Re: Need help in picking type of battery
- From: "Beav" <beavis.original@xxxxxxxxxxxxxxx>
- Date: Mon, 17 Oct 2005 20:22:42 +0100
"Doug McLaren" <dougmc@xxxxxxxxxx> wrote in message
news:FLu4f.41713$0c.39789@xxxxxxxxxxxxxxxxxxxxxxx
> In article <11l1scm99576rc4@xxxxxxxxxxxxxxxxxx>,
> Beav <beavis.original@xxxxxxxxxxxxxxx> wrote:
>
> | 6 volts from the same capacity battery means less flight time too.
>
> This is the standard wisdom, though I wonder just how true it is.
> After all, a pack with 5 cells will have more total energy than a pack
> with 4 cells.
Even so, the time they take to flatten i less with 6 volts than it is with
4.8. That's one of the reasons I stopped using 6 volts aeons ago.
>
> When asked to explain it, people tend to dig up ohms law and after a
> little math declare that a 4 cell pack will last 20% longer than a 5
> cell pack. Which would be accurate if the load had a constance
> resistance, but this is _not_ the case with servos. (Though it
> probably is close to accurate with the receiver and maybe the gyro.)
I wouldn't give it a figure (as a percentage) coz it'd be just a guess.
>
> In any event, taking everything into account, I suspect a 5 cell pack
> probably does get used up faster than an otherwise identical 4 cell
> pack under normal use, though I think the difference is a good deal
> less than 20%. But I haven't tested it.
>
> (Ok, enough rambling.)
>
> In any event, it's hard to tell the difference between servos powered
> by 4 cells and servos powered by 5 cells for most.
Actually, the difference in speed (of the older servo's) is VERY noticable.
>
> | 6 volts speed the servo's up and give them somewhat more torque, but
> | with the digitals, do you NEED that extra?
> |
> | I seriously doubt it, unless you're ragging the bollocks off the heli
> doing
> | extreme flying, which, given the type of question you asked, I also
> doubt.
>
> I concur. It's also extra weight which will reduce performance, use
> more fuel and reduce your flight times ...
Unless of course, the heli needs sme extra nose weight. Then a 6 volt pack
can help.
>
> | As to NiCad or NiMh? Your choice, but NiMh don't tolerate vibration as
> well
> | as NiCads, so I don't use them in the flying bits, although I do use
> them in
> | the Tx. A 3000mAh Nicad will give you plenty of flying time
>
> Do 3000 mAh SubC NiCds exist?
IIRC, I have one siting in my Futura.
The highest capacity subC NiCds I've
> seen are 2400 mAh. (subC NiMH cells, on the other hand, I've seen go
> up to 3700 mAh.)
I've never even investigated "Rx" NiMh's as I won't use NiMh;s in the
helicopter, just the Tx, so I can't comment.
>
> | and if you're smart, you can install it in such a way that it's
> | quickly removable so you can slip a fresh battery in its place,
> | should the need arise.
>
> As another poster suggested, subC cells can be recharged quite
> quickly, especially the NiCds. The car guys sometimes charge them as
> fast as 4C ... and possibly faster. Though I'd not suggest that for
> your RX packs,
But that's what we're discussing here and it's why I never mentioed the fast
charging aspect.
but 2C or 3C (if you're in a hurry) would probably be
> just fine. (But having two packs is a better idea.)
Isn't it just :-)
--
Beav
Reply to "beavis dot original at ntlworld dot com" (with the obvious
changes)
.
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