1. Tandem method. An additional 12-volt battery with normal voltage is connected in series with the entire battery pack. For example, if the original car is a 48V-20AH battery, then we will connect another 12V-20AH battery in series. A fully charged 12V battery has a voltage of about 13V. After being connected in series, it can increase the voltage of the entire battery, and then use its original charger to charge it. In this way, the battery can be charged. After plugging in the charger, the charger is a red light, and you can charge the battery at this time. When the charger turns green, remove the other battery connected in series. Then charge it normally.
2. Parallel method. This method is a bit more troublesome. For example, the vehicle used to have a 48V-20AH battery, and we have another set of 48V-20AH batteries in parallel. Everyone knows that the voltage across the parallel circuit is equal, and the high voltage end will flow into the low voltage end. This method is also used by many battery dealers to detect completely dead batteries. Then charging can also achieve the purpose of charging. This principle is similar to having a battery connected in series. It also raises the voltage of the entire group.
3. Low-voltage charging method. Use a small one-size charger for charging. For example, if it is a set of 60V-20AH batteries, then we use a 48V-20AH charger for charging. In most cases like this, it can be charged. The principle is also similar to the first one, the charging voltage is closer to the voltage at both ends of the battery.
4. Single battery charging method. Charging a single battery with a 12-volt motorcycle charger can activate the battery, but this kind of charging is relatively slow. Generally, it takes more than 7 hours to charge the battery before the battery voltage slowly rises to about 12V. It takes a lot of time to charge all single blocks.