Octopus Ready inverter (batteries)

waqasahmed

So there are inverters out there that are compatible with Octopus Energy, to take advantage of the very rare times that there's plunge pricing 

How much energy could you actually pull into say a 3kWh battery, for half an hour, directly from the grid?

They do very rarely have say a negative 2.2p rate 

pete-20-11

Depends on the maximum charge rate of the inverter and the battery, mine is max 3kW through the inverter and max 2.6kW into the battery (a 5.2kWh battery, max charge is 0.5 of the size with GivEnergy), so in half an hour, 1.3kW. 

waqasahmed

pete-20-11 said:

Depends on the maximum charge rate of the inverter and the battery, mine is max 3kW through the inverter and max 2.6kW into the battery (a 5.2kWh battery, max charge is 0.5 of the size with GivEnergy), so in half an hour, 1.3kW. 

If you have say five of them, would you still be limited to 2.6kW? And not say 6.5 kw? 

propnut

The rate of charge or discharge is determined by the inverter - conversion losses. A 3.6KW Inverter for example can only deliver +- 3.4KW at 96% efficiency. but realistically 3.2KW and then you have to factor in the C. rate of the batteries themselves. Never believe what manufacturers or resellers tell you. The figures are all massaged at higher values and like car mpg never attainable outside of perfect lab conditions.

waqasahmed

propnut said:

The rate of charge or discharge is determined by the inverter - conversion losses. A 3.6KW Inverter for example can only deliver +- 3.4KW at 96% efficiency. but realistically 3.2KW and then you have to factor in the C. rate of the batteries themselves. Never believe what manufacturers or resellers tell you. The figures are all massaged at higher values and like car mpg never attainable outside of perfect lab conditions.

So realistically if I've got 15 kWh worth of batteries and a 6Kw inverter, I'd probably be able to pull say 5 kW during plunge pricing? Ie :, 15kw would probably be five lots of three 

pete-20-11

Each battery could have its own inverter, but obviously that puts the price up.

it can also add complexities, e.g. do the two inverters play nicely with each other or does one battery end up draining to charge up the other. The system from GivEnergy sometimes has this problem, they say they’ll release a new box that can deal with that issue, but not sure when. 

Get solar too for best results! Batteries alone might not break even, complex maths to be considered! And get as many solar panels as you can fit on the roof - whilst paying for scaffolding it makes sense to max out the investment! 

waqasahmed

pete-20-11 said:

Each battery could have its own inverter, but obviously that puts the price up.

it can also add complexities, e.g. do the two inverters play nicely with each other or does one battery end up draining to charge up the other. The system from GivEnergy sometimes has this problem, they say they’ll release a new box that can deal with that issue, but not sure when. 

Get solar too for best results! Batteries alone might not break even, complex maths to be considered! And get as many solar panels as you can fit on the roof - whilst paying for scaffolding it makes sense to max out the investment! 

I've already got solar. I've been told that when I get my next 8 panels I'll have to upgrade my inverter anyway

propnut

waqasahmed said:

propnut said:
So realistically if I've got 15 kWh worth of batteries and a 6Kw inverter, I'd probably be able to pull say 5 kW during plunge pricing? Ie :, 15kw would probably be five lots of three 

In a way yes.

The 15Kwh is the total claimed storage capacity vs the actual useable. There is generally a large discrepancy but anyway consider the battery like a 44 gallon drum and think of the Inverter like a hose pipe. Although the drum can hold 44 gallons you can't just fill it immediately to capacity. The time it takes is down to the flow rate through the hosepipe which is determined not only by the rate of flow of water coming out the tap (your solar panels) but also by the diameter and length of the hosepipe (your inverter) Now if I had two taps and two hospipes then I could fill it at twice the rate (two inverters in parallel) or if I attached it to a larger flow tap e.g. the Fire hydrant and used a firehose (bigger capacity inverter)  then I could possibly fill it in a third of the given time. But then I would just move the problem somewhere else although it may be less notceable. There is always a bottle neck. 

Everything has limitations, you need to understand them and that way you can work within those parameters or design around them.

waqasahmed

propnut said:

waqasahmed said:

propnut said:
So realistically if I've got 15 kWh worth of batteries and a 6Kw inverter, I'd probably be able to pull say 5 kW during plunge pricing? Ie :, 15kw would probably be five lots of three 

In a way yes.

The 15Kwh is the total claimed storage capacity vs the actual useable. There is generally a large discrepancy but anyway consider the battery like a 44 gallon drum and think of the Inverter like a hose pipe. Although the drum can hold 44 gallons you can't just fill it immediately to capacity. The time it takes is down to the flow rate through the hosepipe which is determined not only by the rate of flow of water coming out the tap (your solar panels) but also by the diameter and length of the hosepipe (your inverter) Now if I had two taps and two hospipes then I could fill it at twice the rate (two inverters in parallel) or if I attached it to a larger flow tap e.g. the Fire hydrant and used a firehose (bigger capacity inverter)  then I could possibly fill it in a third of the given time. But then I would just move the problem somewhere else although it may be less notceable. There is always a bottle neck. 

Everything has limitations, you need to understand them and that way you can work within those parameters or design around them.

Thanks. I understand the use of a bottleneck. I was just wondering how much I could theoretically push out. I figured that if I've got 15 kWh of batteries, with my bottleneck being the inverter and having a certain charge rate, that's something to work from

That's pretty good tbf if I could theoretically pull 5 kWh for cheaper than free, and then get the rest from agile and the sun 

Screwdriva

waqasahmed said:

I've already got solar. I've been told that when I get my next 8 panels I'll have to upgrade my inverter anyway

I'm in the same boat - going to get the MyEnergi Libbi battery when the time comes. It would appear to provide the best specs and compatibility with existing high voltage systems. Given their focus on smart tariffs, I wouldn't be surprised if the battery interface is remarkably intuitive. 

waqasahmed

Screwdriva said:

waqasahmed said:

I've already got solar. I've been told that when I get my next 8 panels I'll have to upgrade my inverter anyway

I'm in the same boat - going to get the MyEnergi Libbi battery when the time comes. It would appear to provide the best specs and compatibility with existing high voltage systems. Given their focus on smart tariffs, I wouldn't be surprised if the battery interface is remarkably intuitive. 

What inverter does that support?