PDA

View Full Version : NiCad or Nimh?


thebaldone
08-01-2005, 09:32 PM
Can someone explain the difference between Nicad and Nimh? I was led to believe that Nimh were better than Nicad but it seems that in reality that's wrong! Just got a Multiplex Twin Jet and thought I'd get a good battery pack for it - a 3000Mah 8 cell NimH. Just about flies on this BUT a 2100Mah Nicad throws it around like there's no tomorrow! Doesn't make sense to me but I'm sure some kind soul will show me the errors of my ways!
TIA

Jason T
08-02-2005, 01:04 AM
Well, I cannot tell you much about the chemistry of Nicd or Nimh but I can give you my experience. I would say the "general" rule of thumb is mah to mah the NiMh cells will be lighter and battery technology is allowing Nimhs to handle as much if not more amperage in a given setup than Nicds. Nimh also do not have the memory effect that Nicds do. Where if a Nicd pack is not fully discharged then the capacity will be less over time.

Another point is a Nimh cell's resistance gets lower as they get warmer meaning if you put a Nimh pack in a setup when it is hot off the charger it will be able to put out more power. However, with that said charging and running Nimhs hot will probably shorten their life span.

Nowadays Nicd cells/packs will probably be cheaper Nimhs at the same mah rating.

Maybe someone else can chime in with their knowledge and experience.

Matt Kirsch
08-04-2005, 05:39 PM
Not all cells are created equal. You may be comparing apples to dog potatoes here with the 2100mAh NiCd and 3000mAh NiMH. Cheap no-name cells... well, you get what you pay for. Good quality NiMH cells have just as much punch as NiCds of the same physical size, and 33-66% more capacity to boot. Stick with name brands like Sanyo, KAN, or CBP (cheapbatterypacks.com).

It certainly sounds like your 3000mAh NiMHs are "eBay specials." They seemed like a bargain at the time...

Also, when converting from NiCd to NiMH, always go with cells of the same physical size. Physical size is generally an indication of how much current the cells can handle. In other words, how much "punch" they have. For example, if a model recommends 2400mAh Sub C NiCDs, use Sub C NiMHs. Don't use 2400mAH NiMHs, as they will be physically smaller and will not have the same punch as the NiCds.

Wingdoctor
08-08-2005, 04:27 PM
I agree with all the earlier comments.
Not all cells are the same. Just because a cell has a X number of mah stamped on it don't count on it being a real performer. I've seen some real "pigs" flying around with less than the optimum battery packs in them. Mainly no-name NimH, or NiCD's which commonly are heavy with higher internal resistance. Pay a little extra and get the good stuff i.e. Sanyo, Gold Peak to name a couple. Also the MaxxAmps, or Cheap Battery Packs either of these can hook you up with great cells, and or packs. This all said in the light that you want to fly this type of E-power. Go Lipo if you really want to LIGHT-UP your flying!!

ron_van_sommeren
08-08-2005, 04:30 PM
the Battery Clinic
http://www.rcbatteryclinic.com/

steph280
08-08-2005, 10:04 PM
Good points. I still have some 10 years old Sanyo Nicds working, where as my 2 years old no-name Nimh have already failed.

The latest high discharge Nimh cells are probably the best thing ever, until you go Lipo. I had great luck with Sanyo HRSC2600, FAUP 1960, and GP3300 cells. They produce noticably more punch than anything else, specially when they are hot off the charger. Yes they have to be run hot for the best performance.

kermitdafrog
08-09-2005, 05:57 PM
baldone,

The short easy answer is that for a given mah capacity, Nicads typically have less internal resistance so will provide higher current than a NiMh.

