On-grid domestic battery storage

Right, update, finally got the ASHP connected, will try to answer a few points in previous posts based on what Ive seen.


Losses observed through Solarman/Solaredge apps. Ive found these at times to be spot on (measured using a power meter) and wildly inaccurate, as a result I just use the data as guides for trends rather than absolutes. Sometimes I see a solution for the inaccuracies (not accounting for base load, or applying a different load or perhaps even inductive loads) but its scarcely repeatable. As a result I dont use the base values (more later) just the rough values. For example today my soc on the app was reading 99% and reflecting the accurate load but on the sofar inverter display it was 82% (accurate) and accurate load.

The app usually shows a generation load of 10W or sometimes more for me in the middle of the night so its not solar generation. Hence not really paying too much attention to the displayed values but as mikey mentioned they are more accurate at higher drains, its where it all gets lost in the minimum export, solar panels sticking out 35w scenarios.

I have an always on base load (tropical fishtank, pump etc - not heater as its intermittent) which keeps the battery above the threshold, so when solar goes dark the battery switches once. When it goes dark you cant tell as I mentioned above, panels may be sticking out stuff too low to monitor but enough to stop the circuit switching the battery over tripping. The only time Ive heard the sofar oscillate with battery switching is when solar output is in and around a changing load (so the always export trigger bit goes) and when testing the induction hob in isolation.

I have heard it triggering at night when theres very little load and a good charge in the batteries but that could be anything really.



COP charts. Yes, agree they would be useful but like above only up to a point. My ASHP came with a cop reading but in the small print, not for my region and only for a limited temperature range. Im not even sure how you would measure it accurately in situ. I mean compared to what, halogen heater, resistive electric bar fire etc etc. They are a good guide but particularly with my installation up and running, its just that a guide (again more later). I suspect they arent published for the very reason a lot of the charts arent published, i.e. in a lot of real world examples they dont make good sales patter. gaussian curve, bell curve, exponential drop off, take your guess, I dont think its a good long plateau line though ;-) Well that and the curves would need to be produced for a range of relative humidities, absolute external temperatures and relative temperatures, again I wouldnt think a lot of those would make good reading for sales people... My ASHP has a published cop of 4 on a wee energy sticker. There is a wee map of europe below and there are no published data sets for ireland, southern england, most of spain/portugal, southern italy, greece, scandanavia, russia, most of eastern europe etc. Its all fiddle factor anyway, but there is no doubt its a force multiplier.



Solarman charts, one of the most interesting I find this the SoC (state of charge) over the day and what I use as a main guide rather than power used etc etc. Again I treat it with a large pinch of salt but it gives a good accurate impression and the data from the start of the month is what Im using for my initial ASHP tests. Again its the chart data, not the actual data (again more later).



I mentioned before that its probably the mtbf of the individual cells that is the key to a lot of this with batteries rather than the actual units. I mentioned my history with AA recharging and some go dud quite quickly and some just die a slow death over time. In high drain usage the go dud quickly ones are easy to spot as they kill the rest (sets of 4 only) but the slow death ones need regular checks and management to sort out. I do a manual battery management system where the slow death ones have their mAh ratings tested every so often and they are all matched up to lower drain applications (usually household ones).
I dont see say the pylontech batteries being any different. I havent taken one apart just yet but going by some of their youtube presentations it seems they are in batch units so in a couple of years time alibaba, ebay or amazon will probably be doing modules you can put in yourself, or just if you get one that goes dead might be worth testing if you have the skills or taking to someone to test as these particular skill sets will become more widespread as it starts to happen with electric cars and batteries etc etc.


Right on to the ASHP, few people have asked me for details so here they are. I bought this..
https://www.appliancesdirect.co.uk/p/eiq-12wminvqc/electriq-eiq12wminvqc-wall-split-air-conditioner
and from those guys, no connection whatsover. I also bought the wall mount instead of making one and was soo glad I did, saved me hours of time but more on that later.


