Jump Starting and Charging Batteries with the New 42V PowerNet

1. 1 Jump Starting and Charging Batteries with the New 42V PowerNet Wolf-Dieter Blauensteiner - DaimlerChrysler Jarvis Carter - Motorola Semiconductor Philippe Desroches - Seimens Automotive Alfons Graf - Infineon technologies Tom Keim - MIT Peter Miller - Motorola AIEG Paul Nicastri - Ford Motor Company Good morning. It is a real pleasure to be addressing you at this first 42V International Congress. I�m going to be presenting a paper on Jump Starting and Charging Batteries with the New 42V PowerNet. The paper is a joint effort of 7 authors from 7 organizations. Good morning. It is a real pleasure to be addressing you at this first 42V International Congress. I�m going to be presenting a paper on Jump Starting and Charging Batteries with the New 42V PowerNet. The paper is a joint effort of 7 authors from 7 organizations.

2. 2 Jump Start Team DaimlerChrysler Motorola AIEG Delphi Motorola Semiconductor Ford Siemens Automotive Infineon Technologies Varta JCI Visteon MIT The jump start team includes members from 11 organizations at locations in Europe and North America. It is an outgrowth of a Virtual Engineering Initiative sponsored by Ford and facilitated by the Massachusetts Institute of Technology. The authors wish to thank the many people from these organizations who have greatly contributed to this effort.The jump start team includes members from 11 organizations at locations in Europe and North America. It is an outgrowth of a Virtual Engineering Initiative sponsored by Ford and facilitated by the Massachusetts Institute of Technology. The authors wish to thank the many people from these organizations who have greatly contributed to this effort.

3. 3 Vision Statement Develop strategies for safely jump starting vehicles when the 42V PowerNet is available. Share the results with others in the industry to promote a common/compatible approach across all 42V PowerNet vehicles. The team was formed to develop strategies that would facilitate safe jump starting of vehicles when 42V PowerNet vehicles are available. We also want to disseminate the results of our effort in order to develop a consensus throughout the industry. The specific implementation may vary from manufacturer to manufacturer, but what we desire, is that each approach is compatible, so that it will be possible to give/receive a jump start from any other PowerNet vehicle, and hopefully even from/to non-PowerNet vehicles.The team was formed to develop strategies that would facilitate safe jump starting of vehicles when 42V PowerNet vehicles are available. We also want to disseminate the results of our effort in order to develop a consensus throughout the industry. The specific implementation may vary from manufacturer to manufacturer, but what we desire, is that each approach is compatible, so that it will be possible to give/receive a jump start from any other PowerNet vehicle, and hopefully even from/to non-PowerNet vehicles.

4. 4 Goal Strategies should consider Customer safety and convenience Electrical system protection Reliability, size, weight and cost Jump starts to/from other PowerNet vehicle. Jump starts to/from non-PowerNet vehicles Discharged only and defective batteries Improper voltage and polarity jump starts When comparing different strategies, we wanted to consider the following: Customer safety and convenience Electrical system protection Reliability, size, weight and cost Jump starts to/from other PowerNet vehicles Jump starts to/from non-PowerNet vehicles Discharged only batteries and defective batteries Improper voltage and improper polarity jump startsWhen comparing different strategies, we wanted to consider the following: Customer safety and convenience Electrical system protection Reliability, size, weight and cost Jump starts to/from other PowerNet vehicles Jump starts to/from non-PowerNet vehicles Discharged only batteries and defective batteries Improper voltage and improper polarity jump starts

