The accurate batteries that how optimizes car batteries to run a system measures precision?
[introduction] as batteries chemistry character, dependability and relevant technology stable with each passing day, car batteries runs a system (BMS) the design also develops ceaselessly subsequently. Nowadays, if where,BMS design personnel had mastered electric the optimum behavior that BMS all is optimized to measure below environment of very harsh drive a vehicle and implements a system with exterior condition.
As batteries chemistry character, dependability and relevant technology stable with each passing day, car batteries runs a system (BMS) the design also develops ceaselessly subsequently. Nowadays, if where,BMS design personnel had mastered electric the optimum behavior that BMS all is optimized to measure below environment of very harsh drive a vehicle and implements a system with exterior condition. The batteries of millivolt and milliampere precision is measured still is a key, need real time synchronism to collect these voltage and computation of power of voltaic data in order to.
In addition, BMS still must evaluate the effectiveness that gauges every time, because it needs utmost ground to raise the integrality of data, in order to identify, distinguish and undertake judging according to mistake or doubtful data. Be explored through lasting and optimize, BMS IC manufacturer already can provide crucial system framework, in order to satisfy electric car (EV) batteries management system is right comprehensive monitoring, rigid security, dependability and high-powered requirement.
Because batteries function can be followed,degrade, the choice of BMS IC is accordingly crucial also to prolonging the service life of batteries group. In working process, batteries group health (SOH) accuracy can help car batteries manage electronic equipment to use as aspirant as power supply control travel to optimize in batteries, in order to prolong the odd life of batteries group. Batteries management IC whether its accurate measurement maintains inside car service life precision, it is the crucial essential factor that affects batteries management design directly. Batteries report core measures any medium deviation or not stable metropolis to affect the travel course of development of car and battery life directly, the maintenance that affects car manufacturer then reachs management cost.
For the lithium ion of electric car power supply batteries has 8-10 normally year guarantee period. After this, think its apply to car drawing no longer, but batteries still may maintain his 80% of original size. Because this can use car use old batteries form with appointed odd life migratory need the application from bad news batteries to other in, undertake 2 times use.
To car manufacturer character, successful BMS needs to design initial stage to choose BMS IC carefully in the system. Manufacturer needs understanding to be in the process of whole operation environment and car service life, especially the abominable electromagnetism such as tall voltage batteries and inverter noise is disturbed (EMI) below the environment, the product that each IC suppliers offer gauges the difference between precision and stability.
Admirable lithium ion monitors a system 4 the most important levels:
•Precision —— discharges to having evenness cell type of the curve (like battery of lithium of phosphoric acid iron) , batteries precision is the most important level;
•Comprehensive diagnostic —— besides the condition that monitors every report core, the system still needs uninterrupted ground to undertake to its oneself functional security detects, in order to ensure every IC moves with expectant precision;
•All link of supervisory system of reliable communication —— must coordinate carry to go, the dependability that must ensure to correspond between the system accordingly, and method of most traditional communication cannot satisfy this one requirement in environment of noisy drive a vehicle.
•Security —— system avoids breakdown and safe problem through running lithium ion cell appropriately. When malfunctioning, the system must take proper control step, avoid to sign up for by accident at the same time.
Battery of lithium of phosphoric acid iron because its are low in-house impedance and apply to minor batteries team. Type of this kind of cell makes systematic engineer needs to detect the slight change of voltage of the batteries when batteries discharges. And measure these little change to need complex imitate front (AFE) , accurate and stable voltage is fiducial and accurate modulus converter (ADC) , this is an enormous challenge to personnel of BMS IC design.
Much batteries balances the crucial essential factor in IC
Accurate voltage is fiducial the core that is all BMS IC. The referenced develop that chip place uses attacks type each are not identical, taking unoccupied place structure is the most commonly used, they are between precision and chip area, and the precision inside whole temperature limits made first-rate balance. For example, administrative IC used group of ISL78714 lithium battery to take unoccupied place standard design accurately, this one design has good applied record, suit to ask slashing car applies very much. This technology stability, mature, characteristic is bright, reach through old application optimize. Accurate voltage radical affects a car to guarantee and manage cost index of manufacturer directly definitely, it is the element of a key of the consideration when designing life of batteries of personnel computation car.
Besides precision fiducial, the module of another crucial function that is used at measuring precision is ADC, advocate batteries voltage measures module. Two kinds most popularity and the most commonly used ADC type are successive approachs register (SAR) with Delta-sigma. In these two kinds of technologies, SAR has the rapiddest sampling rate, can offer high-speed to voltage is changed and fight sex of a confusion of voices outstandingly, but often need larger chip area. SAR ADC is to be able to offer data to collect speed, precision, intensity and the optimal choice that refuse electromagnetism to disturb ability to combine.