Heres my rational for the purchase (discount if you like but its my rational for my circumstances).Years ago I signed up for an electricity company that was 100% renewables and then spent years minimising my usage. When it got to a certain level I then redesigned my house to minimise my oil usage. Id gotten to the point on both that Id hit the laws of diminishing returns (e.g. 50cm loft insulation, 12mm floor insulation, resealing the double glazing, patching up every drafty spot and loads of other things. I did shelve the idea of ripping the plasterboard off every external wall and then replacing the 80s timber framed insulation with modern kingspan, refitting the vapour barrier and replastering. I wised up after doing it in just one room (the bathroom, the smallest, needed to fit a false wall anyway.. got builders in for that).
Company got bought out by one of the big guys and went to general population, obviously not 100% renewables any more (they still are in ROI but down to 30% in NI but back up to 36%). My current supplier is about the same, with higher per unit prices but had an initial sign on bonus a couple of years ago which more than made up the difference.
It was then I decided to get the solar panels in and as NI ROCs were halving again it was worth the money. Battery system was always the aim at some point and various other factors came in to play june last year so bought one. Upgraded in Jan to 9.6kW which is probably about twice as much as I need in reality but will pretty much smooth out dull days from late Feb right through to November. In other words Id be surprised if my imported electric bill was more than about 20 quid (or even 10 quid) for that period from now on.
With the batteries and tracking the SoC (state of charge, percentage battery used) it became apparent that I couple load and empty the batteries a couple of times per day in summer at no cost (other than duty cycle cost but again long finger I can probably identify and fix most of those issues myself so not really factored in in my equations). So set about moving things back to electric usages as things wore out (lawnmower back to electric from fossil, less reliance on battery tools to mains, not replacing low voltage battery powered garden lighting, pump, etc and not replacing business equipment ups (as now had a ups for the house)). As I documented before, changed lifestyle quite a bit to maximise this and to make cost savings in areas not associated directly with the panels and batteries but what the free electricity could facilitate.

I used to work in telecommunications and when your company released a new faster, higher capacity bit of kit the americans and the british would ask how much extra they could charge for it, the scandanavian telcos gave it to their people to see what they could do with it. (The chinese now do this so a similar extent).
So I changed my mindset to see what I could do with it.

Ive reduced my home heating oil consumption down from over 2000 litres a year to about 1100 but in winter months theres no alternative for me for heating and hot water.
With the battery system I could now use the push button immersion heater to give enough hot water for the shower so for about 3 months of the year used no oil at all (didnt need heating with the insulation etc).

In shoulder months my oil heating is timed twice - one from about 10pm to say 1pm (times vary with year) and at about 6am-8am, again times vary. If I could replace the first or even both with ashp using the spare battery it might be possible to reduce my oil consumption down to the region of 600l a year.
So that would be it, my entire household and business (outside of car travel) would be down to 600l of oil per year and less than 150 quid of electricity, plus other incidental savings, other lifestyle options (hot tub, infra red sauna etc etc)


So the latest installment is the ASHP pump mentioned above. Dont really care about cop as its not externally installed in an ideal place (would need planning permission here in NI for the ideal spot) and internally its not great either (but better once I was doing it when I thought about it, but I digress). Its in now.
Installing was straightforward enough, have it at the end of the hall in my bungalow facing the front door, doors off the hall into every room. Primarily over main bedroom, bathroom, office. I keep the rooms separate temperatures and each room has separate losses due to external walls, bloody great windows etc etc. Key figures are 18-20C in the main bedroom, 20-21C in the office and around 19C in spare room, 19-20C in living room although large plasma and big home cinema setup in living room so probably about 300-400W of heat losses right there ;-)

When everything measured up, it was pretty much initial cost that was the key decider, get me something at less than one annual oil bill, decent enough guide cop, put it in and see how I get on. Self install to keep costs down as its only an experiment.
Bought the one above as it has the quick connector option so although I have a very well kitted out workshop and garage (including vacuum pump and gauges) it would be less faffing around.
Bought their wall mount and it was excellent (came ready with all the fixtures and fittings - small spirit level built in - not totally accurate but not far off, large wall mounts - 12mm long masonry bit required, 13mm bolt heads). If going to do it yourself I recommend hand tightening all the bolts with a long/large torque wrench/mechanics socket wrench. My house build is ok but the red 80s brick seems to blow a lot when you tighen a bolt with a windy gun, electric or even battery powered torque wrench. Plus it gives you the chance to hand tighten everything up when all in final place. The bracket also comes with rubber anti vibration mounts which are a better quality than the stuff in the ashp kit. Id consider getting a couple of extra rubber/silicone mount rings as you can use those to balance the level out if you dont get it quite right first time.
The QC connector is good, makes the connecting up really easy, they have an online video but it doesnt mention to hold on to the blank cover as you connect up, it shoots off like a bullet and hit my bathroom window frame, from the speed and noise if it had hit the glass Id be going down to the glass suppliers tomorrow.
The units themselves are cheap looking, well most of the differential in this type of equipment is in how the housings are put together. Neither the internal or external will put up with much punishment but I dont have any kids and even I learned not to play football in the hall years ago.
I wouldnt even think of opening them up to invalidate my warranty but if I did I might see reasonable spec electronics, reasonably well put together and core components probably in a format seen in the larger manufacturers... thats if I wanted to invalidate my warranty of course, which I dont.
Its the plastics in the interior and flimsiness of the exterior metals which are the diffence between products (much as I suspected). The internal machine will probably rattle a bit in time (only 3 screws into cheap plastic holding it together with the rest push clips and clips into plastic) but nothing a bit of blu tack, silicone sealer or other fix wouldnt sort out. The flap to access the filters will probably not last its first couple of openings, the hinges might need a bit of plastic welding (blu tack etc) and the catches will break through time but again no biggy. I dont like the look of the shiny cheap chinese plastic cover though and it is what everyone will see coming in, but again if I wanted to invalidate my warranty Id just take some car polish or abrasive pad to it to matt it down a lot.
Externally the case is solid enough for wall mounting or ground mounting out of the way but as one of my mates said 'you'll have to stop kids going near it'. The side protection wires are flimsy (easily bent back to maybe give access to the fan, although they would have to be determined) and if mounting on the ground with toddlers in the vicinity... anyway youd probably have to be more careful with more expensive units anyway.
They are all CE marked with certificates but as we all know CE has come to mean 'chinese equipment' rather than adhere to any european quality mark and yes that lovely iso accreditation for how the plastic doesnt dissolve in uv light might be really good in a tanning salon, pretty much useless to most of us.
I dont think these units will be popular with installers as they just arent robust enough for most jobbing pros, too many bits to easily break off when moving around, throwing up on walls and they look cheap. IF you are charging as much again for installation, may as well do the same again and put a brand name unit in.