5. 5 Today�s Situation Nearly all cars have 12V batteries. Jump starting is done using jumper cables with �alligator� style clamps connected battery to battery. All electrical components are designed to protect against reversed battery connections. Dual battery voltage (24V) jump starts are sometimes employed in cold climates. How many of you have ever needed to jump start a vehicle? SHOW OF HANDS The situation today is fairly simple. Nearly any car you find will have a 12V battery, so all you really need to worry about is getting the batteries connected properly. Jump starting today will most likely be done using a pair of jumper cables with alligator style clamps. If you keep the connectors from shorting against each other in the process, the only other thing to worry about is making sure that the polarity of each connection is right. Now if jump starting was done only in good light with parts that are clean and clearly marked, this probably wouldn�t be a problem. Unfortunately, oftentimes, jump starts are done in the dark or when the weather is bad and the battery terminals markings are not readily identifiable, leading to the reversing of the connections. To protect against this possibility, today�s vehicleshave all electrical devices designed to be able to withstand reverse polarity. Protecting 42V components from reverse battery will be more difficult and expensive. In cold climates, it is common for road service crews to use dual batteries (24V) to jump start customers� vehicles. Dual 36V battery (72V) jump starts may pose a safety risk and protecting the electrical devices also could be expensive. How many of you have ever needed to jump start a vehicle? SHOW OF HANDS The situation today is fairly simple. Nearly any car you find will have a 12V battery, so all you really need to worry about is getting the batteries connected properly. Jump starting today will most likely be done using a pair of jumper cables with alligator style clamps. If you keep the connectors from shorting against each other in the process, the only other thing to worry about is making sure that the polarity of each connection is right. Now if jump starting was done only in good light with parts that are clean and clearly marked, this probably wouldn�t be a problem. Unfortunately, oftentimes, jump starts are done in the dark or when the weather is bad and the battery terminals markings are not readily identifiable, leading to the reversing of the connections. To protect against this possibility, today�s vehicleshave all electrical devices designed to be able to withstand reverse polarity. Protecting 42V components from reverse battery will be more difficult and expensive. In cold climates, it is common for road service crews to use dual batteries (24V) to jump start customers� vehicles. Dual 36V battery (72V) jump starts may pose a safety risk and protecting the electrical devices also could be expensive.

6. 6 Typical Jumper Cables This is a photo of a typical set of jumper cables. In this case, there are two red �alligator� clamps connected by a heavy gauge wire and two black alligator clamps. The are relatively inexpensive and are available at many stores.This is a photo of a typical set of jumper cables. In this case, there are two red �alligator� clamps connected by a heavy gauge wire and two black alligator clamps. The are relatively inexpensive and are available at many stores.

7. 7 Present 14V Architecture Today�s architecture is fairly simple. The vehicle has a 12V battery that gets recharged by a 14V generator when the engine is running. The starter draws power from the battery to start the engine. If the battery is deeply discharged, the engine won�t start. Ofentimes, a jump start is all that is needed to get the vehicle running again. Today�s architecture is fairly simple. The vehicle has a 12V battery that gets recharged by a 14V generator when the engine is running. The starter draws power from the battery to start the engine. If the battery is deeply discharged, the engine won�t start. Ofentimes, a jump start is all that is needed to get the vehicle running again.

