Technical article, new condition of power supply of 48V of electric car new technology

Mix at present use a car (HEV) and pureElectric car(EV) the design is very conspicuous, but automobile industry also has not quite apparent but the development trend with great sense: 48V direct current increases in dynamical system (DC) bus line. 48V is applied to not only mix use car and pure electric car, more and common inside light a car to also will use this kind of technology, from the graph 1 can see pure electric car is mixed mix the market share that uses a car to grow ceaselessly.




Graph 1: Electric car market (include pure electric car and mix use a car) predict to be in can grow quickly in the near future, the adoption of 48V will become an essential factor that is helpful for growth (origin: Delphi science and technology)


The 12V batteries that engineer and car machinist contact nowhere to be absent as a child and car component (this is the occupation standard that already had 100 old histories) , but do not need to fear 12V system won’t disappear very quickly, may mix in the prospective 12V that can foreknow however 48V system is concomitant.


So what distinctive place does 48V system have? The answer needs to look from the angle of electric power, return Ohm’s law, pressure fall (V=IR) , power (P=IV) with loss power (P=I²R) concerned physical law comes up, although press,fall (loss) increase along with voltaic linear, power loss follows voltaic square and increase, but carry power to need electric current and voltage to decide, the in short is in give the output below voltage the electric current with more power bigger need, and electric current is bigger, pressure fall taller, power loss is not recoverable also.


This is not a new development way, the solution provider of electric power domain is early hep these, this also is the account that why they use taller tension, they seek better for street lamp system, family and industrial place power supply solution, but to the car from can charge plumbic acerbity batteries gets 12.6V (nominal value) voltage is a very good compromise proposal, can bulk of give attention to two or morethings, capacity (ampere hour) , the element such as cost, life and safety.


However the car before present car needs to compare a few years more motivation, besides engine, lamp, radio, dynamoelectric scuttle, dynamoelectric aid force to change direction, the basic function such as network and information recreation, return the function with can compositive very much other convenient security now, these functions are met normally classify is advanced drive support system (ADAS) inside the category, ADAS system raised taller requirement to batteries, need more electric power, because this uses 12V power source to be all sorts of core components and peripheral power supply to be able to cause bigger electric current, maintain IR to drop to be in with I²R power loss below 12V however the method of acceptable level is to use more thicker wire, copper to make material and bigger connector, this means the addition of cost, bulk conversely, can appear inside traffic system more crowded.


48V power supplyBe new 12V form?


Passed the decision inside much analytic trade to use 48V to regard new power supply as the system, with traditional 12V lead acid batteries differs, 48V batteries uses lithium cell, have taller weight and bulk energy density, famouser is “mild Hybrid (small mix or mix gently) ” (graph 2) .




Graph 2: 12V/48V of in some way is small mixing a system is an eclectic plan, but differ with other compromise proposal, this kind of plan has a lot of advantages, reduce cost, promotion benefit and return rate (origin: Delphi science and technology)


In this kind of method, 48V batteries —— serves as union of complement and 12V lead acerbity batteries to use according to the formulary —— of car standard LV148 (the rated power that can provide 3KW so) , if pursue,3 are shown. 12V batteries and 48V batteries along with their distribution wiring harness is used together, when need power is outputted two batteries are offerred energy out-put, for instance 12V bus line can think ignition, illume and information entertainment system provide power source, and 48V bus line controls responsible batholith system, air conditioning, adjust suspension, reclaim energy of apply the brake, drive is dynamoelectric supercharger and turbine.


Consider a main component: Start a starter, how does 48V batteries change the basic framework of engine starter, thereby better buildup is opened stop the effect, this kind of means is helpful for decreasing to be mixed in traffic light jockey the fuel when awaiting is used up, enhance fuel efficiency further. The batteries in the car that there is 12V battery only in great majority provides power for starter, the alternator serves as charger, however the combination of 48V and 12V is used can provide the power that is as high as 10KW, the electric machinery that start and independent alternator by the compositive dynamo that start (ISG) or the belt dynamo that start is replaced, batteries of 48V lithium ion and two-way DC/DC converter can be enclosed inside strong case, this is one kind mixes dynamical system infirmly actually, work in coordination with internal-combustion engine. It can provide the benefit of 2/3, but the cost that has 1/3 only, and economic benefits increased 15% to 20% .


Choice 48V is derivative also at the same time two problems: Why not from 12V Where is direct instead 24V? Since taller voltage can bring more profit, why does that restrict voltage in 48V? Have a lot of different answers to these problems.


It is about 10 years ago the discussion about 24V is exceedingly intense, a few main firms begin to produce 24V connector, switch, relay and other basis part even. But use the profit of 24V and can’t support this kind to alter. Whether should wash out 12V batteries completely to use 24V cell only about the car in addition, still make them concomitant, this controversy was not solved all the time.


As to 48V above can be put in user safety problem, the volts d.c. that exceeds 60V in most area is considered as potential insecure factor, because this needs special wiring note, safety lock, use conduit and physical screen,wait. Although 48V system may be achieved actually slightly the peak value under 60V, but it is considered as safety, the problem that avoided this field thereby (the attention is mixed to pure electric car mix move car and advocate the voltage related batteries can exceed 60V far, because all safe regulation and precautionary measures considered in this design) , 48V is traditional small the top level that mixes a system to be able to be achieved, avoid additional safe and relevant design problem thereby.


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