Adding a battery to a hybrid inverter

[nanook]

Hi all,
I'm after some advice, I have a growatt 36000 hybrid inverter with a singular ml33rta battery I'm wanting to add another battery (a simple new lead set from trade sparky) it looks an easy thing to do my question is does the inverter recognise the new battery via the rj45 connection or is there a setup needs to be done on the inverter?

The system was in the house I bought and with current prices I think more battery storage the better.

 

[Mrjmegson]

You'll need the balance the batteries, that's the most important thing.

The inverter won't care, as you say, it will just see extra capacity once you com them together.

With more batteries, you will probably be able to get a higher rate of discharge, so you will probably find settings in your inverter to increase the discharge, but that's only if you want to, otherwise leave it as is.

 

[nanook]

You'll need the balance the batteries, that's the most important thing.

The inverter won't care, as you say, it will just see extra capacity once you com them together.

With more batteries, you will probably be able to get a higher rate of discharge, so you will probably find settings in your inverter to increase the discharge, but that's only if you want to, otherwise leave it as is.

Thanks for your reply , I'm awaiting delivery of my new battery and leads so fingers crossed its all plain sailing.

 

[Mrjmegson]

Do you know how to balance them all?

 

[binky]

Thanks for your reply , I'm awaiting delivery of my new battery and leads so fingers crossed its all plain sailing.

It's usually fairly straight forward, battery charge levels are the biggest issue, sometimes they come fully charged, sometimes half charged, never had a flat one. From reading elsewhere, that can be overcome by setting the inverter to force charge the batteries, that gets them both up to the same level. Once achieved put inverter back to normal settings. I have installed a replacement battery in a stack without doing this, the BMS sorted them out over a couple of days with no ill effects.

 

[Mrjmegson]

It's usually fairly straight forward, battery charge levels are the biggest issue, sometimes they come fully charged, sometimes half charged, never had a flat one. From reading elsewhere, that can be overcome by setting the inverter to force charge the batteries, that gets them both up to the same level. Once achieved put inverter back to normal settings. I have installed a replacement battery in a stack without doing this, the BMS sorted them out over a couple of days with no ill effect

That's interesting Binky.

Everyone goes on about balancing batteries, but my supplier said it doesn't matter, the BMS will balance them itself. I thought they were talking rubbish after everyone stressing how important balancing is.

So that's really good to know, as I want to increase my batteries when I have a space £15k

 

[binky]

That's interesting Binky.

Everyone goes on about balancing batteries, but my supplier said it doesn't matter, the BMS will balance them itself. I thought they were talking rubbish after everyone stressing how important balancing is.

So that's really good to know, as I want to increase my batteries when I have a space £15k

It's quicker if you balance the batteries, but the BMS is there to do exectly that. I'll cover my arse by saying it worked for pylontech, other batteries may not be the same .

The other obvious question is how the hell you balance the batteries when not connected to the inverter?

 

[Mrjmegson]

Yeh, I suppose it all depends on the BMS. But I'd definitely make the assumption that as the BMS is there to stop issues with batteries over/under charging, then they would balance them over time.

 

[johnb2713]

It depends a LOT on the BMS system employed. My BMS (Seplos) is a 'passive' BMS, it doesnt actually balance the batteries (well does but by only the smallest amount), what it does do is disconnect from the inverter if any cell hits a high voltage or low voltage alarm. It actually does this really well BUT very slowly the batteries can become unbalanced the net result is charging is stopped early by 2 cells getting to high voltage cut off and discharging is stopped by other cells in the pack reaching the low voltage cut off. The net result of this is a lower batter overall capacity.
I am just adding to my system and active balancer, a small black box that takes charge from the highest voltage battery in the pack and discharges it into the lowest voltage battery in the back. The predicted result of this is all cells within 1mV of each other. The active BMS does this at 4 amps, my passive BMS balances at 200mA but only by discharging so it wastes energy.

 

[Mrjmegson]

That sounds like a cool little gadget, an active balancer.

So does that then stay on the system, you don't remove it once the pack is balanced?

I'll assume from what my supplier says, that I have an active BMS. My batteries are made by a company called Pytes, and they just look like Pylontech in white boxes.

 

[johnb2713]

That sounds like a cool little gadget, an active balancer.

So does that then stay on the system, you don't remove it once the pack is balanced?

I'll assume from what my supplier says, that I have an active BMS. My batteries are made by a company called Pytes, and they just look like Pylontech in white boxes.

It stays on the system all of the time and keeps them perfectly balanced in all modes of operation - charging / discharging.

 

[Mrjmegson]

Sounds like an essential bit of kit