Heya cincy - it's a 17500-type Lithium-ion battery in the eGrip, so little or no memory effect, and you can start charging from any level.
Keep in mind the eGrip is passthrough, so you can use it while charging - but keep in mind when doing so, that there was an issue with the design / mounting of the USB port on the eGrip's circuit board for early-run units - I think
joyetech resolved it for anything bought after late December / early January.
I say this because the port design doesn't allow for the USB plug body to sit flush to the bottom of the unit when fully plugged in - there's about an 1/8th of an inch space left, which puts strain on the port's solder joints when you handle the eGrip with it plugged in. Also, that issue caused a few people to expect the plug to to be flush with the bottom even after the "click", so they manhandled it and tried pushing it even further, snapping the solder joints of the port off the board and leaving the port disconnected and loose inside the body.
Again,
joyetech redesigned the port, so later units should be OK (my local B&M Cignot is an authorized
joyetech disrtibutor and confirmed it) - but even then, the USB plug will still not be flush when plugged in, the port just won't be as delicate.
Cuz I'm old school, I did run my eGrips (I have two) down to shutoff on the first use out of the box, and then fully recharged before next use. I also do have the habit of waiting to charge until I see the battery telltale flash for the under 10% condition.
I vape at 12.5 watts with a DIY 1.5 ohm vertical coil pretty much constantly all day - I do start at 8 watts for the first hour or so in the mornings - and get about 14 hours out of a full charge. That said, both eGrips behave the same battery performance-wise, which is to say very well.
Charging takes 2-3 hours - I haven't timed it to the minute, as I have the second one to use while the other is charging.
I bought eGrip #1in wood on December 20 - it's an early run, it also has the slightly loose fire button / watt dial issue - and while I've only done passthrough a couple of times on it, and know not to jam the USB plug in, the USB port has been just fine on mine. I also charge them so that it sits vertical at the edge of my dresser with the cord hanging down, so that's added to the longevity.
EGrip #2 in wood I bought December 31 (I had accidentally dropped #1 onto pavement which chipped up the body - a very nicely done mahogany skin from vaporskinz.com, whom I highly recommend, covered that up). The USB port on #2 has a more pronounced "click" when plugging in (using the same cord / plug), so that has me thinking it's one of the newer ones with the port redesign. I haven't done any passthrough with it yet.
So with all that said - yeah, go ahead and plug it on in, even if it's not fully discharged
