be programmed with VE.Configure.

It would work something like this.

Imagine a LVD of 47.5V. When the battery voltage reaches 47.5V, the MP will stop inverting and wait until the battery voltage reaches 51.5V. As mentioned above this will currently never happen without intervention.

At set times of the day, for example in the morning, the MP could enter a recovery mode with the following parameters:

- Recovery V: 47V
- TTR (time to recover): 3 min
- Max AC load: 3A
- Start time: 09:00
- Interval: 15 min
- Stop time: 11:00
- Max attempts: 3

In the above example, the MP would start inverting at 09:00 provided the battery V >= 47V and the AC load remains <=3A. It will wait 3 minutes (TTR). If during that time, the MP senses that the batteries are being charged (ie. AC load = 0A as PV inverter is powering the loads and it has started to charge the battery, the recovery has started successfully.

If either battery V drops below 47V (in this example) or the AC load exceeds 3A while battery V is still below LVD, the MP will stop inverting and try again after "interval" minutes for "Max attemps" number of times. It will also stop attempting to enter recovery mode after 11:00.

A really fancy version would use the time of sun rise for a particular date instead of a fixed start time.

regards,
Jan

MultiPlus Quattro Inverter Charger

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jbakuwel commented · Oct 08, 2018 at 09:50 PM

Meant to say: a really fancy version would use time of sun rise for a particular date and location instead of a fixed start time.

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mvader (Victron Energy) answered · Oct 12, 2018 at 05:23 AM

Hi Jan, thanks for the idea! nice, but I do think adding a small mppt is simpler; less settings, less things to understand as a user/installer, and also less issue-prone.

with lithium this will be harder: voltage curve is more flat.

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Modifications Space

Node Red Space

Answer 1 · 2018-10-12T20:13:03Z

jbakuwel answered · Oct 12, 2018 at 08:13 PM

Hi Matthijs,

I agree that adding an additional MPPT controller (and also additional panels) is the least complex approach and the preferred way to go. There are however cases where this would not be the best solution for a client, for example in places where roof space is limited and all panels should really go on the AC coupled inverter or where an existing array on steep roofs makes rearranging the array difficult.

With Lithium batteries, I would imagine this feature would use SoC instead of battery voltage. In fact that might also work better for lead acid batteries.

Having options is great :-)

kind regards,
Jan

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mvader (Victron Energy) ♦♦ commented · Oct 12, 2018 at 09:55 PM

Hi, yes I see the point of the roof. But still it won’t be a 100% solution; where the mppt will be. Anyway: I’m not convinced that this is something that needs to be made fast, but I wil keep it in mind, thanks again!

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