power

[Roger_tech]

I guess, when I asked for further details, they said to not try and get the answer from them.

I don’t get it. Paralleled cells of different voltages is a no go. Well, of course you can but not advised.
Can you add circuitry to each battery before they are connected in parallel?

 

[Martaine2005]

I’m sure you’re not telling us everything.
They should know not to parallel different voltages.
Also, you applied for a job as a PCB designer without knowing this as well.
I suppose as long as you’re not charging these batteries, you could add a buck converter to the highest voltage and limit it the same as the lowest.
Or series connect two or three diodes to drop the voltage.

 

[Roger_tech]

I’m sure you’re not telling us everything.
They should know not to parallel different voltages.
Also, you applied for a job as a PCB designer without knowing this as well.
I suppose as long as you’re not charging these batteries, you could add a buck converter to the highest voltage and limit it the same as the lowest.
Or series connect two or three diodes to drop the voltage.

I can't use a linear regulator because of heat dissipation, but can I use a switching regulator?

 

[Martaine2005]

As @Harald Kapp mentioned earlier, a switching supply may work as they are ^90% more efficient than a linear regulator.
But the main problem still arises, paralleling different voltages. It’s not impossible, it’s plainly wrong.
Edit: plus, no load information. Perhaps they want you to tell them that you can’t?, the traces would be thicker/wider for current ?

 

[Alec_t]

Two 4s Lipo batteries at 16.8V and 14.8V, connect them in parallel, minimal heat dissipation.

If that is exactly as the requirement was worded, then note that it does not specify zero current or zero heat dissipation. You could just connect them via a 100 MegOhm resistor and challenge the tester to define 'minimal'.

 

[Roger_tech]

If that is exactly as the requirement was worded, then note that it does not specify zero current or zero heat dissipation. You could just connect them via a 100 MegOhm resistor and challenge the tester to define 'minimal'.

They didn't exactly word it as 'minimal heatng', they said 'no heat'. I just assumed minimal heating because 'no heat' is impossible.

 

[Martaine2005]

they said 'no heat'.

That’s simple then.
Design the PCB for the higher voltage and current, assuming the higher voltage carries more current (if not design for max current), and don’t connect the batteries. Tell them it’s wrong!.

 

[Delta Prime]

they explicitly asked me to design a PCB, and send them the Gerber files, I interviewed for the PCB designer position.

It's crucial to acknowledge the limitations of your potential employers approach.
You’re applying for a PCB designer position, and you do not have a schematic of the circuitry necessary in this endeavor.

I think they just want to see how I approach a problem that isn't very common.

Stick with what you know!
By default your design must adheres to standard manufacturing guidelines like appropriate trace widths, spacing, and drill sizes.
Use thermal vias and copper pours to dissipate heat effectively, anticipating this mythical circuit, that some components might generate significant heat.

I just assumed minimal heating because 'no heat' is impossible.

OK!
OK stands for zero Kelvin that is the point where molecules stop vibrating. it is not impossible.

 

[poor mystic]

Like, how do you deal with a client with an impossible brief?
Ya gotta really need the money, for a start, else you'd take one look and fo.
You have to explain. They're always grateful in the end, but it causes bad gutsaches until they know.
Keep yr chin up

oh yeh PS this sort of thing is nearly always a communications stuff-up

 

[Delta Prime]

Like, how do you deal with a client with an impossible brief?

The only way to discover the limits of the possible is to go beyond them into the impossible.
-Arthur C.Clarke

 

[poor mystic]

The only way to discover the limits of the possible is to go beyond them into the impossible.
-Arthur C.Clarke

See!
DP recommends another set of high current sources on the same board.
If ya can't beat 'em, confuse 'em.
Cheese