Marstek Saturn B2500-D
(7 reviews)
The balcony battery that kicked off the trend in Germany: 2.24 kWh expandable to 8.96 kWh, 2 MPPT and 1600 W of solar input, IP65.
Characteristics
- Capacity: 2240 Wh (LiFePO4), expandable to 8960 Wh (4 units)
- Solar: 2 MPPT, up to 1600 W input
- Output: Built in 800 W micro inverter
- All weather: IP65, indoor and outdoor use
- The reference that started the balcony trend, unbeatable value
Detailed overview: Marstek B2500-D balcony solar battery, 2 MPPT and 1600 W
The Marstek Saturn B2500-D, often referred to simply by its code name B2500-D, is the model that popularised the whole balcony battery category in Germany. A best seller there since launch, it remains the reference against which most newer competitors are measured.
This solar storage battery is DC coupled, meaning it sits between the solar panels and a compatible micro inverter rather than on the AC output of an already equipped installation. Its 2 independent MPPT trackers accept up to 1600 W of solar panels in total, enough to connect two separate panel strings without worrying about partial shading on one of them. Its 2240 Wh LiFePO4 battery delivers up to 800 W through its built in micro inverter, a power level designed to cover a household's baseline consumption (router, fridge, various standby loads) rather than large one off appliances.
Capacity expands up to 8960 Wh by stacking up to 3 additional battery modules onto the main unit, for a total of 4 units. Each module connects in a few minutes, with no tools or electrician required, which lets the system grow over time instead of buying everything at once.
Rated IP65 against water and dust, the B2500-D is built for indoor use as well as unprotected outdoor use, on a balcony, a terrace or against a facade wall. Control runs through the Marstek app over Wifi and Bluetooth. Its zero export function continuously reads data from a compatible smart meter (Marstek CT002/CT003, Shelly Smart Meter, HomeWizard P1) to automatically adjust the power fed back and avoid any unwanted export to the public grid.
Installation is designed to be genuinely plug and play: the unit stands on the floor or mounts on a wall, and connects to the panels via the included MC4 connectors. Backed by a 10 year warranty and rated for over 6000 charge cycles, the B2500-D holds an average rating of 4.5 out of 5 across more than 100 verified reviews at the most active resellers.
Availability still varies noticeably by market: very well established and noticeably cheaper direct from the manufacturer in Germany, it does not yet have a localised official store in other European countries, which limits purchase options elsewhere to a handful of third party resellers, at a meaningfully higher price than in Germany.
Full specifications
Detailed characteristics
Battery
| Technology?Battery chemistry; LiFePO4 lasts far longer and can be fully discharged, gel/AGM is maintenance-free and cheaper. | LiFePO4 (lithium) |
|---|---|
| Energy?Stored energy in watt-hours. | 2240 Wh |
| Cycle life?Rated number of charge/discharge cycles, at the stated depth of discharge. | 6000 cycles |
| Expandable up to?Maximum capacity reachable with add-on modules. | 8960 Wh |
Power and protection
| Output power?Maximum power delivered (for storages with a 230 V output). | 800 W |
|---|---|
| Built-in BMS?Battery management system protecting against overcharge, deep discharge, short-circuit and overcurrent (lithium batteries). | Yes |
Solar section
| MPPT controllers?Number of built-in MPPT solar controllers (lets you connect panels facing different directions). | 2 |
|---|---|
| Max solar input?Maximum connectable PV power. | 1600 W |
| Micro-inverter?Power of the inverter that feeds energy back into the home grid. | 800 W |
Connectivity
| Bluetooth?Monitoring and settings via an app over Bluetooth. | Yes |
|---|---|
| Wi-Fi?Remote control and updates over Wi-Fi. | Yes |
Durability and format
| Ingress protection?Water and dust resistance (IP rating). | IP65 |
|---|---|
| Weight?Weight of the battery. | 20 kg |
Availability and warranty
| Warranty?Length of the manufacturer's warranty. | 10 years |
|---|
Comparison
How does the Marstek Saturn B2500-D compare to other plug and play balcony solar batteries in the £250 to £450 price range, for searches like "B2500-D vs Growatt NOAH 2000" or "Marstek vs Anker Solarbank"? Here is how it stacks up against three references already in our catalogue and heavily searched in the same price bracket: the Growatt NOAH 2000, the Anker Solix Solarbank 2 E1600 and the Zendure SolarFlow 800.
| Criterion | Saturn B2500-D | Growatt NOAH 2000 | Anker Solix Solarbank 2 E1600 | Zendure SolarFlow 800 |
|---|---|---|---|---|
| Capacity | 2240 Wh | 2048 Wh | 1600 Wh | 960 Wh |
| Coupling | DC, built in micro inverter | DC, separate dedicated micro inverter | DC, built in micro inverter | DC, built in micro inverter |
| Solar input | 1600 W (2 MPPT) | 1800 W (2 MPPT) | 800 W (2 MPPT) | ≈ 400 W (1 MPPT) |
| Expandable to | 8960 Wh | 8192 Wh | ≈ 5000 Wh | 1920 Wh |
| Observed price (Germany, converted) | ≈ £264 | ≈ £513 | ≈ £342 | ≈ £256 |
Overall, the Saturn B2500-D stands out for the best capacity to price ratio in the comparison on its home market, with a higher base capacity than every direct rival and the most generous expandability of the group. The Growatt NOAH 2000 offers a slightly higher solar input but at a noticeably higher price, the Anker Solix Solarbank 2 E1600 leans on a more polished software ecosystem for a smaller capacity, and the Zendure SolarFlow 800 targets an entry level budget but with far more limited capacity and expandability.
Related video
Video: Marstek B2500-D Battery Best DC Coupled Balcony Battery - Published on 11/12/2024
Our tester's review: Julien De Jurquet
The B2500-D is more or less the model that started it all: in Germany it is hard to spot a balcony fitted with solar panels without one or more of these small grey towers stacked against the wall next to it. In practice, setup really does live up to the promised 15 minutes: MC4 connectors on the panels, a mains socket, the Marstek app over Wifi, and storage begins right away. Several owners report solid compatibility with Shelly smart meters and the German Ecotracker, with a genuine satisfaction at seeing the household's baseline consumption covered automatically in the evening. The clearest drawback concerns availability and price outside Germany: it is noticeably cheaper and far better distributed through the manufacturer at home than through the handful of resellers available elsewhere. The otherwise solid app also has occasional hiccups after an update, according to recent reports. For anyone able to buy at the German price, the value for money remains among the best in the whole plug and play category.
Frequently asked questions: Marstek B2500-D balcony solar battery, 2 MPPT and 1600 W
Up to 3 additional battery modules can be stacked onto the main unit, for a total capacity of 8960 Wh spread across 4 units.
Yes, units stack physically and connect electrically to each other via the dedicated connectors, with no electrician or special tools required.
The official Marstek app (iOS and Android), over Wifi or Bluetooth, handles control, production and consumption monitoring, and the zero export setting with a compatible smart meter.
Not yet through a localised official store: at the time of writing, purchases go through the manufacturer's general EU store or third party resellers, at a noticeably higher price than direct from the manufacturer in Germany.
Up to 1600 W of panels in total, split across the 2 independent MPPT trackers, typically 2 to 4 panels depending on their individual power.
In the UK, small balcony solar systems generally fall under permitted development and the microgeneration certification scheme (MCS) rules, but requirements vary by supplier and property type: always check with your electricity supplier and, where applicable, your local planning authority before buying.
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Published on 30/08/2026