The premise
Robbert posted a 16 kWh DIY home battery build. The comment sections on YouTube, Facebook, and TikTok lit up. Some of it was useful feedback. A lot of it was variations on "you are going to burn the neighborhood down." This video is the rebuttal.
The short version: lithium is not one chemistry. The cells that burn down hoverboards, e-bikes, and Teslas are not the cells in a properly built home battery. Lumping them together makes a worse argument than treating petrol and diesel as the same thing.
Three chemistries that get called "lithium"
Lithium polymer (LiPo)
Soft-pouch cells. Found in tablets, drones, RC equipment. Extremely energy-dense and capable of dumping huge current quickly, which is why they're popular for drones where three or four are stacked in series for higher voltage. The catch: no rigid shell. Puncture one with a knife and it ignites violently.
Lithium-ion (Li-ion)
The 18650 cylindrical cell and its relatives. Found in phones, Makita tool packs, hoverboards, e-bikes, and Teslas. Higher energy density than LiFePO4 and can deliver power fast. In a thermal runaway they release oxygen from the cathode, which feeds the flames. Cells in a pack ignite their neighbors and the cascade is essentially impossible to stop. Robbert lists the recurring news stories: e-bikes, hoverboards, Teslas, laptops. The chemistry is the common factor.
Lithium iron phosphate (LiFePO4)
Larger prismatic cells, lower energy density per kilo, slower discharge. The trade-off is fundamentally better thermal behavior. A LiFePO4 cell in trouble tends to swell, vent, and smoke rather than torch the room. Each cell carries a vent membrane on top that opens under pressure. The chance of a LiFePO4 cell igniting with flame jets is much lower than a Li-ion equivalent. Not zero, but the difference is meaningful.
This is the chemistry Robbert used in his 16 kWh, 314 Ah pack. The choice was deliberate.
What actually triggers a fire
Cells fail when something inside the cell or around it crosses a limit:
- A short circuit that a fuse doesn't catch
- A BMS that fails to do its job
- Mechanical damage (puncture, crush)
- Severe overcharging
- Sustained overheating
The BMS exists to prevent the first four. On a healthy pack, the BMS continuously monitors per-cell voltage and pack temperature. If any cell drifts out of its voltage window (too high or too low), the BMS stops charging or discharging. If pack temperature climbs above its threshold, the BMS shuts down. On Robbert's setup, the Victron Cerbo also reads extra temperature sensors and can be configured to drop the whole battery if those go out of bounds. That's a second safety net on top of the BMS.
What about salvaged 18650 packs
A trend Robbert calls out: people stripping old e-bike packs, laptops, and other gear for 18650 cells and welding them together into homemade thuisaccu's. The problem is that the resulting pack is only as safe as the weakest cell. Thousands of cells, mixed ages, mixed conditions, with no per-cell history. One cell goes into runaway and the chain reaction does the rest.
This is a different proposition from a freshly built LiFePO4 pack with a proper BMS. Robbert is direct about it: he would not have salvaged 18650 packs in his own house.
Two corrections from his own build
Two things in the original 16 kWh build that he flagged after viewer feedback:
MEGA fuses on a battery pack. MEGA fuses cannot interrupt the very high fault currents a lithium pack can deliver. The right part for a battery main fuse is a Class T fuse, which is rated for those currents and breaks them cleanly. He's swapping them out before the pack goes into service. (A separate article covers fuse selection in detail.)
Thin red wires on the cells. Several commenters thought the small red wires running between cells were the main current path. They're not. The actual current runs through the thick metal busbars connecting the cell terminals. The thin red wires are BMS sense leads, used only for per-cell voltage measurement. They carry milliamps, not battery current.
The wooden frame. Same thread of comments: "why is your battery in a wooden crate?" The wooden plates are clamping the cells under permanent pressure, which counters cell swelling over time. They are not the final enclosure. The cell blocks will go into a steel cabinet in the actual install, with an additional fire-suppression system planned for the room.
Where this fits
The headline-grabbing battery fires almost always trace back to lithium-ion (18650-style) packs in densely-packed devices. Home batteries built from large LiFePO4 prismatics with a real BMS and proper fusing operate in a different risk regime. The chemistry choice is the first safety decision, and it is the one most easily missed by people who learned about lithium fires from a hoverboard video.
Takeaways
- "Lithium" covers three distinct chemistries with very different failure modes.
- LiFePO4 vents and smokes; lithium-ion can chain-ignite and feed itself oxygen.
- The BMS, not the cell chemistry alone, is what stops everyday failures from escalating.
- Class T fuses are the right pack-main fuse, not MEGA fuses.
- Salvaged 18650 packs are the configuration that actually deserves the "fire risk" reputation, not a properly built LiFePO4 system.
