question

bulraydin avatar image
bulraydin asked

How to keep Cerbo safely powered on ?

It has been now my third Cerbo GX that was broken at the second power up. I have examined all posts regarding this issue and also read the solution with the capacitor. The newest broken Cerbo GX had the serial number with 2247, hence outside the known problematic lots, which is 2200 - 2220.

It is very frustrating to encounter such problems, especially when you are installing off-grid, far away from any city or supplier.

Therefore I need to know how to best protect the Cerbo GX, besides the fuse, which comes with it. Obviously something happens during power-up, either a current rush or a voltage peak, which damages the power supply part of the device. Which protection do you advise , to avoid such damages ?


I think this information is very valuable for all installers worldwide, and it should even be added into the manual.

Best Regards


cerbo gx
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4 Answers
nickdb avatar image
nickdb answered ·

Are you sure there isn't an external issue affecting the Cerbo? The newer batches don't have issues and what you are describing isn't normal.

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bulraydin avatar image bulraydin commented ·

hi @nickdb


I don’t know what coul have affected. We have grounded everything to the same place. Even the minus pole of the dc bar is grounded. Maybe powering up with the SmartSolar and without the batteries was not a good idea ? I explained below.

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dmsims avatar image
dmsims answered ·

A small UPS

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Kevin Windrem avatar image
Kevin Windrem answered ·

You could add a small DC-DC converter to isolate Cerbo from the battery. There are many for under $30 on eBay and Amazon.

Or do a small DC-DC charger and a small separate battery to keep Cerbo up even after the main battery shuts down.

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groningen avatar image
groningen answered ·

@bulraydin


Just for curiosity, do you have a layout of the system (including the connection of the GX + -) and what is your "power on" sequence.

Also, do you use a pre-charge resistor or mppt before switching on?


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bulraydin avatar image bulraydin commented ·

@Groningen

Hi cerbo’s power supply is connected directly to the DC bar with its cable. The batteries are pylontech and there are two SmartSolar 450/200 connected . This is what we do as usual. The First power-on sequence was with the victron solar charger 450/200, without the batteries. Cerbo powered on with the 50v coming from the charger. All was fine . However as we turned on the batteries cerbo just shut down and never come back again . Maybe this sequence was wrong ? Maybe we should have powered on with the batteries ? This is maybe our eleventh system with cerbo. I think I will add a dc-dc converter in between to protect

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Michelle Konzack avatar image Michelle Konzack bulraydin commented ·
ALWAYS connect the batteries FIRST and then the Solarchargers.


The Solarchargers can produce very well an overvoltage which kill the Cerbo


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nickdb avatar image nickdb ♦♦ Michelle Konzack commented ·
Typically that can only happen if the battery is dropped mid charging from solar.

Starting with no load, or just the inverters attached to precharge and then turning on an mppt shouldn't cause that behaviour.

It is quite commonly done in the field.

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Dean Perry avatar image Dean Perry Michelle Konzack commented ·
The real trick with this combination is the Pylontechs going out on High Discharge Current.

But that aside, it shouldn't blow up the Cerbo - it's rated for 70vdc.

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groningen avatar image groningen bulraydin commented ·

@bulraydin

OK, interesting. As pointed out by Michelle, it could be that the MPPT is giving you the spike.

I am no expert, but if you wish to determine the issue on hand (for knowledge to pass on) I would suggest to run a quick oscilloscope test (with good refresh rate) to check what and where is it spiking (if any).

As nickdb also mentioned, the new batches are good. I have a few effected CerboGX's running and they all perform well (with Capacitor installed - 48V systems).

Would be interesting to see the result (if it is a spike).


Lastly, I assume it is well earthed and no static is effecting it nor do you have a problem with the neutral?



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groningen avatar image groningen bulraydin commented ·

I also think it might be a combination of "incoming MPPT" and "incoming battery (SOC dependent)" that is pushing back, but I am purely guessing.


As Dean Perry indicated, it might very well be the High Discharge current from the Pylon-tech.

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bulraydin avatar image bulraydin groningen commented ·

Thanks a lot for the comments. If the fluctuation in the startup procedure is really the problem , in this case I should put a switch to the supply of the Cerbo. And in any maintenance or commissioning situation I should first switch the Cerbo off, to make sure that first my dc part is stable .

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