CF4.0 with 11.1v battery pack?

[MoonDragn]

I wonder if you can use a buckpuck between the CF board and the 3 li-ion batteries.

It regulates current, but with a fixed load that means the voltage should stay constant.

[erv]

no you can't

[MoonDragn]

How about just a couple of resistors then? Take the voltage down to about 11V with the resistors and it should solve the problem.

[neophyl]

Resistors arent used to reduce voltage on their own, they are used to reduce current.

If the designer of a peice of circuitry says dont do it, its usually a good idea not to. Id listen to Erv if I were you.

[erv]

"nope you can't" is going to be a copyright sentence of mine now, I suppose
neophil is right, you can't use a resistor.
Eventually, you could use a bunch of 1N4xxx diode in serie to get rid of the extra voltage... Then the nominal voltage will drop to about 10V.
Not the best idea but why not.

[MoonDragn]

Ahh I see what kind of circuit you have in there now. I can think of some other ways, but since it is a copyright thing, I'll keep it to myself.

Resistors arent used to reduce voltage on their own, they are used to reduce current.

If the designer of a peice of circuitry says dont do it, its usually a good idea not to. Id listen to Erv if I were you.

Guess you've never heard of a voltage divider.

I like Erv's idea better though, rectifier diodes don't have the loading problems resistors would have.

[neophyl]

Guess you've never heard of a voltage divider.

I like Erv's idea better though, rectifier diodes don't have the loading problems resistors would have.

As a matter of fact I have. I also know enough not to suggest using them for this application. You suggested using a single resistor, which isnt the same as a voltage divider network. I merely pointed out that wouldnt work on its own. There are lots of other options depending on size, efficiency, cost etc constraints that you have to work under.
If you already know about the problems of using a resistor in this capacity then why post potentially misleading information on a forum that can confuse those without the background in electronics some have ?

[xwingband]

Jeez, MoonDragn... I thought you said you were an EE?

I'll echo Neophyl why do you keep suggesting these silly things like a resistor to drop voltage?

[MoonDragn]

As a matter of fact I have. I also know enough not to suggest using them for this application. You suggested using a single resistor, which isnt the same as a voltage divider network. I merely pointed out that wouldnt work on its own. There are lots of other options depending on size, efficiency, cost etc constraints that you have to work under.
If you already know about the problems of using a resistor in this capacity then why post potentially misleading information on a forum that can confuse those without the background in electronics some have ?

Because I didn't know what Erv had packing under that CF. Just because I'm an EE doesn't mean I know whats in the black box. All I know is that theres a certain load condition that can't exceed a max voltage. A voltage divider can certainly work, and I didn't mean just one resistor, that was a typo there.

I had assumed the reason for the limitation was because the CF had some kind of current limit. Not a limitation on the supply voltage max of the regulator.

If you had noticed, all of my comments were posted in a form of a question, because I didn't know. I ask questions when I don't know something. Erv being the designer, knew more about his circuit, and was the perfect person to answer that question. This is a legitimate question, because some of us would like to run over 11 volts to the CF. Knowing how to get around its limitations is very helpful.

Thanks Erv.

[Novastar]

Ok, a typo it is. I will say these things though... that is the kind of thing that can be instantly edited (or edited anytime) on the TCSS threads. I actually am glad for this, as I like to fix my mistakes as quickly as I discover them for fear of others using the wrong info.

And on the other side of being a devil's advocate... I think we're all trying to discuss interesting ways of looking at >11v... and as long as none of us suggest things that are brainless, impossible and/or insulting, we should be good.

As it is, in my post before Eandori's... that is what I meant to say "rectifier diode" instead of the "xener" suggestion. Which is why I just suggested it with a "?"... since I wasn't totally sure.

In any case--it makes sense to me that if you have your cells... then PRIOR to *ANYTHING* getting to CF... you alter the cells current and voltage BEFORE they get to CF... it won't matter HOW you achieved it, as long as CF is essentially "oblivious" to the fact that the cells were once higher than what it likes.

I mean... you could take a 24v solution and hoover deluxe it down to 10v if you like. I don't know WHY anyone would do THAT to such an extreme, but... I'm assuming here that it could indeed be done.

Would this be wrong? Could you convert "high" voltage X to 10v prior to going to CF and CF would be "none the wiser", so-to-speak?