Twin Jet problems!

Not with a twin jet tho :-)

Gunther? Gee D.H. Your bigotry is showing!

Again!

What are you on about?

You sad fat bastard.

... for less successful launches and flights ...

Despite not beleiving the advice about the 3000 Nimh I now have to admit that haiving got this thing flying, there IS a noticeable difference between using a 3000 Nimh and a 2100 NiCad. Gues who wins

--- the Nicad!! Still doesn't make any real sense to me but I'll be getting some more Nicads instead of Nimh! Anyone explain the reason for the difference please?

cheers, Len

NiMh's are simply a different chemistry than NiCd's. They are excellent in some applications, like with geared drives, or as transmitter packs, but generally they don't like high Amp rates which are common with direct drive brushed motor apps. Depending on producer and size, max Amps I would recommend is for AA size 8 - 12, for SC size (Sub C, like used for Twin Jet)

15 - 20A. Another serious disadvantage is you should not charge them with the charge rates higher than 1C or with more than 1A (max. 1,5A), whichever comes first.

There are some excellent sites you can find out there explaining the topic in details. Unfortunately I can't help you now with links because I am on holidays right now using my cell phone as a link. I am sure someone else could also jump in and help you with additional info.

regards, boris

Many thanks for the info. I did wonder why the manufacturer only recommended a max of 1C charge for the NimH. Looks like I need to find some decent NiCad's then !!

cheers, Len

| NiMh's are simply a different chemistry than NiCd's.

That's true.

| They are excellent in some applications, like with geared drives

That depends.

| or as transmitter packs

Yes. AA NiMH cells excel there.

| but generally they don't like high Amp rates which are common with | direct drive brushed motor apps.

That's not as true as it used to be.

Many modern NiMH cells can tolerate discharge rates almost as high as NiCd cells.

Really, the problem is the AA cells. AA cells suck at high discharge rates, NiCd or NiMH. SubC, now that's another matter entirely ...

The R/C car guys generally do 4 minute races, so they probably pull

14C (any power left in the cell after the race is power wasted) or so out of their pack, and they really seem to love their SubC NiMH packs.

| Depending on producer and size, max Amps I would recommend is for AA | size 8 - 12, for SC size (Sub C, like used for Twin Jet) 15 - 20A.

SubC can go higher. 15C discharge rates are tolerated well by most of the NiMH SubC packs used by car racers, for example.

| Another serious disadvantage is you should not charge them with the | charge rates higher than 1C or with more than 1A (max. 1,5A), | whichever comes first.

More than 1 amp is fine for SubC NiMH cells. But 1C is still a good guideline, though you can probably do 2C safely.

But definately, to add my voice to the crowd, AA cells are not anywhere near adequate for your plane. Instead, I'd suggest a 10C or better discharge 3 cell LiPoly pack, around 2200 mAh or more. But if it'll take SubC cells, a 3000 mAh or more NiMH pack won't do you wrong either.

the latest crop of quality 3300 NIMH outperform almost any nicad in te class.

Needless to say, cheap imitations do not.