All this C/x and voltage measurement stuff is far more complicated that it may initially seem, and is only serving to obscure a practical answer to the OPs original question. The last article cited, while containing no truly misleading information, was written in 2008, long before the Samsung 35E (or equivalent?) cells used in our Rad batteries were released (2015), and the Battery Management Systems (BMS modules) inside our battery packs reached their current level of sophistication. If one wants to design their own charger, bear in mind that our Rad batteries are 13 Series/4 PARALLEL packs, and that affects the C value (as in multiply by 4). Also, did you have your battery switch Off or On when taking voltage readings (it makes a difference)?
So, if an average Rad user wants to try get a little more life out of their battery pack without getting a math headache every time they think about charging it, and don't want to build a special contraption to charge to ~3.81 volt per cell termination overshoot voltage (to provide the Samsung specified 3.60 nominal "rested" voltage), only ride ~5 miles or less at no more than Assist Level 1, and keep it in the refrigerator between uses, then something like the Luna Advanced 48 Volt Charger is a proven commodity that's hard to beat (when it's available).
Here's the bottom line; Charging to 80% at 2 or 3 Amps whenever possible is probably the best thing most typical users can do to add significantly to their Rad battery longevity IF most trips are short enough to not go below 2 Battery Capacity Bars showing on the Rad LCD Display. If you find yourself frequently ending up with 1 Bar showing, it would probably be safer to charge to 90% (the Luna Advanced charger will also do that) initially to try to reduce the number of times you end up at 1 bar. If you've already charged to 80% and decide to go on a longer trip, topping up to 100% JUST BEFORE THE TRIP will be less harmful to the battery than charging to 100% and letting it sit in a fully charged "just in case" state (100% charging has two negative aspects, just doing it, and leaving the battery in that state for significant periods of time, and the same applies to leaving batteries sitting around in a FULLY discharge state, avoid it). Charging to 100% in two time separated stages also reduces individual cell heating, another plus.
Here are some more factoids relevant to using a Luna Advanced 48 Volt Charger, in no particular order:
A Rad Battery pack charged to 80% will still show ALL 5 Battery Capacity Bars on the Rad LCD Display, you just won't get as far before dropping to 4 Bars.
Always charge with the power switch on the Rad battery pack in the ON position, it WILL make a difference in charge termination profile & behavior (PARTICULARLY with current Luna Advanced chargers, at least as of early 2021). You can turn the Rad LCD display OFF, but if you don't, it should go off by itself after a while (at least until Rad fixes the PITA thing about losing your Trip Odometer count every time you stop to smell the roses, or something).
Like any other charger, ALWAYS plug a Luna into the AC wall/mains outlet FIRST, so the spark that comes from the surge associated with filling up the chargers capacitors will happen at the more robust power plug/wall socket where it will cause the least damage, rather than the wimpy 5.5 x 2.1 mm DC coaxial connectors on the charger/battery pack (which should be connected LAST and disconnected FIRST).
The Luna comes with an XT60 DC Male output connector (could be replaced with an anti-sparking XT90 if you like re-engineering things) so it needs an adapter with an XT60 Female to 5.5 x 2.1 mm Male Coaxial connector to fit the 5.5 x 2.1 mm Female (plastic) socket on the Rad Battery Pack. When shopping for 5.5 x 2.1 mm Male plugs to make your adapter (if Luna doesn't have them in stock at the time, a frequent occurrence) you may note that many of the listings on Ebay and Amazon say theirs are rated at 10 Amps, don't believe it, they're either lying or talking about Chinese Amps. Figure 4 Amps at best to be safe, (which makes the maximum 5 Amp charge rate of the Luna Advanced of questionable use, at least with our present batteries). I noticed the coax connectors getting warm with ALL my chargers, so attached is a thermal scan of the back end of a 5.5 x 2.1 mm coax connector plugged into my battery while being fed 4 Amps by my Luna. The plastic cover has been removed from the back of the plug to get a more accurate temperature measurement. 140.7°F is as high as I'm going to let things get, considering that the internal temperature at the actual connector contact junction(s) has to be even hotter than that. Limiting charge current to 3 Amps would be safer.
Most current Rad full size Battery Packs have a 5 Amp fuse in the charging circuit, which should be OK for charging at up to 4 Amps (as long as you follow recommended practices/sequences to avoid connector plug in surges). Samsung says the normal charge rate for 35E Cells can be up to 1700 mA, which multiplied by 4 (because of the parallel circuitry use in our battery packs) would be OK for a 6.8 Amp charge rate. Samsung also specifies a "Maximum Cycle Life" charge rate of 1020 mA for the 35E cells, which would be 4.08 Amps for the pack, which fits nicely with Lunas next to the highest switch selectable charge rate. I sometimes charge at 4 Amps just before going out the door after a last minute change of plans, and although it's nice to have that option, I'd limit the rate to 3 Amps with all but the best coaxial connectors (verified by actual thermal scans).
For those who hang up their bikes for longer periods of time during winter and want to store their batteries at the Samsung recommended life maximizing long term storage voltage of 3.6 volts per cell or 46.8 volts for the pack (resting voltage after at least 20 minutes, NOT charge termination voltage) Luna chargers don't offer and easy way to do that, but fortunately our bikes do, sort of. Just run the battery down a little past the point where 2 Bars show up and "stick" on the LCD Display and it should be fine. Avoid high storage temperatures, the colder the better as long as the battery pack doesn't get below ~0°F. When it's time to use it again, let it warm up to room temperature before charging/use (8 hours or so should be fine, no forced heating/condensation).
If you have a choice of parking your bike in the shade or in direct sunlight on a hot day, go for the shade.
Don't slip into a state of Analysis Paralysis! Treat your battery with the respect it deserves, but remember to have fun. I'm only planning on my Rad batteries lasting 5 or 6 years (even though I'm current using MANY individual 18650 Lithium Ion cells much older than that on a regular basis, I just don't charge/discharge them as often as I do my Rad batteries). If some of the things I enjoy doing end up shortening the lives of my battery packs by a few months, I could care less.