Please help me identify these Unknown Components

[ThermallyFrigid]

Hello!

I have a small circuit board that I think is a PFC board, but I'm not sure.
It's a smaller board, on a 48v LiFEPO4 battery charger.

The unknown components are marked as UK1, UK2 and UK3
I realize I may have to desolder them to test them better, but I was wondering if they could be identified without doing so.
Here are the measured characteristics and a photo......

UK1
Resistance Test: 2.18K ohms with VOM leads connected either way
Capacitance Test: No reading regardless of VOM lead connections
Diode Test: Beep and 0.728v when positive lead on Left, 1.6v when Positive lead connected on Right side with no VOM beep.
Continuity Test: No continuity regardless of which way the leads are connected

UK2
Resistance Test: 6.93M ohms with VOM Positive Lead connected to the bottom, Negative lead to the top terminal, 5.17M when the leads are reversed
Capacitance Test: No reading regardless of VOM lead connections
Diode Test: Beep and 0.643v when positive lead on top terminal, 1.988v when Positive lead connected to bottom terminal with no VOM beep.
Continuity Test: No continuity regardless of which way the leads are connected

UK3
Resistance Test: 0.740K ohms with VOM leads connected either way
Capacitance Test: .0L reading regardless of VOM lead connections
Diode Test: VOM Beep and 0.803v when positive lead on top terminal, 0.807v when Positive lead connected to bottom with VOM beep.
Continuity Test: No continuity regardless of which way the leads are connected - 0L

[fzabkar]

Whenever I see a white smd component, I expect it to be a precision component. I've seen quite a few precision resistors, but no capacitors. However the following article suggests that your mystery component may indeed be a precision capacitor.

https://www.elprocus.com/what-is-a-smd-capacitor-types-its-applications/

The capacitors like NPO and COG ceramics are generally available in white color. They have less capacitance that ranges from 1pF to 10pF.

[strawberry]

definitely not precision for product that cost 10$ , lucky getting 5% parts
0.47..1nF capacitors for TL494 timing and feedback compensation
sometime they solder some resistors upside down (to cut price?) but seems not in this case

[gamalot]

They look like common ceramic capacitors to me.

[picburner]

I found only one other pcb on the net called "XLS3.PCB" and it is also a different revision.
However in the latter UK1 and UK2 would appear to be capacitors while UK3 would appear to be a resistor.
This pcb, from what I could understand, should be part of a 60V lithium battery charger.

[ThermallyFrigid]

definitely not precision for product that cost 10$ , lucky getting 5% parts
0.47..1nF capacitors for TL494 timing and feedback compensation
sometime they solder some resistors upside down (to cut price?) but seems not in this case

That would seem to make sense, but oddly, I have two of these and on one of these boards they used a LM358 and on the other an OPA1612 (which is a prohibitively expensive OpAmp for such a low cost device?

Well, if you buy these chargers they cost about $60 I believe.

[MathWizard]

Have you mapped out the circuit ? That would help a lot too, to guess what they are

[strawberry]

I have two of these and on one of these boards they used a LM358 and on the other an OPA1612 (which is a prohibitively expensive OpAmp for such a low cost device?

could be the same LM358 to get into 10$

[ThermallyFrigid]

Have you mapped out the circuit ? That would help a lot too, to guess what they are

I'm mapping out some of it in an attempt to do just that.
Thanks

[fzabkar]

definitely not precision...

I consider NPO capacitors to be precision types (if that's what they are), but maybe others would not.

[strawberry]

NPO (C0G) better tempco and less microphonic
can get precision between +/-1pF...20%
https://eu.mouser.com/ProductDetail/YAGEO/CC0805KRNPO9BN102?qs=57cj7OiSijl0sOrTylTGAQ%3D%3D

[DavidAlfa]

I'd say they're 100pf or so.
1nf+ are usually slightly darker, but doesn't always apply.