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Pylontech US3000C + Axpert King 5KV Rack [SOLVED by precharging inverter capacitors!]


jofemodo

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Hi guys!

Here a newbie in all this, nice to talk with you after 2 days of intense reading. This forum is really the best i've found. Congrats!

I'm building my first "small-but-serious" PV system:

+ 8 x 400V panels

+ 1 x Axpert King 5KV Rack

+ 1 x Pylontech US3000C  (i hope to add more ASAP)

I just finished the installation and double-cheked everything: continuity, polarity, protections, grounding, etc.

The problem:

Having the battery connected to the inverter, no matter if AC input/output or DC input is connected (i've tried all combinations), when i switch-on the battery, all leds light once for 1-2 seconds, and the inverter seems to soft-start (it always does, no matter if inverter switch is on or off.). The display backlight shines and the fan start to work, but after 1-2 seconds, it switches off and the battery goes to protection mode with red led solid light and all the rest off. It tries to restart automatically after a few seconds,  minutes and so on, but the result is always the same.

If i disconnect the battery from the inverter and switch on, then, after the initial all-light, the RUN green led starts to blink. It blinks 0.2s and stay off for 3-4 seconds, what manual says is normal idle operation (no charge/discharge). When i measure the battery voltage in this state, i get 50.5V, what seems quite normal to me.

The battery has been stored for 13-14 months but i did a recharge 6 months ago, using the same inverter connected to the grid. Everything worked fine when i did the recharge. Perhaps i should had recharged more frequently in this time, but i think it's not so bad.

I've reached the point where i'm stuck, so any fresh idea or thought would be really appreciated.

What do you think could be the problem? Is it battery or inverter related? What can i do? 

 

Thanks a lot!

Edited by jofemodo
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50 minutes ago, Tinbum said:

You need another battery really. The start up current of the inverter is too much for one battery.

Really? I want to add a second one, but first i wanted to see the system running.

Also, 6 months ago i managed to run the system (inverter+battery) connected to the grid and recharge the battery.

50 minutes ago, Tinbum said:

(Batteries like to be stored at 50% SOC)

But manual says that you should recharge battery every 6 months if it's going to be stored for a long time. Should i had been recharged it to 50% only ?

Could be this the problem, that i recharged to 100% and stored for 6 months? What if a slowly discharge the battery? Could the problem be solved like this?

Thanks for your help, @Tinbum!

Edited by jofemodo
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Energy-Jason
This post was recognized by Energy-Jason!

Tinbum was awarded the badge 'Helpful' and 15 points.

The batteries have a soft start and don't like surges on start up. The battery will see it as a short and shut down. I don't know your inverter so am not sure how it started last time. Is it possible it was powered up from the grid before you started the battery? Some times hitting the battery start button in quick succession may work, as when starting the second time, the capacitors in the inverter already have some charge in them from the first attempt. You could try pre-charging the capacitors first- do a search for methods, eg light bulb.

New batteries only come charged to 50% but the manual does say to recharge to min 90% every 6 months, so that's not your problem.

Edited by Tinbum
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The inverter is already connected to the grid, but it don't boot without a battery. In fact, it's the battery who boots the inverter. I mean, the inverter is off when i switch on the battery, then the battery boots and (supposedly) sends the soft start signal to the inverter . And it seems to really do it, but 2 seconds after, the inverter stops without displaying anything (only the display backlight) and the battery enter protection mode.

I've new info. I just tried to connect a resistive load (an ancient electric radiator) to the battery. It worked OK. The battery start dicharging and the SOC green leds lighted all of them, showing the battery is almost fully charged, the radiator heated a little bit (it was a 220V device). I kept this running a few minutes. So, the battery seems to be working OK.

I don't understand what happened to the inverter. I worked perfectly the first time, and now, as you say, seems to drain too much current from the battery, what causes the self-protection response.  As i told, i've tried a few combinations, connecting the inverter to the grid, loads in the AC output, DC from panels, nothing, etc. but the behaviour is always the same.

I've no problem with buying a second battery if this is really the problem, but Pylontech US3000C is not a small beast and i can't believe it's not capable of booting the inverter. Also, i already did in the past. I will recheck everything and retry everything again.

Thanks again!

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I will try to precharge the inverter capacitors. It seems the most probable cause of issue. Anyway, i can't understand why this wasn't needed the first time i connected the system together for recharging the battery. Perhaps wiring was not so robust and resistance between battery & inverter was higher? I can't remember the details

Thanks!.

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Hi @Tinbum!

It worked! You saved my ass! Thanks for your advice!

I pre-charged the inverter caps using an old electric heater (couldn't find any legacy bulbs around here!) and everything started to work like a charm. The system is now running smoothly awaiting for the sunrise to take the first sunlight-breath!

Now i understand a little bit better how all this work and my little PV system is alive. I just ordered a good 30ohm/200Watt resistor to have a more reliable precharge system. Of course, a second battery is a good idea anyway, but first, i will enjoy a few days of my sweet victory! Step by step!

Really thanks!

Edited by jofemodo
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  • jofemodo changed the title to Pylontech US3000C + Axpert King 5KV Rack [SOLVED by precharging inverter capacitors!]
4 hours ago, jofemodo said:

Hi @Tinbum!

It worked! You saved my ass! Thanks for your advice!

I pre-charged the inverter caps using an old electric heater (couldn't find any legacy bulbs around here!) and everything started to work like a charm. The system is now running smoothly awaiting for the sunrise to take the first sunlight-breath!

Now i understand a little bit better how all this work and my little PV system is alive. I just ordered a good 30ohm/200Watt resistor to have a more reliable precharge system. Of course, a second battery is a good idea anyway, but first, i will enjoy a few days of my sweet victory! Step by step!

Really thanks!

What's more is every time the inrush short to the inverter bus caps occur, it shortens the life of the cap. So its a good thing to perform pre-charging always. 

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  • 1 month later...

😎

I had exactly the same problem and realized it was a high current capacitor charge problem.

Because the Solar system runs for only 16.5hrs a day I need to start the system every time.

So I made this little kick starter powered by a Cheap 36V 2A Chines power supply.

Works like a dream every time 👍

Pylontech Kick Starter.JPG

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