On-grid domestic battery storage

chamelion

Solarchaser said:

chamelion said:

Solarchaser said:

chamelion said:

Solarchaser said:

chamelion said:

Very limited and specific use case here but I've found something interesting...
I had switched to go faster tariff from agile. I have the batts charge up to 100% during the 5.5p 830pm - 130am slot, and from 130 onwards they contribute to the house. 

I previously had it trickle contributing - approx 300/350 watts to lower my profile for the day. However last night I bumped that to 1500w (my home baseline over 2500w) and got 15% more power out of them... 
I'll try again tonight with 2kw output. 

Sum of it is if you're doing something similar on go, sounds like you get more efficiency at higher wattage contributions rather than trickling. 

I'm not exactly sure what you mean.
Are you saying that you only usually get 6kw of discharge and now you get 7kw?

Basically yep. Not 7 (7.2kw system with 90% DoD) but there's a marked increase in total amount squeezed out the batteries when running at higher wattages. 

That is strange right enough, id put it down to a hiccup at this point to be honest, it's definitely not what I've found.
The only time I've had more than the 8.5kwh of discharge on my system is on sunnier days when after discharging for some of the morning its charged up by solar, and so discharges again later.

Running at 2kw output last night yielded 6.2kwh. At 1.5 it was 6, at 300w it was 5.8!!
Definitely a correlation. I'd chalk it down to a set 'overhead' that doesn't vary based on output, so the longer you have the unit on the more you're wasting to cover the overhead... 

So you have just set it to output a set amount?
And so you are exporting most of the output?

How long have you been tracking this for?

As Ev and PV said it should be more efficient lower down as not as much power is lost to heat. 
Unless of course you have it in an unheated part of the house and so the heat you generate actually helps get past the inefficiency of running it all cold

Yep have it at a set output. My home baseline is 2500w so I don't export anything running these at 2000w. 

Haven't really been tracking - only switched to go couple of weeks ago and noticed that the most I was contributing was 5.8kwh or so in a day from a fully charged battery outputting 300w, far less than 7.2 even after DoD consideration. 

Just tried to give it a shot to bump up the wattage and got a whole lot more out of it...
It's in an indoor closet which generally is warm - 18 degrees +. 

Only thing I can think of is the overhead of generation from the batteries that proportionally are smaller for larger outputs over a shorter period of time? 

Solarchaser

So your house uses 2500w constantly yet you were only using the lux for 300w?
If your base is 2500w, then surely they should always be discharging 2500w?

chamelion

Solarchaser said:

So your house uses 2500w constantly yet you were only using the lux for 300w?
If your base is 2500w, then surely they should always be discharging 2500w?

Was just testing during the 'high' period of my go faster tariff. Initial thought was averaging down my per unit costs for electricity by part contributing from a charged battery. 

Starfrog

Just trying to understand my usage and where i can minimise the use of energy and maximise my new Solar and battery solar is a 5460kw array and battery is a 4.8kw currently on bulb but moving over to Octopus. I only have oil boiler for all heating and electric, the electric heats hot water but i use an electric shower. (This will change when i get rid of oil and move to underfloor heating and air source heat pump, yes i know my electric use will go up) and the cooker is all electric but old and will be replaced but what with ? . I’m seeing over the last few days my consumed electric is around 14kw per day ! And it reached 22 yesterday !!! 4 showers a day cant help but that should be reduced when using air source heat pump for new hot water tank. Yesterday was 22kw but lots of baking. So my question is how best to minimise that usage. right now the solar is just not going to get enough sun to fully charge the battery (it did on the very first day the system was installed a week ago but that was the sunniest day) but should I charge it fully on the octopus 5p rate in the early hours 1am to 4am ? Is that long enough to charge a battery of 4.8kw and then let it power the morning usage before the solar kicks in to help and then hopefully it will be charged up again for use when the solar is done for the day. I’m trying to get the battery to power during the evening but not sure if i should get another 2.4 or 4.8 to give me a total of 9.6 which should maybe last from 5pm through the high cost period of electric to the cheap rate ?  Any tips very welcome. PS the house is getting a complete renovation so oil is being taken out and all new underfloor heating and new full house insulation as well as under floorboards and new triple glazing as the old double glazing is shot. Thank 

Starfrog

When am i allowed to add a signature ? It says I I’m not allowed ? At the moment 

EVandPV

To give you some idea, we have 7.2kwh batteries which charges in about 3 hours on full power so 4.8kwh will charge no problem during the Octopus Go period. I reckon 9.6kwh would probably make it too.
At this time of year, we charge it full every night on Go and probably will need to keep grid charging until about April before the pv (3kw) is able to provide enough power to charge the battery fully and get us through to the following morning. From then on, we can get right through 24 hours with very little import on good sunny days, some days as little as 0.2kwh.
We average around 10kwh a day and at the moment, the battery can make it to late evening most days provided we get enough pv to cover the base load through the day. If we don't use any high power stuff like the oven and washing machine, the battery lasts until the next Go period and we import very little, if any, at the full price.
 

Starfrog

Thanks for the really insightful info its very helpful. I need to get onto octopus quick even if i dont have a smart meter yet it would still benefit from the go period of charging the battery. I think the electric shower is what is driving my usage up but i think your right with my 5460kw solar array it should on good average sunny days be able to charge the battery ready for the evening, sounds like a 9.6kw system it would be more than enough to do that. 

Starfrog

Today looks bright already and exporting and charging battery although it says no power to the house which is strange as it should say at least something for fridge etc ? Ignore the location as the site is in Lochinver 

Starfrog

Another thing i notice is that solar production seems to top out at 3.5kw on the emphases report i assume thats due to the inverter lux being 3.6 ? So what happens with my excess production especially during the summer months i assume on a normal summer day with sun from 0800 to 1800 that ten hours at 3.5 potentially so 35kwh to the house/batteries and grid export ? Should i have a larger inverter ? Just curious its all new so not going to go crazy with adding stuff other than an extra battery but if I add an air source heat pump then i know I’ll want to get even more cover potentially but need to wait and see how the reduction in electric showers affect the usage as well as electric hot water tank 

EVandPV

You need a smart meter to get onto Go or Agile unfortunately.

Is your Lux a hybrid inverter ? That is, does it convert the dc from your solar to ac as well as controlling the batteries ?
Or do you have an inverter for solar and another (Lux) for the batteries ?