What's Fast charging about - Page 1
Forum section: electronics / general

author: abdulbadii
author_rank: Frequent Contributor
timestamp: October 02, 2021, 12:50:08 am
content: Anyone please elaborate explanation on (refutation of, if it's argued to be false) :"Fast charging shortens battery life"and explain what actually the definition and mechanism ofFast charging

author: beanflying
author_rank: Super Contributor
timestamp: October 02, 2021, 02:30:20 am
content: You cant ask that question without knowing FIRST the Chemistry of the Batteries in question and then SECOND how that particular cell is made, so what its impedance is and a final level of charge at the end of a fast charge among other specifics.If you pick NiMh as an example as they are less fussy than LiPo's charge cycle. Garbage 2500mAh (claimed) AA's will cook under even a 1C charge rate while a similar capacity Panasonic or Sanyo R/C type cell we will happily charge at 2-3+C (I have seen them charged at 5+C) partly as the cells get hotter prior to use their impedance goes down even further so you can push them harder in use.If you take as an example a High Grade 'reputable' LiPo R/C pack you can fast charge them at multiple C (2-2+) but for me I keep them to around 1C as I have time and plenty of packs. Some of the early LiPo packs we had were pushing to accept a 1C charge rate and there was issues in particular with some cheapies going up in flames.Canned Lithium's are a different can of worms again and in particular as the market is flooded with garbage and clones. So peddle softly if you have a battery of suspect origin.Lead Acids (or similar secondary storage types) have a huge size range, physical and chemical differences but a lot of AGM's for example are fine with really high charge rates while you will kill even a large Golf Cart sized Gel cell if you push it. This is in particular worthy of a whole thread or even threads as traction uses vary from renewable storage use.Anyway just some preamble but maybe consider a more specifically focused thread otherwise it will get really messy

author: IanB
author_rank: Super Contributor
timestamp: October 02, 2021, 03:14:39 am
content: Quote from: abdulbadii on October 02, 2021, 12:50:08 am"Fast charging" is basically charging faster than "slow charging". You are in "how long is a piece of string" territory here, so the question needs to be more precise for a good answer.You can think about it like this: when charging any kind of battery, the charging process is a chemical reaction (an electro-chemical reaction) driven by the electric current. All chemical reactions have some kind of rate limit, so the first important thing is that the desired charging reaction can keep up with the electric current. If not, then undesirable side reactions will happen that might cause wear and damage to the cell. In the extreme, something like an alkaline cell, which is not designed to be recharged, can only sustain the tiniest charging current before bad things happen.The second important thing is that higher currents tend to lead to higher temperatures, and this also can lead to wear and damage to the cell.So it's generally best to keep charging currents low enough that excess wear on the cell is minimized.

author: Kerlin
author_rank: Regular Contributor
timestamp: October 02, 2021, 12:59:44 pm
content: I thought they use an MCU to read the battery voltage and also monitor the battery temperature using a thermistor.They adjust the charging current so that a reasonably high battery temperature is not exceeded but also maintains that reasonable high battery temperature while its charging.They stop charging when or when the battery temperature drops below a particular temperature which indicates its charged or in an emergency case when it gets to high. Or when the battery reaches a required voltage and is therefore fully charged.So in that case the designed battery charging temperature can be designed as a compromise between charging time and battery life.Sometimes the battery charging temperature is settable by the user so they can make the choice between battery life and charging time on a per charge basis.

author: Siwastaja
author_rank: Super Contributor
timestamp: October 04, 2021, 05:41:36 pm
content: For a very typical energy-optimized (not high power) modern li-ion cell, as used in a cellphone, laptop, etc., "normal charging" would be like 0.5C, and "fast charging" would be like 1.0C. High power cells, as used in power tools, can take more but usually not over 2.0C."0.5C" means, a 1000mAh cell is charged at 500mA and it takes roughly 2 hours from empty to full (ignoring CV phase which makes it somewhat longer).Exact numbers depend on the exact battery product. Sometimes small changes make a big difference. A certain cell could last 500 cycles when charged at 0.7C but only 100 cycles when charged at 0.9C.