[introduction] electric car design must face a such reality — the problem is in all BMS to go up somehow is mutual and associated and rather than is isolated (graph 1) . Accordingly, when produce change as the state of batteries or condition when BMS and handling corresponding issue, can produce a kind ” ripple effect ” . The one big target of BMS architecture is as far as possible these child the function departs, let each child the function can be optimized independently, conduce to implementation overall situation optimizing a design thereby.

Electronic engineer wants only and electric car (include pure dynamoelectric and mix dynamoelectric) contact with, often want to use all sorts of batteries technologies in the job, they belong to the lithium ionization of some kind of form to learn commonly. However, if want to manage a large number of battery that make batteries group, only by these technologies be ability not equal to one’s ambition, because this designs personnel to must implement batteries management system (BMS) , come with this:

? Protect single cell and whole batteries group to not be damaged bad
? Prolong battery life

Once these targets incorporate, you will harvest a long detailed list, include battery protection, charge control, charge affirmatory, health decides condition to wait for a function evenly with batteries. One of functions of BMS of article with a view to — batteries balance, have very much in the grim challenge that it must settle in personnel of electric car design representative.

Electric car design must face a such reality — the problem is in all BMS to go up somehow is mutual and associated and rather than is isolated (graph 1) . Accordingly, when produce change as the state of batteries or condition when BMS and handling corresponding issue, can produce a kind ” ripple effect ” . The one big target of BMS architecture is as far as possible these child the function departs, let each child the function can be optimized independently, conduce to implementation overall situation optimizing a design thereby.

Graph 1: In system of electric car power source, batteries management system is one of the most important subsystem. This is one covers the complex system of the respect such as hardware, software and batteries chemistry, involve a lot of with ” normal ” run concerned advantages and disadvantages balance and judgement. Picture origin: Maxim Integrated, “The Automotive Experience” (the car experiences)

In addition, be like commensurate majority the project is decision-making and same, can come true those who give a cause is onefold ” correct ” the method is nonexistent. Every kinds of method needs to be mixed in the appearance the dimension that pack, can replace integrality of unit, weight, data, system balance has between degree of confidence and cost. Specific use why to plant method, still depend on the end that wants implementation, group of the batteries battery life with longer add boat time, longer such as, batteries is behaved to individual batteries not of beautiful patient degree, still have the problem of security. Accordingly, ” optimal ” the solution depends on the need in the design is preferential settlement problem.

Batteries is a complex issue evenly

To the batteries group that forms by many batteries, a fact that does not circle is the total presence is little difference between every batteries, this differentia different is come from be produced at what differ and run a condition (especially temperature gradient, may more apparent to large batteries group) . Fill discharge to be able to magnify circularly every time this differentia different, cause the batteries with weaker performance to become weaker, till ultimate be no longer in force, bring about whole batteries group then premature invalidation.

Batteries tries to let the charge on all batteries in batteries group reach balanced position evenly, will compensate the influence that the batteries with weaker performance brings. Industry already developed a variety of batteries to balance a method to solve this problem now. Batteries balances a method to still involve the concern of a function of batteries chemistry: Lithium battery can be able to bear or endure more suffer those who mix electric car generation ” small ” fill discharge loop, but get more easily however the influence of the difference between batteries. However, group of plumbic acerbity batteries and group of nickel hydrogen batteries however natively is put in balancing machine of a kind of batteries to make, after because this kind of batteries is in,filling report, can release redundant energy through giving off gas, need to lengthen only consequently charge time, the batteries that can make function weaker also fills report.

Active balance and passive balance are two kinds of the commonnest batteries balance technology. Charge billabong, nondestructive still exists to wait for other method evenly in applying actually, but the advantages and disadvantages that a kind of any methods do not escape to cross hardship balance. Balance passive still balance actively no matter, they only then at surveillance of every batteries charge condition (SOC) . The electric current that this condition is entered through convection and pours out of batteries undertakes ” coulomb computation ” will measure, sometimes batteries impedance is measured also can complement as a kind. Below certain circumstance, the voltage that goes up to every batteries only undertakes metrical can. Next, switch circuit is charging the control in the process brings to bear on the charge of every alone batteries, with the charge of all batteries in balanced batteries group.

In active balance, batteries management system is met from n charge taller batteries transmits the batteries with inferior n. This process is very time-consuming, because every batteries must get assessment, and batteries gross may be amounted to thousands of. The method that plan of active batteries balance uses the part is to stop full already to n batteries to undertake charging, continue at the same time weaker to function batteries charges, till all batteries are full of, fill those who divide favourable geographical position to use cell to fill capacitance as far as possible thereby.

In passive balance, many energy meets the batteries with taller n be used up automatically through bypass resistor, till its voltage or charge and performance are weaker the voltage on batteries is identical. This is method of a kind of low cost, but bypass resistor can waste one part energy, make the function of whole batteries group depends on completely the batteries with the weakest performance. Why to no matter use,plant method, want to squeeze the last percent that gives capacity and performance, will increase size of BMS system complexity, BOM, hardware size and cost and software greatly compositive problem.

