How do fast chargers work?

[john61ct]

I'd recommend getting some better leads for that power supply. If the power supply is putting out 4.2V and 2.5A, yet the voltage at the cells is still 3.69V, that voltage difference is being wasted in the wires. With better wires you'd be able to put out higher current with the same 4.2V setting

Maybe, but not AWG too high, could be faulty connection though.

What you are missing, is that in the circuit there are three voltage levels involved.

A. What the PSU could put out if the battery weren't so much lower

B. Battery voltage without the PSU on

C. The circuit voltage as measured at the batt posts, "negotiated" between the two, as SoC rises so does that voltage (depends on C-rate too)

 

[john61ct]

irrelevancies deleted

 

[DogDipstick]

Addy buddy..

If it was a foot of wire.. ( 1/1000)(1000)... ( 1)

4.2v power source at one end..

and the resultant voltage read at the other end of the wire..As 3.7v... ( losing 0.5v, through 1 foot, a resistance of 200mOh, @ )

That wire is .... very very small... 1.25w ( 0,5(v) x (2.55(A))... would be dissipated in the circuit and the wire would be between 32g and 33guage wire.. and.. would not support the 2.5A.. but only about 0.5A... before.. getting really hot really fast.

A 18 gage wire does NOT drop 0.5v in 1 foot. VoltagePotential.

A 33g wire does. 33g wire is 206mOh / foot. (0.2Ohm per foot. ) Applya voltage (X) to a 33g wire, and.. in a foot, length, you will measure (X-0.5)v

I very highly doubt he has 32g multimeter wires.

I betcha he has 18gage multimeter wires. 18g should not drop half a volt (0,5v) potential/foot. Maybe there was a (hidden?) break in the wire that was a bottleneck/high resistance point.. some broken strands, not making good contact... .. a failing wire.. . ( that would create a hotspot.. Too)... Then when ( He, She) replaced wires, everything was fine again.. IDk

Im not saying " Try another wire" was not a good idea. It was, and is. The wire may have been dropping (v) but @ 2.5A it would have certainly burnt.. if it was... 200mOh.. ( resistance req for our mystery 0.5v drop)

200mOh resistance WILL burn (dissipate power calculations) a 33g wire at 2.55A/3.7v..... Certainly. The wire (33g) cannot dissipate 1.25w...( waste power) ( dissipate power).... when it is feeding 10w through it.. NOOOPe...It wont last long trust me... It can only handle like... 0,5A before getting hot... ( 1.85w MAX for a foot of 33g)( then magic smoke, above that.. ).

Thats all I'm seeing. Given the basic nature of the equations. Given what we know offhand.

 

[DogDipstick]

Let me guess. You SET the Power supply to ( 4.2)v... but MEASURED the terminal @ 3.6v. Watch that EEEVBLog vid relating to DC compliance.

Yes?

Compliance voltage. Watch that EEVBlog vid relating to the nature of power sources and DC compliance.. The nature of electrical nodes. Ect.


An electrical engineer and teacher, genius to boot, directly telling you about power sources, batteries, DC theory, and how it works.. and .. how they work together. The Thevelin Equivalence circuit. How the " ESR ( Rs) of the ( battery) is nonlinear with output voltage.. Can change with temperature, voltage, curernt, and pressure, even, Ect"... Specifically.
EEVBLOG VID<<<<<<<<<<<<<<<< https://www.youtube.com/watch?v=AQK7RyecVW0 >>>>>>>>>>>>>EEVBlog VID


https://en.wikipedia.org/wiki/Node_(circuits)

"According to Ohm's law, V = IR, the voltage across any two points of a node with negligible resistance is
V = I R = I ⋅ 0 = 0 , ... and this is showing that the voltage at every point of a node is the same."

 

[bymannan]

WHAAT???!!! Are we now saying these are LFP cells???

OP stop and **discharge** immediately down to 3.2 or even lower!!!

You are murdering your bank treating them as if it is li-ion

???

 

[john61ct]

irrelevancies deleted

 

[DogDipstick]

see we
which translates
very stressful
need feeding from
ought was what you have?
respectively.
known #cycles lifespan, maybe only 1-2% NBD

But lucky you

Lol No John.

OP ( Original Poster) confirmed for us that in fact, the are 3.62vn LION cells,.... NOT LFP, and they have a nominal voltage of 3.62v/cell and a nominal wH capacity of 185wH. The QR code was posted on page 1. bymannan confirmed this for us.

Your browser must be lost in the space time continuum or something. Not updating as you are polling the forum.

But yea I panicked srry. The whole " Oh No It MiGhT bE LIfePo4!" thing was an incorrect assumption on my part.

 

[Addy]

I betcha he has 18gage multimeter wires. 18g should not drop half a volt (0,5v) potential/foot. Maybe there was a (hidden?) break in the wire that was a bottleneck/high resistance point.. some broken strands, not making good contact... .. a failing wire.. . ( that would create a hotspot.. Too)... Then when ( He, She) replaced wires, everything was fine again.. IDk

Yeah, it could have been poor contact or some other issue, but bad wires are still possible. I've had test leads with 24 AWG copper inside. A 3 foot set of those would be in the ballpark to drop 0.5V when you factor in contact resistance as well.

 

[john61ct]

OK sorry brainfarts, rather than nominal I interpreted 3.6x as termination voltage