Are 72v32a and 72v20a interchangeable?
3 Answers
72v32a and 72v20a chargers are generally not interchangeable. Reasons why these two chargers are usually not interchangeable: If a 20ah battery charger is used to charge a 32ah battery, there is generally no problem except for slightly longer charging time. However, if a 32ah battery charger is used to charge a 20ah battery, this constitutes fast charging which is very dangerous. Typically, after continuous use for about a week, the battery capacity will significantly decrease, and you'll noticeably experience reduced driving range. Introduction to chargers: An electric vehicle charger is a dedicated charging device designed for electric bicycle batteries. Charger classification: Based on the presence or absence of a power frequency (50Hz) transformer, they can be divided into two main categories. Freight tricycle chargers generally use transformer-based chargers, which are large, heavy, and power-consuming but reliable and affordable; electric bicycles and electric motorcycles typically use switching power supply-type chargers, which are energy-efficient and highly efficient but more prone to failure. The correct operation for switching power supply-type chargers is: when charging, first connect the battery, then connect to mains power; when fully charged, first disconnect mains power, then unplug the battery. If the battery is unplugged first during charging, especially when the charging current is high (red light), it can easily damage the charger.
The voltage is consistently 72V, but the current specifications differ. When dealing with electric vehicle issues, I found that 32A and 20A are not directly interchangeable. For example, if your battery is 32A but the controller can only handle 20A, using it may overload and burn out the device. Conversely, a smaller 20A battery connected to a high-load system may fail to supply enough power, resulting in startup failure. They are also incompatible during charging—a 32A charger used on a 20A battery will charge too quickly, causing overheating and damaging the battery cells. The safety risks are significant, and it also affects the driving range. Ordinary users should avoid mixing them for convenience. I’ve seen many vehicle owners encounter problems this way, ultimately spending more on repairs. Always check the device manual for the specified current range—matching voltage alone doesn’t guarantee safety. As batteries age, internal resistance changes can worsen the issue, so from a maintenance perspective, sticking to matched specifications is the safest approach.
As an ordinary electric vehicle user, I used to think that as long as the voltage was the same at 72V, I could freely swap between 20A and 32A batteries. But that turned out to be a big mistake. Once, I replaced a 20A battery with a 32A one, and shortly after driving, the controller smoked and burned out, costing me hundreds to repair. Different current ratings affect the actual load capacity, and charging becomes problematic too. Charging a small-current battery with a large one takes too long and reduces efficiency, while a high-current battery wastes energy in a low-power system. Compatibility is poor, so I suggest you check your electric vehicle's manual for the clearly marked maximum current rating. Do your homework before swapping batteries—don’t be careless like I was. Now, I only buy original specifications. Range is also affected—high-current batteries have larger capacity but drain faster, which isn’t worth it.
