The answer is no, if you are in a very urgent situation, you can do this, he will not be urgent for a special situation, it will only prevent the battery from being full, but if you do this for a long time you will surely damage your battery and charger.
In fact to understand how the battery charging is carried out we can compare the current to the flow of water, the charger voltage is compared to the water level, the battery is a container of water storage, of course, the charging method is to flow into the container, when the two are connected due to the charger is located in the voltage is higher than the battery is not charged, so no matter what voltage you use the charger battery will have electricity, but with the increase of the battery’s charge the current rate is slowly reduced! A 12-volt charger will not work for an 18-volt battery, and will only fill the battery two-thirds full.
First of all, this charging method certainly cannot meet the battery, and secondly, consider the current strength of the battery and charger, if the charger’s current is greater than the battery may cause the battery to age quickly, greatly reducing the life of the battery, if the battery still contains a large amount of electricity, the result may make the charger heat fire, such as the charger at this time is still connected to the battery may cause an explosion.
(1) If you don’t have the option of replacing the charger with one that is suitable for 18 volt batteries then to be safe it is better to use a charge controller, in fact this is not cost effective at all and will not charge the batteries, using an inappropriate configuration will only damage both sides.
(2) Using a voltage converter, a voltage converter can be used to increase the output to meet the voltage required to fully charge the battery.
Charger voltage and battery voltage does not match, simply can not achieve efficient charging of the battery, and will not meet the expected requirements, no matter what you choose any need to charge the devices to choose the appropriate charger, this kind of chaotic matching behaviour of the results must be bad.
