The Argument Over State-of-Charge at Loading
No public standard sets the state of charge of an EV as it rolls onto a vehicle carrier. The number is argued hard behind closed doors — and it matters.
There is no international rule on what state of charge a battery-electric vehicle should be in when it is loaded onto a RoRo. Some OEMs prefer 50–60% to enable delivery test drives. Some operators want 30% or lower to limit thermal energy on board. The argument is real and almost entirely private.
Why SoC matters thermally
- Stored energy is roughly linear in SoC — more charge, more available energy in a runaway event.
- Peak cell temperature in runaway rises with SoC, raising the propagation risk to neighbours.
- Some BMS firmware paths are more sensitive at high SoC, particularly under vibration.
The number is going to become a published policy somewhere — either at IMO, at a class society, or in a major operator's loading manual that becomes a de-facto industry standard. Worth watching.
Sources
- Larsson, F. et al. — "Toxic fluoride gas emissions from lithium-ion battery fires," Scientific Reports 7, 10018 (2017).
- IUMI — "Risk mitigation for the safe ocean and short-sea carriage of electric vehicles" (Sept 2025 revision).
- Vehicle Carrier Safety Forum (VCSF) — published guidance on EV loading practice (2024–2025).
- ICCT — research notes on EV logistics and state-of-charge in maritime transport.
- [VERIFY: 30% operator-preferred and 50–60% OEM-typical loading SoC — operator/OEM-internal practice; no public consolidated source.]
- [VERIFY: "~2x available-energy ratio between 30% and 60% packs" — engineering rule of thumb; depends on chemistry and cell architecture.]
Questions, answered
Is there a standard state of charge for EVs loaded onto car carriers?+
No international rule exists. Some OEMs prefer 50–60% to enable delivery test drives; some operators want 30% or lower to limit thermal energy on board. The argument is real and almost entirely private, conducted in loading manuals and contracts rather than public standards.
Why does loading state of charge matter thermally?+
Stored energy is roughly linear in SoC, so more charge means more energy available in a runaway. Peak cell temperature in runaway rises with SoC, increasing propagation risk to neighbouring vehicles, and some BMS firmware paths are more sensitive at high SoC, particularly under vibration.
How much difference does SoC make to stored energy?+
As a rule of thumb, a pack at 60% holds roughly twice the available energy of one at 30%. That is why the gap between an OEM-typical 50–60% delivery charge and an operator-preferred 30% is operationally significant, not cosmetic.
Continue the thread
What the New Vehicle Loading Guidance Requires
ICS/IGP&I Common Guidance sets a booking-to-discharge data chain for vehicles: declared propulsion type, recorded SOC, and an OEM emergency guide.
Can Battery Passports Screen EV Fire Risk?
The EU battery passport carries state-of-health data from 2027 — but it was built for recyclers, not the loading ramp, and won't screen EV fire risk yet.
The EV-Percentage Tipping Point
Operators talk about 'mixed cargo' in public; internally it's a hard EV percentage above which sailings get re-routed. That number is moving.