A solar battery for solar panels: which one, how big, and how to read the sheet
Panels make electricity while the sun is up. A battery holds some of it for the evening, and with the right inverter it keeps chosen circuits alive when the grid drops. Which battery and how big are questions a datasheet answers, if you know which of its thirty lines to read.
This page reads one current lithium battery’s sheet line by line, sizes it against four appliances sold here, and works out which warranty line runs out first. What happens in a brownout, and which system type has a battery at all, is a page of its own.
The ten lines that matter
From the Deye RW-F10.2 product page, read 1 October 2026, which lists it for the EU and Australian markets. The battery is an example of how a sheet is written, not a recommendation; any current lithium battery prints the same lines under slightly different names.
- Chemistry
- Lithium iron phosphate (LiFePO4)
- The chemistry sets the cycle life, the heat tolerance and the depth it can be emptied to. Every other line on the sheet follows from it.
- Rated energy
- 10.2 kWh (200 Ah at 51.2 V)
- The headline figure, and the one the price is quoted on. It is not the figure to plan with.
- Usable energy
- 9.2 kWh at 90 percent depth of discharge
- The figure to plan with. The maker only means it to be emptied to 90 percent, and 90 percent of 10.2 is 9.2.
- Rated and maximum DC power
- 6 kW continuous, 12 kW peak
- How much can be drawn at once, which is a different limit from how much is stored. A full battery still cannot start everything in the house together.
- Recommended charge and discharge current
- 100 A
- At 51.2 V nominal that is about 5.1 kW, so a refill from empty takes about two hours of that much surplus, and rarely gets it.
- Cycle life
- At least 6,000 cycles
- Measured at 25 °C, 0.5C charge and discharge, 90 percent depth of discharge, to 70 percent of rated capacity. Change any of those conditions and the figure no longer applies.
- Warranty and throughput
- 10 years, 32 MWh
- Two limits, printed side by side. How they combine is set by the warranty document, so read that before relying on the years. The section below works out when each would arrive.
- Temperatures
- Charge 1 to 55 °C, discharge -20 to 55 °C, storage 0 to 35 °C
- Check these against the place the battery will actually sit, such as a west wall at three in the afternoon in April.
- Weight and size
- 104 kg, 600 by 760 by 200 mm
- Wall or floor mounted, and a wall that takes it has to be a wall, which a hollow-block partition may not be.
- Enclosure and scaling
- IP65, up to 32 packs in parallel
- IP65 is a rating against dust and jets of water. The parallel limit means packs can be added later rather than the battery replaced.
Sizing it from what runs after dark
The sum is short. For each appliance that runs after the panels stop, multiply the watts on its plate by the hours it runs and divide by 1,000. That is the kilowatt-hours it takes from the battery. Add them up and compare the total with the usable figure on the sheet, which is 9.2 kWh for the battery above. The draws below are the named models on the appliance wattage page, and the hours are one evening’s worth.
| Appliance | Plate watts | Hours | kWh | Alone, from one pack |
|---|---|---|---|---|
| Carrier WCARH010EE, 1.0 HP window aircon, 10 pm to 6 am | 930 W | 8 | 7.44 | 9.9 hours |
| Sharp PJ-S161M(WH) stand fan, the same night | 50 W | 8 | 0.40 | 184.0 hours |
| Philips HD3030/00 rice cooker, dinner | 600 W | 0.5 | 0.30 | 15.3 hours |
| Sharp ES-TL8010P-GY washing machine, one evening load | 470 W | 1 | 0.47 | 19.6 hours |
| The whole evening | 8.61 | 94 percent of one pack | ||
So that evening fits in one pack of this size, with 0.59 kWh to spare, and the aircon is 86 percent of it. Take the aircon out and the same battery carries the rest for days. Put a second aircon in and it does not carry one night. That is the whole of battery sizing: the night is decided by the one or two large loads, and everything else is a rounding error.
Two cautions. The aircon figure is its plate draw for every hour. Its compressor switches off once the room reaches the thermostat setting, so a real night can come in lower, which the aircon page works through. And the battery only ever gives back what the panels put in, so the evening’s kilowatt-hours have to be made in daylight on top of the day’s use. The solar panel calculator sizes an array to the whole month for exactly this case.
Stored energy and instant power are two different limits
The 9.2 kWh is how much the battery holds. The 6 kW is how fast it can give it out, with 12 kW allowed briefly for a motor starting. A house that switches on two aircons, the rice cooker and the water pump at the same moment is asking for more than 6 kW at once, and that limit has nothing to do with how full the battery is. When a system is designed, the backed-up circuits are chosen so that everything on them together stays under the continuous figure, and that is why a hybrid system backs up some circuits rather than the whole board.