In operation both units are quieter than I thought it would be. I was going to say the external unit was quieter than my hot tub pump but thats a bit like the billy connolly afghan melon sketch..


Function set is quite good (heating, cooling, dehumidifier, fan, ioniser). If we get another summer like last year the air con will be a god send (part of the reason for buying, had a couple of fans running here in the office last year but too hot to work and couldnt buy a portable air con unit anywhere on the island of ireland for love nor money).


Despite the finish, it was easy to put in, function set suits my needs and all I need to do is test it. Mine came with the connection pipes attached in a handy wrapped cable. If doing it yourself and beyond basic straight lines, curves then anyone who has made copper brake pipes for a car before will be able to do it. I even used the cheap tool I have for doing brake pipes in the alfa for this. Tip, again if doing yourself, take the protective velcro wraparound material off the pipes at bend sites so you can bend each pipe individually and then replace, much easier that way.
I put the drain pipe through the wall into the bathroom and put the extension pipe (supplied) on it and directly into the shower. I will tidy that up a bit but occasionally I need deionised water which doesnt need to be sterile/pure so the output will save me a couple of trips to suppliers a year ;-)


Overall Im pretty pleased with it, it meets my requirements from all of the above and that was before I put it into use.
Since 1st April my overnight SoC has never dropped below 50% (working to 10 most nights, background stuff, coffee, toast in the morning before starts charging again etc).
I figured I could probably stick about 1.8kWh into the ASHP and see what happens for a week or so. Its been exceptionally cold here this weekend though and below 2C overnight so probably not going to give an accurate result for what I want.

The unit comes with a 3 pin plug, so Ive given it a dedicated spur in the loft and also put an accurate power meter on the socket to give me an exact figure. I'll probably just be lazy though and limit it to 25% SoC on the solarman app on my phone.

I realise this isnt the way most people would use it but Im used now to doing a burst of oil heating late and night and with the way my house is insulated its not until mid morning that it needs another burst.
I dont fancy sitting up late all night monitoring it so decided to stick to this burst approach and turned off the first oil burst.
The first time I tried it I put the ashp up full and didnt reach 1.8kWh before it had brought it up to the levels of room temp I was getting with oil. Pretty much using it as a one shot space heater for the house.

Went to bed, woke up at 4am and bedroom had gone to 17C which is probably why I woke up in the first place. Not bad though and certainly plenty of scope there, suspect the very low temps outside had something to do with both and again to be honest dont know if my latest oil setting would have coped with the cold snap either.
Will of course experiment with using it as a constant temperature tool, the way it is intended but first want to get an idea of the electricity usage to just run the thing under different external temperatures.



Way too early to make a call but it is encouraging. In the short term I can see it definitely using the overnight excess to remove at least one of my timed oil bursts. In fact today had friends round to see the match and when I came in house temp was down to 15C, instead of doing a +1 hour on the oil heating I put the ASHP on full blast for about 1/2 hour and it was only slightly drawing down from the battery (daytime, about 1.5kw produced).


