After having the battery on order for a couple of months we've finally had it installed. We also had an EV charger installed at the same time. Thats a great addition as I can now fast charge at home and not need to use 7kW public charging in my nearby town.
install wasn't as straight forward as we'd hoped
As we had a hybrid inverter installed with the solar we'd hoped adding a battery would be a simple process. I have to say it was, except for one thing...... these weren't the Pylontech batteries we had ordered!
We were also unlucky that only half the screen worked on the Zappi charger. This meant it couldn't be set up properly as the bottom of the screen is pretty important! It could be used by you didn't know which charging mode it was in so it was a bit like playing Russian roulette with EV charging!
Prior to the Zappi/battery install date I was concerned charging the EV would drain the home battery. This concern centred around the home battery being much smaller than the EV. The EV could quite quickly drain it whilst charging at 7kW meaning there would be no power stored in the battery to run the house later.
I'd spoken to our installer about an alternative hard wired option (Hybrid PV & Battery - Set up & Avoid Draining). I'd come across when reading the Myenergi Support website. This should stop the EV draining the home battery whilst the EV is charging. Our installer said they hadn't done this before but they should be able to do this. Unfortunately crossed wires meant the installer on the day didn't know about this request. As the Zappi unit needed to be changed they would return with another unit and change the hard wiring at the same time.
Our installer offered for us to keep the two Dyness 5.1kW batteries that had been installed at no extra cost, or for them to order the Pylontech battery we had originally ordered. We decided that whilst the Dyness batteries weren't what we had ordered the higher capacity would future proof us much more so we decided to keep them. The Dyness batteries aren't as aesthetically pleasing to look at as the Pylontech battery but they are installed in our garage (aka the 'plant room') where no one but us will see them. It was definitely a function over form based decision.
Install Visit No. 2
Up to the second visit the home battery had been working fantastically as we'd hardly used any imported electricity to run the house. I'd also manage on a few occasions to get the faulty Zappi to run on Eco mode to use the excess solar generation. That was more luck than judgement getting it to work.
The good news was the replacement Zappi was working perfectly.
This time the Zappi was hard wired via its own consumer unit. Our tests pointed towards it working correctly as the Zappi wasn't draining the battery when fast charging at 7kW. We did noticed the inverter had now swapped the self sufficiency and exported readings around. I thought this wouldn't be too much of an issue as I could work out this data using the Octopus app.
It wasn't until the next day that I noticed things weren't working as they should. The battery wasn't discharging at all, even after the solar had stopped generating. It was obvious now that the reason the EV charged without draining the battery was because the battery wasn't discharging at all!
Having checked the data graphs I noticed a worrying trend. The battery was discharging at a constant 0.1kW, but was intermitterntly charging at 2kW for very short periods several times a day.
I spoke to our installer who said they would come back out to look at to see what's wrong. It was also decided that I should switch off the batteries in case the short charge periods could cause damage.
Researching a different solution
Considering the issues I was experiencing with the hard wiring solution I thought it would be best to research option potential solutions. On the Myenergi.info website I came across a forum post by brendan_donlon that was discussing how to do exactly what I wanted to do.
The basis of this solution is that if the battery is set to charge from the grid mains supply the battery won't discharge whatever the house load was. Brendan was also very kind to confirm that even if the battery recharged to 100% it would still hold off discharging until the scheduled time period had ended.
Install Visit No. 3
Our installer found the inverter reading/battery data readings issue was due to the position of the mains CT (Current Transformer). Once the CT was moved to the mains incoming cable close to the electricity meter it worked fine.
Whilst that resolved the battery issue it didn't stop the EV drain the battery when on fast charge. As programming the inverter for a scheduled battery charge was quite easy and quick we decided to test this first before looking again at the hard wire solution. Thankfully it worked perfectly so I decided it was best to stick to that solution than carry on trying to get the hard wiring option to work.
Our battery charge settings
My installer showed us how to set the battery charge settings, but I was glad to find a guide on the internet how to do this.
We decided to initially set the battery to charge at 1A between 01:00 to 07:00.
We have since dropped this to 0.1A between 02:00 - 05:00 to coincide with the Octopus Flux low cost period.
Our battery charge & discharge schedule
The reason for this schedule is because I only want to charge the EV when electricity is at its cheapest kWh rate. I'd rather charge the EV more often than charge it in the higher cost day time period. The other point is whilst the battery is set to charge the house loads will be met by electricity imported from the grid. This isn't really an issue as we will be asleep and using very little electricity.
The inverter data below shows the EV is charging at 7kW and not discharging the home battery which is perfect. It's only charging the home battery at 27W, which is good as during the summer we don't need to charge the battery due to the high solar generation. During winter there will be less solar to recharge the battery sufficiently each day. I will likely raise the charge rate to store energy from the low cost period to use later in the day.
ECO mode benefits
One thing I hadn't considered before was there could be a time when I'd like to discharge the home battery into the EV. In the summer our home battery can be recharged to 100% by 10-11am. With the hard wired solution it wouldn't have been possible to send excess solar generation to the EV until the home battery was fully charged. Whilst this is still true when using the ECO+ mode, the ECO mode overrides the home battery SoC (State of Charge) and sends excess power to the EV straight away. This is quite useful if I'm at home in the morning but will be out in the afternoon. I can charge the EV in the morning then let the home battery recharge in the afternoon when I'm out.
Another benefit is that it also lets stored solar power in the home battery be discharged to 'top up' the solar power if solar generation drops below the minimum 1.4kW charge rate required by the ECO+ mode. Even if there is no solar I can discharge stored solar from the home battery into the EV at a rate of 1.4kW. It's quite slow at 1.4kW, but it does mean there is no chance of using any imported grid electricity if there is sufficient home battery charge. I'd love to see a variable charge mode where you could set the charge rate above 1.4kW. That would be a great way to use some of the excess in the home battery, especially now we have a larger battery capacity than we initally planned.
Conclusion
I'm glad we've had both the battery and EV charger installed. There were quite a few unexpected issues, and it took much longer than we were expecting it to take. To be honest, this isn't too unusual considering we're still in the early adopters phase of solar and EV home charging technology.
I've found out Hybrid Inverter with DC batteries are a bit harder to get them to play nicely with the Zappi charger than an AC inverter and AC battery would be. That's mainly due to the power transfer between the inverter and battery being DC so the Zappi can't use a CT by monitor current flow to and from the battery.
What this has shown me is that there are potentially compatibility issues in how equipment from different manufacturers interacts with each other. Recent releases of new technology such as Myenergi's Libbi home battery has shown you can now install equipment from just one manufacturer. Like how Apple's iPhones, iPads and Mac's work seamless together due to being one eco-system I can foresee Myenergi's equipment working well together as they will be designed to do so. It's much easier to design equipment to work well if they are all one manufacturers equipment than to design equipment to working with numerous different manufacturers.
The battery charge solution isn't much of an issue for us. That's mainly due to our inverter being easily accessible in our garage. If it was in the loft that would be a bit different. I'm also quite a 'techie' person with experience of HMI's (Human Machine Interface's) so delving into the inverter settings isn't too much of a worry for me. For older non techie people it could being a concern if the system needed quite a bit of setting adjustments to get the best from it.
In all, both the home battery and EV charger are good additions to our solar system. They should help us get the most from our solar generation and help to reach our goal of reducing our reliance on the nation grid, well at least for home use.