Range of electric vehicles
Topic number

LI54.10-P-061051

Version

2

Design group

54.10 Battery, voltage supply, voltage converter

Date

04-20-2015

Validity

W242 electric drive

Reason for change

Country distribution revised

Reason for block

Complaint:

Range does not meet customer's expectations. Customers usually differentiate as follows:
1. Total of distance driven + indicated range remaining with one HV battery charge too low
2. Actual range until the drive system shuts down too low
Notes:
• When the HV battery has been fully charged (100% SOC) the instrument cluster (IC) displays the expected range.
The calculation is based on the individual driving style during the last trip(s).
• During a journey the progress of the range can change, e.g. if a different driving style is used or if there are idle periods with active electrical consumers. This means that the total of the distance driven + indicated range remaining can
vary from the reality, especially initially, because the actual consumption values are calculated on the basis of recent
trips.
• Above approx. 30% SOC the available power of the vehicle is reduced in stages relative to the HV battery temperature and the SOC (this can be seen on the power indicator in the bottom right-hand corner of the IC).
• At 12% SOC the message "HV Battery Reserve" is displayed in the IC. This message can be canceled.
• At 0% SOC the message "HV Battery Reserve" is displayed in the IC. This message can be canceled. The range is
not shown.
• 30 seconds before the drive is shut down, the message "Battery Power Too Low - Stop Vehicle - Charge Now" is
displayed.
It is not possible to restart the vehicle.
• The Eco display in the IC generally expresses how well an environmentally aware driving style can be achieved in
terms of acceleration, steady driving and coasting in relation to the customer's requirements. 100% Eco does not necessarily mean that the full range will be achieved (see variables under "Cause").

Cause:

The indicated range is always the certified value according to the applicable procedures (e.g. NEDC for Europe).
Particularly in cold and very hot temperatures the ranges of electric vehicles may be reduced. While at moderate temperatures (approx. 20°C) only approx. 10% of the total power consumption is required for electrical accessories, the
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percentage of the total consumption used by additional consumers increases to 20-30% in very cold or very hot temperatures. The following influencing variables play a particularly large role:
• Electric vehicles are heated via electric heater boosters/PTC, while in vehicles with combustion engine the waste heat of the engine can be utilized. Electric vehicles have the advantage that warm air is available immediately. This also
means that vehicles with combustion engine profit in terms of heating from the poorer efficiency of the engine as the
waste heat is utilized, while electric motors are more efficient. The electric heater booster/PTC initially requires a peak
power of up to 7kW . As soon as the interior compartment has reached the desired temperature and the temperature
only needs to be maintained, the power is approx. 3kW at outside temperatures of approx. -15°C.
• If the HV battery temperature is < 10°C, it is heated via the HV PTC. The power requirement may be up to 2.8kW.
• Additional consumers (12V on-board electrical system) in electric vehicles are supplied from the HV battery and not
via the alternator as in vehicles with combustion engine (guideline values: Lights: approx. 130W / Heated rear window: approx. 150W / Seat heater: approx. 150W per seat / Blower: up to 500W / Heated windshield: 380W)
• Increased rolling resistance: When the snow cover is closed, the rolling resistance rises, and so does the power consumption of the vehicle.
• Physical limits/HV battery: At low temperatures the internal resistance of the HV battery is higher.
• Idle times: When 12V consumers and e.g. the heating are activated while stationary, the above variables play a substantial role, since the HV battery is discharged yet no distance is covered, i.e. the energy ratio between driving and
electrical accessories shifts (approx. 5kW power requirement from the heating means e.g. that the HV battery will lose
approx. 50% of its charge after 3 hours).

Remedy:

1. Explain the relationships in a customer interview. For this purpose a "range spectrum" is attached as information for
customers.
Use this interview to explain possible courses of action and useful vehicle functions to the customer. Consistently following the instructions below can help to increase the range of the vehicle:
• Use the preconditioning function (with departure time) while the vehicle is connected to the charging infrastructure:
In this way the interior will be acclimatized and the HV battery can, given sufficient charging power (10kW), be kept
at 100% SOC (vehicle plugged into the mains), i.e. PTC/air conditioner compressor only have to maintain the temperature after the charging cable is unplugged and while driving. Alternatively, parking in garages or in the shade (summer) can help.
• Use the seat heaters more often instead of the interior heating: The interior temperature setting can be reduced by
using the seat heaters. Less energy is therefore required for the PTC/heater booster and the seat heaters operate
more efficiently compared to the interior heating.
• Driving style/regenerative braking: Power consumption can be reduced considerably by the consistent use of
recuperation (energy recovery) and a preventive driving style. The effects of recuperation can be seen in the "Power"
dial. In this way about 30% of the energy can be recovered when driving in mountains. In addition, driving at high
speeds should be avoided if the maximum range is desired.
• Use of the transmission modes: The use of the transmission modes E+ (as of code 805 + 055) and E help the driver
to optimize/ increase the range.
2. If necessary, perform a consumption measuring drive as follows:
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2.1 Acclimatize the vehicle (charge the HV battery to 100% SOC, leave the vehicle parked overnight in the workshop
at approx. 20°C or program the preconditioning function for the planned departure time)
2.2 Reset all consumption indicators (trip counter + consumption after start + consumption after reset). Important: The
SOC must be >80% SOC before the IC indicates a normal consumption value.
2.3 Set heater/blower to speed 1 and 22°C
2.4 Drive the vehicle mainly on urban/intercity routes (max. 90 km/h), and without stopping for long periods, until approx. 10% SOC remains (see IC displays under "Complaint")
2.5 Note down the values displayed in the IC for "range" + "distance driven" at 100% SOC, 75% SOC, 50% SOC,
25% SOC and 10% SOC
Guideline values:
• In very poor conditions (below -10°C, increased rolling resistance due to snow, heating activated) a range of approx.
85km should be possible (without traffic jams)
• In temperatures around freezing on cleared roads, approx. 110km should be possible without traffic jams
Note:
• When the above instructions on driving style etc. are observed, then the effects of quick acceleration, urban traffic
and topology are even less significant for electric vehicles than they are for vehicles with combustion engine.

Attachments
File

Description

Reichweitenspektrum_B-Klasse_Electric_Drive.pdf

Range spectrum

range_spectrum__B-Class_Electric_Drive.pdf

Range spectrum

Symptoms
Power generation / Engine management / Electric drive / Regenerative braking / Nonfunctional
Overall vehicle / Power supply / High-voltage on-board electrical system / High-voltage battery / Display message
Power generation / Engine management / Electric drive / Electric machine / Power reduced
Power generation / Engine management / Electric drive / Electric machine / Range reduced
Power generation / Engine management / Electric drive / Electric machine / Display message

Validity
Vehicle

Engine

Transmission

242.890

*

*

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