8. 8 The Future Situation Vehicles may only have 12V batteries or could have both 12V and 36V batteries. 42V PowerNet vehicles may have DC/DC converters to power 14V loads from the 42V bus and, if the converter is bi-directional, power 42V loads from the 14V bus (enabling internal jump starts). System voltage specifications minimizes voltage range. The future will a bit more complicated once 42V PowerNet vehicles are roaming the streets. Then, when you need a jump start, it will be important to know what voltage battery is in each vehicle. It is imperative that jump starting is only attempted between batteries of the same voltage in order to prevent personal injury and/or vehicle damage. Many 42V PowerNet vehicles will have dual 42V/14V systems equipped with a bi-directional DC/DC converter. Normally they will convert 42V to 14V for load support and charging the 12V battery, but they can also convert 14V to 42V, providing the capability for a built in jump start. This can greatly reduce the likelyhood of ever needing a jump start from another vehicle. Additionally, by having two batteries in the vehicle, with key off load support primarily on one battery and cranking support on the other battery, the probability of having the cranking battery depleted is reduced (key off loads are devices that draw power from the battery when the ignition key is off - i.e. the clock). The other system improvement is the proposed voltage specification for the 42V PowerNet. Limited high voltage transients and elimination of negative voltages will help to make sure that electronic module costs can be kept low. The future will a bit more complicated once 42V PowerNet vehicles are roaming the streets. Then, when you need a jump start, it will be important to know what voltage battery is in each vehicle. It is imperative that jump starting is only attempted between batteries of the same voltage in order to prevent personal injury and/or vehicle damage. Many 42V PowerNet vehicles will have dual 42V/14V systems equipped with a bi-directional DC/DC converter. Normally they will convert 42V to 14V for load support and charging the 12V battery, but they can also convert 14V to 42V, providing the capability for a built in jump start. This can greatly reduce the likelyhood of ever needing a jump start from another vehicle. Additionally, by having two batteries in the vehicle, with key off load support primarily on one battery and cranking support on the other battery, the probability of having the cranking battery depleted is reduced (key off loads are devices that draw power from the battery when the ignition key is off - i.e. the clock). The other system improvement is the proposed voltage specification for the 42V PowerNet. Limited high voltage transients and elimination of negative voltages will help to make sure that electronic module costs can be kept low.

9. 9 Proposed PowerNet Architecture This is a typical proposal for a dual 42V/14V PowerNet architecture. When the engine is running, the 42V generator will provide the electrical power for the vehicle, charging the 36V battery, running 42V loads and powering a DC/DC converter. The DC/DC converter will in turn power the 14V loads and charge the 12V battery. Key off loads (devices that draw electrical power when the ignition key is off such as a clock) would primarily be drawing power from the 12V battery, leaving the 36V battery at a high state of charge, thus ready to start the vehicle. In the event that the 36V battery is discharged, but the 12V battery is not, energy can be transferred via a bi-directional DC/DC converter from the 12V battery to the 36V battery, thus providing an internal jump start.This is a typical proposal for a dual 42V/14V PowerNet architecture. When the engine is running, the 42V generator will provide the electrical power for the vehicle, charging the 36V battery, running 42V loads and powering a DC/DC converter. The DC/DC converter will in turn power the 14V loads and charge the 12V battery. Key off loads (devices that draw electrical power when the ignition key is off such as a clock) would primarily be drawing power from the 12V battery, leaving the 36V battery at a high state of charge, thus ready to start the vehicle. In the event that the 36V battery is discharged, but the 12V battery is not, energy can be transferred via a bi-directional DC/DC converter from the 12V battery to the 36V battery, thus providing an internal jump start.

10. 10 Forum Bordnetz Proposed Voltage Specification Sican�s Forum Bordnetz has proposed these voltages for the new Powernet systems. The proposal eliminated negative voltages and keeps the peak voltages below the 60V limit that is considered to be the safe threshold. Some form of centralized suppression will likely be required in the vehicles in order meet these requirementsSican�s Forum Bordnetz has proposed these voltages for the new Powernet systems. The proposal eliminated negative voltages and keeps the peak voltages below the 60V limit that is considered to be the safe threshold. Some form of centralized suppression will likely be required in the vehicles in order meet these requirements

