Hello, I associate the dV/dt and pulse changing to Ni chemistries, could you explain better the differentials you are
talking about (dV/dT dI/dT) and pulse charging for lithium chemistries?
Initially the cell is charged with a constant current. At a certain point we switch to constant voltage charge . From now on we need to look at the current. So we monitor now di/dt. If this falls under a certain level the remaining charge time required would become very long. For example : we take a specific cell. The charge specs claim that you can charge this particular cell to 90% capacity in let's say an hour. To get the remaining 10% in there you need to go on for another 4 to 5 hours ... At this point the system switches to pulse charging. ( they go back to CC mode but this time we pulse currents. after every pulse the cell voltage is analyzed. The cell voltage actually falls back in a few milliseconds. there is a technique where this dv/dt is monitored as well. i forgot who has the patent on that on. i believe Asahi Kasei. ) The handoff between CC and CV causes problems. it is posible that the step-up to CV actually causes current to increase beyond the allowed charge limit. This is where pulse charging can be employed as well. They modulate the on/off time until CV can be maintained.
All the wile you need to monitor cell temperature.
If all you are after is getting 80% charge in 5 hours .. be my guest : muck around with the lab supply , but quadruple check the output voltage !!! going 0.1 volt over can cause the cell to explode ...
if you want to fill the cell to 80% in a reasonable time : you need an intelligent system. If you want to get 100% in a reasonable time .. pulse charging but this get s very complex very fast.
As cells age the electrode changes. the solvents used create an isolation barrier ( this happens actually immediately after construction as well. this isolation barrior still allows for the exchange of ions. i'd have to go back to my notes for the finer details... last time i messed with this was 1997 .. ). these solvents can decompose under heat. -> kaboom ...
smart lithium chargers ( doesnt matter if it is lipo or liion ) actually tack the curves over time. Benchmarq has really good chips for that. they maintain a record in eeprom of what has happened to the cell eand the charging system adapts itself depending on age. ( that is why in some laptop battery packs replacing the cells never gets you back to 'full' energy. simply because the eeprom data causes the charge controller to treat the cells as 'old'.
Lithium chemistry batteries are NOT TOYS. Even the big boys like Sony , Dell and others mess it up big time ( look at all the battery recalls ). We had our cells in blastproof containers. ( a kind of plexiglass box. dont know if it was lexan or some other material ). and i have seen 4 or 5 go 'off'.. and these were the tiny cellphone cells. One time we had a kodak flexible battery. that thing bulged up like one of those drink puches you poke a straw in ... and then went kaboom.
Whenever i see people 'muck about' with lithium cells i take a detour... these things are very dangerous if mistreated. oh, and never-ever throw water on a burst cell.. lithium is so agressive it can strip oxygen molecules from water ... giving hydrogen... combine that with oxygen in the atmosphere and the heat generated .... you know ... 1+1 is sometimes larger than 2 ...