general information on electric power consumption general

Electric power consumption for the 24 V system
General information on electric power consumption
General information on electric power con-sumption

IMPORTANT!

To prevent battery damage, the vehicle charging capacity must be adapted to the ve-hicle’s electric power consumption. The batteries, charging capacity and electric power consumption must be adapted to the way the vehicle is used and be in charge balance with each other.

IMPORTANT!

To ensure the correct function of all the vehicle's electrical components, the body-work electrical system must only be connected to terminals intended for the purpose.More information can be found in the document Bodywork interface.

The vehicle's electrical system consists of a large number of electrical components. The electrical components are dependent on the variations in the electrical system voltage levels not being too large.

The electrical system for bodywork must be designed to ensure minimum permissi-ble voltage variations in accordance with Scania requirements.

More information on voltage variation requirements can be found under the heading General requirements.

Optional equipment installed must be equipped with electric dampers that suppress voltage variations and current surges. It is particularly important that all inductive loads, such as relays, solenoid valves and other solenoids, are suppressed. Electric motors, regardless of size, must have blanking capacitors fitted to reduce the risk of radio interference. The size and type depend on the design of the electric motor.

Scania Truck Bodybuilder 22:10-664 Issue 2 2021-10-06© Scania CV AB 2021, Sweden 1 (19)

General information on electric power consumption


P

U I

315

936

• P = power in watts (W)• U = voltage in volts (V)• I = current in amperes (A)

General requirements• An electric load connected to the truck's electrical system must not cause a volt-

age ripple at the connection point that exceeds ± 1.5 V in a frequency range be-tween 0-30 kHz.

• An electrical load connected to the truck's electrical system must not cause cur-rents or return currents that exceed 1.5 times the fuse's rated current for the load.

Calculating the electric power consumptionCalculate the electric power consumption to determine dimensions for fuses and ca-bles when connecting optional equipment.

If 2 of the 3 units (P, U or I) are known, it is possible to calculate the third using the following formulas; see illustration:

Example:Power P = 200 W, voltage U = 24 V.

U =P

I =P

P = U × II U

I =200 W =

> I = 8.3 A24 V


Charging capacity


Charging capacityOn vehicles that only have a combustion engine, the 24 V batteries are charged by an alternator, which can be specified with different performances depending on the ve-hicle's electric power consumption.

Battery electric vehicles (BEV), hybrid electric vehicles (HEV) and plug-in hybric vehicles (PHEV) do not have alternators. The 24 V system is charged via a DCC (di-rect current converter), which converts the voltage in the propulsion batteries to 24 V.

The charge balance in the vehicle varies depending on how the vehicle is used.

• The current that is taken from the batteries must be recharged within about 24 hours.

• Cold temperature conditions causes the charging ability of the batteries to be sig-nificantly lower than at higher temperatures.

To ensure the alternator’s service life, the current consumption may only be 80% of the values in the table below during 95% of the operating time.


Charging capacity


PrestoliteA 150 A 180 APulley 80

mmPulley 70

mmPulley 80

mmPulley 70

mmPulley 80

mm85 A 93 A 87 A 162 A 148 A

128 A 103 A 96 A 197 A 177 A152 A 124 A 115 A 217 A 215 A183 A 187 A 182 A 234 A 233 A

The table below shows examples of alternators. The values in the table specify the guaranteed current delivery during all operating conditions on condition that the above factors are satisfied.

On battery electric vehicles, the DCC unit has a maximum capacity of 270 A.

More information on long-term storage can be found in the document Battery main-tenance.

Engine speed Melco100 A 130 A 120

Pulley 70mm

Pulley 80mm

Pulley 70mm

Pulley 80mm

Pulley 70mm

500 rpm 60 A 50 A 53 A 35 A 106 A600 rpm 69 A 62 A 76 A 60 A 144 A800 rpm 78 A 74 A 93 A 89 A 172 A

1,500 rpm 96 A 94 A 120 A 116 A 185 A


Charging capacity


Variable idling speed – applies to vehicles with al-ternatorsThe variable idling speed function is intended to ensure that the batteries receive enough charging current. The function increases the idling speed automatically ac-cording to the batteries’ requirements, but to max. 640 rpm.

The function can be activated and deactivated by a Scania workshop.

Note:• If the current consumption exceeds the alternator’s capacity, this function will not

ensure that the batteries get sufficient charging.• If the bodywork equipment has a high electric power consumption, the operation-

al working range should be above 640 rpm to compensate for a lower charging current from the alternator at low engine speeds.


