question

sesshoumaru avatar image
sesshoumaru asked

Extending Pylontech battery bank

Hi @ all

I have a system with 8x Pylontech US2000C batteries, which are connected with 4 cables to a busbar.
I am planning to extend the system with two more US2000C, which will also be seperatly connected to the busbars. Can I just hook the new batteries up and start them? Or is there something more to consider? The SOC will definitly be different e.g.


Thanks

cerbo gxLithium BatteryPylontech
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Alexandra avatar image
Alexandra answered ·

@Sesshoumaru

Pylontec claim their batteriss can handle different SOCs, so technically you can. Their manuals dont include any special methods foe connecting new batteries to a bank.

Just make the new ones the master.

I personally prefer them to be at least the same voltage. But will usually charge and balance both banks before combining them.

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sesshoumaru avatar image sesshoumaru commented ·
Thanks. I plan to upgrade the second bank to 8 batteries as well (own 250A breakers).

I have no special equipment for balancing, so I will just throw them together hand have them doinig their thing, I guess.

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kevgermany avatar image kevgermany ♦♦ sesshoumaru commented ·
I did this with mine (US5000), was in a hurry and had no other option. @Alexandra would not be impressed and I fully support her recommended method. But it worked. In fact the lower charged batteries seemed to be charging from the full one when there was no external charger.
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nickdb avatar image nickdb ♦♦ kevgermany ♦♦ commented ·
Yip, this is why the recommended procedure in the docs is to leave the batteries on but isolated from the inverter until the LEDs have balanced.
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sesshoumaru avatar image sesshoumaru nickdb ♦♦ commented ·
I thought its not a good idea to disconnect the batteries from the inverter.

I mean I do not plan to power the system down. I assume tne new batteries will be loaded to 50% and I would wait for the current battery bank to reach 50% to smoothly connect them -- while is all up running.

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nickdb avatar image nickdb ♦♦ sesshoumaru commented ·
The inverters would be powered off.
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sesshoumaru avatar image sesshoumaru nickdb ♦♦ commented ·
Nah, the entire house runs over them. Cannot power them down.
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Alexandra avatar image Alexandra ♦ sesshoumaru commented ·

Unless there is someone on life support in your home there is no possibile reason why a short 10 or 15 minite shut down cannot be managed.

Your next planned upgrade should be a system bypass installed for maintenance/upgrade or repair reasons.

I cannot over emphasise how freaking dangerous working on a live battery bank and system is.

There are literally thousands of amps available waiting for a small mistake.

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sesshoumaru avatar image sesshoumaru Alexandra ♦ commented ·

@Alexandra

The system has a bypass, I am just reluctant to use it for just adding a battery to the DC side. And yes, there are running some very important servers which of cause have their own power backup, but never try a system without need.

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Alexandra avatar image Alexandra ♦ sesshoumaru commented ·

All the more reason to have a bypass in. All our systems that run servers have them.. what happens if athere is an unrecoverable error inverter goes down and the only way to repair is a shutdown and replace.

You would then need to switch to an alternative power source.

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