A few days ago, I heard a famous electric bicycle charging in the user's home exploded, there is an old injury.
This was the third time the brand of battery bombings : the
The first was in January 2012 a college students exploded in a moving time was small batteries within the battery, such as bullets spraying out, but fortunately no one was injured.
For the second time in March 2012, also in user charging at home, the results of the users of the houses were burned, the expected loss of 180,000.
The third thing is that a few days ago.
I lithium industry as a senior technical staff, very reluctant to hear about lithium battery explosion news, but from a technical point of view, point out the problem or, convenient to analyze the reasons.
From a macro point of view, the causes of lithium battery explosion from three aspects : Batteries, Pack assembly, the user's misuse.
Currently, the electric bike market is in a vicious competitive environment, the more pressure, the lower the cost, no good goods cheaper, which is causing the battery frequent cause of the problem, not only the cost of batteries to a minimum, Pack design is also able to save the Province.
Below is the focus of this post : Electric bicycle lithium batteries cost analysis ---- contained and Pack, the Pack 36V10Ah this post as an example to analyze.

1. Battery Cell
A 10Ah LFP batteries : Batteries theoretical material costs 26.7 yuan, the harvest rate is generally up to 90%, labor costs and management costs about 0.5 yuan / Ah, so the portion of the total monomer batteries cost is 34.7 yuan.
LFP cathode active material amount of about 85g, in accordance with the market price of 70 yuan / Kg calculations, the active material cost of 5.95 yuan, accounting for the total cost of materials, 22.3% of theory.
The amount of the negative active material is about 39.4g, in accordance with the market price of 75 yuan / Kg calculations, the active material cost of 2.96 yuan, accounting for the total cost of materials for 11.1% of theory.
Diaphragm material consumption is about 0.87 square feet, in accordance with the market price of 6.3 yuan / square calculation, the diaphragm costs about 5.48 yuan, accounting for the total cost of materials, 20.5% of theory.
Electrolyte dosage is about 45g, according to market price 80 yuan / Kg calculations, the electrolyte costs about 5.63 yuan, accounting for the total cost of materials, 21.1% of theory.
Four main material costs accounted for a total cost of batteries for 75% of theory, in line with the design of conventional batteries.
Based on personal nearly eight years of technical experience, made ​​of the material system battery at room temperature 0.5C charge-discharge cycle 1000 times no problem.

2. Pack Assembly Section
A 36V, Pack, LFP batteries monomer used number 12Pcs, so the total cost of the battery is 34.7 * 12 = 416.4 yuan.
Protection board part, the price difference is heaven and earth, the general low-grade panels, the price is about 30 yuan / piece, brought the following functions:
Overcharge, over discharge, short circuit protection, no temperature control, no balance, usually pure hardware boards, software failure rate is relatively lower plate.
Chargers, charger also 40 yuan low / Pcs.
Battery box, wires and electrical components, a total of 20 yuan / pcs.
So the whole 36V10AhPack (including batteries, protection board, box, charger) The total cost is: 416.4 +30 +40 +20 = 506.4 yuan.
With the 20% gross margin will offer little more than 600 yuan.