Extending battery array - levelling charge

[xanld]

Hi, I have 3 x Growatt ML33RTA 3.3kWh batteries coupled to a Growatt SPH6000 Hybrid Inverter, and would like to add one more battery.

The installer wants to charge me over £1000 for installation as compared to buying myself. They say there are complications with levelling out charge before they can be installed. Does anyone have experience with this?

 

[johnb2713]

Thats ridiculous.

Charge your existing batteries to a known voltage slightly above the new batteries voltage eg 0.1v above, connect up, switch on.

I have done this with my new batteries that I have currently connected onto my existing SPH6000 and battery. The new battery isnt acknowledged by the inverter because of comms issues with the BMS (its going onto a Victron Inverter soon), the discharge current with 0.1v difference was less than 2 amps, not a problem at all.

 

[xanld]

@johnb2713

Thanks for this, that sounds exactly as I'd envisage. I'm not quite following your comms issue but it sounds like that probably wouldn't affect me, (what is BS?) Should I expect it to automatically recognise the increased battery capacity, or do I need to update any system configuration?

Thanks again.

 

[xanld]

oh, and how do I know the voltage of the new battery?

 

[johnb2713]

oh, and how do I know the voltage of the new battery?

A BMS is a battery management system, it’s built into the battery system.
You need a voltmeter, look on ebay at multimeters, you don’t need to go mad, £20 or so should be enough.
Measure the voltage on the new battery on the large power terminals, it will be in the order of 50v. Note the reading, check your existing battery and either charge or discharge to get the voltage close.

Set the switches for the battery number, connect up, switch on, job done.

 

[xanld]

No problem. I have a voltmeter I can check it with.

Set the switches for the battery number, connect up, switch on, job done.

Which switches?

 

[johnb2713]

There’s usually switches or maybe software setting to set a battery address.

 

[johnb2713]

There’s usually switches or maybe software setting to set a battery address.

Looking online at try he manual, there are no switches that I can see, it will be plug and play.

 

[johnb2713]

You can daisy chain up to 6 batteries according to the manual, it looks like the data link is also daisy chained.

 

[xanld]

Yes perfect, that's what I thought. Thanks for the confirmation.

I need to connect them up with a couple of bus bars. These 300A ones look like they're generally recommended.

 

[xanld]

Battery ordered!

 

[apprentice87]

oh, and how do I know the voltage of the new battery?

Not sure that someone that asks a question like that should be playing with electrics at all..

john..

 

[johnb2713]

Not sure that someone that asks a question like that should be playing with electrics at all..

john..

And if you don’t help / advise they may just go it alone. I’m perfectly happy to help the op via zoom call or whatever to get him through his battery install. Whilst I appreciate there’s a huge amount of current involved, the voltage is low.

Have you never asked for advice to tackle something new?

 

[johnb2713]

Battery ordered!

Did you order connecting leads as well or are they included with the battery?

 

[xanld]

Unclear. I contacted sales and they weren't sure either. It's been delivered now, but I'm away until Monday. We'll see. I'll order connecting leads separately if necessary.

 

[karlboldy0]

I’ve been looking into the same - where did you get your battery from out of interest?

I’ve found cables to get here - https://distribution.voltalia.com/e...cables-for-three-3-3kwh-battery-packs-growatt

 

[xanld]

I’ve been looking into the same - where did you get your battery from out of interest?

I’ve found cables to get here - https://distribution.voltalia.com/e...cables-for-three-3-3kwh-battery-packs-growatt

I got the battery from https://www.tradesparky.com/solarsparky/batteries/growatt/growatt-33kwh-battery-ml33rta-ip20

Thanks for the link on the cables, that's exactly what I needed. The battery did not come with cables.

 

[karlboldy0]

I got the battery from https://www.tradesparky.com/solarsparky/batteries/growatt/growatt-33kwh-battery-ml33rta-ip20

Thanks for the link on the cables, that's exactly what I needed. The battery did not come with cables.

Legend thanks for sharing that link - I’m trying to decide if I want 3 x 3.3kw batteries or to sell my 1 x 3.3kw existing battery and go for 2 x 6.5kw.

The process to check voltage and sync batteries to connect seems fairly straight forward too.

 

[xanld]

Legend thanks for sharing that link - I’m trying to decide if I want 3 x 3.3kw batteries or to sell my 1 x 3.3kw existing battery and go for 2 x 6.5kw.

The process to check voltage and sync batteries to connect seems fairly straight forward too.

I've decided to upgrade from 9 to 12 against general wisdom that 9 is plenty. I'm not sure it makes 100% economic sense, but I've been running for a couple of months and alread have had a dozen situations where some additional battery headroom would have helped avoid some export/import.

I think a key consideration is if you charge battery from the grid at off peak rates. During the winter I'm expecting to use a lot more than 12kwh including all the heating and car charging. The ability to have a full 12kwh of off peak energy available to see me through the dark days is some justification.

Honestly, a large factor is simply the satisfaction of having it. How much battery is enough is a topic we can rant on for hours. Go with your heart!

FWIW you could upgrade up to 18kWh with the ML33RTA s. I'm not sure what expansion options there are with the 6kwh ones?

 

[karlboldy0]

I've decided to upgrade from 9 to 12 against general wisdom that 9 is plenty. I'm not sure it makes 100% economic sense, but I've been running for a couple of months and alread have had a dozen situations where some additional battery headroom would have helped avoid some export/import.

I think a key consideration is if you charge battery from the grid at off peak rates. During the winter I'm expecting to use a lot more than 12kwh including all the heating and car charging. The ability to have a full 12kwh of off peak energy available to see me through the dark days is some justification.

Honestly, a large factor is simply the satisfaction of having it. How much battery is enough is a topic we can rant on for hours. Go with your heart!

FWIW you could upgrade up to 18kWh with the ML33RTA s. I'm not sure what expansion options there are with the 6kwh ones?

Sounds like a plan, if running 4 x 3.3 batteries are you going to run two double battery cable runs? I seem to recall the cables are available with 2 batteries or 3 on a single connection to the inverter.

Have you already added any batteries to get it to its current status?