IC design personnel also is met apt Delta-sigma ADC, because they need lesser chip range normally,accumulate and relatively easy implementation. But because used draw-out filter, their speed often slower, this meeting reduces sampling rate and data to gather speed. The another consideration element when using Delta-sigma ADC is tend when be disturbed by EMI saturated, this may be brought about appear when voltage of core of accurate report report defer (change cycle thoroughly for 3 normally) .
The interface of single cell is managed by AFE, this AFE includes to input shift of bumper, n implement detect with breakdown circuit. When batteries receives BMS repeatedly at first, AFE is to handle heat to insert unplug transient is crucial. BMS IC uses design of the complete AFE that need branch, negative input voltage is measured below the situation that can not affecting photograph adjacent batteries to measure (±5V) , this is very advantageous in the system that needs bus line interconnection. To increase the strength below transient state condition, end of batteries voltage input increased exterior low connect filter.
The design course that inputs filter wave is optimized, affecting speed or precision while obtain the biggest EMI and heat to insert unplug immunity to interference. Under photograph comparing, the precision of the integrated circuit that uses AFE of coupling of charge of ambipolar and rather than and the component that because exterior input filter chooses,long-term deflection meets are worth and reduce greatly. Graph of the 1 3 functions module that showed BMS IC and its interconnection simplify graphic representation.
Graph 1. Group of ISL78714 lithium battery manages implement simplify block diagram
Stable linear belt is unoccupied place fiducial, SAR ADC and photograph of the complete AFE that need branch are united in wedlock, make lithium battery group manages appliance to fast data collects ability, intensity and precision. The pinpoint accuracy of BMS IC is not relied on merely when leaving factory measure precision to be worth, still need to installing printed circuit board (PCB) test and verify of junior travel independence. Graph 2a and 2b showed integrated circuit the precision inside batteries voltage and temperature limits, this is crucial to personnel of batteries system design, because they need value of systematic error budget to assure the service life of car, must consider reliable and the precision index that can calculate.
2b of graph 2a graph
Graph 2. 30 BMS board assemble the test data after 1000 hours
Accordingly, the proposal designs personnel microscope, the data that should provide in every IC supplier is compared in detail between the watch, especially precision, data collects speed and input filter requirement (include them the influence to precision) wait for a respect.
PCB cloth board the note with configuration
Solder stress can arise on PCB, make BMS integrated circuit is in two plane happening curve X and Y, produce subatomic stress in silicon character thereby, affect the performance of integrated circuit then. As a result of fiducial it is the crucial factor that measures circuit, any its characteristic change can affect the precision of ADC directly, this is the well-known phenomenon in accurate chip industry. Chip architect can pass will sensitive circuit to be placed carefully in getting the chip area that solders to make stress affect with other unlikelily, will solve this one problem.
Or, IC designs personnel to be able to choose higher standard design technology, enclose in same IC for example inside place alone fiducial naked piece or use alone disperse fiducial chip. No matter use technology of which kinds of IC, the design of PCB and production phase is crucial. Accordingly, accurate IC cloth board technology and be installed to chip and solder of plan meticulous think, meeting help alleviates a lot of problems.
For example, cloth board guideline mixes the PCB that BMS designs personnel to abide by ISL78714 to recommend solder circumfluence curve, can see precision of reading of unit of IC board class and long-term drift character all are logarithm and can forecast. Real test and acceleration life test the lab that the data of long-term drift performance of this IC comes from 25°C. Precision of whole service life is initiative board class precision and life deflection (for example, total average and RSS standard deviation) vector and. Graph the 3 cell that showed the pattern inside the service life in 15 years read the result that takes error.
Graph 3. In ±6σ (after solder) those who fall is initiative Vs of error of board class batteries. Service life
Conclusion
A crucial factor that batteries management designs is batteries function, and in car service life, BMS IC is capable to maintain its to measure precision to be able to affect batteries performance directly. The travel course of development that batteries n measures any medium deviation or not stable metropolis to affect vehicle directly and battery life, affect car manufacturer then guarantee reach management cost. Have all sorts of having different precision measures develop to attack to be able to be offerred with technical BMS IC choose, because this system is designed,personnel must consider carefully how to choose and be used. Optimize BMS to design and understanding is measured, plan and develop attack potential difference of the structure, and between them correlation, the BMS chip that uses to choosing to suit its EV most is crucial.
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