On-grid domestic battery storage

joefizz

Reed, as others have said, thats roughly what you would expect. Your earlier posted graph seemed to show regular load spiking to 200w or so, more on than off and if it was only the fridge and freezer then there might have been something wrong.


Youd mentioned the boiler not coming on during the graph period and that spike shows on there.


Ive a similar base load as well to keep the battery going during the night and not switching (fridge, freezers, tropical fishtank etc).

mmmmikey

An update after a few days experience with the 4kWh PowerVault (no big surprises).....

1. The accuracy of the monitoring at the low levels I've been using is not up to detailed analysis - think along the lines of the whole house monitors with current clamps. Perfectly adequate to see what's going on but not up to accurately measuring low power consumption (less than about 0.5kWh). I had expected this (more accurate data was more of a nice to have than essential for me), though I suspect for many here it would be a disappointment. The montioring is very good at doing what it is designed to do - giving a clear, easy read display for the typical user - but it's not a scientific instrument! I have to say I think the web portal is superbly designed, I can see straight away what's flowing where and how big the flows are without my glasses on from a quick glance at the display. I've also got a better idea of export than I've ever had before. Ticks the boxes for me, but probably not for everyone here.

(Edit - this could be nonsense, I may just be seing the effect of frequency response / grid services)


2. It looks like I'm importing about 0.5kWh per day, loaded towards off peak usage, even though there's plenty of energy in the battery. This could be explained by use below the switching threshold and use during the switching delays (a second or so). Again, in line with recent expectations, although slightly more than I had budgeted for when I did the sums (but not enough to make a material difference). I need to run this for a lot longer to get accurate figures from my supply meter, which only displays to the nearest kWh. (Not related to the battery, but the fridge-freezer and washing machine I replaced last year are using less energy than expected so my potential for summer savings are less - putting me a bit down on expected savings - an error rather than a bad assumption).

(Edit - same again, load could be due to frequency response / grid services)

3. Very easy to control the water heating manually to fully heat the water and keep the battery charged so far, but we've had wall to wall sunshine here for a few days so not much of a test. It's just a question of putting the PowerVault into charge only mode when the sun's shining and the battery's charged and then switching on the immersion that the Solic 200 controls. I've got the bits and bobs of electronic stuff out the loft to start prototyping a control to automate this, will report on progress as and when if anyone's interested.


(Edit - will hold fire until I have understood what frequency response / grid services is doing)


4. The next few days will be a much better test as more typical April weather is forecast. If all goes well, I'll be able to charge the battery twice a day to provide enough free heating during the e7 peak period without buying any. I'll charge it once overnight on e7 for early morning use then allow it to charge from the solar pv for evening use. If this works (and I don't see why it won't) I'll be in a somewhat better place than budgeted for, as I only allowed for one cycle per day during the heating months.

So current best guess is the economics are going to work out about as expected, with an overestimate of summer savings balanced out by better heating season savings, but not enough data yet.

Very pleased with service from PowerVault - small trim piece that was missing when the unit was delivered arrived in the post today.

Hope this is of interest.....

Zarch

mmmmikey wrote: »

Hope this is of interest.....

Battery geekery is ALWAYS of interest...... keep it coming folks!! :rotfl:

mmmmikey

Err - hold the press - think I may have been talking nonsense when I wrote that last post. The effects I'm seeing around accuracy and background import could be explained by the frequency response / grid services functionality doing it's thing. Will check with Powervault later and post an update

1961Nick

Zarch wrote: »

Battery geekery is ALWAYS of interest...... keep it coming folks!! :rotfl:

On Sunday I got round to fitting an import/export meter to the battery inverter to accurately measure the round trip loss. The job went fine, but unfortunately the meter is set to record import & export but only display import....Grrrrrr.

To get it to alternate between import & export I'll need an optical probe to reconfigure it. I've contacted all the electricians I know. but nobody has this elusive bit of kit - most hadn't even heard of it!

Plan B is to buy another meter with a 'scroll' button or a meter already configured to display import & export. I could then fit this meter before the consumer unit to accurately measure export.

Zarch

1961Nick wrote: »

Plan B is to buy another meter with a 'scroll' button or a meter already configured to display import & export. I could then fit this meter before the consumer unit to accurately measure export.

I know I bang on about my emonPi all the time for differentiating between ins and outs, but maybe something like that could be an option in this situation?

There is always talk over on their forum about tinkering with self-built projects and arduino boards etc?

https://community.openenergymonitor.org/

1961Nick

Zarch wrote: »

I know I bang on about my emonPi all the time for differentiating between ins and outs, but maybe something like that could be an option in this situation?

There is always talk over on their forum about tinkering with self-built projects and arduino boards etc?

https://community.openenergymonitor.org/

I've looked at this kit before & it seems very good.....although the forum was too geeky for my limited knowledge.:D

My battery inverter already monitors charge/discharge using clamps...but with the usual clamp inaccuracy. The reason for the meter is to get a truly accurate reading of the round trip loss.

Martyn1981

1961Nick wrote: »

Plan B is to buy another meter with a 'scroll' button or a meter already configured to display import & export. I could then fit this meter before the consumer unit to accurately measure export.

Please don't laugh, as this may be complete gibberish, but could you just get a basic import meter and 'wire it backwards*', so it records export, whilst the meter you have records import?

*I don't really mean wire it backwards, but I'm assuming that if you took a standard meter and swapped the cables round, so the in was now in the out and vice versa, then it would continue to only record units in one direction, but that would now be the direction you desire?

1961Nick

Martyn1981 wrote: »

Please don't laugh, as this may be complete gibberish, but could you just get a basic import meter and 'wire it backwards*', so it records export, whilst the meter you have records import?

*I don't really mean wire it backwards, but I'm assuming that if you took a standard meter and swapped the cables round, so the in was now in the out and vice versa, then it would continue to only record units in one direction, but that would now be the direction you desire?

Wiring it backwards is actually how it's done.:D

I did consider getting another meter & having 2, but there's no cost benefit over getting one that's already programmed to display both registers.

joefizz

1961Nick wrote: »

To get it to alternate between import & export I'll need an optical probe to reconfigure it. I've contacted all the electricians I know. but nobody has this elusive bit of kit - most hadn't even heard of it!

MCS installer might have one, as might PAT testers.
Current or ex utility service engineers should have them as well.


Probably cheaper just to get 2nd meter. If I lived near the manufacturer Id give them a shout in person and see if they would do it or sell you one already configured and stick yours on ebay. They probably cant do it legally online or on the phone or such like so probably wouldnt be able to do it in person either or by return of post or...