[Newbie] How to use more of the battery during peak? (Octopus Cosy)

danhaywood

Hi,
I'm using WW to charge my battery during the cheap periods on Octopus Cosy (4-7am, 1pm-4pm, 10pm-12am) and then switch to Eco mode outside of those hours, in particular during peak period (4pm-7pm) in order to minimise costs.

Generally the battery is pretty close to 100% by the time 4pm comes around, and then I do indeed see the battery picking up some of the load at 4pm. However, it doesn't fully use the battery during this time

zooming in on 4pm-7pm, you can see that about 2/3 of the load was picked up by the battery, but there was plenty of capacity.

I'm wondering if a discharge schedule would be the right approach? On the advanced panel I also see:

but I didn't yet figure out what they are for or if they are relevant?

WindyMiller

If the battery isn't supplying all the load first check all the settings in the portal to make sure there is nothing there limiting the battery. This might include the battery discharge current level which should be at your inverter limit (be it 3KW, 3.6KW or 5KW depending on model).

The graphs seem to be showing that the batteries are providing a proportion of the load eg 2/3rd. So if the house wants 3KW the battery supplies 2KW but the grid still provides the other 1KW. The proportion seems to stay the same whatever the house load eg if the house wants 1.5KW, the battery supplies 1KW and the grid 0.5KW. Do you think this is what is happening? It could be that the inverter is mis-calculating what the load really is so I would check the current clamp to make sure it is on the right cable and is clipped tight shut. It should be on one of the wires from the meter cabinet to your distribution unit but it might be inside your distribution unit (box with the MCB/fuses) as mine is.

If you don't feel comfortable with mains voltage items then ask for some advice from your installer who should be able to tell you what to check.

WindyMiller

I have also noticed in the graph that the battery sometimes supplies the full 3KW when the load is much higher. This happening at 3am and again for a bit after 10am. This seems to say that it isn't a limit in the inverter.

I've attached my graph to show you what to expect (although mine is also showing Solar for today).

You can see that after the charge at 5am the battery picks up the whole house load (even 3KW of the Kettle spike at 7am and dishwasher and washing machine later in the day were supplied by Solar and Battery with no grid import.).

PS I'm on the Agile tariff rather than Cosy but that shouldn't matter here. It's just I charge at different times to you.

danhaywood

Thanks for sharing that graph, I'm very envious of your low consumption! And yes, I agree with your analysis - for some reason my inverter never wants to use the battery to cover more than 2/3 of the load, and usually somewhat less (1/3 to 1/2). On those cases where we go over about 5kW then it does indeed draw up to the 3kW from the battery.

It does kinda feels like it is mis-calibrated. As your first post suggested, I'll see if I can find and check this current clamp.

Thanks

danhaywood

So, I think I found it ...

what do you reckon? I see a gap there so my suspicion is that this is clamp is designed for a thicker cable, and the installers didn't have quite the correct clamp on hand. But I'm just guessing, I don't understand the physics here.

WindyMiller

danhaywood That looks ok to me. The gap around the cable is fine as it doesn't need to be tight round the cable. What is important is that the clamp completely goes round the cable with no gap where the clip is and I can see that the clip is tight with no gap.

So the problem must lie elsewhere. I would send your graphs and that photo to your installer and ask them why it is happening. They may not know but should be able to ask Givenergy to take a look to make sure everything has been installed correctly and that all the registers are set to the correct values. There may well be a register that tells the inverter to limit how much current to take from the battery. At the moment it is difficult to get Givenergy to respond directly to customers as they are prioritising requests from installers.

(The physics is that it creates a transformer with a single turn on one side (where the brown wire goes through) which is why the clip needs to be tight so that the magnetic coupling is complete. The transformer converts electric current in the large brown wire to magnetism round the clamp and then back to electric current in the white and black wires you see. This avoids the mains electricity being sent to the Inverter sensor input. But the current in the white and black wires follows the current in the brown wire thereby allowing the inverter to measure the house load).

WindyMiller

You could also try asking your question on the main Givenergy forum where there are a lot of people more knowledgeable than myself. Someone may already have fixed this type of problem.

https://community.givenergy.cloud/

danhaywood

Thanks for the advice, Windy! Will do.