Battery maximum output

Reed_Richards

My battery, which has a 6.5 kWh capacity (LG RESU6.5), seems to have a maximum output of about 2.67 kW.  I'm not sure if this limit is set by the battery or by the inverter but it's a bit irritating because it means even if the battery is fully charged I cannot boil a 3 kW kettle without importing some electricity.  I don't recall ever seeing this issue discussed here so I don't know if this issue is normal or not.  If it's something that can vary then it should be quite an important consideration when choosing an inverter & battery conversation.  Thoughts?  

DougMLancs

In Givenergy’s case it’s inverter driven- their 1st Gen Hybrid would charge my 9.5kWh battery at 2.6kWh but the Gen 2 or 3 will charge the same battery at 3.6kWh. I found this out just before my install and immediately got the installer to swap the specced Gen 1 for a Gen 2. Some hybrid inverters like Sunsynk boast they will charge batteries at the full capacity of the inverter e.g. at 5kWh for a 5kW inverter. 

QrizB

I'm on my phone with dodgy 4G coverage, so I can't search effectively - the specs for your battery and inverter should tell you what discharge power each of those are capable of. The only other limits will be the connections from battery to inverter, and inverter to house.

I would expect there to be a battery discharge current limit in software in your inverter, and a separate charge current limit.

(For slightly involved reasons, I've limited my homebrew battery to a maximum output of 1250W (25A at 50V-ish). I bought a lower-powered kettle )

Reed_Richards

I was thinking more about discharging than charging as it looks to me as if the charging limit may vary according to the state of charge.  And my inverter knows what model of battery I have but seems to be imposing a smaller limiting discharge power than the battery specifications suggest, if I am reading these correctly.   

Exiled_Tyke

Discharge rates are limited to preserve battery life. I can change them for my (Solax) battery but wouldn't want to ask I presume the manufacturer has chosen a fair balance between maximising power and looking after the battery.  I'm also limited to about 2.7kW. If the sun is shining I'm find but otherwise I start to import  - but it's not a great deal.  

Charging also follows a similar pattern. It starts off at a maximum rate (which I'm never at risk of wanting to exceed) but then reduces as it gets close to maximum. 

ed110220

It's not something I thought much about either. My SPH5000 inverter can output 5 kW from the PV but is limited to 3 kW from the batteries. It's a bit irritating importing when you have energy in the batteries, as we often do because we have an induction hob and electric oven. I've learned to not use too many rings at once, bring things to the boil a bit more slowly (medium high rather than full power) etc. But the plus side is that it's more of an irritation and typically we don't go above 3 kW for long, so although you might be drawing a lot of power it doesn't add up to much.

1961Nick

Both the battery & the inverter will have a maximum output so in this case it could be either.

Pylontech US2000 batteries each have a maximum output of 1.2kWh. So if you want to maximise your Sofar ME3000 or Luxpower inverter you'll need 3 batteries.

ispookie666

They are limited by Inverter usually.  Sometimes, the BMS might have these limits set in.  But often, it will be set at 1C max, which means the battery will be able to supply energy but will empty in 1 hr, which would be 6.5KWh.  But you will unlikely be able to extract this, as the conversion losses and heat built-up will reduce the output efficiency.  

Yes, choosing the inverter output sizing and response times would be important.  

Mikeyboy01443

Exiled_Tyke said:

Discharge rates are limited to preserve battery life. I can change them for my (Solax) battery but wouldn't want to ask I presume the manufacturer has chosen a fair balance between maximising power and looking after the battery.  I'm also limited to about 2.7kW. If the sun is shining I'm find but otherwise I start to import  - but it's not a great deal.  

Charging also follows a similar pattern. It starts off at a maximum rate (which I'm never at risk of wanting to exceed) but then reduces as it gets close to maximum. 

Do you have a single battery setup? My dual battery solax can charge / discharge at 5kw+

zeupater

Reed_Richards said:

My battery, which has a 6.5 kWh capacity (LG RESU6.5), seems to have a maximum output of about 2.67 kW.  I'm not sure if this limit is set by the battery or by the inverter but it's a bit irritating because it means even if the battery is fully charged I cannot boil a 3 kW kettle without importing some electricity.  I don't recall ever seeing this issue discussed here so I don't know if this issue is normal or not.  If it's something that can vary then it should be quite an important consideration when choosing an inverter & battery conversation.  Thoughts?  

Hi

First thought ... if it's an issue, buy a ~1kW kettle - it's the cheapest & most easily addressable solution by far!

HTH - Z

Qyburn

zeupater said:

Reed_Richards said:

My battery, which has a 6.5 kWh capacity (LG RESU6.5), seems to have a maximum output of about 2.67 kW.  I'm not sure if this limit is set by the battery or by the inverter but it's a bit irritating because it means even if the battery is fully charged I cannot boil a 3 kW kettle without importing some electricity.  I don't recall ever seeing this issue discussed here so I don't know if this issue is normal or not.  If it's something that can vary then it should be quite an important consideration when choosing an inverter & battery conversation.  Thoughts?  

Hi

First thought ... if it's an issue, buy a ~1kW kettle - it's the cheapest & most easily addressable solution by far!

HTH - Z

There are plenty of 2200W or 2400W kettles available. Having said that, have you measured yours? Our Russell Hobbs is sold as "3000W" but actually draws 2700W.