john316

As a long time nicad user, is their any downside to switching over to nickel metal hydride batteries??? My understanding is cell voltage is nearly identical as is charging techniques. Any problem areas I might need to look for??

jmw

fancman

My Feedback: (16)

Try this.

http://members.aol.com/davthacker/nimhfaq.htm

sweetpea01

My Feedback: (10)

Your biggest concern is not to charge them with a Nicad only charger, unless you can watch the heat. Heat is bad for NIMH....... but as long as your careful you'll be fine. Most newer chargers of the day have a NIMH setting. You'll like them, they tend to last longer on a charge than NICAD's (over the life of the battery).

the-plumber

NiMh packs can be turned into boat anchors on the very first charge if it gets too hot. DAMHIKT.

If you plan to fast-charge NiMh packs, get a charger with a temperature probe, like the GP Electrifly Triton.

Very good charger.

Diablo-RCU

My Feedback: (1)

Ace Smart Charger works great for NiMH packs. Charges 530 mA rate into each of the two outputs. Can charge two 5-cell or 4-cell receiver packs in parallel. One output will also handle your transmitter pack. Uses a 12 volt source for power. The packs do not get warm at all because it is a peak detector. It's the only charger I have used for the last 3 years. With a NiMH pack you should do a forming charge at C/10 for 14 hours before you try to use a peak charger.

TLH101

My Feedback: (90)

The only down side I have heard of wont be a problem with your location, but they tend to run down very fast in cold weather. Or so say the guys on the electric forums. I have never had to deal with it here.
I have noticed that they will drop of the top charge fairly quick, and then stay at a stable voltage for a long time. I have them in my transmitter, and they peak at about 11.4v when charged, then drop to 10.4 or 10.3 failry fast, but stay there for a very long time. Seem to last a lot longer than my Nicads did.

scottfl78

All you need to know is that NiMH's are better than NiCD's and safer than Lithiums.. Lithiums are the best, but there are hazards if they are misused/charged wrong.. I didnt want to take the risk of airplane/apartment fire so I went with NiMH's.. I use the hobbico MKII field charger to charge mine.. I charce them at .7 amps and they charge relatively fast but not so fast a to heat them up..

john316

TLH101, hmmmmmm your NiMh transmitter pack voltages sounds nearly identical to my nicads, I get about 11.3 off the charger with a drop to about 10.5 where she stays for awhile. I'm curious if the NiMh cell charge/discharge curves look very similar to those of the nicad cell? Anyway, I.m looking hard at both NiMh and Li-Polys for my next big project. The Li-Polys certainly are the handsdown winner if you are comparing energy density only. The potential weight savings make the Li-Poly look very attractive. How are they working out for you guys in the real world?

jmw


"Chance favors the prepared mind"

Rodney

The three major faults relative to NiCads are 1: about half the lifetime approx. 500 charge/discharge cycles versus 1000 for NiCad before noticable degradation and 2:higher internal resistance (lower useable voltage at high currents) and 3oorer cold weather performance

john316

Hi Rodney, are you referring to NiMh or Li-Poly?

jmw




"Chance favors the prepared mind"

aegis

Here's a web page that has battery info. (I'm not affiliated in any way, nor trying to make a sale for the company). Hope the info helps.

Dan

http://www.hangtimes.com/nobsbatteries.html

Rodney

John, yes I'm refering to NiMh versus NiCad. LiPo has an even less lifetime, typically 300 charge/discharge cycles.

sweetpea01

My Feedback: (10)

But here is the real reason people use NIMH over Nicad........................NO MEMORY!!!!!



You don't have to discharge your batts after use. they are not supposed to retain a partial charge memory that Nicads do.

I still cycle mine occasionally but you don't even have to do that.

Silent-AV8R

I love this argument. This refers to full cycles, 100% depletion then recharge. So a little simple math is in order.

It takes me 20 flights to get to the recharge point on my 35% Extra (2x4,400 lithiums). That is a total of 4.5 hurs of flying.

