How to wake up battery after full discharge

Q&A and troubleshooting
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Hello,

During the weekend we experienced a new kind of problem.
At the moment, our solar panels have trouble with providing enough to keep the lights on all the time. I am working on installing a wind turbine next to the solar panels, since any kind of permanent grid connection won’t be an option for at least 10 months.
In the past weeks I have regularly woken up in the morning to find electricity out and the Cerbo GX beeping fanatically (lost WiFi since the modem lost power, low battery, enough reasons to beep).
Generally around 10:00/10:30 from work I would check in and see the system was slowly charging.

Saturday evening the light cut out at the beginning of the evening, I connected to the Cerbo via Wifi direct and silenced the alarm, went to bed shortly after.
In the morning we started up without electricity without thinking much of it.
Since we were out the whole morning I only checked at lunch time how the system was faring, and it appeared it was still offline.

Once back home I noticed that the Cerbo was out, as are the LED indicators on both the Voltsmile V10 batteries.

I tried to restart the batteries, they blink a couple of lights for a few seconds, the go back to black.

I gather that de Cerbo drained whatever was left in the batteries during the night, and that as long as the Cerbo remains out, the input from the solar panels won’t be able to charge the batteries, which will cause the Cerbo to remain out….

So to break this cycle I read I need to wake-up the batteries (or at least one I guess).
What I am not sure about, is how I need to to that.
The search results go from just hooking up a charger to the poles of the battery (suggesting even a 12V of 24V charger may wake a 48 V battery up) all the way up until a rather dangerous procedure, with remarks suggesting that since the LiFePo4 batteries experienced a deep discharged they’re probably permanently damaged.

The set-up is:

  • Victron MultiPlus-II 48/5000/70-50 230V

  • Victron SmartSolar MPPT 150/45 charge controller

  • Victron Lynx Distributor

  • Victron Cerbo GX MK2

  • 2x Voltsmile RPC V10 - 6DIP - LiFePO4 - 5.12 kWh in RPC cabinet

As an emergency solution right now we have a cable running from the neighbour’s, with a 3600W limit on it, which is what I have to work with to wake up the batteries. Maybe for the time being we will be able to use that as a back-up to help keep the charge up (“grid” from the neighbour through ET112 energy meter and into AC-in 1 of the MultiPlus, no direct feed from that “grid” to the groups).

For now I am mostly looking for some help with the waking up of the batteries.

1 Like
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It seems there’s something wrong with your Cerbo/inverter settings.

  1. How do you know the panels, not your batteries are at fault?
  2. Have you reached out to your battery manufacturer? They usually provide a procedure on how to restart a depleted battery. This can vary from battery manufacturer or even model to another manufacturer.
  3. What is your min SOC? Under normal circumstances, your system shouldn’t go below that limit.
  4. Is your Multi connected to the grid? If so, why does it not charge from the grid?
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  1. Well, I supposed the panels were at fault…
    Everything is new from last spring, the installation was fired up in April last.
    The whole summer we had no issue whatsoever, except fot a bit of trouble connecting the Cerbo to my phone (pairing over Bluetooth failed, but cannot be attempted again as the Cerbo registers as already connected)

    When the weather got a lot greyer we had once that the batteries ended up low. I made another attempt to connect to the Cerbo, this time via WiFi direct, and was succesful in connecting it to the house WiFi.
    From that point I have been keeping an aye on things, and although we have 6 panels with 460 Wp, we hardly get more that 150 W out of it at the moment.
    Since the solar yield is daily under the estimate, I just thought the shitty weather was the source of the problem, together with the recently finished house of the neighbour’s which shades the panels with the lower sun.
    Now I come to think of it, I realized a discrepancy between what the LED’s at the front of the battery indicate as charge level and what I can see in the VRM, didn’t think much of it at the time.

    1. As far as I could see, the user’s manual doesn’t mention a restart procedure. Since I started diving into the issue only yesterday, I haven’t come to the point of contacting the manufacturer.
      But it does sound like the restart procedure might vary depending on the model.

  2. I wouldn’t even know what my min SOC is… Nor where to find it, provided I can make connection with the system again.

  3. As I mentioned, we do not have a grid, as an emergency move we extended an extension cord from the neighbour’s yesterday, but that’s all there is. For that extension cord aside we are totally off-grid.

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  1. It is most likely the panels. But it could be your batteries or even some loads. For example, your BMS (if you have one, as you should) could for some reason shut down charging. Or a problematic load could be small enough for the batteries to survive its surge demands but big enough to drain them. Your battery capacity seems ok.
  2. With ESS, it is easy to read minimum SOC. I remember mine being 20% as an example. So the batteries can’t be drained unless grid fails (in that case, my BMS kicks in to protect the batteries). In your case, when not using ESS (you shouldn’t because you are off grid), I don’t know how, or if it is even possible, to get minimum SOC
  3. Understood.
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For a correct SoC reeding I would recommend you a Victron SmartShunt. We often read here, that batteries report a wrong SoC. Then use an adequate Limit, e.g. 20% like suggested. With this you should always have enough capacity left to avoid such a complete shut down of your system.

I thinkg that wrong SoC reeding might be the root of the problem, - you see a SoC that seem still fine, but suddenly a cell drops below a limit and the battery is completely off.

The solar energy we can get in these days (winter on the northern hemisphere), can really be so low, that you system is producing only few watts.

To restart the battery I would assume you have to put some voltage on the terminals that is higher than the battery voltage itself.

In best case your MPPT should do this. The MPPT can power up from solar and charge the battery, but in case there is no terminal voltage on the battery and on the MPPTs battery input, then it can’t start charging anymore. Don’t know the BMS inside this battery you have, but this should be the normal behaviour I would expect.

Is there still voltage on the battery terminal in this situation?