Batteries for photovoltaics
Batteries for photovoltaics store the surplus your solar array produces during the day so it can be used at night, shifted away from peak tariff hours or held as backup when the grid fails. Choose by system voltage: low voltage around 48 V or high voltage from roughly 100 to 600 V, and further by voltage size or by brand: AEG, BYD, Dyness, Goodwe, Huawei, LG ES, Marstek, Pylontech, SolarEdge, Solinteg, Solis, Soluna, Victron Energy and Vision Battery. Commercial storage and accessories are stocked alongside. Guide
The accumulators (batteries) store the energy produced by the solar panels, thus ensuring energy independence and continuity of electricity supply. The batteries are, therefore, used to store the excess energy produced by the PV system or as a backup energy source in the event of a power failure.
What are the advantages of the battery?
A solar battery can help maximize the use of solar energy. During the day, when the sun is shining, and the solar panels produce more electricity than you use, the excess energy can be stored in the battery. Then, during the night or on cloudy days, when the solar system's production does not cover the consumption, you can use the stored energy from the battery.
During a power outage, the battery can give your home backup power. Using the battery, you can power appliances and devices even during a power outage.
Suppose the utility company charges you different rates for electricity at other times. In that case, you can use the energy stored in the battery when the higher rate is applied to avoid an increase in your electricity bill. This procedure is known as "peak saving."
Choose batteries for photovoltaics according to parameters
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List of products
Related storage categories
- Low voltage batteries
- High voltage batteries
- Batteries by brand
- Batteries by voltage size
- Commercial energy storage
- Accessories for batteries
Battery storage: voltage class, usable capacity and inverter pairing
A photovoltaic battery is a DC energy store with its own BMS (battery management system) that talks to a hybrid inverter over CAN or RS485. Four values decide whether a given pack suits an installation: the voltage class (low voltage or high voltage), the usable capacity in kWh, the continuous charge and discharge power in kW, and the communication protocol the inverter manufacturer has approved. Capacity alone tells you how long the house runs; power tells you how much of the house runs at once.
Almost the whole current range uses LiFePO4 (lithium iron phosphate) cells, valued for thermal stability, a flat discharge curve and a cycle life measured in thousands of cycles rather than hundreds. Stocked brands include AEG, BYD, Dyness, Goodwe, Huawei, LG ES, Marstek, Pylontech, SolarEdge, Solinteg, Solis, Soluna, Victron Energy and Vision Battery. Use the filters in the left column to narrow by brand or by voltage size.
FROM THE FIELD
"The first question on site is never how many kilowatt-hours. It is which battery the inverter has on its approved compatibility list, because the BMS protocol is the hard constraint. A pack with the right voltage and the wrong communication firmware will sit there charging to nothing, and no cabling change fixes that. Check the manufacturer's list before ordering, not after."
Ladislav Proc · Photovoltaics specialist, ONSA Plus
How to choose a battery for photovoltaics
The battery is chosen after the inverter, not before it. The inverter fixes the voltage class, the approved brand list and the maximum charge and discharge power, so those three constraints narrow the field before capacity is even discussed.
Work through it in this order: inverter compatibility first, then usable capacity against evening consumption, then power in kW against the loads you want to run, and finally the practical points of expansion, siting and warranty.
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Low voltage or high voltage
Voltage class is set by the inverter, not by preference. A low voltage battery operates at a nominal 48 V (typically 40 to 58 V in service) and connects to inverters designed for a 48 V DC bus. A high voltage battery stacks modules in series to reach roughly 100 to 600 V and pairs with inverters that expect a high voltage DC input. The two are not interchangeable, and no converter in the accessory range bridges them safely.
- Low voltage (48 V): the common choice for off-grid and hybrid builds, small expansions and off-grid inverters. Higher current for the same power, so DC cabling is thicker and fuse sizing matters more.
- High voltage (100 to 600 V): standard on most modern residential hybrids. Lower current means thinner DC cable, lower resistive loss and slightly higher round-trip efficiency, at the cost of stricter isolation and installation requirements.
Usable capacity, nominal capacity and DoD
Datasheets quote both a nominal capacity and a usable capacity in kWh. The difference is the DoD (depth of discharge), the share of the pack the BMS will actually release. A 10 kWh nominal pack at 90 % DoD gives 9 kWh usable. The related figure SoC (state of charge) is the momentary fill level shown in the monitoring app.
- Lead-acid is usually limited to about 50 % DoD, so half the rated capacity is unavailable and the pack must be oversized to compensate.
- LiFePO4 typically allows 80 to 95 % DoD. Soluna quotes 90 % and BYD 95 % or more, which is why lithium packs of the same nominal size deliver far more usable energy.
- Compare usable kWh, not nominal kWh, when you put two quotations side by side. It is the only figure that reaches your appliances.
Charge and discharge power in kW
Capacity in kWh is the size of the tank; power in kW is the size of the tap. A 10 kWh battery rated at 5 kW continuous discharge cannot run a 9 kW instantaneous load even when it is full. Check the continuous rating, the short peak rating and the charge rating separately, because charge power is often lower than discharge power. Adding modules to a stack usually raises the power rating as well as the capacity, since each module contributes current.
Tip from practice
Size the battery to the evening and night consumption, not to the annual total. Take the load between sunset and sunrise, add a margin for a cloudy day, and check that figure against the usable kWh. A pack sized to the yearly surplus will spend most of the year sitting full and never pays back. Do the sums before you compare brands.