I fly an average of 10 flights per week. 2 weeks to get a full charge cycle.

300 charge cycles will take me 600 weeks (2 weeks for a full charge cycle times 300 cycles).

That is a little over 11.5 years of flying.

Even if I was to fly them flat every day I flew (4.5 hours of flying per day = 20 flights) it would take me 300 flying sessions to reach the endpoint. three sessions per week still gives me nearly 2 years of flying.

Point is that using the cycle life as a factor seems a little weak.

Rodney

Life cycle can be very important for the electric powered flyers. It is not unusuall to do at least 4 complete cycles on a LiPo each day, and here in Florida, we can often fly 5 to 7 days a week or 20 complete charge/discharge time on a battery each week. We are lucky to have a LiPo last for a full season of flying. Doing the fast charges further decreases the lifetime.

john316

Looks like you were both right!

jmw

ptgarcia

My Feedback: (36)

I will never use NiCd again. I use Li-Ion and NiMH exclusively. And I only use NiMH on the ignition of my 50cc gassers. The only reason I don't use Li-Ion on the ignition is because I usually mount my ignition battery on the side of the engine box and there usually isn't much room left over for a regulator. If there is room, I will use Li-Ion on the ignition also.

When using Li-Ion be sure to have a suitable charger. I use my Triton with great results. If you're flying giant scale you should have one of the better chargers no matter what chemistry battery you use.

Silent-AV8R

Of course, I was referring only to the use for receiver power in normal set ups. Not for use in electrics.

Wings-RCU

My Feedback: (2)

Yes there is!! When you are talking about giant scale aerobatic planes with many digital servos, I would stay away from Nihms. Rodney stated correctly that Nihms have a higher internal resistance....ie they cannot supply the necessary power to multiple digital servos under heavy or stalled load. When that happens all kind of funny things can happen, like digitals that go full over (the reason Hitec is saying no to nihms and their digitals). That being said, you can compensate buy getting a much larger Nihm than a comparable Nicad but you loose the advantage of lighter weight. If you look at the last two years of the TOC, no one used Nihms. They used Nicads or more often Lion/Lipo's. Nihm's are fine on your ignition or most other applications but not the multiple digital servo 3D aerobats

Diablo-RCU

My Feedback: (1)

Really? Hitec says no mixing NiMH and digital servos?
Where can I go to see this in print?

Wings-RCU

My Feedback: (2)

In the Hitec support form Mike (Hitec) has warned about inadaquate current from Nimhs.
Here is a great explanation in the Hitec support form:
http://www.rcuniverse.com/forum/Powe...2082006/tm.htm
Like I said you can always put in a extra large NiHM to compensate for the reduced power but then you have lost the weight advantage from nihms.

Diablo-RCU

My Feedback: (1)

I read the thread. It discussed low voltage due to REGULATORS. Not MiMH batteries.

cygnet

My Feedback: (33)

You guys are full of it I live in the cold old north and fly 40%'s and use NiHm's thats a load about the cold affecting them no such problem, way better than Nicads Just my .02

mglavin

My Feedback: (31)

FWIW:

NiMH cells individually have higher IR than NiCD, but cumulatively have similar IR of Lithium cells in 2S @ 6.0V.

NiMH cells maintain a flatter discharge curve at higher sustained voltage levels, but fall of the chart quickly for our needs.

NiMH cells do not support high discharge currents as well as NiCD.

NiMH are not nearly as robust and or trouble free as NiCD. Specifically they are not as resilient to use and abuse as the aforementioned NiCD's.

Jimmy Bananas

My Feedback: (13)

John316:

I have used NIMH batteries for the past three years..Have them in my transmitters also...NO MEMORY is the big + for them...My whole fleet is made up of 1650ma batteries and only one pack has been bad...One out of 15 batteries isn't too tacky..Try this site: www.radicalRC.com
Dave will take care of you.....