Adding batteries to a Sunsynk inverter
Sunsynk hybrid inverters work with the batteries on Sunsynk's compatibility list, including its own L5.1 and many other brands. Sunsynk's UK warranty excludes mixing battery types or using batteries it hasn't approved, so add more of the same approved battery.
Compatibility by existing system
“General statement” means the battery maker says it can be added to existing solar in general, without naming Sunsynk. Your installer should confirm the details.
| Your existing system | Sunsynk L5.1 with ECCO inverter | myenergi libbi |
|---|---|---|
| Sunsynk hybrid inverter (adding or expanding a battery) | CompatibleThe L5.1 is on Sunsynk's battery compatibility list, which applies to all Sunsynk hybrid inverters. Sunsynk's UK warranty excludes connecting different battery module types, or other makers' batteries it hasn't approved.Source: Sunsynk compat matrix, p.2, Sunsynk rowSource: Sunsynk warranty, p.2, §8 exclusions (xi) | Works via AC couplinggeneral statementmyenergi lists "I have solar and a battery already and want to add more storage" as a supported retrofit: libbi goes alongside the existing system. General statement, not specific to this brand.Source: myenergi datasheet, p.1–2, Flexible install; use-case table |
Not listed: Tesla Powerwall 3, Sigenergy SigenStor, Fox ESS EVO 10, Enphase IQ Battery 5P, SolarEdge Home Battery 400V, Huawei LUNA2000-S1. We haven't found manufacturer documentation for adding these to an existing Sunsynk system, so we don't claim they work.
Before you add batteries
- Sunsynk's compatibility list applies to all its hybrid inverters, including three-phase models.
- The L5.1 can run up to 32 modules in parallel. Each module gives 4.61 kWh usable.
- The inverter limits battery current: the ECCO 3.6 kW takes up to 90 A and the 5 kW up to 120 A. Sunsynk recommends 50 A per L5.1 module (100 A maximum).
- Sunsynk's battery warranty needs daily cycling of fewer than 700 cycles a year, and the battery must be bought from Sunsynk or an authorised reseller.
Full specs: Sunsynk L5.1 with ECCO inverter. Compare it with Fox ESS EVO 10.
How long would it run your home?
Try the runtime calculator, or compare two batteries side by side.
Questions people ask
What batteries are compatible with Sunsynk inverters?
Sunsynk publishes a battery compatibility list that applies to all its hybrid inverters. It includes Sunsynk's own batteries, such as the L5.1, and many other brands, including Pylontech, BYD and Dyness.
Can I mix different batteries on a Sunsynk inverter?
Sunsynk's UK warranty excludes cases where the product is connected to different battery module types, or to other makers' batteries it hasn't approved. Stick to one approved battery type.
How many Sunsynk L5.1 batteries can I add?
Sunsynk's datasheet says up to 32 L5.1 modules can run in parallel (163.8 kWh of total energy). How many make sense depends on your inverter's battery current limit and your usage.
Does Sunsynk work with Intelligent Octopus Flux?
Sunsynk isn't on the list of battery brands Octopus says it can control on Intelligent Octopus Flux. Standard Octopus Flux works with any solar and battery, with times set manually.
Sources
- libbi Home Battery datasheet (DS-00001) — myenergi, Revision A, October 2023. Checked 26 Sept 2026.
- Sunsynk Battery Compatibility datasheet — Sunsynk, V.4 (10/17/23). Checked 26 Sept 2026.
- Manufacturer's Warranty — Warranty Agreement Terms and Conditions — Sunsynk. Checked 26 Sept 2026.
- SUNSYNK-L5.1 datasheet — Sunsynk, v.6 (28/06/24). Checked 26 Sept 2026.
- ECCO Hybrid Inverter SUN-3.6/5/6/7.6/8K-SG05LP1-EU datasheet — Sunsynk, v.4 (29/03/23). Checked 26 Sept 2026.
- Intelligent Octopus Flux: Frequently Asked Questions — Octopus Energy. Checked 26 Sept 2026.
EnergyPicker is independent and not affiliated with Sunsynk. Always confirm your final design with an MCS-certified installer.