I'll never probably use it in winter, and it wont replace my oil heating (need planning permission to do that anyway) but there is scope there and looks promising for achieving my initial aim. If it does payback time should be well could be 1-2 years 2-3 years depending on oil price, although it might also shift me into summer oil buying season when prices are lower. Without the battery though, running it at night and in early morning wouldnt be a goer, although again if you were to get a couple of dull days forecast it might just be handier to switch the oil.

From just a couple of days use though it does give me remarkable flexibility to hit either +1 on the ASHP or +1 on the oil central heating to give the same effect and I hadnt really considered that before getting it up and running.


I know Ive to get back to a couple of you on pms with stuff and I will do those tomorrow but wanted to get this out there now whilst it was all still fresh.

mmmmikey wrote: »

joefizz - you get the prize for the longest post in the world ever! Picking up on one point....

A question for the battery owners club (which I shall hopefully be joining tomorrow) - how much of the capacity of your battery do you actually use? Does the battery spend most of it's time towards the top of it's charge state, constantly topped up by solar, or do you regularly hit the bottom while you wait for the sun to come out again?

1961Nick - any stats on this?

I have some stats.....:D

These are the number of days the batteries have made it through to sunrise with some remaining charge......

Feb: 1
March: 3
April: 5 (outside chance tonight as well)

With the original 8.2kWh it was unlikely that the charge would last the night. Even with 10.4kWh usable, it's still pretty marginal at this time of year.

The total export over that period was 60 kWh. 10kWh was due to me setting the wrong profile on the inverter, 20kWh is due to ramp up/down & flipping between charge/discharge, the remaining 30kWh is due to fully charged batteries.

I'm toying with getting a 6th battery & raising the DOD to 20% for longer battery life. That will mean I always have spare capacity for the EPS, even when they're in standby. During the winter months, I'd take two fully charged ones offline for EPS duty - 4.4kWh can run lights, shower pumps, the TV & the GCH for several hours.

Agreed....Joe's post is the longest I've ever seen.....Epic!

At the risk of diverting the thread discussion:


My present inverter is looking unwell (at least its LED screen has now died though it seems to still be generating) I've been thinking of putting in battery backup anyway and I understand its easier to do with a new (designed to go with battery packs) inverter at the same time.


I can take it to another thread but whose good to look at. many seem to have whole package deals ie panels/invet/battery now which is no use to me.

mmmmikey wrote: »

Had my first jacket potato cooked solely with battery power this evening - feels like one of life's great milestones


Thanks for posts re: battery state of charge, reason for asking is that I suspect that my combination of load, solar generation and battery capacity mean that I'll be using it a bit differently than expected, with multiple small cycles during the day as it smooths out the peaks and troughs of solar generation, wouldn't be surprised if I run it at 80% + charge most of the time, but still get the 3kWh per day from it during e7 peak.



Time will tell....

Congratulations on your new arrival.:cool:

It’ll take a few days, but you’ll soon get the hang of how to get the best out of it...despite Mrs Mikey doing her best to scupper those plans!

mmmmikey wrote: »

We got divorced a few years back. Some might think this is a bit of an extreme reaction to running the washing machine and dishwasher together, but I take this green energy stuff very seriously.....

Based on the last 2 hours data, the battery will pay for itself in about 4.5 years. This is much better than expected, although I will concede might be best to collect a bit more data before I bank on this

A couple of initial observations, confirming expectations:

The instantaneous monitoring shows me consuming more than the battery, solar panels and grid are providing. So round trip losses are in fact round trip gains. Z must have been completely wrong, these things presumably have the same magic clay in them that make Fischer Future heaters so efficient Or possibly some issues with accuracy of current clamps monitoring at low levels? So although the portal gives me decent visibility of the big picture it's going to be of limited help fine-tuning. Expected this, no big deal. The upside is I now have visibility of export, albeit with limitations around accuracy, but more than I had before.

The immersion controller (Solic 200) is already jealous of the battery and refusing to play nicely with it! Kettle comes on, battery detects import and starts to power kettle, kettle goes off but unbeknown to battery the immersion controller is waiting to pounce and sees this before the battery does and tricks the battery into continuing to drain itself by heating the water. The immersion controller is a spiteful little !!!!!! - I've turned it off for now! Lots I can do with scheduling to avoid this and PowerVault warned me it can be a bit fiddly to get them working togther, so again no big deal.

I can see I'm going to become completely absorbed by this for a few days (or weeks, or months....)

Thanks, Mike

I am pleased to hear first impressions are good. Keep up the reports.

Did you consider the 3eco option which uses second life EV batteries? I was wondering how the costs compared.

I had a similar issue of incompatibility between the IBoost and Moixa battery. I never really got to the bottom of it before the battery went back but there were times when the battery was heating hot water when it shouldn’t have. Moixa acknowledged there was an issue.