Charging Cloud 9 7-cell 120mah NiMh? - RC Groups
Thread Tools
Nov 26, 2001, 11:49 PM
Like to build
Ken Kaiser's Avatar

Charging Cloud 9 7-cell 120mah NiMh?


My ACE Digipulse can charge at 10 or 20 ma, for 16 hours, as a typical c/10 slow charger.

I've heard these cells are very sensitive. Since I can't get 12 ma, do you think they'll get a full charge at 10ma? Is 20ma OK, or would it damage them?

Once I get them charged I can try my Roadkill Corsair!
Sign up now
to remove ads between posts
Nov 27, 2001, 08:06 AM
in persuit of low wing loading
Gordon Johnson's Avatar
I was overly cautious when I first got mine. In converstations with John Worth, he says he routinely charges them at 1C, and sometimes higher. I also read about "forming" NiMH cells, which means charging them at 2C for the first couple of charges. Note, I wrote Todd Long, Dave Lewis, and John Worth to see if they had heard of this term, forming. None had heard of it. John's response was that he doesn't believe in low charge rates for these, but to monitor temperature using my hand.. I potentially sacrificed one pack to the charger gods by taking a new 120x5 pack and forming it at 2C. It did outperform the pack that I had originally charged at C/10. So, there may be something to this concept for SOME NiMH batteries. I did the same for a 70x5 (from Westechnik) and did not get any improvement. They may be different manufacturers. BTW, John Worth says he is on his second manufacturer for the cells he sells and that these are the best yet. I've also read that NiMH technology is getting better all the time.

So, the short answer is that I slow charge my 120's at 30ma from my Astro 110D charger. When charging at the flight site I have been using 60-70ma. BTW, the Astro 110D charger is not very accurate at low charge rates, I've checkd using their micro meter. If you need an inexpensive peak-detect charger to charge at low rates, Bob Selman makes them and sells them direct http://www.bsd.domainvalet.com/. He also uses these cells and can tell you his recommendation for a charge rate. I have two of his chargers and they are a very good value.

BTW, I've bought all of my 120's from John Worth, but understand that Balsa Products sells the same cells. I've been leery of buying from any of the battery only houses since I don't know enough to evaluate them. I rely on someone like John Worth to verify that a particular cell will work for our applications.
Last edited by Gordon Johnson; Nov 27, 2001 at 08:09 AM.
Nov 27, 2001, 08:21 AM
AMA 697691 / FAA 13675
Ken,

I have several packs that I throw on my Hitec CG-335 peak charger. The lowest that charger will go is .5 amps and it charges just fine.

Regards.
Latest blog entry: Greg's Web Hangar
Nov 27, 2001, 04:21 PM
Registered User
nolasco's Avatar
I have 7-cell packs from both Cloud9 and Radical RC. They are all peaked charged using the Jeti micro charger at the lowest (i.e. 300mah) setting.

The Radical RC packs performed better than the Cloud9 ones after they were all first initially charged at C/10. A few months and several charges later, the Cloud9 packs now seem to be performing better. Either they got better in time, or my Radical RC packs are going bad.

Ken,

For how long have you been charging these cells at 500mah? I know John Worth said his original packs should be ok at these rates. Have you noticed any improvements or degradation over time?

Jun Nolasco
Nov 27, 2001, 06:57 PM
Like to build
Ken Kaiser's Avatar
Well, they sound more robust than I thought. Your all charging them at around 3C or better, I would have thought that too much for NiMH from what I had been reading. Thanks for the feedback.

It sounds like if I slow charge mine at 20ma for 16 hours they should be fine.
Ken