Balance this challenge that face in the light of BMS and batteries, the MAX14920 of Maxim Integrated and to it two batteries measure similar MAX14921 imitate front (AFE) integrated circuit can is opposite the batteries voltage in batteries group undertakes accurate sampling, highest support + 65V voltage; MAX14920 supports 12 batteries at most, and MAX14921 supports 16 batteries at most, divide this beyond both and complete consistent (graph 2) . This parts of an apparatus is opposite at the same time sampling of all batteries voltage, with accurate and affirmatory charge condition and source resistor, this to large batteries group character is the function of an economic time. All batteries voltage all has n shift on unit gain, make serve as reference in order to receive ground voltage, simplified greatly exterior modulus converter (the data changeover of ADC) amends the job.

Graph 2: The MAX14920 of Maxim and to it similar MAX14921 batteries measures imitate front (AFE) integrated circuit aims to simplify pair of batteries groups are medium undertake batteries balances this one crucial job between a lot of batteries. (Picture origin: Maxim Integrated)

Passive batteries is balanced but exterior FET driver comes to have the aid of support. The compositive diagnostic function in these two products can undertake the line detects and give out owe pressure / control warning too, with ensuring systematic integrality further. The BMS parts of an apparatus of two products all by can realize control of interface of SPI of chrysanthemum catenary connective, can have link through individual SPI port consequently, find location and management, and the share is controlled in SPI can choose any batteries voltage reading with aleatoric order (graph 3) .

Graph 3: The batteries of BMS balances a function to be able to pass the SPI control of Maxim MAX14920/MAX14921, choose any batteries voltage reading with aleatoric order. (Picture origin: Maxim Integrated)

Want monitoring batteries, with respect to the problem that must face accuracy, very even to discharge curve chemical material especially such. Product of these two Maxim has very tall precision, the batteries chemistry that suits the discharge curve evenness such as phosphate of monitoring lithium metal very much reacts. They are contained low noise, low maladjusted amplifier, but amortize does not exceed + any voltage needing branch of 5V, thereby can monitoring all sorts of common lithium are ionic (Li+) batteries technology.

Union is in-house from calibration function, the batteries voltage error that two products measure all is ± 0.5mV. Is their rated temperature range wide amount to? 40 ° C comes + 85 ° C, this is place of environment of electric car work is indispensible.

The connector type selecting below big electric current nots allow careless

To been contact before ” high power ” do not exceed hundreds tile, the engineer that perhaps has handled 10A the following electric current only, want to realize interconnection of electric car power source, need uses the train of thought that is different from associate with completely. In electric car design, big electric current, tall voltage is the normal between all sorts of subsystem and component, for this design personnel must choose right string to be opposite board be opposite with the line line connector, fall in very difficult vibration, stress and temperature condition, contented the power capacity that has challenge sex quite, insert unplug life and mechanical intensity ask. because of such, in choose related to batteries subsystem when the power source connector of couplet, its characteristic nots allow to ignore. Look of problem of the big electric current in electric car environment, tall voltage is not gotten any ” opportunistic ” or ” say again later ” manner — this is what must designing a process is inchoate the problem that solves with respect to the key.

The E-Mobility solution of Phoenix Contact is a kind of connector range of products that applies to electric car platform. All sorts of sheet taste this series use a variety of crust styles and contact layout form, supportive AWG 12 and AWG 16 two kinds of wire gauge (specific depend on picks contact position) , electric current of highest supportable 25A; Dimension is the contact of 12 AWG 14 of – of acceptability AWG 12; Dimension is the contact of 16 AWG 20 of – of acceptability AWG 14.

Combination charges system (CCS) is a kind of standardization that is used at electric car charges system, support convention communication to charge with dc quickly, these two kinds of connector all can insert CCS car to carry socket in. Phoenix Contact E-Mobility is offerred those who accord with a variety of dc to charge to fill standard of electric coupler international with communication quickly is various fill plug. Besides comprehensive product combination, the special requirement that Phoenix Contact still can be aimed at a client (it is the demand that the standard did not cover even) development individuation solution.

Phoenix Contact can offer all-around electric car to charge solution, include out the connector that single source accords with Type 1, Type 2 or GB/T standard, and apply to what all sorts of E-Mobility apply to fill electric controller, cover use from family expenses and business, fill electric controller to public and large, electric car, arrive again all sorts of application setting of custom-built solution.

Summary

The electric power that electric car place needs comes from batteries and batteries group in aeriform but crucial chemical reaction, and go up in the district that carries electricity place to want the seat, corporeal and conspicuous connector and contact formed each key node, must try to height pays close attention to and be handled carefully in respect of a lot of detail. The parts of an apparatus in electric car is mixed in environment of voltage and power level, work the respect such as user expectation has distinct specific characteristics, be opposite consequently portable consume kind of equipment to be not formed how old the problem of the influence, likely however in electric car count for much, these problems include batteries group to be in extreme condition and even the function that are not normal condition to fall (include to come loose heat treatment, batteries is balanced) , connector IR is pressed fall, and how to let connector be in fixed firm while pull out easily again, etc. These problems must try to examine and be solved from many angle, and want the respect of balance of the first step of clear attention target, need and the interaction between all sorts of solutions.

(Author: Bill Schweber)

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