Charging capacity


Adaptive battery chargingWith the Adaptive battery charging function, the charging voltage will vary depend-ing on battery temperature. The value can vary between 26 V and 30 V. The charging voltage is normally 28.3 V.

At a low battery temperature, the batteries need a higher charging voltage for opti-mum charging.

At a high battery temperature, a lower charging voltage is needed for optimum charg-ing. Electrolyte evaporation is also reduced at a lower charging voltage.

This function is most useful in extremely cold or extremely hot conditions or during operation where the batteries are alternately under load and heavy charging. The function also recharges the batteries more quickly when the electrical system has been used with the engine off.

The function can be activated and deactivated by a Scania workshop.


Charging capacity


The vehicle's charging capacityThe vehicle must have adequate charging current for current consumers when the ve-hicle is in operation and also to charge the batteries. The current supply should be sufficient to ensure that the batteries will not need to be used when the vehicle is run-ning

The alternator must have the capacity to meet the needs of the current consumers and also have a certain overcapacity for battery charging.

The following overcapacity is required by the alternator or DCC:

• 20 A for vehicles with long distances driven without stopping, such as long-haul vehicles.

• 30 A for vehicles with short distances driven between each stop, such as distribu-tion vehicles.

Methods for checking the vehicle's charging capacity:

• Check the system voltage when the current consumers are connected and the al-ternator is charging. If it exceeds 26.5 V, the current will be enough for current consumers and for charging the batteries. System voltage can be read in the in-strument cluster.Check the voltage during normal use of the vehicle when normal current consum-ers have been switched on for at least 15 seconds; a longer time is required at low temperatures.

• An approximate way of checking that the alternator has enough capacity is by adding up the electric power consumption and then adding the overcapacity.

More information on the instrument cluster can be found in the Driver’s Manual.

The vehicle's basic consumption during operation without a trailer is 10-15 A de-pending on configuration.


Charging capacity


The values for electric power consumption in the following table are used together with the basic consumption to estimate the total electric power consumption for a complete vehicle depending on equipment and how it is used.


Charging capacity


The following table shows examples of current consumers.

Vehicle current consumers Number x AmpereHeadlamp 2 x 3 ATail lamp, position lamp 4 x 0.25 ATail lamp LEDa

a. With position lamp, end-outline marker lamp and registration plate lighting.

2 x 0.25 APosition lamp, front 2 x 0.25 AEnd-outline marker lamp, rear 2 x 0.25 AEnd-outline marker lamp, front 2 x 0.25 ASide marker lamp 2-8 x 0.25 ASide marker lamp LED 2-8 x 0.05 AInstrument panel lighting 20-30 x 0.05 AFan motor 1 x 0.25-14b A

b. If the starter lock is in drive mode, the fan motor runs constantly, even if the fan control is set to 0, and then consumes approx. 0.25 A. At maximum fan speed, the motor consumes 10-14 A.

Windscreen wipers 1 x 4 ARadio, standard 1 x 2 A

Trailer current consumers Number x AmpereTail lamp, position lamp 4 x 0.25 ATail lamp LEDa

a. With position lamp, end-outline marker lamp and registration plate lighting.

2 x 0.25 ASide marker lamp 8 x 0.25 ASide marker lamp LED 8 x 0.05 AEnd-outline marker lamp 2 x 0.25 ABox lighting 4 x 2 A


Charging capacity


hare of operating ime0%00%00%0%0%0%0-100%5%00%%0%

5%

More information on electric power consumption can be found in the document Har-ness-to-harness connector C162 – trailer connection.

On battery electric vehicles, the electric power consumption from the vehicle's 24 V system varies widely depending on environmental factors, for example in cold cli-mates, there is a need for heating the propulsion batteries and in hot climates there is a need to cool them. This means that, for example, cooling fans and pumps are acti-vated automatically, resulting in varying loads on the 24 V system.

Optional equipment current consumers Guide values (Number x Am-pere)

St

Auxiliary light 2-4 x 3 A 5Side marker lamp 4-6 x 0.25 A 1Side marker lamp LED 2-8 x 0.05 A 1Roof lighting, exterior 1 x 4 A 5Loading lamps 2 x 4 A 5Electrically heated seats 2 x 2.5 A 1Electrically heated mirrors 2 x 5-14 Aa 5Electrically heated windscreen approx. 40 A 2Active steering 0.5 A 1Electrically steered tag axle 50 Ab 5Refrigerator 1 x 2 A 6Tail lift 1 x 100 AExtra cab heater: 2Engine and cab heater 6 ACab heater 3 AShort-stop heater 4 AKitchen module:Microwave oven 1 x 40 A at full power


Charging capacity


5%

hare of operating ime

Coffee maker, keeping warm or brewing 1 x 10 A or 20 AAuxiliary cab cooler 15 A 2a. Temperature-dependentb. The above codes only apply when the steered tag axle is lowered and during operation.

