Should I fully charge the unit as soon as I get the device?
Yes.
Generally considered good advice for this class of 'batteries'. Important to fully charge (many sources recommend 'overcharging' several hours after charging stops) before the first serious discharge (heating), this determines the maximum capacity ever, it will only go down from there throughout it's useful lifespan.
Not so important with easily replaced cells like with ArGo (as opposed to say Solo) but doing so gives you best possible performance over time.
I know it's tough, but I recommend 'overnight' charges for such new gear. After that best battery life actually comes from not completely charging, counter intuitive as that is. For instance, stopping 10% early (4.1 not 4.2 Volts)
DOUBLES the cycle life. Double. Drop that to 20% and you now get a nominal
1200, not 300, cycles. Four times as many. Avoiding 'hitting bottom' is important as well.
FWIW I understand Tesla recommends this (avoid full discharge and full charge for best battery lifespan). There the battery packs (also made of 18650s BTW) cost a lot more than here......
Short answer, yes, fully charge (even overcharge) before any serious use. If you 'cheat', forget it, it no longer matters. First time. After that avoid full charge and full discharge for longest life.
BTW, don't store them at 100%, that alone will kill them over time. 60 or 70% is proper, which is why your unit should not come fully charged, which is why you have to do it?
Good stuff on the topic here:
http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries
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