Relatively new install, but already feeling like my 9.5 just isn't quite enough. Ideally I'd like to add another 5kWh storage to feel more comfortable.
Are all the existing batteries compatible with each other? I note there's a 5.2kWh (though 80% DoD) which would probably be the prime target. Perhaps there's gen 2 versions of the smaller batts coming?
You can mix and match the batteries but the larger one needs to be first. I had a 9.5 with a 5.2 quite happily.
Look at what your daily generation to grid is which'll give you an idea of the electricity you're generating but not being able to store.
Depends on your solar capacity and whether you are on night and day tariff and what the price difference is. I've tried the maths several times and calculated that the payback for a third battery (I have two inverters, one with a 9.5 and one with a 5.2) would be at best 4 years or up to 24 years depending on different assumptions!
Pity as I hate seeing the solar go to waste.
geoffreycoan thanks for the info... do I have the option to run both from my current AC3, or would I need another AC inverter for the 5.2?
You can have two batteries on one inverter, but you won't increase the charge or discharge power by doing that (only the amount of energy that can be stored).
Two AC3 inverters, each with their own battery, will give you twice the power output (so oven plus kettle, for example) and twice the charging speed. But this mode (often called 'plant' mode) is not officially supported, so it will come with some downsides. This is the setup we use, and for us the benefits outweigh the issues.
So the question becomes: Which is more important to you - more battery capacity, or more power and more battery capacity?
ToothyChris Thanks - kind of both really... I'd like the extra storage but also the extra power
So plant mode works but unsupported - how is that manifesting in drawbacks right now? Is there a chance that they basically stop it working with a firmware upgrade at some point and don't care to fix?
If you can afford both then go for it and get as big a battery as you can afford.
GE has a 'box' under development which should resolve the issues, which include:
1) Occasional cross-charging from one battery to the other. If you see this happening just re-start the inverter via the Portal.
2) Batteries do not charge or discharge evenly, so you will always get one system with a lower SOC. A bit of manual intervention in terms of charge and discharge rates keeps them closer, if you can be bothered. I believe that some of the HA and GivTCP systems can be used to automate this.
3) The Portal and App do not always report correct data, because they are not set up for the additional calculations. You get used to this.
4) If one or other dongle drops its connection to your WiFi you can get some spikes on the graphs (when the SOC values are different). Once you understand this, you learn to ignore them.
Anything else I have forgotten, anyone?
The box has been under development for quite a while, and GE has never been clear if it will be a chargeable or a free upgrade. Personally, I only found out that AC plants were unsupported after the system was installed, but I am glad we have this setup. By having the two parallel systems, it also gives some resilience in case one of the systems should go down.
Do you have enough solar to charge more than one AC3 at a time?
What's this "box" called - is it a new product?
I have 5kW of solar coming in on a good day, and charging at 2.8kW max right now on the AC3, leaving me with a lot of excess. I have Solar iBoost to snap up the dregs but it interferes with battery charging, so I have it off until battery is 100% (annoying!), so end up a lot of export for a few hours or we turn on dishwasher/washing machine/dryer to try use it up. But all that's annoying management I don't want to do.
I don't think I could regularly charge or need two 9.5s tbh, I use about 12 kWh a day, but one 9.5 just doesn't cut it on the bad or winter days. Especially as it seems like I don't really get 9.5 out of it...
Not released yet. Think they call it BMS? Have a hunt around this forum to find it.....TheDragon (Paul) may have commented on it recently, so scan through his posts. It is primarily for twin AC3 systems, with twin hybrids to follow, I think.
Having the twin AC3 inverters is great to minimise the export - much better to store and use the energy, instead of selling for pennies.
We have two 8.2 batteries with a daily usage of 10-12kW.h. Having the extra capacity allows us to use more solar energy from previous days, if the weather turns bad.
ToothyChris BMS
"EMS" (Energy Management System?) and @pacemaker I would agree that if you go for a smaller battery than you can afford/accommodate, you will eventually wish that you'd gone the extra mile for the additional capacity.
Thanks Tim. I knew BMS was wrong, but had a feeling it was close.
pacemaker I have 5kW of solar coming in on a good day, and charging at 2.8kW max right now on the AC3, leaving me with a lot of excess
Just bear in mind that the multiple Hybrid inverters work independently so each has to be dedicated to its own set of panels. So if you add a second inverter and its own battery you will have to get some of your panels moved onto that inverter.
And then you get onto questions about which panel orientation to inverter to battery and trying to figure out the optimum solution!
We have 16 panels on the front of the house on one inverter and 12 panels (6 on the front and 6 on the back) on the second inverter. Like @ToothyChris I knew I was getting a twin inverter system to handle the number of panels we have, but didn't realise that this "plant" configuration isn't supported by GE (its in their FAQs as being unsupported).
I didn't realise that the two inverters and their panels would be completely independent, I had assumed they worked together so when my installer fitted both batteries to the 16 panel inverter I thought nothing really of it.
Turns out as the two inverters knew nothing of each other the second one would end up dumping all its energy either into the house, or out to the grid, and often pushing the house voltage above limits which shut the first inverter down for hours at a time. Solution was to move the batteries so I have one battery on each inverter and its been much better behaved since then.
My 16 panel array has the 9.5kW battery and the 12 panel the 5.2 on the basis that the larger array is charging the larger battery. On a sunny day both batteries charge up fully, often by mid morning. As half of the 12 panel array is on the back of the house I do see higher solar output on that inverter in the afternoon, and maybe there would be some advantages to having the bigger battery on that array so if it discharges I would get more 'later day' topup. Dunno, all too complex to get 100% right.
GE did confirm that the EMS box when it comes out will be retrofittable to existing installations. Personally other than the excess voltage issue I had I have seen no issues with my multiple inverter setup. Never seen one battery discharging to fill the other one for example, but I have it only set to solar charging so maybe that prevents it.
geoffreycoan Look at what your daily generation to grid is which'll give you an idea of the electricity you're generating but not being able to store.
Depends on your solar capacity and whether you are on night and day tariff and what the price difference is. I've tried the maths several times and calculated that the payback for a third battery (I have two inverters, one with a 9.5 and one with a 5.2) would be at best 4 years or up to 24 years depending on different assumptions!
Here, if its useful to others is my payback calculation spreadsheet: https://docs.google.com/spreadsheets/d/10NLAyNAWC6Aun8oTCCyG9fjfXoRTh9qf/edit?usp=sharing&ouid=111899597625099510452&rtpof=true&sd=true
Make a copy of it and enter your current electricity tariff and the night/day rate price differential in the yellow cells. Alter the cost of the different battery options if you want to.
Gives you the payback from the three options I could identify of (1) charging the battery overnight, (2) storing excess solar in the battery and (3) doing both.
(I couldn't upload the spreadsheet direct to the forum, so sharing it on my Google Drive)
pacemaker but it interferes with battery charging, so I have it off until battery is 100%
You could try reducing the charge rate for the battery so that there’s more for the iBoost sooner. This sounds counter-intuitive but if you know you’re going to have a good solar day it won’t matter whether the battery charges over 3 hours or 6 by which time, between the two, you will have diverted more export to home consumption.