SortedCE04
Member
Storage Temperatures
Recommended Storage Temperatures: Ideally 15°C to 25°C (59°F to 77°F) in a dry,
ventilated space. The BMW manual allows storage of the CE-04 at temperatures below
freezing but warns of significantly impaired performance upon restart and potential cell
damage if charged at low temperatures (below 0°C).
Cold Weather Effects: Below 0°C, self-discharge in batteries accelerates, and the coolant
(frost-resistant to -25°C/-13°F) must also be checked. No permanent damage to the battery
will result if the SOC is maintained. However, it is still critical to avoid extreme temperatures,
especially below -40°C (-40°F), to prevent premature cable failures.
Ontario specifically: With 4-6 months of sub-zero weather, it is important to aim for a garage
where the temperature will always be above (-5°C/23°F). If temperatures might drop below
-10°C (-4°F), insulate the CE-04 with a breathable cover and consider using a heat mat on a
thermostat.
General Battery Information - and cold weather
The CE-04's HV battery uses nickel-manganese-cobalt (NMC-811) prismatic cells licensed
from Samsung SDI (similar to BMW i3 packs: ~8.9 kWh total, 3.7V nominal per cell). These
are very safe and robust, but still very sensitive to cold charging and deep discharge. BMW
recommends fully charging to 100% before entering cold storage. In contrast, this appears to
contradict some general, non-Samsung-specific NMC advice, which usually recommends
storing at an SOC of c.50%. The literature and manufacturers vary, but the consensus is that
30-80% is the best SOC range for storage to minimise battery stress. That may be true for a
normal temperature range of 15°C to 25°C (59°F to 77°F), but due to increased cell
self-discharge at low temperatures, the upper end of this range is recommended.
This is where things get more complex.
BMW and SOC percentages are not quite what they seem.
The story starts with a deep collaboration with Samsung, which built a state-of-the-art battery
manufacturing plant at BMW (initially at Leipzig). The plant was constructed mainly in secret
during 2013. The plant was critical to BMW’s strategy at the time: to focus on advanced
materials and technologies to help secure a big leap into the future. It was a huge gamble
that nearly paid off, but sadly, they were about 3 years too early.
Remember that this is before the BMW i8 and i3 pioneering BEVs were ready to be
launched to the world. The i8 and the i3 were incredibly well-engineered (even for BMW),
but the general market wasn’t quite prepared for such a big leap. These vehicles used the
new prismatic NMC-811 cells.
This specialist prismatic NMC-811 battery plant produces the SDI cells (rectangular blocks)
that make up most of the battery packs BMW uses. Also, these same SDI cells form the
pack contents, which are now used in the CE-04 electric motorcycle and are assembled in
Munich at BMW Motorrad.
During testing and development, it was realised that these new prismatic NMC-811 cells
lasted much longer and behaved much more predictably if always kept at an SOC between
20% and 80%. To ensure nobody was ever tempted to drop the SOC below 20% or enter the
80%+ zones, BMW pulled a neat trick.
They simply changed the measurement scaling in the battery management unit software.
A simple but effective solution for all users, where the battery management unit reported an
SOC indication of 0% to 100%. In reality, the actual SDI battery SOC (realSOC) is held
between 20% and 80%.
To try and reduce the confusion, in this document, “SOC” refers to BMW's “State Of Charge”
of the battery pack as reported by the battery management software. The “State Of Charge”
of the battery pack, as far as the SDI cells within the pack are concerned, is the “realSOC”
Recommended Storage Temperatures: Ideally 15°C to 25°C (59°F to 77°F) in a dry,
ventilated space. The BMW manual allows storage of the CE-04 at temperatures below
freezing but warns of significantly impaired performance upon restart and potential cell
damage if charged at low temperatures (below 0°C).
Cold Weather Effects: Below 0°C, self-discharge in batteries accelerates, and the coolant
(frost-resistant to -25°C/-13°F) must also be checked. No permanent damage to the battery
will result if the SOC is maintained. However, it is still critical to avoid extreme temperatures,
especially below -40°C (-40°F), to prevent premature cable failures.
Ontario specifically: With 4-6 months of sub-zero weather, it is important to aim for a garage
where the temperature will always be above (-5°C/23°F). If temperatures might drop below
-10°C (-4°F), insulate the CE-04 with a breathable cover and consider using a heat mat on a
thermostat.
General Battery Information - and cold weather
The CE-04's HV battery uses nickel-manganese-cobalt (NMC-811) prismatic cells licensed
from Samsung SDI (similar to BMW i3 packs: ~8.9 kWh total, 3.7V nominal per cell). These
are very safe and robust, but still very sensitive to cold charging and deep discharge. BMW
recommends fully charging to 100% before entering cold storage. In contrast, this appears to
contradict some general, non-Samsung-specific NMC advice, which usually recommends
storing at an SOC of c.50%. The literature and manufacturers vary, but the consensus is that
30-80% is the best SOC range for storage to minimise battery stress. That may be true for a
normal temperature range of 15°C to 25°C (59°F to 77°F), but due to increased cell
self-discharge at low temperatures, the upper end of this range is recommended.
This is where things get more complex.
BMW and SOC percentages are not quite what they seem.
The story starts with a deep collaboration with Samsung, which built a state-of-the-art battery
manufacturing plant at BMW (initially at Leipzig). The plant was constructed mainly in secret
during 2013. The plant was critical to BMW’s strategy at the time: to focus on advanced
materials and technologies to help secure a big leap into the future. It was a huge gamble
that nearly paid off, but sadly, they were about 3 years too early.
Remember that this is before the BMW i8 and i3 pioneering BEVs were ready to be
launched to the world. The i8 and the i3 were incredibly well-engineered (even for BMW),
but the general market wasn’t quite prepared for such a big leap. These vehicles used the
new prismatic NMC-811 cells.
This specialist prismatic NMC-811 battery plant produces the SDI cells (rectangular blocks)
that make up most of the battery packs BMW uses. Also, these same SDI cells form the
pack contents, which are now used in the CE-04 electric motorcycle and are assembled in
Munich at BMW Motorrad.
During testing and development, it was realised that these new prismatic NMC-811 cells
lasted much longer and behaved much more predictably if always kept at an SOC between
20% and 80%. To ensure nobody was ever tempted to drop the SOC below 20% or enter the
80%+ zones, BMW pulled a neat trick.
They simply changed the measurement scaling in the battery management unit software.
A simple but effective solution for all users, where the battery management unit reported an
SOC indication of 0% to 100%. In reality, the actual SDI battery SOC (realSOC) is held
between 20% and 80%.
To try and reduce the confusion, in this document, “SOC” refers to BMW's “State Of Charge”
of the battery pack as reported by the battery management software. The “State Of Charge”
of the battery pack, as far as the SDI cells within the pack are concerned, is the “realSOC”