Every BYD EV sold outside China — Atto 3, Dolphin, Seal, Seal U, Sealion 7, Tang, Han — carries a Blade Battery, and every Blade Battery is lithium iron phosphate. Two things follow that most owners discover by accident: the charge gauge is guessing more than on an NMC car, and charging to 100 % is expected, not harmful.
What it is#
LFP is a cathode chemistry: lithium iron phosphate (LiFePO₄) against a graphite anode, with no nickel, cobalt or manganese. Blade is BYD’s cell format and packaging for that chemistry. The chemistry decides how a cell behaves; the format decides how much of it fits in the car.
| Property | LFP | NMC, for context |
|---|---|---|
| Nominal voltage | 3.2 V | 3.6–3.7 V |
| Specific energy | 95–172 Wh/kg; newer cells 180–205 Wh/kg | above 300 Wh/kg |
| Cycle life | 2,500–9,000 cycles, conditions dependent | about 1,000–2,300 |
| Thermal stability | higher decomposition temperature | lower |
Less energy per kilogram is the trade for cycle life and thermal behaviour: the iron–phosphate bond holds its oxygen tightly, which is why the cell resists thermal runaway.
How it works#
The flat voltage curve#
An NMC cell’s voltage falls steadily as it discharges, so voltage is a usable state-of-charge reading at any moment. An LFP cell sits on a plateau between roughly 20 % and 90 %, so in the middle of the range the BMS has to count charge in and out instead. Small errors accumulate and the displayed percentage drifts. Only at the top of charge, where the voltage knee is visible again, can the BMS re-anchor its estimate and balance the cells.
That is the mechanism behind two things owners notice: a range figure that jumps after a full charge, and the manual asking for one regularly.
The Blade format#
A Blade cell is a long, thin prismatic cell — about 96 cm long and 9 cm high — inserted directly into the pack housing side by side. BYD’s launch claim is more than 50 % better space utilisation than a conventional LFP block-cell pack, which is how a pack with lower cell-level energy density reaches a competitive capacity. On e-Platform 3.0 cars (Seal, Sealion 7) the pack’s upper cover is also the cabin floor — cell-to-body — a stiffness and packaging change, not a chemistry change.
Disclosed January 2020, launched 29 March 2020, first shipped in the Han EV in June 2020; built by BYD’s battery subsidiary FinDreams. A second-generation Blade was announced in 2025 at a reported 190–210 Wh/kg with the chemistry unconfirmed; no car sold in Morocco or Europe that we know of carries it.
In a Sealion 7#
A 150 kW peak against a 115 kW average is the usual LFP taper, and why a 10–80 % session takes over 30 minutes on a pack this size.
What it means for owners#
- Charge to 100 % on AC regularly. Not because the car needs it to drive, but because the BMS needs the top-of-charge voltage to correct its estimate.
- Between charges the gauge is an estimate. A range figure that changes after a full charge is the BMS correcting itself, not lost capacity.
- The pack is not the wear item. At 82.5 kWh usable and a realistic 180 Wh/km, one cycle is about 450 km; even the low end of the LFP cycle-life range is over a million kilometres. Calendar ageing and temperature matter more.
- Cold reduces what the pack accepts. LFP charges more slowly when cold and will not reach the 150 kW peak; where the car offers preconditioning before DC charging, use it. Not yet measured on a BYD by us.
- Read the safety claims as BYD’s own. Consistent with what LFP chemistry allows, but not independent results.
What we have not verified#
This is an explainer built from published sources; nothing in it is our own measurement yet.
- The owner’s manual wording on full-charge frequency in the Moroccan Sealion 7 manual specifically.
- The Sealion 7 cell count and nominal voltage (secondary database, consistent with arithmetic, not confirmed by BYD).
- A real DC charging curve on a Moroccan-market Sealion 7 (HU 2606) — planned as a lab note.
- Cold-weather charging behaviour on any BYD.
- Blade 2.0 chemistry.