Solar Batteries

Updated April 2024

Most, but not all home battery storage systems are modular.
There's a BMS (Battery management system) and power control unit on top of a stack of smallish batteries.

Like this iStore/Huawei battery...

Around 13kWh is a popular size for battery storage.
I've tried to get as close to that 13kWh in the comparison below.

Goodwe Home Lynx F G2 12.8kWh battery (4 x 3.2kWh modules & BMS), $9,350.
Alpha ESS B5-13 13.3kWh battery (1 x 13.3kWh module, 5kW inverter & BMS), $9,360.
SAJ B2 13.5kWh battery (3 x 4.5kWh modules & BMS), $9,800.
Growatt Ark-XH 13.8kWh battery (6 x 2.3kWh modules & BMS), $10,690.
Sungrow SBR 12.8kWh battery (4 x 3.2kWh modules & BMS), $10,810.
SolaX T-Bat 13.2kWh battery (4 x 3.3kWh modules & BMS), $10,930.
SolarEdge Energy Hub 9.7kWh battery (1 x 9.7kWh module & BMS), $11,880.
BYD HVM 13.8kWh battery (6 x 2.3kWh modules & BMS), $12,635.
iStore/Huawei 15kWh battery (3 x 5kWh modules & BMS), $16,445.

Click any of the blue links above to see the battery datasheet.
I've highlighted in bold where there is a signficant divergence...
e.g. iStore has 2kWh more storage than 13kWh, which is worth about $2,000.
SolarEdge has 3.3kW less than 13kWh, and therefore about $3,000 less value.

Installation costs for the battery, consumption meter and backup with a changeover switch are $2,000 for all.
The inverter consumption meter is typically $200 for single phase and $400 for three phase.
Sungrow, SAJ, Goodwe (3 phase only) hybrid inverters include the consumption meter.
Backup components (power from the battery & solar during a blackout) is included with Goodwe, Sungrow, SolaX, SAJ and Alpha.
The other brands have a separate backup box costing...priced below as Single phase/Three phase backup box.
Growatt $330/N/A, iStore $790/$1,200, Fronius/BYD $925/$1,475, SolarEdge $515/N/A

Monolithic v Modular batteries.
Alpha and SolarEdge are monolithic, the rest are modular.
Monolithic simply means the battery is 'one size fits all'.
e.g. SolarEdge is 9.7kWh. If you want more than that then you buy another 9.7kWh battery.
Same for Alpha. 13.3kWh, if you want more than that you buy another 13.3kWh battery.

Modular means you build the battery up in smaller modules.

Usable energy
I've used the battery usable energy value, not the rated value.
e.g. Each SAJ battery unit is rated at 5kWh, but you can only use 4.5kWh.
Growatt rated 2.56kWh, 2.3kWh usable, SolarEdge 10kWh, 9.7kWh usable, Solax 3.66kWh, 3.3kWh usable.
Goodwe, Sungrow, iStore, BYD, Alpha the rating is the usable power. I wish they all would do that.

Series-connected v Parallel Connected
The only parallel connected battery above, also with a battery optimiser inside each module is iStore/Huawei.
Parallel connection and an optimiser means each module is independent of the others.
New batteries can be added to old without any losses.
Charging and discharging of each battery module is done independently which 'treats' them better over time.
iStore/Huawei is also the only one with multiple (8) temperature sensors and a fire-extinguishing bag.

Cell Chemistry.
They all use Lithium Iron Phosphate cells (LFP/LiFePO4)
Ultra-safe unlike the cheap Lithium Ion batteries in scooters and E-bikes.

Life Expectancy
These LFP batteries are typically designed for a useful life of 6,000 to 8,000 cycles.
Cycled once a day 6,000 cycles is 16 years, 8,000 cycles is 22 years.

2% Reduction in output each year.
At 2% a year, after 10 years expect the battery to be at 80% of it's original output.

High voltage v low voltage
A high voltage battery (typically 400V-600V) needs much smaller cables than a low voltage battery (typically 48V).
Higher voltage = lower current = smaller cables.
This means a cheaper, easier, neater installation, also allowing battery and inverter to be some distance apart.
It also means the battery can work with both single and three phase inverters.

