Battery for solar panels — why you need one and which to choose
A battery in a solar power system does one job: stores energy produced by panels during the day so you can use it at night or during a grid outage. Without a battery, all "excess" energy goes to the grid (if you have a feed-in tariff) or is simply lost.
For home solar systems with a hybrid inverter, there are three battery types: LiFePO4, AGM, and GEL. Our recommendation is LiFePO4, and below I will explain why this is math, not marketing.
Three battery types for solar systems
LiFePO4 (lithium iron phosphate)
The standard for new systems since 2022. 4,000-6,000 cycle life, 80-90% depth of discharge, one-third the weight of lead-acid equivalents. Price starts from 18,000 UAH for a 5.12 kWh module.
AGM (Absorbent Glass Mat)
Lead-acid battery with fiberglass separator. 400-600 cycles at 50% depth of discharge. Price from 6,000 UAH. Problem: with daily cycling, capacity drops by half within 1.5-2 years.
GEL
Lead-acid with gel electrolyte. 500-800 cycles. Price from 7,000 UAH. Still loses to LiFePO4 by 5-8x on cycle life.
Comparison: the numbers speak for themselves
| Parameter | LiFePO4 | AGM | GEL |
|---|---|---|---|
| Cycle life | 4,000-6,000 | 400-600 | 500-800 |
| Depth of discharge | 80-90% | 50% | 60% |
| Weight (5 kWh equivalent) | 40-50 kg | 140-160 kg | 140-160 kg |
| Lifespan with daily cycling | 10-15 years | 1.5-2 years | 2-3 years |
| Module price (5 kWh) | 18-28K UAH | 12-18K UAH | 14-20K UAH |
| Cost per cycle | 3-7 UAH | 20-45 UAH | 18-40 UAH |
Cost per cycle is the metric people rarely check, but it determines the real economics. See our detailed LiFePO4 vs AGM vs GEL comparison.
How to size the battery for your solar array
Simple rule: battery capacity should match the panel array output and your nighttime consumption.
- 2-3 kW panels: 5-10 kWh battery
- 4-6 kW panels: 10-15 kWh battery
- 8-10 kW panels: 15-30 kWh battery
No point putting a 30 kWh battery on a 2 kW array — the panels physically cannot charge it in a day.
Account for seasonality
In June, a 5 kW array generates 25-30 kWh per day. In December — 5-8 kWh. Size the battery for winter generation if you want year-round autonomy.
Connection diagram with hybrid inverter
A hybrid inverter is the system center. It takes energy from panels via MPPT controller, charges the battery, and powers the load simultaneously.
- Solar panels → DC cable → MPPT input of inverter
- LiFePO4 battery → DC cable + CAN cable → battery input of inverter
- Grid 220V → AC cable → AC input of inverter (backup)
- Home load → AC output of inverter
The inverter decides where to draw energy: panels first, then battery, then grid. Fully automatic.
Common mistakes when choosing a solar battery
- Bought AGM "to try": after 1-2 years they switch to LiFePO4 anyway. Double the cost
- Battery without communication: inverter cannot see real charge, charges by voltage only
- Too much battery, too few panels: 20 kWh battery + 2 kW panels = battery never fully charges
- Panels facing north: it happens. Generation is half of what it should be
Our brand recommendations
For solar systems we recommend Deye, Veichi, Felicity Solar. Browse the solar battery catalog on our website.
Frequently Asked Questions
Can a solar system work without a battery?
Yes, with a grid-tied inverter. But during a grid outage the system also shuts down — no battery means no autonomy.
How many panels to charge a 10 kWh battery?
3 kW of panels (6-8 units at 400-550 W) will charge 10 kWh in 4-6 hours on a clear day.
Does the battery charge from the sun in winter?
Yes, but slower. In December-January, a 5 kW array produces 5-8 kWh per day instead of 25-30 in summer.
What inverter do I need for battery and panels?
A hybrid inverter with MPPT controller and battery input. Grid-tied inverters do not work with batteries. See our hybrid inverter catalog.
Can I add a battery later and start with panels only?
Yes, if you install a hybrid inverter from the start. It will work as grid-tied until you add the battery, then switch to hybrid mode automatically.
Next steps
Determine your panel array size, calculate nighttime consumption, and size the battery using the formula from our capacity calculation guide. Browse the LiFePO4 battery catalog with current prices on our website.
