Service Information: Lithium-Ion Battery - SI54.10-P-0068A
Model 451.390/391/490/491, 453.091/391/491
Model All (CAR)
With Code ME01 (Electric motor)
Model All (CAR)
With Code ME02 (Fuel cell)
Model All (CAR)
With Code ME04 (Mild hybrid drive)
Model All (CAR)
With Code ME05 (Hybrid drive 85 kW-94 kW variant (incl. plug-in))
Model All (CAR)
With Code ME06 (Hybrid drive 60 kW variant (incl. plug-in))
Model All (CAR)
With Code ME08 (Hybrid drive 75-84 kW VARIANT (INCLUDING PLUG-IN))
Model All (CAR)
With Code ME10 (Hybrid vehicle (plug-in, PHEV))
Lithium-ion batteries are highly-efficient and complex energy storage units. Lithium-ion technology is currently the most efficient battery technology on the market. No other battery technology satisfies the required parameters such as quality, output, service life and costs required for automotive applications. Further development of lithium-ion technology means that high electric operating ranges are now almost within reach, while charging times too have been significantly reduced thanks to the rapid charging technology. While lithium-ion batteries are low-maintenance, handling an electric vehicle battery requires electrotechnical expertise. As with other component parts, all lithium-ion batteries are also subject to a certain degree of wear.
The intelligence of the battery system lies not in the cell alone, but in the overall system. This consists of the control electronics, including software, the integrated cooling, the highly-reliable housing that is tailored to the vehicle and last, but not least the cells themselves.
Aging of lithium-ion batteries
The lithium-ion batteries installed by Daimler AG are designed to be used throughout the entire vehicle life cycle. As with many other component parts however, they too are subject to some degree of wear. Where batteries are concerned, this is covered by the term "aging".
Generally, with lithium-ion technology, a differentiation is made between two basic aging mechanisms:
- Calendrical aging
- Cyclic aging
Aging of lithium-ion batteries can be recognized by the fact that their usable capacity is reduced over the course of their full service life.
To exert a positive influence on the effects brought about by these various mechanisms, it is important to understand several general basic mechanisms and to handle the lithium-ion batteries accordingly.
Calendrical aging of lithium-ion batteries
Lithium-ion batteries are subject to the natural effect of so-called calendrical aging. This occurs both during vehicle operation as well as during nonoperational phases of the lithium-ion batteries. Calendrical aging is affected primarily by two influencing factors. The primary influencing factors are:
- temperature
- state of charge (SOC)
The influence of temperature and SOC on the aging of lithium ion batteries should be understood as follows:
- The higher the temperature, the greater or faster the aging
- The higher the SOC, the greater or faster the aging (during the nonoperational phase)
Bearing this in mind, the following recommendation can be made:
If lithium ion batteries have to be put into storage, then...
- an average temperature of 25°C should not be exceeded
- a charge level of less than 40 % SOC
... should be set to keep the effects of calendrical aging as low as possible.
If lithium-ion batteries are installed in a vehicle, the same aging processes and mechanisms occur with them as for lithium-ion batteries that are placed into individual storage. Important information on how to put vehicles equipped with lithium-ion batteries into storage is available in SI54.10-P-0024A Service information: Battery maintenance.
Cyclic aging of lithium-ion batteries
Lithium-ion batteries from Daimler AG are specifically developed for use in automobile applications, and they have been optimized for traction and drive support. They are characterized by a high level of cycle stability (long service life) and a high energy and output density. The intelligent software ensures that the lithium-ion batteries used are operated at their optimum temperature and performance limit.
Despite all the technically-possible measures that can be used, over the course of time lithium-ion batteries - when used - will suffer an irreversible loss of usable capacity. This is an unavoidable electrochemical process that affects all lithiumion batteries. The capacity of lithium-ion batteries is reduced to a small degree with every cycle of use. The following applies here, the greater the difference in a cycle's SOC, the greater the influence on cyclical aging.
The cyclical aging of lithium-ion batteries is a natural process that occurs within the lithium-ion battery cells. Technically it is not possible to stop it. Extensive measures have made it possible to reduce cyclical aging. Consequently, the capacity and power of our lithium-ion batteries remain at a high level for a very long period of time.
Some of the measures taken by us to reduce the amount of aging can be experienced by customers themselves in extreme situations. As temperature exerts a tremendous influence on the aging of lithium-ion batteries, and to help avoid damage to the lithium-ion batteries, the electric power is reduced on a lithium-ion battery that is too cold or too warm. However, as soon as the lithiumion batteries are returned to their optimum temperature range through our intelligent cooling and heating strategy, the full electric power becomes available once again in the normal way.
Instructions on using or maintaining lithium-ion batteries
Aging of lithium-ion batteries can be recognized by the fact that their usable capacity is reduced. Customers can deploy various measures during the usage phase to exert a positive influence on the effects based on these different mechanisms:
- Avoid any lengthy non-operational times when SOC is high:
If lithium-ion batteries are used for a long period at a high SOC, the calendrical aging process is more pronounced than when the SOC is at a lower level. This is why, if possible, lengthy non-operational times should be avoided when the SOC is high. A SOC of approx. 40 % reduces the calendrical aging of lithium-ion batteries, and is therefore recommended where lengthy non-operational periods are involved.
- Regular recovery phase:
Lithium-ion batteries should not be recharged immediately after the discharge process. Charging lithium-ion batteries immediately after discharging them means they do not have any time to recover. This recovery phase is of great significance for lithium-ion batteries. It reduces chemical secondary reactions in the cell thereby increasing its service life. Therefore, our advice is to run through the following procedure at regular intervals:
- Park vehicle at regular intervals (e.g. once weekly) for an extended period (e.g. overnight or over the weekend) at a low SOC (e.g. 20 % - 30 %).
- After this recovery phase the vehicle can then be charged again as usual.
- Charging on as and when required basis:
An average SOC of approx. 30 % - 70 % reduces the aging of the lithium-ion batteries. To achieve this, for maintenance reasons, we recommend fully charging the lithium-ion batteries immediately before they are about to be used.
| Service Information: Battery maintenance | SI54.10-P-0024A |