Electrification from the beginning Source: BMW presentation by Ottmar Sirch The new voltage level: 48 volt in vehicles Presented at the 6th annual conference Steering Systems 2012, 14.11.2012 2
48 Volt a controversy In the early 1990 s there was a lot of excitement around the introduction of a 42V power supply, initially intended to augment the 12V in passenger vehicles. However twenty years on and the 42V didn't materialize even though a few vehicles did make it into production. Mainly because engineers found ways to limit power consumption, implement intelligent power control, install buffers and increase the capacity of on board generators. These improvements made the need of a 42V system, with the incumbent extra costs, redundant. Some experts still believe that a 48 volt power supply system is merely a pipedream. Interview with Dieter Nazareth Automotive IQ spoke about 48 volt power supply with Professor Dr. Dieter Nazareth who is Professor of Computer Science at Landshut University of Applied Sciences and a Guest Professor at Shanghai Jiao Tong University. Could you give your thoughts on that and if it's actually feasible or if we're going to have a repeat of ten or fifteen years ago where we talked about it and nothing really happened? The problem is really that about 15 years ago we already had that discussion and we invested a lot of money in that topic and it never came and I'm not sure whether now it will be successful because it will be a huge step to switch from 12 volt to 48 volt. There are two possibilities: either we have both voltage levels in one car, so then we have 12 and 48 volts which mean that we have to manage the isolation between 12 and ground, between 48 and ground, but also between 12 and 48. If we have different voltage levels we need a battery on both levels and a DC/DC converter to convert from 48 down to 12 volt. Everything's really, really complex. The other way would be much easier: to switch completely to 48 so there's only 48 in the car. But that requires that all electronic parts have to be switched to 48-volt level - everything in the car. So if you want to switch one car to that level then you cannot use any old parts anymore. So that means complete new development. 3
Drivers toward 48 Volt In light of the failure of 42 volt to gain any real market acceptance, the question has to be asked as to why a 48V system would be under consideration 20 years later. The answer lies in this comment by Frank Briault, a PSA engineer: An increase of onboard electrical needs alone won t justify changing the voltage network, But each gram of CO2 which is saved, we accept (having) to pay for that. Automotive IQ surveyed a group of international experts working in and around vehicle power supply and electronics to confirm the most important drivers toward 48 volt technology. Our 48 Volt survey identified 2 particularly compelling drivers: 1. Meeting the increasing demand of E/E features in vehicles 2. More stringent global CO2 fleet targets 4
Why is it different today? A different century and the 48V is set to succeed At the Ludwigsburg Elektronik Congress in 2011 German carmakers, including Audi, BMW, Daimler, Porsche and Volkswagen agreed on a 48V embedded-supply to support the growing current-load requirements in modern vehicles. Over and above the normal operating systems already mentioned, energy conservation and recovery systems are seen as fundamental in achieving future emission standards, and these could more than double the current electrical power requirements. Start-stop systems already push 12V technology to its limits, and when used in mild hybrids, 10 to 15 kw will be required. At these levels current draw would be 1000 A and require cables of 10 to 15 mm. This, obviously, is not feasible. It must be remembered that both the 42V and 48V systems were/are auxiliary systems linked to the 12V supply by a DC/DC converter - meaning a duplication and vehicle on-cost. However, whereas there was no substantial financial penalty/ reward to offset this cost in the 1990 s, the penalty for 3 g of CO2 above the limit of 120 g now costs 45 per vehicle, and would be an incentive to fund the additional hardware required by the tandem 48V architecture. According to Wolfgang Bernhart, an expert in electrified powertrains at Roland Berger Strategy Consultants, recovering energy during braking or deceleration with 48V is twice as efficient when compared to 12V. He says: If you can save 5%-10% with 48V, you could only save 2.5% to 5% with 12V. And with 12V, boosting would be zero. Source: http://www.all-electronics.de/texte/anzeigen/42481/deutsche-oems-setzen-standards 5
Challenges & Potential Overall, our survey revealed that the single greatest inhibitor to 48 volt system development is Return On Investment (ROI) as 70% of those surveyed gave that answer. Looking specifically at OEMs, 3 out of 4 respondents gave ROI as the main obstacle. Expert interviews revealed that a further decision needs to be made whether to run tandem 12 and 48 volt systems or to develop a purely 48 volt system though it looks likely that a tandem system will be the short-term solution. The costs of developing a purely 48 volt power supply are likely to be significantly higher and therefore it is unlikely that this system will appear in vehicles anytime soon. The introduction of a 48 volt system is likely to lead to several outcomes including the creation of new standards. Our survey revealed that reduced CO2 is the most likely outcome/benefit of the upgraded power supply. 6
Investing in R&D Nearly 53% of those surveyed stated that their companies plan to invest at least marginally more in R&D on 48 volt systems in 2014 relative to 2013 spending. Interestingly, 81% of our OEM representatives will increase their R&D investment in 48 volt. Earlier this year Continental and SK Innovation launched SK Continental E-Motion to jointly develop, produce and distribute lithium-ion battery systems. The company has already started working on initial development programmes in the 48-volt mild hybrid sector, as well as the commercial vehicle sector. The joint venture will offer a broad range of lithium-ion battery systems, from 48-volt to EV including HEV/PHEV and special applications for commercial vehicles, using both air-cooled and fluid-cooled technologies. Products will be based the complete cell line up developed by SK Innovation and the modular battery management systems provided by continental. 7
Summary Unlike past developments, whose pace was largely dictated by the OEM s and available technology, the timing of 48V is largely being determined by emission and fuel consumption requirements. The regulations for the reduction of CO 2 emissions are getting ever tighter, and OEM s face a tough task to meet the targets. The need for an affordable, fuel efficient alternative to existing hybrid vehicles is pressing. 42-volt electric systems were discarded as uneconomical in the past, but today, there is a clear trend towards the introduction of 48- volt systems to achieve the necessary emission targets. 48-volt systems offer a variety of functions to assist with fuel saving, and the reduction of CO 2. Stop and start technology helps to save fuel while the vehicle is stationary, and torque assist can also be supplied to the engine for launch and low speed transient acceleration. Increased storage and regeneration of brake energy is also possible with 48-volt batteries, further improving on overall efficiency. In addition there are other possibilities with the use of a 48-volt supply that would not be viable with a 12-volt battery, such as fully electric power steering and electrically controlled air-conditioning compressors. Since the five premier German OEMs announced their intention to integrate 48-volt technology there has been a concerted push by manufacturers and suppliers to develop the relevant components suitable for 48-volts. Initially the systems are likely to be implemented alongside a 12-volt battery to produce efficient hybrid vehicles while retaining the standard power supply. Sooner or later, many more OEMs are expected to join the bandwagon in implementing a supplementary 48V power supply to support the existing 12V system. Perhaps farther into the future the 48V system will replace the 12V system entirely. Source: BMW presentation by Ottmar Sirch The new voltage level: 48 volt in vehicles Presented at the 6th annual conference Steering Systems 2012, 14.11.2012 8