@ecuadorche - Depending on your charger and how high amperage it can charge at (i have the 306b which can do 30, but rarely does) - I try to slow charge at .25-.5C so 1/4 or 1/2 the Ah. So your pack is 4Ah or 4000mAh - so 1 C would be 4 amps charging. I would slow charge at 1 or 2 amps - which increases pack life and is easier on the battery (less heat etc.).
Nice thing about having higher amp charging is when you get home and want to ride before it gets dark! Being able to charge your pack (each pack will state it’s max C charge rate) at higher C is perfect for a quick charge and then go ride. Did this last night - sunset ride w/ GF at Alki. quick 30min charge and out the door (not even 2C, but fast enough).
Looking at the Turnigy 4000mAh 5s pack - it has a max charge rate of 2C - so i could charge it at 8 amps, but normally would still do 1 or 2 amps for 1/4 or 1/2 C.
Speaking of C - 15C on this pack will only equal a claimed 60Amps continuous discharge capability. I personally doubt the marketing department of all battery manufacturors… So i shoot for a minimum of 100Amp discharge capability. Expecting roughly half that in real world use. Using an inexpensive (not lab grade, but hey…) inline watt meter on my boards i’ve rarely seen more than 45A peak draw - so i feel like this is a reasonable short draw use and shouldn’t over-tax my packs.
Get a small battery voltage alarm - a few bucks on HK or Amazon:
any like this - you set the voltage to alarm at a cutoff point (i usually use a conservative 3.7v or 3.6v). It also will cycle through the pack showing your cell’s individual voltages. Plus total voltage.
Your 5s pack should be 21v fully charged (5 * 4.2v). Nominal voltage (for calculating Wh) and what they show on the pack will be 3.7v *5 = 18.5v.
HTH - GL!