What exactly is a solar energy bank?
The term "energy bank" is the commercial name given to an electricity storage system associated with solar panels. Technically, it is a lithium battery pack (LFP or NMC) coupled with a hybrid inverter, which automatically performs two functions: storing the surplus solar production during the day, and returning it to the domestic grid when production is insufficient (in the evening, at night, on cloudy days).
Other terms you may encounter for the same thing: solar battery, photovoltaic storage pack, self-consumption system with storage, or simply home battery.
Why buy second-hand rather than new?
Price is the main reason. A new 5 kWh solar storage battery (the standard size for a family home with 3 kWp of panels) costs between €750 and €2,000 from major brands (BYD, Pylontech, Sungrow, Growatt). Add a few hundred euros for installation by a professional and the total generally stays under €2,500.
An equivalent 5 kWh second-life pack, reconditioned from individually selected and tested LFP cells, is available from €462 at cirBATT. The saving remains significant — around 40–75% on the pack price — while sharply reducing the carbon footprint of storage.
Is a second-hand battery reliable?
It depends entirely on how it was reconditioned. A serious second-life battery stands out on three points:
- Cell-by-cell selection: only cells exceeding a SOH (State of Health) of 70% are retained. Degraded cells are eliminated before assembly.
- Adapted BMS: the management system must be recalibrated for the specific characteristics of second-life cells, not just copied from the original battery. A quality BMS manages active balancing, thermal protection and charge/discharge protection.
- Clearly displayed SOH: a serious seller shows the workshop-measured SOH on each pack. Avoid offers without this information.
How to choose the right capacity for your installation?
The basic rule: your energy bank should cover your evening and night consumption, generally between 3 and 8 kWh for a standard home.
| Home profile | Evening/night consumption | Recommended pack | Second-life indicative price |
|---|---|---|---|
| Flat / small home | 2–3 kWh | 5 kWh LFP | from €462 |
| Family home (3–4 people) | 4–6 kWh | 6.5 or 8 kWh | from €628 |
| Large home or heat pump | 7–12 kWh | 10 kWh industrial | from €893 |
Inverter compatibility
All cirBATT packs are 48 V, the standard voltage compatible with the vast majority of hybrid inverters: SMA Sunny Boy Storage, Victron MultiPlus, Growatt SPF, Deye SUN, Sofar Solar, Solis RHI…
Where to find a second-hand solar energy bank in France?
- LeBonCoin, eBay: private sellers sometimes resell complete systems. Advantage: very low prices. Risk: no guarantee on the actual condition of cells, no technical documentation.
- Solar installers: some offer reconditioned batteries. Variable quality depending on the installer.
- cirBATT: workshop reconditioning with cell-by-cell selection, certified SOH displayed on each product, proprietary BMS, based in Grenoble.
The most important selection criterion, whatever the source: documented SOH with test data. Without this, you are buying a black box.