Optional equipment current consumers Guide values (Number x Am-pere)

St


Direct current converter, DCC


Direct current converter, DCCThe direct current converter can supply up to 270 A and charges the 24 V batteries when the electrical system for voltage class B is active. Charging of the 24 V batter-ies is activated when the starter lock is in drive mode and the propulsion battery con-tactors are closed and supplying the electrical system for voltage class B with 650 V DC (nominal voltage).

Since the 24 V batteries in a battery electric vehicle have a smaller capacity (Ah) compared to vehicles without propulsion batteries, there is a risk of discharging the 24 V batteries. This applies where the 24 V system has a high load and the propulsion batteries are switched off and the 24 V batteries are not charged by the vehicle. For example, when using a tail lift.

To reduce the risk of a low state of charge in the 24 V batteries, there is an option to keep the charging function from the propulsion batteries active even when the vehi-cle has been switched off. This function with the designation "Keep voltage class B at 24 V after driving" is programmed at the factory to be active for 15 minutes after the vehicle has been switched off. However, the active time may be adjusted using SDP3 for bodybuilders to the desired value between 0-180 minutes.

Connecting external chargingExternal equipment may be connected in order to charge the batteries in the 24 V sys-tem. However, the external charging must not damage the vehicle's electrical system. One example of such equipment is solar panels, and the equipment must be voltage-controlled and have the same charging voltage as the vehicle. An incorrect charging voltage can cause overcharging that results in battery damage; the equipment's qui-escent current, connection point and satisfaction of ADR requirements must also be taken into account during installation. Contact your local Scania distributor for more information.


24 V batteries


24 V batteriesNote:The batteries should be dimensioned so that they are never discharged to less than 50% of their capacity. Extensive discharge to less than 20% of the capacity will quickly reduce their service life.

Note:Use the starter lock radio mode instead of drive mode when the vehicle is parked and the radio is active. This reduces the electric power consumption and therefore also the battery discharge.

The task of the batteries is to provide power for starting the vehicle and to be a power source for current consumers when the vehicle is switched off.

If the capacity of factory-fitted batteries does not correspond to the consumption re-quired by the bodywork, the vehicle must be fitted with a greater battery capacity.

The battery capacity (Ah) is determined by how much current (A) can be consumed and for how long (h) the current can be consumed with the engine switched off.

Quiescent power consumptionWhen the vehicle is switched off and no external consumers are connected, some cur-rent is still consumed, also referred to as quiescent power consumption. The tacho-graph and alarm system are examples of 2 units that need to be able to function while the vehicle is parked. For such units, the quiescent power consumption must be kept so low that vehicles can be parked for a longer period without draining the batteries to less than 50% of their capacity.

All other units that do not have a significant function while the vehicle is parked must either be disconnected or have a quiescent power consumption that is less than 0.5 mA so as not to affect the batteries.


24 V batteries


There are systems that require a longer shutdown process, such as the reductant dos-er, which circulates urea to cool the dosing nozzle after the combustion engine is shut down. The practice for these systems is to allocate them 1 Ah for shutdown.

Other systems that are only used when the batteries are supplying power to the vehi-cle include short-stop cooling and auxiliary heaters. These climate units have an elec-tric power consumption of 60 Ah when in use. This type of system is subject to the requirement for quiescent power consumption only when they are switched off, not during the time they are used. The electric power consumption of factory-fitted sys-tems is dimensioned for the choice of battery and alternator.

Some bodywork functions can be used when the engine is switched off, e.g. a tail lift. These systems are allowed to consume a moderate amount of energy during use as long as they do not compromise the battery's ability to start the vehicle.

Common to all different types of consumers is that the quiescent power consumption should be kept so low that the entire vehicle's quiescent power consumption is below 30 mA. This limit is calculated to ensure that the batteries are not damaged during extended periods of vehicle use, e.g. when the vehicle is delivered or during a month's holiday period.

If the vehicle is fitted with a battery master switch, this must be used during extended periods of operation to protect the batteries from harmful discharge. The low battery quiescent power consumption requirement cannot be cancelled by fitting vehicles with battery master switches because battery disconnection depends on operation.

If optional equipment from the bodybuilder has a higher quiescent power consump-tion than recommended, other measures must be taken, e.g. increased battery capac-ity or automatic disconnection after a period of time.