Inverters compatible with these batteries.
A few years ago there were very few 'hybrid' inverters, and they used third party batteries like BYD, Pylontech and LG.
Once demand ramped up, the inverter manufacturers started making their own batteries.
So from the list of batteries above here's what works with what...

I've used the format single phase/three phase below...

Goodwe battery - Goodwe EH (5kW)/Goodwe ET (5-30kW) inverters.
Alpha battery - Alpha (5kW) / N/A inverters.
SAJ battery - SAJ H2-V2 (5-10kW)/SAJ H2-T2 (5-10kW) inverters.
Growatt battery - Growatt MIN-XH, MIN-XA (5kW)/MOD-XH (5-10kW) inverters.
Sungrow battery - Sungrow SH.RS (5-10kW)/SH.RT (5-10kW) inverters.
SolaX T-Batt battery - Solax X1 (5-7.5kW)/X3 (5-15kW) inverters.
SolarEdge battery - SolarEdge Home Hub/Genesis (5-10kW)/ N/A inverters.
BYD HVM battery - Fronius Primo GEN24Plus (5-10kW)/Fronius Symo GEN24Plus (5-10kW) inverters.
(BYD HVM also works with Goodwe and Sungrow single and three phase hybrid inverters above).
iStore battery - iStore And Huawei (5kW-6kW)/ iStore and Huawei (5kW-6kW) inverters.

10 years defect warranty with an additional 60-70% guaranteed output at ten years is typical.
Alpha is only 5 years but you can buy an upgrade to 10 years for $450.
Obviously the battery warranties are conservative.
They don't want to replace your battery under warranty in ten years time simply because it's lost too much output.
The battery BMS (and battery optimisers in iStore/Huawei)ensures the battery is looked after very well.

Cheap and nasty, or ok?
We are happy to install any of the above and support them throughout their long warranty.
I'm a little less keen on SAJ because its an exclusive brand to just one Australian wholesaler and therefore riskier.
You can't really compare the quality of an Alpha (cheapest because it also includes an inverter) with an iStore (most expensive).

My recommendations

Best bang for buck
Goodwe first choice, Alpha next if you buy warranty extension to 10 years, SolaX and SAJ equal third.

Best quality/featured battery
iStore/Huawei and Sigenergy.

Best 'somewhere in the middle' battery
Sungrow first choice, BYD second.

Other batteries.
There are many other batteries than those listed above...Dyness, Sofar, Solplanet etc etc.
We recently lost one brand, Redback, who have gone into liquidation, but hopefully will re-emerge.
They were an Australian company, and it's never good to see one of our own fail.
But, how they all these manufacturers make enough sales/profits to stick around here is beyond me.

Why isn't Tesla Powerwall 2 on the lists above?
It's an entirely different type of battery.
I've written up in more detail on this battery and the new Tesla Powerwall 3 here.
It cannot connect to solar panels, although it can intercept surplus solar power from any solar inverter to charge its battery.
All of the listed batteries are DC Coupled, meaning they are plugged directly into their compatible hybrid inverter.
This gives efficiency benefits, and allows for considerably more subsidised solar panels to be added to help charge the battery.
Tesla Powerwall 2 is an 'AC Coupled' battery that includes 13.5kWh of storage, a battery charger, a 5kW single phase inverter and meter.
There's a second Tesla box that among other things provides backup and the whole thing is around $15,000 installed.

What if the price of batteries fell 50% ?
An abundance of lithium and projections from some of the World's largest battery manufacturers predict...
...Battery prices may fall by 50% by the end of 2024. Some say 80%.
That's great news. We would all love that, but everything is not quite as simple as it first looks.
The battery cells that make up the battery might well fall by 50%.
But what about the cost of the rest of the battery components?
Installation costs won't fall. In fact quite the opposite.
What about the power control unit/BMS that controls the battery? That won't fall either.
The backup box? Nope.

I expect some modest falls by the end of 2024 for some batteries. Maybe 10%?
Maybe not.
We can only hope for the sake of next year's battery buyers.

iStore/Huawei 10kWh battery
Fronius GEN24+ inverter & 16.5kWh BYD battery

This review was written by Andrew MacKeith, Solar4Ever service manager since 2011.