11. 11 Why Are Jump Starts Needed? Batteries can be drained Key-off loads Extended cranking Excessive electrical loads Batteries can be defective Engines can be difficult to start Poor fuel Improper maintenance Extreme conditions There are lots of reasons why it may be necessary to jump start a vehicle. A few are listed here to illustrate the problem. Most of the time, it is just a case of the battery being discharged. The battery is basically good, just drained of energy. This can be the result of an extended storage where key off loads have slowly drained the battery or a case where lights have drained the battery while you are at work. You can also have cases, especially in extreme temperatures, where extended cranking has depleted the battery. Sometimes the battery is defective. Maybe a weld inside the battery has broken or the case has been damaged and the battery acid has leaked out. Other times it may be that the engine is very hard to start. This might be the result of poor/contaminated fuel, improper maintenance or extreme tempratures. Whatever the cause, the driver continues to try to start the vehicle until the batttery is depleted. There are lots of reasons why it may be necessary to jump start a vehicle. A few are listed here to illustrate the problem. Most of the time, it is just a case of the battery being discharged. The battery is basically good, just drained of energy. This can be the result of an extended storage where key off loads have slowly drained the battery or a case where lights have drained the battery while you are at work. You can also have cases, especially in extreme temperatures, where extended cranking has depleted the battery. Sometimes the battery is defective. Maybe a weld inside the battery has broken or the case has been damaged and the battery acid has leaked out. Other times it may be that the engine is very hard to start. This might be the result of poor/contaminated fuel, improper maintenance or extreme tempratures. Whatever the cause, the driver continues to try to start the vehicle until the batttery is depleted.

12. 12 Options Available When Your Car Won�t Start Replace Battery Dealer/Auto Parts Stores Closed May need to be towed Recharge Need 36V battery charger and power source May need to be towed Jump Start Personal and vehicle safety If the car won�t start, what can you do? If you are fortunate enough to have this happen at the car dealership or an auto parts store, you can simply replace the battery. If it is late at night or on a weekend, this may be more difficult to do. Sometimes you may need to have the vehicle towed into a garage for a battery replacement. You might also be able to recharge the battery, but you would need a 36V battery charger and a power source, which may not be available to you where your vehicle fails to start. In addition, it may take several hours to recharge the battery with some of the low power chargers in use today. Once again, you may need to have the vehicle towed. Alternatively, it may be possible to jump start the vehicle. This requires that you find someone with a compatible battery voltage, jumper cables and the knowledge and willingness to perform a jump start. Personal safety and vehicle safety need to be considered.If the car won�t start, what can you do? If you are fortunate enough to have this happen at the car dealership or an auto parts store, you can simply replace the battery. If it is late at night or on a weekend, this may be more difficult to do. Sometimes you may need to have the vehicle towed into a garage for a battery replacement. You might also be able to recharge the battery, but you would need a 36V battery charger and a power source, which may not be available to you where your vehicle fails to start. In addition, it may take several hours to recharge the battery with some of the low power chargers in use today. Once again, you may need to have the vehicle towed. Alternatively, it may be possible to jump start the vehicle. This requires that you find someone with a compatible battery voltage, jumper cables and the knowledge and willingness to perform a jump start. Personal safety and vehicle safety need to be considered.

13. 13 Jump Starting Ten alternatives were considered Pugh Analysis and FMEA were used to compare the functionality of alternatives Bi-directional DC/DC converters enable �internal� jump starts Operation with a defective battery may need to be prevented on future vehicles which rely on electronics for safe functionality In the paper we considered ten alternative strategies for jump starting. We used Pugh Analysis and Failure Mode and Effect Analysis to compare the functionality of the alternatives. We chose to constrain the alternatives to an architecture that has a 42V generator, a 36V starter, a 36V battery, a bi-directional DC/DC converter and a 12V battery. This would likely be the architecture of choice, at least for the initial stage of a 42V PowerNet. Many of the strategies would still work with different architectures, but comparing the alternatives gets to be fairly complex. The strategies range from simply making the 36V battery inaccessible and only allowing 12V jump starts and using the DC/DC converter to charge up the 36V battery to having intelligent control of the battery connections to the vehicle electrical system and having a start aid post that would be readily accessible for jump starting and would be electronically controlled to allow current to flow to/from one vehicle�s battery, through the DC/DC converter, and into the other vehicle�s battery. The later system protects the customer and the vehicle from accidental reversal of battery connections, connections to the wrong battery (improper voltage matches) and will prevent starting the vehicle if the battery is defective (open internal connections), which may necessary as future safety related systems may rely on the battery for safe functionality.In the paper we considered ten alternative strategies for jump starting. We used Pugh Analysis and Failure Mode and Effect Analysis to compare the functionality of the alternatives. We chose to constrain the alternatives to an architecture that has a 42V generator, a 36V starter, a 36V battery, a bi-directional DC/DC converter and a 12V battery. This would likely be the architecture of choice, at least for the initial stage of a 42V PowerNet. Many of the strategies would still work with different architectures, but comparing the alternatives gets to be fairly complex. The strategies range from simply making the 36V battery inaccessible and only allowing 12V jump starts and using the DC/DC converter to charge up the 36V battery to having intelligent control of the battery connections to the vehicle electrical system and having a start aid post that would be readily accessible for jump starting and would be electronically controlled to allow current to flow to/from one vehicle�s battery, through the DC/DC converter, and into the other vehicle�s battery. The later system protects the customer and the vehicle from accidental reversal of battery connections, connections to the wrong battery (improper voltage matches) and will prevent starting the vehicle if the battery is defective (open internal connections), which may necessary as future safety related systems may rely on the battery for safe functionality.

