You didn't mention what you are using for a lipo battery charger. You need to use a charger/power supply designed for lipo batteries and it should have a balanced charging option where you connect main leads and balancing connector to the battery. You select number of cells and charging rate in amps. For example if you are using a two-cell (2S lipo) and it is rated at 5000mah set charger for 2S and 5 amps. Usually lipo balancing chargers display number of milliamps put into the battery and the voltage of each cell when fully charged, it should be around 4.2 volts per cell when fully charged. It is not good to charge lipos fully and not use/discharge them for more than one week, they deteriorate faster when stored fully charged. Your charger may have a "discharge" or "storage charge" feature which you use to discharge a battery pack to 3.8 volts per cell which is the safe storage voltage. It is not good to discharge lipos too far. Speed control low voltage cutoffs should be set for around 3.7 volts per cell. Voltage will usually recover to 3.8 or more volts per cell after disconnecting from the load( your truck) . You can make a battery discharger from 3 automotive tail light bulbs connected in parallel with a connector to mate with your battery packs. You can connect a simple cell checker to the battery balance connector that will sound a loud beeping alarm when total voltage drops to the preset 3.8 volts per cell.
If you already knew all this, sorry !