4 tips for DIY lithium batteries pack

Since our FS-SW1 mini intelligent spot welder released, many customers have consulted about DIY lithium battery packs recently, which are used to modify electric skateboards, electric toys, electric scooters and other battery packs. We have compiled the following 4 tips for reference.

1. The choice of batteries

(1) 3.2V lithium iron phosphate/3.7V ternary lithium battery, this is a simple distinction.

(2) Batteries are divided into many grades, which are distinguished by models of 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 batteries.

(3) How to distinguish good from bad after receiving the battery. It is necessary to use internal resistance tester and power test. Test the nominal MH, and the actual MH. The larger the gap from the nominal parameter, the worse the quality. The lower the internal resistance of the battery, the better. Conventionally, it is below 50. Above 50 may be old or poor batteries.

2. Battery processing

When you get the battery, it does not mean that you can handle it immediately. It must be processed again before it can be used. (For the power 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 detection of the battery protection board to fail and the battery pack will not work. How to deal with it?

(1) If possible, you can also screen by machine. If there is no machine, just use the internal resistance tester to measure one by one, put together the voltage, internal resistance, and capacity, and let it stand for a period of time (7~15 days). After standing, test again. If it is still consistent, you can process it. Up. This is also a physical method for judging the stability of the battery cell.

(2) Many friends will also ask if it can't be assembled and used directly? Of course, but in 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%. More seriously, if there is a bad battery in the battery pack, the whole pack will not work. Inspection and maintenance work is more cumbersome.

3. Selection of battery protection board

(1) Two electric wheels below 40A are sufficient. The specific choice should be judged according to your own motor power.

(2) The voltage should also be matched. 60V is mostly conventional. It is necessary to distinguish between ternary and iron-lithium, as well as the number of strings.

(3) Try to use large capacity and low power, stable and durable. If the battery is high-power and small, be sure to calculate whether the discharge rate is supported.

(4) Try to choose the protection board with low protection voltage to give the battery a certain margin. For example: 4.25V protection is not as good as 4.2V~4.1V, because it will not put the battery to 100% power.

4. Battery spot welding

In the welding process, safety is undoubtedly the key. Therefore, choosing a good spot welder is very important. What’s more,the thicker the battery connection wire, the better. The thicker the nickel sheet, the better. As a container for charging and discharging, the battery will also release heat during energy conversion. Irregular processing may cause problems in the battery pack. Care must be taken when processing the battery pack. If you don’t know how to assemble it, please find a professional for help.

For DIY players, having a simple and easy-to-operate mini spot welder is undoubtedly the best choice. The above is the difference among FS-SW1 and other spot welders on the market.Happy holidays and send a newest and mondern spot welder by yourself !

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