14. 14 To better understand why jump starts are sometimes needed, it may help to look at why batteries may not be able to deliver enough power to start a vehicle. The cranking current required to start a vehicle is fairly high, especially at low temperatures. The internal resistance of the battery tends to increase as temperature goes down or as the battery discharges (high state of discharge). This means that the terminal voltage of the battery will be lower at low temperatures or high states of discharge. The lower the voltage, the slower the engine will crank and the less likely the engine will start. To better understand why jump starts are sometimes needed, it may help to look at why batteries may not be able to deliver enough power to start a vehicle. The cranking current required to start a vehicle is fairly high, especially at low temperatures. The internal resistance of the battery tends to increase as temperature goes down or as the battery discharges (high state of discharge). This means that the terminal voltage of the battery will be lower at low temperatures or high states of discharge. The lower the voltage, the slower the engine will crank and the less likely the engine will start.

15. 15 As a battery ages, it also experiences an increase in internal resistance. The chart on the left shows the change in internal resistance for several groups of stationary batteries.As a battery ages, it also experiences an increase in internal resistance. The chart on the left shows the change in internal resistance for several groups of stationary batteries.

16. 16 When you charge a battery with short pulses of energy, there is a surface charging effect that significantly lowers the internal resistance of the battery for a short time, thus allowing an increased power delivery capability. This surface charging capability has been demonstrated to be capable of allowing the starter to crank an engine for several seconds after charging a depleted 36V battery from the 12V battery through the DC/DC converter for about three minutes (drawing approximately 50 amps from the 12V battery). Under normal conditions, this would normally be sufficient to get a vehicle started.When you charge a battery with short pulses of energy, there is a surface charging effect that significantly lowers the internal resistance of the battery for a short time, thus allowing an increased power delivery capability. This surface charging capability has been demonstrated to be capable of allowing the starter to crank an engine for several seconds after charging a depleted 36V battery from the 12V battery through the DC/DC converter for about three minutes (drawing approximately 50 amps from the 12V battery). Under normal conditions, this would normally be sufficient to get a vehicle started.

17. 17 Starting in the upper left, the slide shows what happens inside a fully charged battery as it is discharged. The acid is the current carrying path and the reactions take place at the outer edges of the lead.. As the battery continues to discharge, the outside edges of the lead get converted to lead sulfate and the reaction moves inward as shown the lower left. Since lead sulfate has higher resistivity than lead, the battery�s internal resistance is rising. In the upper right, it shows that during charging, the outer edges of the now sulfated lead reacts first. The lower right picture shows that during a subsequent discharge the reaction will then occur at the outer edges, which means the current path is similar to a fully charged battery current path and therefore resulting in lower internal resistance.Starting in the upper left, the slide shows what happens inside a fully charged battery as it is discharged. The acid is the current carrying path and the reactions take place at the outer edges of the lead.. As the battery continues to discharge, the outside edges of the lead get converted to lead sulfate and the reaction moves inward as shown the lower left. Since lead sulfate has higher resistivity than lead, the battery�s internal resistance is rising. In the upper right, it shows that during charging, the outer edges of the now sulfated lead reacts first. The lower right picture shows that during a subsequent discharge the reaction will then occur at the outer edges, which means the current path is similar to a fully charged battery current path and therefore resulting in lower internal resistance.

18. 18 A Minimal Approach This approach basically makes the 36V battery inaccessible, thus reducing the chance that someone could accidentally connect the 12V battery to the 36V battery during a jump start. The 12V battery would be accessible, much like today�s vehicles and jump starting would be accomplished with alligator style jumper cables. When a 42V PowerNet vehicle is receiving aid, the current flows from the good vehicle, through the DC/DC converter and into the depleted 36V battery. This process will take more time than jump starting does in today�s cars, where power flows from the good battery directly to the starter. Also, if the 12V battery in the PowerNet vehicle is a deep cycle load support battery, it may not be able to provide sufficient power to directly crank a traditional 12V vehicle, so it will be necessary to allow sufficient time to surface charge the other vehicle�s 12V battery. If the cranking battery is defective (open circuited), it will not be possible to jump start the vehicle. This approach basically makes the 36V battery inaccessible, thus reducing the chance that someone could accidentally connect the 12V battery to the 36V battery during a jump start. The 12V battery would be accessible, much like today�s vehicles and jump starting would be accomplished with alligator style jumper cables. When a 42V PowerNet vehicle is receiving aid, the current flows from the good vehicle, through the DC/DC converter and into the depleted 36V battery. This process will take more time than jump starting does in today�s cars, where power flows from the good battery directly to the starter. Also, if the 12V battery in the PowerNet vehicle is a deep cycle load support battery, it may not be able to provide sufficient power to directly crank a traditional 12V vehicle, so it will be necessary to allow sufficient time to surface charge the other vehicle�s 12V battery. If the cranking battery is defective (open circuited), it will not be possible to jump start the vehicle.

19. 19 A Mechanical Approach This approach allows jump starts from either a 12V battery or a 36V battery. The smart batttery terminal would be able to sense the voltage at the positive terminal of the 12V battery and would open if that voltage where outside an acceptable range. If for example, the battery voltage were negative, either because jumper cables were reversed or the battery was installed with reversed connections, the switch S1, would open, thus protecting the vehicle electrical system. Since the 36V battery has a unique polarized connector that would not connect to the 12V battery terminals, it eliminates accidental connection of the wrong battery. Since only a unique jumper cable would be able to connect to the 36V battery, it also could prevent accidental connections during jump starting - assuming someone doesn�t make up a special cable that has alligator clamps on one end and the unique connector on the other. Since the connectors would be polarized, reversed connections during jump starting could also be eliminated. If the cranking battery were defective, it would still be possible to jump start this vehicle. This approach allows jump starts from either a 12V battery or a 36V battery. The smart batttery terminal would be able to sense the voltage at the positive terminal of the 12V battery and would open if that voltage where outside an acceptable range. If for example, the battery voltage were negative, either because jumper cables were reversed or the battery was installed with reversed connections, the switch S1, would open, thus protecting the vehicle electrical system. Since the 36V battery has a unique polarized connector that would not connect to the 12V battery terminals, it eliminates accidental connection of the wrong battery. Since only a unique jumper cable would be able to connect to the 36V battery, it also could prevent accidental connections during jump starting - assuming someone doesn�t make up a special cable that has alligator clamps on one end and the unique connector on the other. Since the connectors would be polarized, reversed connections during jump starting could also be eliminated. If the cranking battery were defective, it would still be possible to jump start this vehicle.

