Can I use a 12V charger to charge a 36V battery? The answer is no.

1. Understand the charging process
The charging voltage of the battery is certain, too low a voltage is difficult to make the battery charge properly, the current will generally only flow from the side of the voltage is large to the side of the voltage is small. Usually, the charging voltage is greater than the battery voltage, the charging process will occur.
2. the reason
When using a 12V charger to charge a 36V battery, the charging voltage is less than the battery voltage, and the battery may be in a discharged state instead of a charged state, which will make the charging process ineffective and bring many hazards, even if it can be charged, it will be very slow, so it is not recommended to use a 12V charger to charge a 36V or a battery with a larger voltage.
3. charging hazards
Long time charging may cause the battery to stay in a discharged state and end up over-discharged, shortening the life of the battery. Even if your charger can charge your battery, your battery may be undercharged or slow charging, which will affect the effectiveness and lifespan of the battery for a long time; in addition, due to the mismatch between the charger and the battery, it may lead to the instability of the current of the battery, and the charger and the battery will be damaged, and there will be the risk of overheating and explosion in the long run.
4. Solution
If you still use this charger, there are some ways to help you improve the compatibility between the charger and the battery. For example, you can prepare a boost converter or boost coil, and you can use them to increase the voltage to match your battery. However, this method may increase the complexity and cost of operation, so it is not recommended.
The best way is still to repurchase a 36V charger, which can also effectively improve the life and effectiveness of your battery, and it is also the safest method.