The same line sets the refill. At the recommended 100 A and 51.2 V the battery takes about 5.1 kW, so a full refill needs around two hours of that much surplus from the roof. A roof rarely has that much left over after the house, which is why a battery is usually refilled over the whole afternoon rather than in a burst, and why a battery larger than the night it serves is a battery that never fills.
When each of the three limits arrives
The sheet gives three limits: at least 6,000 cycles, 10 years, and 32 MWh of energy through the battery. The cycle figure is the one quoted most often, and on a battery emptied every night it is not the first to arrive.
- 6,000 cycles, one a day
- About 16.4 years. Measured at 25 °C, 0.5C charge and discharge, 90 percent depth of discharge, to 70 percent of rated capacity, which is cooler than a cabinet here in the afternoon.
- 32 MWh of throughput
- 32,000 kWh divided by 9.2 kWh a day is about 3,478 full cycles, or 9.5 years if the battery is emptied every night. Cycle it half as deep and the same throughput lasts twice as long.
- 10 years
- The calendar limit, and for a battery used lightly the one that arrives first.
All three end at 70 percent of rated capacity, which for this battery is 7.1 kWh rated, or about 6.4 kWh usable. A battery that fits the evening with nothing to spare on day one will not fit it in year eight. The spare 0.59 kWh in the table above is the margin that absorbs that, and the lifespan page sets the same cycle figures beside a panel’s.
Where it goes, and what it connects to
The sheet allows charging from 1 to 55 °C and storage from 0 to 35 °C, and it is rated IP65. The manual for the unit you are quoted says where it may be mounted, and the condition to check is the wall it hangs on at three in the afternoon in April. A shaded, ventilated wall or a floor stand inside the house is kinder to the cycle figure than a sealed box in the sun. It weighs 104 kg, which a concrete wall takes and a hollow-block partition may not.
It connects to a hybrid inverter in a grid-connected house, or to an off-grid inverter and a charge controller in a house with no utility line. A grid-tied inverter has no battery terminals at all. Net metering is unaffected either way: the Department of Energy’s own primer describes the programme as open to systems “with or without battery energy storage”, and how net metering works does not change when a battery is added.
Adding a battery to a system that was installed without one is a battery and inverter upgrade, and the first question on that job is which inverter is already on the wall.
What people ask about batteries for solar
What battery do I need for solar panels?
One sized to what the house runs after dark, not to the panels. Add up the watts of each appliance that runs at night times its hours, divide by 1,000 for kilowatt-hours, and compare that with the battery’s usable energy. The evening on this page comes to 8.61 kWh across four named appliances, which is 94 percent of the 9.2 kWh one Deye RW-F10.2 holds.
What size battery for a 5 kW solar system?
The array does not set the battery. The array sets how fast the battery refills, and the night sets how big it has to be. A 5 kW array feeding a house that uses little in daylight has a large surplus and fills a battery quickly; the same array on a house that runs an aircon all afternoon may have no surplus at all. Size the battery from the evening, then check that the array has the surplus to refill it.
Can I add a battery to an existing solar system?
If the inverter is a hybrid, yes, and a battery of the matching voltage and communication standard is added to it. If the inverter is grid-tied only, the inverter is replaced or a second one added, because a grid-tied inverter has nowhere to connect a battery and is required to shut down when the grid does. The battery and inverter upgrade page covers that job.
How long does a solar battery last?
The sheet on this page gives at least 6,000 cycles to 70 percent of rated capacity, a 10 year warranty, and 32 MWh of throughput. Cycled fully once a day, the throughput figure is reached in about 9.5 years, before the cycle count would be. How the limits combine is in the warranty document of the battery you are quoted.
How much does a solar battery cost in the Philippines?
This page does not say, and that is a rule of the site rather than an oversight. A battery is priced with the inverter it connects to and the circuits it backs up, after somebody has looked at the board. The sizing is the half of the question a page can answer honestly.
Tell us what runs after dark
List the appliances that run in the evening and the hours they run, and name the inverter you have if there is one. You will get a written answer with a battery size in usable kilowatt-hours and what it would connect to.
Tell us the property and what you are trying to cut, and you will get a written answer with a size and a next step. No visit is booked and nothing is charged for asking.
Sources: Deye ESS product page for the Deye RW-F10.2, read 1 October 2026, for every battery figure; the named appliance draws are those sourced on the appliance wattage page, read 23 September 2026; Department of Energy, “The 5 Ws of Net-Metering”, Renewable Energy Management Bureau, September 2022, read 8 October 2026. The years and cycle counts in the warranty section are arithmetic on the sheet’s figures, not a promise about any battery. Named products are examples of how a datasheet is written, not a recommendation or a quotation.