Capacitors limit converter life
DC-link capacitors are among the weakest parts of a power converter; electrolytic types age with heat and ripple current.
H. Wang & F. Blaabjerg, IEEE Transactions on Industry Applications, 2014
Our battery and the software behind it.
BTTRY is developing a modular battery that can switch each of its cells individually, with the power electronics built into the battery itself. Alongside it, we build the software that decides when a battery stores and when it delivers.
Our battery · in development
Every grid battery measures its cells. Ours switches them.
A conventional grid battery has a battery management system, or BMS, that measures the voltage and temperature of each cell and stops the battery when a cell leaves its safe range. But it cannot switch a cell. The cells in a string are wired in series, so they all carry the same current, all the time. Yet cells always differ a little, and that becomes the problem: a cell that is emptier or more worn than the rest has to keep up anyway, ages faster, and ends up setting the life of the whole pack.
In our battery, every cell can be switched on its own. That lets the battery set each cell’s duty cycle: how much of the time it carries current. Cells with a lower state of charge or state of health get a lighter duty, and stronger cells carry more. On our lab prototype this already balances the cells during operation and relieves a weak cell. Over a battery’s life, this is designed to keep weaker cells from wearing out faster than the rest, so the weakest cell no longer sets the life of the battery.
For a long time this was hard to justify at every cell, because switching a cell takes power MOSFETs, and every one adds cost and losses. AI server boards have changed that. Their power supplies use low-voltage MOSFETs in large numbers, which has pushed production to far higher volumes, with chipmakers building new factories to keep up. The best parts now conduct with less than a milliohm of resistance, so switching costs very little energy. We use the same kind of parts to switch the cells of a grid battery, and benefit from their economies of scale.
Sources: Infineon, “The Rise of AI Makes Power MOSFETs Critical in Data Center Architecture”, Power Electronics News, May 2025; Infineon, Q3 FY 2026 results, August 2026.
No central inverter, no separate BMS.
Today’s grid batteries connect thousands of cells into long strings behind a central inverter. Every conversion step costs energy and hardware, and the inverter often wears out before the cells do.
Integrated power electronics
Power conversion and battery management are built into the battery itself, with fewer conversion steps.
Designed for 20+ years
In today’s systems the inverter usually wears out before the cells, because its large electrolytic capacitors age with heat. Our design does without them, and uses each cell according to its own condition to slow ageing.
Sodium-ion and LFP
Designed for both chemistries and tested on the bench with each. Sodium-ion cells swing across a much wider voltage range than LFP; cell-level switching is designed to use all of it.
Built for real-world cells
No two cells are equal. Designed to tolerate the spread between them, which opens the way to second-life cells, with data on every cell for targeted servicing.
Modular by design
Standard modules, designed to scale from commercial sites to grid-scale installations.
Built in Europe
We design and build the power electronics, control and battery management in the Netherlands, and the battery is designed to work with cells from any maker, including Europe’s new cell producers. EU policy increasingly values that resilience: the Net-Zero Industry Act brings resilience criteria into public procurement and renewable-energy auctions.
Today’s grid battery and ours.
| Aspect | Conventional grid battery | BTTRY |
|---|---|---|
| Each cell | Measured, but carries the same current as the rest of its string | Measured and switched; its duty cycle follows its charge and health |
| Power conversion | A separate central inverter | Built into the battery |
| Battery management | A separate BMS; balancing often burns surplus energy as heat | Built in; cells balanced during operation |
| Service life | Inverter typically replaced mid-life as its capacitors age | Designed for 20+ years, without electrolytic capacitors |
| Cell chemistry | Built around one lithium chemistry and its narrow voltage window | Designed for sodium-ion and LFP, using each cell’s full range |
| A weak or failing cell | Holds back or takes down its string | Given a lighter duty; designed to be worked around if it fails |
| Insight | Data per string or module | Data per cell |
Comparison at concept level. Our battery is in development; specifications and service life are design targets, to be validated on our prototypes.
The problems we solve are well documented.
Converter wear-out and cell-to-cell differences are established findings in peer-reviewed research. Our battery is designed around them.
The industry sees the same
A survey among converter makers and users rates power semiconductors and capacitors as the most failure-prone components.
S. Yang et al., IEEE Transactions on Industry Applications, 2011
New cells already differ
Even 1,100 new cells of one type differ in capacity and resistance. In a series string, the weakest cell limits the pack.
K. Rumpf, M. Naumann & A. Jossen, Journal of Energy Storage, 2017
From one lab module to a 5 MWh container.
Our battery is a lab prototype today. Each next step makes it bigger and brings it closer to a product.
- 2025
BTTRY starts
The idea for a new kind of grid battery, built from the cell up.
- Spring 2026
Concept & simulation
Battery pack simulations and the control concept for switching individual cells.
- Aug 2026
Synchronised with the grid
Our lab prototype generates 50 Hz AC directly from its cells and runs in step with the grid.
- Oct 2026
Lab prototype
Switches each of its cells individually and balances them during operation.
Current stage - Step 1
Real-scale module
A module at full scale, built and connected to the grid.
- Step 2
Full single‑phase prototype
A complete single-phase battery: our biggest step from the lab towards a product.
- Step 3
Certified commercial prototype
A three-phase battery of about 220 kWh, certified to IEC 62619, EN 50549 and CE, running at a partner site.
- Step 4
First 5 MWh container
A 5 MWh battery built by BTTRY, in operation and building our track record.
The timing of the next steps depends on engineering, funding and partner sites.
Software that decides when to store and when to deliver.
A battery is only as valuable as the decisions behind it. We are building the software that makes those decisions, starting from the market and site data we already analyse today.
Today: site analysis
Our analysis platform models a battery on a site’s 15-minute metering data against historical day-ahead and imbalance prices, to size it and estimate what it adds.
Building: market optimisation
Deciding every day when to charge and deliver: day-ahead and imbalance markets first, balancing services next.
Building: grid awareness
Using TenneT’s published grid-balance data so the battery can respond to shortages and surpluses on the grid.
Open reporting
Every action of the battery logged and reported back to the site owner at 15-minute resolution.
Partner with us.
We are looking for pilot sites, technology partners, engineers and investors.