[David_Moen]

Hi all,

I run NiCD batteries in all my airplanes so far. My favorite has a 1700ma pack on the RX and a 700ma pack on the ignition. Both are 4.8V packs. The ignition pack is a bit on the light duty side, so I was thinking of removing it, swapping my RX pack in it's place and replacing the RX pack. I noticed that GH has some great deals on batteries right now, $20 for a 2100ma 4 cell NiMH pack and $24.95 for a 5 cell pack.

Any reason not to switch to NiMh? Is it worth-while to go to 6 volt? The plane is an Ultra Stick 120, I have 4 standard servos on the wing and 2 digitals in the tail.

Thanks!

[Frank Klenk]

I went to NiMh last year and there is a learning curve with them. Fly R/C had a good article a few months back, basically a comparison between the battery types. I'll have to search for it though. I find they do not like to be fast charged, as you would a Nicad. That being said I trickle mine and have had good results at te field. Others can chime in here too, that way we can both learn.

[R Plante]

I use both with no problem and fast charge only using a Sirius quad charger from Chief Aircraft.All my batteries test well using an ace abacus discharger.

I believe you should use the charger you use for flying on a daily basis as the charger you use for testing your batteries.

Randy

[ronm]

David, everybody I know is using Nimh batteries now.
Most guys are using 5-cell packs. You can get a 5-cell 1500mah pack now that weighs about the same as your old 4-cell 600mah nicad packs. (and about the same price as the old nicad packs cost)

Lets see, increased voltage = more powerful/faster servos
Higher MAH= Longer flight-time
Lighter weight= better performance
Cycling helpful for monitoring packs, but not required to
eliminate "Memory"

Downside,
-A little extra care required for charging (use a good charger)
-If you use a 5-cell pack, it may reduce the life of your servos slightly.

[Peter Gordon]

Walmart sells Energizer NiMh AA 2300 mAh cells, 4 for $16. Pick up a few packs, solder them together, and you have a pack for about $20. I use these packs in my 33% planes with NO issues. When I started making my own packs with these types of cells, they were rated at 1850 mAh. Within 2 years, they are getting 2300 mAh into that tiny cylinder now. Give it a try. If you have any questions on how to put the pack together, pm me. I'd be happy to help. Start to finish including shrink wrapped, it takes me about 20 minutes now for a 5 cell pack.

Also, on the charging end of things, from what I've been able to piece together in all the articles that I've read, the rates for charging are:

NiCd - 3C max, 2C typical
NiMh - 2C max, 1C typical
LiPo - 1C max, 1C typical

That means for a NiMh 2000 mAh pack, your max charge rate is 4 Amps, typical is 2 Amps. I've used the 2C rate to charge some E-flight packs (730 mAh) and have eventually seen performance degradation. Ultimately, if you require fast charging, have a spare charged pack ready instead!

Peter

[ronm]

I was going to mention those 2300 AA packs, I bought a couple last week but haven't tested them yet.
The ones I have are duracell, and they cost me $12 for a 4 pack.
(We sell them where I work)
If they are "up to snuff", this is a great deal!

Amazing how good batteries are getting!

Peter, how do you solder your packs?

[4*60]

My 2100 NiMH's indicate 650mah for "fast" charge rate.

[luv2flyrc]

I've been using nimh for about 3 years now, no problems with them except that I have never been able to get them to fast charge with out my charger false peaking and shutting off. So I always have to slow charge .

This could be an issue with my charger"Super Nova 250s" or the battery type.

I've been contemplating a change to Li-ion but at the cost of about $500 for Duralites to set up a giant scale plane ( this includes new charger) I'm not sure if it's worth it.


Mike

[David_Moen]

I've got an Accucycle Elite for carging/cylcing, it should be just as good for NiHM as it is for NiCD, which is great. I've been peak charging at 1C before flying, and discharging to 1 volt per cell for storage of a week or longer.

I think I'll go ahead and get one of the 2100mah 6 volt packs. This means that I could fly two dayts in a row without charging (does anyone who works for a living and has kids ever actually manage that feat?). I've got to order some skis anyway - I learned yesterday that just because there's no snow on my lawn, doesn't mean the field is clear. Too bad, after the month I've had I was looking forward to some flying!

[rscamp]

David.

Application information for NiMH indicates full-discharges will reduce life. This is good practise for NiCds, but apparently it doesn't translate to NiMHs.

NiMH cells vary drasticlly. There are high-current cells that charge great at 3C using NiCd delta-peak charge termination settings. Most NiMHs would be destroyed by this treatment. Generally speaking, the higher the capacity per unit volume, the less likely it will charge well using delta-peak charge termination.

Rob