Maintaining a LiPo
Q: Why does my battery have two connectors?
A: The first is the power connector, and is used to discharge power from the battery into the gun. If you have a smart-charger, you can also charge or discharge the battery through this connector. The second is the 'balance' connector (a.k.a. 'JST-XH' or 'breakout' connector), and is used to balance the individual cells of your LiPo pack. If you have a 'balance charger', you can also charge the battery through this connector, but not discharge it. Balancing is less of a concern for 2-cell (7.4V) LiPos, but 3-cell (11.1V) LiPos will occasionally discharge and/or charge unevenly, causing an imbalance of the voltage levels in the cells. If this imbalance allows one or more cells to fall below the 3.0V minimum while others do not, the battery can appear to be functioning normally, while actually dropping the low-voltage cell(s) into 'Deep Discharge State', damaging them. The balance connector allows your balance charger to check the voltages of the individual cells, and charge/discharge them appropriately.
Q: What do I do with my LiPo between Airsofting events?
A: To prepare your LiPo for medium- to long-term storage you should charge it (or discharge it, as necessary) to about 3.8V per cell (0.1V above nominal). You can store LiPo batteries fully charged, but this will degrade the battery's chemistry, reducing its capacity. You should not store LiPo batteries close to empty because they self-discharge, albeit very slowly - about 2% per month if above 50% charged, and about 1% per month if below that. If you store them close to 3.0V per cell the chances of them dropping below that before you remember to charge them are substantially increased. Even when charged to a storage voltage, you should check their voltage every few months to ensure they don't drop below 3.0V in any cell. Be sure to remove your LiPo battery from the airsoft gun when no longer in use, as leaving the battery plugged in will drain the cells more quickly. This is due to the mosfet continually drawing power from the battery.
Q: My LiPo is kinda inflated, is it going to explode?
A: Not if you properly handle the situation. A puffy or inflated LiPo is a dead LiPo. Continuing to use a puffy LiPo is how guns catch fire. If you've followed the best-practices above, you will likely never have to deal with a puffy LiPo. If you're on the field and your LiPo becomes puffy, return to base, remove the battery from the gun, put it into a LiPo-safe container, and take it home with you (but keep an eye on it). If you notice it becoming puffy at home (or have already brought home a puffy LiPo from the field), clip the leads off (one at a time to avoid shorting them), soak the whole battery in salt-water for 24 hours, and take it to an E-cycler or hobby-shop, they'll be able to properly dispose of the drained corpse.
Q: How do I keep my LiPo from being overused in the field?
A: There are several options for this, I’ll list them in order of price: listening (your rate of fire will decrease as your voltage gets closer to the danger-zone and at that point you should stop using that battery and start charging it.), LiPo low-voltage alarm (this will make a beeping noise when the voltage gets below a pre-set point. Most LiPo low-voltage alarms will allow you to set the voltage level at which it provides a warning. You should set that level to 3.1-3.3v, slightly above the minimum safe per-cell voltage.), or a low-voltage cutoff MOSFET (this will disable your trigger when the voltage drops below a pre-set point. These are very customizable but also much more expensive.)