20. 20 An Electronic Approach This approach provides the highest level of personal and vehicle protection. Both batteries are intended to be inaccessible for jump starting. A start aid post is provided for making connections between vehicles at 12V only. If the connection is made to the wrong voltage or reversed, switch S1 remains in position A and the vehicle electrical system is protected. If the PowerNet vehicle is receiving aid, and if the voltage is within a specified range, S1 will move to position B and S2 will open. Energy will flow from the start aid post to the DC/DC converter, where the voltage is boosted up to 42V to charge the 36V battery. Once the 36V battery has been surface charged, S1 will move back to position A and S2 will close and the 36V battery will charge the internal 12V battery if necessary. This may require several cycles of charging the 36V battery from the external battery and charging the internal 12V battery from the internal 36V battery until both batteries are at an acceptable state of charge to safely operate the vehicle. If giving aid, the S1 moves to position A, S2 open and the external battery is charged by the DC/DC converter. Opening S2 protects the low voltage bus from external transients that may arise from a non-PowerNet system. If the cranking battery is defective, it will not be possible to jump start the vehicle.This approach provides the highest level of personal and vehicle protection. Both batteries are intended to be inaccessible for jump starting. A start aid post is provided for making connections between vehicles at 12V only. If the connection is made to the wrong voltage or reversed, switch S1 remains in position A and the vehicle electrical system is protected. If the PowerNet vehicle is receiving aid, and if the voltage is within a specified range, S1 will move to position B and S2 will open. Energy will flow from the start aid post to the DC/DC converter, where the voltage is boosted up to 42V to charge the 36V battery. Once the 36V battery has been surface charged, S1 will move back to position A and S2 will close and the 36V battery will charge the internal 12V battery if necessary. This may require several cycles of charging the 36V battery from the external battery and charging the internal 12V battery from the internal 36V battery until both batteries are at an acceptable state of charge to safely operate the vehicle. If giving aid, the S1 moves to position A, S2 open and the external battery is charged by the DC/DC converter. Opening S2 protects the low voltage bus from external transients that may arise from a non-PowerNet system. If the cranking battery is defective, it will not be possible to jump start the vehicle.

21. 21 Recommendation The wide range of alternatives we considered provided varying degrees of protection. Each manufacturer will make the decision based on various criteria, such as; safety, reliability, size, weight, cost and their customers� expectations. At a minimum, the system should prevent connections between the 12V & 36V batteries. There are many alternative, all of them offering an improved level of protection over the baseline system. Each manufacturer will have to make decisions based on their own criteria, including such things as safety, reliability,size, weight, cost and their customers expectations. They should at least prevent connections between the 12V and 36V batteries during jump starts. This can be accomplished by using a start aid post and controlling the flow of energy between batteries using sophisticated electronic controls linked to the onboard DC/DC converter or by developing a unique 36V battery connection that cannot be connected via traditional alligator style jumper cables and is polarized to prevent reverse connections. What is key is that each manufacturer�s approach is compatible with the other manufacturers, so that two different cars may be able to give and receive aid as needed.There are many alternative, all of them offering an improved level of protection over the baseline system. Each manufacturer will have to make decisions based on their own criteria, including such things as safety, reliability,size, weight, cost and their customers expectations. They should at least prevent connections between the 12V and 36V batteries during jump starts. This can be accomplished by using a start aid post and controlling the flow of energy between batteries using sophisticated electronic controls linked to the onboard DC/DC converter or by developing a unique 36V battery connection that cannot be connected via traditional alligator style jumper cables and is polarized to prevent reverse connections. What is key is that each manufacturer�s approach is compatible with the other manufacturers, so that two different cars may be able to give and receive aid as needed.

22. 22 Summary In the initial stages of 42V PowerNet usage, it may be desirable to limit start aid to the low voltage bus, as few 42V vehicles will be available to give aid. As more 42V PowerNet vehicles are in use, the need to provide cost effective 36V battery jump start capability will drive manufacturers to pursue other approaches, but they need to be compatible.