LiPo batteries can be charged even without fully draining them. But be very careful with these batteries. LiPos can be toxic and can cause fire if mishandled or charged improperly.
There are only two important rules when charging these batteries.
Charge LiPo batteries to their specific charging requirement. Basically, each cell in a battery should only be charged up to 4.2v and should never be discharged below 3.0v. Therefore, if you want to charge a 4-cell LiPo battery, it needs to achieve about 16.8v first before it can be fully charged.
Use only the specific charger that was designed to charge specific LiPo batteries. Since every LiPo battery has specific needs, it is more practical to use only a charger designed to charge a certain battery.
You can also use the common LiPo battery chargers. But make sure that you know how to properly charge the batteries using them. These chargers can be classified on how they count the battery cells—automatic and manual. Automatic LiPo battery chargers can automatically detect how many cells a battery has and will charge the LiPo based on its count. The manual charger requires manual setting, which means you’ll have to enter how many cells the LiPo battery has and it will charge it based on your given data.
The proceedure for Lipo balance charger is as follows.
Connect the battery to the changer. Connect the charger to your power source, either a 12v battery or the outlet of your mains transformer.
The red LED shows that power is connected to the charger and will stay on until the charger is disconnected from the power source.
The green LED should come on steady, showing that your battery is charging. If it doesn't, your battery is either fully charged or duff. As the battery approaches full charge the green LED will start to flash and when it goes off, the battery is fully charged.
Disconnect the charger from the power source and then disconnect the battery from the charger.
Don't leave the battery connected to the charger when the power to the charger is disconnected or switched off as this will discharge the battery. If you discharge a LiPoly below about 3.1v per cell (9.3v for a 3 cell 11.1v battery) it will not take a charge with a normal charger.
The charger will then start to charge. You should be charging it on something non-flammable in a non-enclosed space (i.e. the floor of the garage is good)...just in case. Check in on it every 5 min.
Besides charging LiPo batteries properly, take note also of how you should handle, store, and take care of these batteries. You can avoid fire or explosion caused by these batteries if they are always dry, they do not short circuit, and they are always away from sharp objects. Never play with the batteries, too. Never let children to play with them. Hitting these batteries with a hammer might cause explosion. Even the smoke from these batteries can harm people and might cause fire.
It’s not enough that you know how to use LiPo-powered devices. It’s much more important that you know how to be responsible on your possession, especially if it is potentially harmful.
Here is a instruction video about how to use a Lipo balance charger correctly,enjoy it.