Rick

stuff
08-09-2005, 08:28 PM
I like to say that if you had both a large bottle and a pail of water then
you turned them upsidedown. The pail is your nicad as it will give you lots of power but for a short while.the bottle is your nimh cells and I bet it is still pouring but at way less volume.thus giving you a longer ride.If you notice Most pylon racers are powered by the red sanyo 500r cells which are very scarce now.They discharge fast as well as being able to take 2amp charging rate .4 packs and 2 charrgers ond you could fly all day.( but only 5 min filgts, At 51/2 you are walking to get your plane.) Stuff

fdix
08-09-2005, 08:46 PM
New NiMH cells are extremely powerfull.
For example the INTELLECT 3800mAh can deliver up to 250 amps for 30sec if pushed! That is enough even for F5F.
Just buy the right NiMHs and you should have no problems

Jason T
08-10-2005, 02:45 AM
I agree with fdix. If you need smaller cells the GP2000s and GP2200s are very good too.

tann200
08-19-2005, 10:21 AM
i have GP 1800 cells, and they doesnt seem to have the punch needed

Slent thndr
08-19-2005, 12:33 PM
www.batteryuniversity.com (http://www.batteryuniversity.com)
I have found this to be one of the best sites for battery information.

rahtware
08-19-2005, 02:19 PM
At a local hobby store the only NiMHs on display were for aerobirds etc. Everything else was LiPos. When asked why, the owner compared the NiMHs to a 280 computer... OK, but short lived as things go. An example of this is the new Kolcam 6400! Here is a battery with almost the same dimensions as a 6-cell NiCd or NiMH “car” pack but with at least twice the storage, 4oz lighter and a discharge rating of 128Amps!

I tried to fly my T-moth on NiMHs but gave up due to disappointing results, but Its current LiPo pack flies it great with twice the storage at 2/3ds the weight.:cool:

Slent thndr
08-19-2005, 02:28 PM
Lipos make a big differance I know

But still most of my stuff runs great on Nickle based. Like my Combat wing for example. To buy a good lipo for it would be over $100 but the High Output brushless rated Nicds are like $35 and not alot worse. Plus they wont blow up on you :) . But they will melt through your camping air matress (thats another story)

rahtware
08-19-2005, 06:30 PM
Lipos make a big differance I know

But still most of my stuff runs great on Nickle based. Like my Combat wing for example. To buy a good lipo for it would be over $100 but the High Output brushless rated Nicds are like $35 and not alot worse. Plus they wont blow up on you :) . But they will melt through your camping air matress (thats another story)

True, but...

After checking out the list of fires/explosions on:

http://www.rcgroups.com/forums/showthread.php?t=209187

It hit me that most were due to operator error, not the batteries. As for the price/AH it is getting very close. I bet it would take two or even three of your NiCds to equal the run time of that $100 LiPo. My T-Moth runs so long on the Lipo that I usually break the time into two or three flights.

Slent thndr
08-19-2005, 08:20 PM
Thats true. Lipos dont often just 'blow up' with out you having done something wrong. And the tiny 1500 mih 3S lipos for my formosa didn't cost much more than a 1500 mih NiCd High Discharge combat wingg battery.

joelrindy
09-02-2005, 04:06 AM
Could it just be that your 2100 nicd pack is just that much lighter than the 3000 nimh? It only takes a couple of ounces to make a difference in some of these foamies.

rahtware
09-02-2005, 04:56 AM
Could it just be that your 2100 nicd pack is just that much lighter than the 3000 nimh? It only takes a couple of ounces to make a difference in some of these foamies.
Have you tried NiMhs?:confused:

I sat out many a good winter flying day until I figured out that Ni cells are not created equal. I won't give up my AA NiMh cells that I use in my digital camera, but I have all but junked all of my RC packs for Lipos. As for NiMhs, follow the instructions, ie fly them freshly charged and WARM!

ForestCam
09-02-2005, 10:45 PM
If this is your first set of NiMh batteries you need to "condition" them. Get a few full charge/discharge cycles on them and you'll see a marked difference in their preformance.
Whenever I get a new set I anchor my plane and let it run full throttle untill the ESC cuts off, let the batt cool down, charge at 1C and repeat for about three cycles. If I didn't the initial charge wouldn't even get my plane off the ground.

It's also a good practice to do this after having the batts stored for an extended period of time.

rahtware
09-03-2005, 03:50 AM
True, but......
If you have a Shelby Mustang would you drive your Pinto?

My point is that NiMh cells are good, but not that good when compared to Lipo technology. I have to admit that I haven't converted my two FlyZone planes yet. I have converted three other Park Flyers, GWS T-Moth, GWS Sweet Stick and my home built Desert Duster. All three planes flew noticeably better (more power, longer lasting usable power, and longer flight times) with LiPos.