What are the problems of DIY assembling lithium-ion batteries

1. The problem of battery cell selection 1. 3.2V lithium iron phosphate, 3.7V ternary lithium ion battery, this is a simple distinction. 2. Batteries are divided into many levels, and there are models with capacity and power. The difference involved is the discharge rate. In theory, the higher the discharge rate, the better, but there are also high, medium and low power lithium batteries. 3. In terms of operation, novices can't buy good batteries if they buy in retail. Good batteries are given priority to electric vehicles, and only those that have been screened can flow into the market. Large merchants in the market will re-screen, the good ones are used for battery packs, and the poor ones enter the retail market. Note: Regardless of the brand, it will not be too good to enter the retail market, even the first-line brands are no exception. Of course, the higher the premium you pay, the better you can get. 4. The problem of battery screening, how to distinguish between good and bad after the battery is in hand. Internal resistance tester and power test must be used. Check the nominal MH, and the actual MH. If the distance from the nominal parameter is greater, the quality is worse. The lower the internal resistance of the battery, the better. Conventionally, it is below 50. More than 50 may be old or poor batteries. 5. The problem of cycle life is a big problem. Many friends assemble it by themselves, the capacity is not up to the standard, and the power loss is obvious after a period of time. This is mostly a battery cell problem, and it is difficult for retail customers to get around this pit. After all, there is no channel to get good products and no equipment to check the quality of the battery cell. (The author recommends his own electric vehicle battery pack, which can be cycled for more than 2000 times.) Second, the problem of battery cell handling does not mean that we can deal with it immediately after we get the battery cell. It can only be used for production processing again. (For the power lithium battery pack) The battery pack must be assembled with a matching protection board! The battery requires matching consistency, the more consistent the better, the more stable. If the matching is inconsistent, there will be insufficient capacity, which will seriously cause the battery protection board test to fail and the battery pack will not work. How to deal with it? 1. If you have the conditions, use the machine to screen. If there is no machine, use the internal resistance detector to measure one by one. Put the voltage, internal resistance, and capacity together, and let it stand for a period of time (7-15 days). If it is still consistent, it can be produced. This is also a physical method for judging the stability of the battery cell. 2. Many friends will also say, why is it so troublesome, can't it be directly assembled and used? Of course, it can be used directly, but in the case of mismatch, the battery pack will follow the barrel theory, and the capacity is limited to the lowest board. The worst battery in the battery pack is the upper limit. In layman's terms, the capacity of the battery pack will drop by 10-40%. To be more serious, if there is a bad battery in the battery pack, the whole group will not work. Inspection and maintenance work is more cumbersome. (This is the author's personal experience. Basically, one battery will cause the entire battery pack to be scrapped. After all, the production process of repairing the battery pack alone is to do it again, and it is troublesome.) Third, the battery spot welding problem 1. The battery pack production and assembly are given priority to machine production , Manual assembly is not recommended. (Multi-string and other battery power packs, the requirement for single parallel is not high) 2. Why is manual spot welding not recommended? The battery spot welding strength is not well controlled, the battery spot is leaking, and the nickel spot is not solid and welded. Manual soldering iron soldering. If the soldering temperature is too high, it will damage the pole piece. Low temperature soldering is recommended. (Most households use high-temperature solder) 3. The thicker the battery core connection line, the better. The thicker the nickel flakes, the better. 3. The battery is used as a container for charging and discharging, and heat is also released during energy conversion. Irregular production may cause problems with battery packs. The production of battery packs must be cautious and cautious. Many industry personnel suffered a lot. There was no battery that year. The PACK manufacturer caught fire. Fourth, the use of battery pack environmental issues. 1. The battery pack is required to be waterproof! High probability of short-circuit fire! 2. The battery pack is required to be shockproof! Electric vehicles cannot be used as off-road vehicles in use! The outer skin of the battery pack cannot be used to buffer the collision, and deformation will cause a short circuit! Try to use the grid bracket + cushion + outer box. Without the grille bracket, the battery pack will cause the nickel sheet to fall off under the squeeze of many years of activities! 3. The battery pack is conditionally supplied with heat conduction channels, and during energy conversion, timely heat conduction can optimize the battery. Steel outer box + fan assist are both conventional solutions. The power glue package proposed by the author before is also a solution, which is troublesome post-maintenance. 4. Anti-corrosion problem. The battery will rust after being left for a long time. If possible, take anti-corrosion measures as much as possible. V. Lithium-ion battery protection board selection 1. Electric two-wheels below 40A is sufficient, and three-wheels above 80A. The specific choice should be judged according to your own motor power. 2. The voltage should be matched. 60V is mostly conventional. It is necessary to distinguish between ternary and iron-lithium ions, as well as the number of strings. 3. Try to use large capacity and low power, stable and durable. If you have a small battery with high power, you must calculate whether the discharge rate is supported. 4. If possible, choose the protection board with low protection voltage as far as possible, and give the battery a certain amount of surplus. For example: 4.25V protection is not as good as 4.2V~4.1V, because it will not put the battery to 100% capacity and not stick to the limit. However, most protection board designs do not pay attention to this point, and a few manufacturers are doing it. Six, charger selection 1. According to the protection voltage of the protection board, how many strings of iron lithium ion/ternary lithium ion 2. Choose how many A/H chargers are suitable according to the total capacity. The 8A/H routine is now recommended on the market. 3. The charger should also be protected against water and shock. If you don't cherish it every day, it will break quickly. Seven, electric vehicle brakes as far as possible, choose electric vehicles with double disc brakes, lithium-ion battery discharge rate is high, acceleration speed is fast, without good brakes, accidents are easy to occur. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete.