BMS and lithium battery technology

At present, aluminum nickel and cobalt acid lithium (NCA)The battery although the dominant in the field of electric vehicles, but it may also be replaced by other techniques. For the battery management system (BMS) is usually a weak link of electric vehicle batteries.

Although lithium cobalt oxide is cheap and can be high, but cannot offer 14 to 18 in moped peak current.Although Ni-Mh batteries have been used, but its than cannot nickel and cobalt aluminate the lithium battery in the half. Titanium lithium battery can lower than, higher than the titanium lithium battery and lithium manganese battery only a little.

lithium iron phosphate batteries temperature higher than 250 ℃ (LFP) of thermal runaway, this makes the security is very high battery, its life is also very long.However, its low than can (less than half of the NCA) make its application in small moped is not common.

Lithium nickel and cobalt aluminate (NCA), with its 250-290 wh/kg than can be over the highest can compound, but the higher cost and lower security.Its service life also each are not identical, universal rechargeable number between 500 to 1000, only about half of lithium iron batteries.Thousands of 18650 tesla using nickel and cobalt lithium battery and in a more rigorous testing (equal to ensure the quality of each battery in the battery pack) to improve the service life, in order to avoid completely discharge and fully charged.And other brands of electric cars, tesla with 8 years quality assurance, ensure the battery capacity will keep within 80% and no charge.However, electric bicycle batteries are seldom fully tested, even if it improve yield.

(NMC) nickel cobalt manganese acid lithium battery has been Renault and BMW company for its electric cars.According to the Samsung, at present the ratio for 130 wh/kg (about half the NCA), but to reach 250 in 2019/2020-300 wh/kg.The cost of the NMC now than 12% to 19% higher than that of NCA.With its gradually become the mainstream of the electric car battery, its cost will decrease, however the cost of the NCA hardly fell again.Life and safety of the NMC were higher than that of NCA many, so it will be a strong contender for the future of electric bicycle batteries.

Oakes energy company (OxisEnergy) claims that the lithium sulfur batteries will be cheaper, can live longer, and you have the highest ratio.In July 2013, the company's CEO, says that with the GP battery company has been "gaining momentum", but so far its and boundless signs.At present, 300 wh/kg version of lithium sulfur batteries for nickel and high-end drill aluminum acid battery was flat, but slightly less than its life.According to industry BBS, tesla would like to get the prototype in its hind to evaluate new compounds, but they still have not received any product.Lithium sulfur batteries has its merits, but will take time to mature.

Battery management system

A good battery management system has a temperature sensor, can detect single battery voltage, and detect the poor performance of the battery in front of the battery pack packaging.This 100% test to ensure the higher yield, higher battery capacity and reduce the warranty commitment.A good battery management system also recorded the mechanical impact, deep discharge date and information, thus can avoid false warranty application.Excellent BMS can also detect the humidity of the battery pack to avoid accidents.

BetterBMS group (by the university of Maryland CALCE electronic products and systems research center, high-tech electronics expert erigineering spiirit and I) in 2014, according to the above information in Eurobike show BBMS specification was released.A large electric bicycle system company please Engineer spirit members (BCT) to design this BMS.In particular, they do not charge for production development costs and allows a third party

Electricity flow, in 4 a discharge battery resistance (0.1 ohms) and a poor battery (0.4 ohms) on the capacity of the gap is not obvious.Low discharge current can make the difference of the builders also become good battery.Voltage is reduced, the difference of the battery (0.4 ohms) 30% faster than good battery power.Good BMS can monitor the internal resistance and take the initiative to reduce current power to postpone.But also declined significantly from acceleration: it's time to change the battery.

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