What's the best way to get a fixed 10v from a vairing dc supply?

Hello
Wonder if someone could help me please I need to get a fixed 10v dc from a vairing dc voltage but unsure how to get this, not sure how a zenner diode behaves when the supply voltage varys.

I want to tap off a 10v from a 12s battery which will vary as it is used ie go down, was hoping to use a 10v zenner but unsure how it will behave

Was thinking of of Maby a dc to dc converter step down Maby? But again unsure if a vary voltage would be possible?

Thanks

dc to dc converter (buck) works all the time

that toy gives constant output with a varying input

A voltage regulator (linear or switching) will work down to a certain voltage, but there is a "dropout voltage". For example, if a 10V regulator has a dropout voltage is 0.5V then the regulator will drop-out of regulation at 10.5V and the output will fall below 10V. (The popular 78xx series regulators have a dropout voltage of 2V, so that's no good in your application.)

A boost/buck regulator is a kind of switching regulator that can boost or cut voltage. If you go with a switching regulator, I recommend you buy a board/module because they can be tricky to build.

Switching regulators are very efficient and a boost regulator can, of course, extend the life of the battery because you can get 10V out (to a point) after the battery drops below 10V.

If you mean a 12S (44.4V nominal) Lipo battery then dropout voltages aren't going to bother you. But you've missed out an important part of your specification. How much current do you need to have available at 10V? Zeners are only useful if you need to draw very low current.

So a DC-DC converter is probably going to be your best bet. It will maintain a stable 10V down to any voltage that it's sensible to let the Lipo get down to. But check the maximum input voltage carefully. A fully charged 12S battery is around 50V.

Steve

What do you want your system to do when it (the battery) eventually runs out of juice? shutdown immediately or live long enough to do an orderly shutdown (that's about the only two options I can come up with). If you want an immediate shutdown, you could crowbar it to death (probably a bad idea with a LIPO supply), or just let it flop (also a bad idea with LIPO's). if you want an orderly shutdown, you are going to have to have a way to detect battery depletion while you still have enough power to do that shutdown. I guess you could add a bunch of capacitance in your supply line the make up the difference when the battery starts to poop out (sorta like filtering only BIG scale), but you have to remember that the more capacitance you put in a DC supply line, the more that looks like a short to the supply (until the caps charge up: this also bothers LIPO's). And the more power you need for the shutdown, the more storage you need in the caps.

Note: ALL of the above assumes that your design does not include sparks and flying flaming polymers.

Sounds perfect will use a dc to dc I'm only drawing about 100ma
Also didn't think of it but I can tap into the battery at a lower voltage at different cells so it can be a much much lower voltage like 10 or 20v

Don't tap into a battery like that, you'll unbalance the cells.

12S = 44.4V, so a DC-DC converter designed for 18--72V input sounds about right(*). Unfortunately the cheap LM2596 DC-DC converters aren't rated for 44V.

(*) this is a semi-standard rating for commercial DC-DC converters designed to operate from 48V nominal.