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Technical guide · Bilotex
The battery decides your real autonomy
Without a battery, panels only save you in the daytime. With the right battery, you cover the night too and use 95% of the energy generated. We explain which to pick by inverter and load.
The problem: cheap batteries die in 3 years
A bad battery wrecks a great system. The data matters: chemistry, cycles, depth of discharge, BMS, and the inverter brand it talks to.
Lead-acid: dead in 3-5 years, weighs a ton and only allows 50% discharge. Justified only in extreme off-grid setups.
Lithium NMC: high density but less safe, fewer cycles (3 000-4 000). Was the standard up to 2022 — obsolete today in residential.
Lithium LiFePO4 (LFP): the current standard. 6 000+ cycles, much safer thermally, supports 90-95% DoD and most top brands use it.
3 batteries · 3 ecosystems
The brands that cover almost all Spanish residential. This is the logic our calculator uses to enforce compatibility:
Deye SE-G5.1 / SE-G5.3
For Deye inverters (also Pylontech & BYD LV compatible)
€950-1 050 / 5.12 kWh
- LiFePO4 · 6 000 cycles · 95% DoD
- 48 V LV — open CAN bus (RS485/CAN)
- Stackable up to 16 units = 81.9 kWh
- Plug & play with every Deye SUN-K hybrid
- 10-year warranty · EU stock
Huawei LUNA2000
Only for Huawei SUN2000 inverters
€1 150-1 200 / 5-7 kWh
- Modular HV stack (5/7/10/15 kWh) — scalable on site
- Needs a Power Module (LUNA2000-5KW-C0) per stack
- 100% Huawei · 1-click integration with SUN2000
- FusionSolar app (best monitoring on the market)
- HV (350-560 V) — zero loss in long cabling
Growatt ARK / AXE / APX
For Growatt inverters (LV and HV)
€744-922 / 5 kWh
- AXE 5.0L (LV, 48V) — cheapest €/kWh on the market
- ARK 2.5H (HV stack) — for larger systems
- APX 5.0 (battery cabinet with internal BMS)
- Proprietary CAN · native integration with Growatt SPH/MIN hybrids
- Best €/kWh for large energy storage
Which battery fits your inverter?
Real compatibility (not marketing). This is exactly the matrix our calculator uses:
What to check when buying a battery
Guaranteed cycles
Minimum 6 000 cycles to 80% capacity. If you see <4 000, it's old NMC chemistry — avoid.
Depth of discharge
Useful DoD ≥ 90%. Spec sheets sometimes give 'rated capacity' (without DoD): always ask for usable capacity.
LV vs HV voltage
LV (48V) = cheap, modular, multi-brand. HV (200-560V) = more efficient in long cabling, but usually closed to one brand.
BMS and app
The BMS protects the battery from overcharge and imbalance. Apps like FusionSolar or SolarMAN show every cell — invaluable to spot issues.
Frequently asked questions
How many kWh of battery do I need?+
Rule of thumb: the battery covers night-time loads (typically 30-40% of daily consumption). For an 18 kWh/day house, 6-8 kWh of battery is ideal. More is waste unless you have an EV.
LV (48V) or HV (>200V)?+
LV is the universal, affordable option — works with almost any inverter. HV is more efficient on large systems (>10 kWh) and long cabling but ties you to a brand. For 5-10 kWh residential, LV is optimal.
Does the battery self-discharge if I don't use it?+
Minimally (~3%/month). Modern LiFePO4 has very low self-discharge. The BMS shuts it off below 5% to protect it.
Can I add more kWh next year?+
Yes, all listed batteries (Pylontech, LUNA2000, ARK/AXE) are stackable up to 5-16 modules. The only thing that changes: if you exceed the inverter's power, you'll need a bigger hybrid.
Calculate your ideal battery bank
Set your load and priority ('savings' or 'full autonomy') — the calculator sizes the battery bank compatible with your inverter in seconds.
Open the free calculator