BUG: Charging disabled when on GX and battery low

Q&A and troubleshooting
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1

dear Victron engineers, dear experts,

scenario:

  • on a boat (or anywhere else without grid):
  • the MPPT Smart Solar Chargers are connected to a GX device (powered from batt)
  • the battery runs that low that the BMS cuts down discharging
  • the GX device stops working since no power supply anymore
  • the Smart Chargers say “connection lost, charging disabled”
  • → DEADLOCK

even if the sun comes up, the chargers do not charge, the battery stays low, GX does not start working.

Or do I miss something?

I would like to have a flag/switch to determine if
a) the chargers stop charging for safety (like it is now) -or-
b) the charges fall back to their individual settings (probably including Smart Networking) and would charge accordingly.

Thank you & greetings!
Phil

2

So why don’t you let the mppt’s manage themself ?

For me a gx is suitable for a large installation or when connected to a grid.

3

simple: Usually I have my own algorithm to control the max SoC. When SoC is at 85% I decrease charge voltage to float level.

I have 7 Smart Chargers and SmartShunt. I like to monitor and log all these devices. I prefer wired connection better than BT, …

4

SoC limitation is not possible with mppts ‘on their own’.

5

I do have a ‘large instalation’ and usually it is connected to grid. But I experienced the situation in a black-out when GX was powered from the Grid. Especially in a black-out situation when you really require power from the sun, it is not available.

Now I will change the supply of the GX to DCDC from batt, but that does not change the sutiatuion when the batt goes down. Even if the grid returns, the chargers would not start charging…

6

So for a 12v system reduce the absorption voltage by 0.4v, for other systems correspondingly, you’ll have the same effect, your batteries wiil never be able to equalize.

7

my cells do. also from time to time I let them go 100%.

but all this is not the point here! The point is the deadlock when SmartChargers connected to GX. what is all this Smart and GX worth if you must not use it?!?

8

Interesting finding.
I have a similar setup in my camper.

At the moment without sun, I will run into this next week.
Let’s see, what the MPPT will do.

9

As i said : don’t use it for non-grid applications.

Ofc somebody will try to sell this to you, probably the same guy that will sell you an ev with 1000+ hp :wink:

10

as I said: I am on grid but the grid disapeared… How do you manage remote access to your off-grid system without GX?

@MitchMe do you have similar DVCC settings?

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11

A GX device is a useful device for off-grid systems too.
And for some batteries it is a requirement.

@Philippoo The system should be designed in a way that you don’t run into that (easily).
All normal loads should be shut down before the battery switches off completely.
Only the GX device should be powered until the end.

12

@Philippoo

I helped a fried who’s system (MP2, Cerbo, MPPT) did not charge and the MP2 went offline with low battery short after start up. In the evening the Cerbo alos disconnected.

I turned out, the battery fuse was blown.

When sun rised, the MPPT powered the bus bar. Cerbo started. Than the MP" started. As soon as the MP2 started inverting, the DC power collapse.

Short: there must be some blocking setting in your MPPT which prevents cold starts.

13

thank you @M_Lange , @BjoernK !

but ‘after the end’ the Smart Cargers are in “connection lost, charging disabled” state and will not start charging even the sun comes back up.

no, they don’t. they are in “connection lost, charging disabled” state. perhaps with your friend’s system it was not set to “charging controlled by BMS”? you can easily test by disconnecting the power supply of the GX or shuting it down.

If then the chargers go into “connection lost, charging disabled”, you will always run into that deadlock when battery is ‘fully empty’.

The alternative would be to power the GX from grid, but then the chargers will not charge as long as the blackout lasts, what is also not what you intend in case of a blackout.

14

I’m confused: I just tried disconnecting the power suppy of the Venus Raspi. This time the chargers switched from ‘externally controlled’ to float mode.

Now I wonder what might be the difference to when the blackout happened some time ago?!?

15

Ah so a PI.

A GX normally in a black start condition will power up from the DC bus when the mppts begin to produce power at sunrise, which then wakes up the battery and the bms. Charges the system up and the inverters restart when the preset level is met.

I think maybe it is a system design issue here.
Deadlock is described and explained in a few manuals for victron.
The better way to do it is to have the inverter system shut down before total battery depletion so the battery remains on at lower SOC.

16

but if the mppts do not begin to produce because of loss of connection?!? this is the dead-lock I experienced.

but don’t care, as I said it seems to work now even when connection is lost. don’t ask me what caused that change in behaviour, perhaps a firmware update of the MPPTs I did in the meanwhile…

17

I find it very interesting definitely as it has always been how systems have worked for me. (And have unattended systems installed that are over 5 years old) So obviously am keen to find out what the difference is in your set up that made the behaviour change