LiFePO4 chemistry and cycle life
Cycle life is the number of full charge and discharge cycles before capacity falls to a defined threshold, usually 70 or 80 % of the original. Lead-acid manages roughly 500 cycles at 50 % DoD. LiFePO4 packs are commonly rated in the range of 6000 cycles at the manufacturer's stated DoD, which is why the cost per stored kilowatt-hour over the pack's life is lower even though the purchase price is higher. LiFePO4 also has no cobalt, a high thermal runaway threshold and tolerates partial states of charge without the sulphation that damages lead-acid cells.
Stackable modular systems and later expansion
Most current systems are modular: identical modules stack on a base or in a cabinet and the BMS treats them as one pack. This lets you start at the minimum module count and add capacity later, within the limits the manufacturer sets. Three rules apply when expanding. Keep the modules within the same product family and firmware generation, respect the maximum stack size for that inverter, and add modules while the existing pack is still relatively young, because a new module joining an aged stack will be pulled down to the behaviour of the older cells.
Backup power or self-consumption
A self-consumption system stores daytime surplus and releases it in the evening, and it stops working when the grid drops. A backup system additionally has a changeover point, a backup port on the inverter and a defined backup circuit, so selected loads keep running during an outage. Backup capability depends on the inverter and the wiring, not on the battery alone. Decide early which loads belong on the backup circuit, because that decision sets the required discharge power in kW and often the whole inverter choice.
Quick comparison of selection criteria
| Criterion | What to compare | What it affects |
|---|---|---|
| Voltage class | Low voltage 48 V or high voltage 100 to 600 V | Which inverters can be used, DC cable size, efficiency |
| Capacity | Nominal kWh, usable kWh, DoD in % | How long the house runs on stored energy |
| Power | Continuous and peak kW, charge and discharge | Which loads run at once, how fast the pack refills |
| Chemistry and life | LiFePO4 or lead-acid, rated cycles, warranty years | Cost per stored kWh over the system's life |
| Compatibility | Approved list, CAN or RS485 protocol, firmware | Whether the BMS and inverter communicate at all |
| Installation | Module weight, stack height, IP rating, temperature range | Where the pack can be sited and who can lift it |
Swipe the table to the left
Frequently asked questions about batteries for photovoltaics
What is the difference between a low voltage and a high voltage battery?
Low voltage packs run at a nominal 48 V, high voltage packs stack modules to roughly 100 to 600 V. The inverter decides which one you can use. High voltage draws less current for the same power, so cabling is thinner and losses are slightly lower.
How do I know which battery works with my inverter?
Check the inverter manufacturer's compatibility list. It names the approved battery models, the required firmware and the communication protocol, usually CAN or RS485. Matching voltage alone is not enough, because the BMS and the inverter also have to speak the same protocol.
What capacity in kWh should I choose?
Size it to consumption between sunset and sunrise plus a margin, not to annual production. For a typical family house that lands somewhere between 5 and 15 kWh usable. Compare usable kWh rather than nominal, since depth of discharge differs by product.
What is the difference between usable and nominal capacity?
Nominal is the total energy in the cells, usable is the part the BMS will release. The ratio is the depth of discharge. A 10 kWh nominal pack at 90 % DoD gives 9 kWh usable, and only the usable figure reaches your appliances.
Why is LiFePO4 used instead of other lithium chemistries?
LiFePO4 offers high thermal stability, no cobalt, a flat discharge curve and a long cycle life, commonly rated around 6000 cycles. It is heavier per kWh than other lithium chemistries, which matters in vehicles but not in a fixed home installation.
Can I add more battery modules later?
Yes with stackable modular systems, within the maximum stack size the inverter and battery manufacturer allow. Keep the added modules in the same product family and firmware generation, and expand while the original pack is still young, because mixed ages drag the stack down.
Will the battery power my house during a blackout?
Only if the inverter has a backup port and the installation has a dedicated backup circuit with proper changeover. A standard self-consumption system disconnects when the grid fails. Backup capability depends on the hybrid inverter and the wiring, not on the battery alone.
What does discharge power in kW mean in practice?
It is the maximum load the battery can supply at any moment. A 10 kWh pack rated at 5 kW cannot run a 9 kW load even when full. Check continuous power, short peak power and charge power separately, as they often differ.
How many cycles does a solar battery last?
Lead-acid manages roughly 500 cycles at 50 % depth of discharge. LiFePO4 packs are typically rated in the region of 6000 cycles to 70 or 80 % remaining capacity, so cost per stored kilowatt-hour over the system life is considerably lower.
Where can the battery be installed?
Indoors in a dry, frost-free space with the temperature range and clearances the datasheet requires, typically a utility room, garage or cellar. Outdoor siting needs a pack with a suitable IP rating. Check module weight and stack height before choosing the location.
Usable capacity, backup behaviour and inverter compatibility depend on the specific inverter model, the wiring of the installation and the manufacturer's approved combination list.
About ONSA Plus
Why installers across Europe buy storage from us
ONSA Plus is a European B2B distributor of photovoltaics, battery storage, heat pumps and EV charging stations. In our own EU warehouses we keep over 1,500 products from 25+ brands, including Huawei, Solis, SolaX and Dyness.
We are not just a trading company. We design and service energy systems ourselves, so we answer questions on battery sizing, inverter pairing and backup wiring from engineering practice, not from a catalogue. You handle a warranty claim directly with us and you buy per job.