The vehicle can be factory-fitted with a built in Battery charger (variant code 3826A). The battery charger can be used when the vehicle is parked. The battery charger is automatically activated when the charging cable is connected to the charg-ing socket. On vehicles fitted with 0 or 40 mm protruding bumpers, the charging socket is located in the cab front, by the left-hand headlamp.


24 V batteries


3 1

2

370 1

19

1. Starter battery2. Starter battery relay3. Service battery

Dual battery systemThe vehicle can be factory-fitted with a Dual battery system (variant code 00095D). The option consists of 2+2 batteries as follows:

• Separate starter batteries for the starter motor• Service batteries for other current consumers when the engine is switched off

The battery capacity and charging ability are well suited for their tasks. The installa-tion can be ordered from the factory.

Note:Do not use a voltage guard in connection with dual battery systems. The service bat-teries can withstand being extensively discharged without risking their starting abil-ity. A voltage guard limits the possibility of utilizing the full capacity of the service batteries.If connected equipment cannot be connected without a voltage guard, the maximum recommended setting is 20 V (18 V for tail lift) or lower voltage.

More information on dual battery system is found in the Dual battery system docu-ment.


24 V batteries


1

3

2

370

120

1. Starter batteries2. Starter battery relay3. Service batteries

LocationThe batteries are located in the battery box on the chassis frame.


24 V batteries


city climated climate

Ah

ca.

Ah

Alternator size and battery capacityThe following table shows recommended selections of alternator and battery capac-ity from the factory depending on vehicle type and usage.

Vehicles powered with a combustion engineVehicles fitted with dual battery systems have lower service battery capacity (85 Ah). This means that the choice between 230 Ah batteries or a dual battery system must be based on the vehicle's electric power consumption when the engine is switched off and how much guaranteed engine start is prioritised.

Example 1: A vehicle with frequent use of equipment connected to the service bat-teries (e.g. tail lift) when the engine is switched off and where the engine cannot cool down between engine starts should be fitted with 230 Ah batteries.

Vehicle type Alternator Battery capaVehicles with low/medium electric power consumption. For example, vehicles without much optional electrical equipment.

100 A 140 Ah in hot180 Ah in col

Vehicles with medium electric power consumption. For example, distribution vehicles with tail lifts.

100-130 A 180-225a/230

a. Note! 225 Ah maintenance-free batteries are only available for vehicles manufactured in Latin Ameri

Vehicles with high electric power consumption. For ex-ample, distribution vehicles with tail lifts and short dis-tances driven with frequent loading and unloading.

130-150 A 180-225a/230

Vehicles with very high electric power consumption. For example, long-haul vehicles with auxiliary heaters, kitch-en modules, short-stop coolers or PCs. Or timber trucks, tankers and other vehicles with long distances driven at low engine speed

150-180 A 180-230 Ah


24 V batteries


Example 2: A vehicle where guaranteed engine start is prioritised over the use of equipment connected to the service batteries must be fitted with a dual battery sys-tem.

For vehicles where guaranteed engine start is prioritised at temperatures below -10°C, it is recommended that the vehicles are fitted with 230 Ah batteries or a dual battery system.

Vehicles powered with a propulsion batteryThe battery capacity for vehicles with a propulsion battery is as follows:

• Battery electric vehicles: 50 Ah service battery• Hybrid vehicles: Dual battery systems with a 50 Ah starter battery and 85 Ah ser-

vice battery.

The dual battery system has service batteries that can withstand deeper discharge without being damaged, but they have a relatively low capacity (85 Ah). This may be a disadvantage for vehicles that have a high electric power consumption with the engine switched off.

Example:

• Use of short-stop cooling in the following circumstances:– The vehicle is parked and the engine is switched off– The outdoor temperature is +30°C– The desired cab temperature is +20°C

• 85 Ah is enough for the short-stop cooler to be activated for 4 h with a dual battery system.

• The corresponding time for vehicles with a battery capacity of 210 Ah is 8 h while retaining the engine start option.

The above values are only for reference and assume that the batteries are fully charged when parking and that they have not been degraded in terms of capacity/ser-vice life.


24 V batteries


For vehicles where guaranteed engine start is prioritised but which also have a high electric power consumption with the engine switched off, it is recommended that the vehicle is factory-fitted with a special order Dual Battery where the dual battery sys-tem is combined with a battery with a capacity of 210 Ah AGM (Absorbent Glass Mat ) or 210 Ah GEL as service batteries.


general information on electric power consumption general

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