Solo

My Feedback: (63)

Hi,
I fly 1/4 scale and I am looking wanting to use a 6v battery to for my receiver. I have two digital servos and the rest are not. Total servos are 6 servos. Thinking of using about 1400mah, but don't know if the NICAD or the NIMH would be better. Only wanting to charge every 3 to 4 flights which last about 15 min each.

Thanks
Solo

3DFanatic

My Feedback: (5)

Neither are "better". Each just haS different qualities.

a NiCd has a higher output then an equivelent NiMH but less capacity. The NiMH has more capacity but less output.

Snyperx

My Feedback: (11)

DOH!!!!

Lynx

Nicad's Nimh's and Li-ion's Are each a step up in capacity, and a step down (or three) in weight. Given a 1000mah cell. you can draw (roughly) 10amps off a nicad, 5 off a nimh or 2 off a li-ion before the voltage becomes too low. It is possible to draw more current than this from each type of battery but it has a corresponding decrease in cell/capacity life.

SMALLFLY-

My Feedback: (19)

NIMH doesnt suffer from memory effect nearly as bad as Nicad. That alone is reason enough to use it. It is also a little lighter. I have converted all my planes but 1 over to nimh, my transmitter runs on them as well. I recommend the 1650 ma AA 6v pack. Im using 3 right now on planes from fun fly's to my gp Patty wagstaff. Radicalrc has good prices and service if your interested

Red B.

Hi!
Some "facts" about NiCd and NiMH batteries

*The NiMH delivers roughly 40-50% more capacity than a NiCd of the same size.

*NiMH batteries are considerd to be more environmetally "friendly" than NiCd batteries.
Cadmium is a nasty metal!

*The recommended discharge current of NiMH cells is considerably less than that of the NiCd. For best results, manufacturers usually recommend a load current of 0.2C to 0.5C. For high current applications, such as when using several digital servos, the more rugged NiCd is the recommended choice.

*Both NiMH and NiCd are affected by self-discharge . The NiCd loses approx. 10% of its capacity within the first 24 hours, after which the self-discharge settles to about 10% per month. The self-discharge of the NiMH is approximately double that of the NiCd.

*The NiMH is usually rated for only 500 charge/discharge cycles. Shallow rather than deep discharge cycles are preferred. The battery’s longevity is directly related to the depth of discharge.

*Memory effects in NiCd cells, meaning that a NiCd battery can remember how much discharge was required on previous discharges, is a thing of the past
There is however other effects to be considered, the most important one being crystalline formation. The active materials of a NiCd battery (nickel and cadmium) are present in finely divided crystals. The crystal should be as small as possible in order to maximise the surface area. Under certain circumstances the crystals grow and drastically reduce the surface area. The result is a voltage depression which leads to a loss of performance. Some of the capacity may still be present but cannot be retrieved because of the battery’s low voltage. In the end the crystals can become so large that they cause an electrical short in the cell.

The effects of crystalline formation are most pronounced if a NiCd battery is left in the charger for days, or is repeatedly recharged without a periodic full discharge.
In order to avoid crystalline formation it is often recommended to cycle NiCd batteries once per month. Between these monthly exercise cycles, no further attention is needed and the battery can be used with any desired user pattern without the concern of memory.
NiMH batteries are less affected by crystalline formation and because of its shorter cycle life it is sufficient to cycle the batteries once every three months.

In the end the choice is yours!

/Red B.

Bob Talley

Better the devil you know than the devil you don't know.

Bob T.

Lynx

.2 to .5C discharge rate for NiMh's is EXTREMELY conservative, that will make the battery last about two years if you use it every day. Li-ion's are an option but the discharge rates for them are even lower, however they're about 1/3rd the weight of a comparably sized nimh pack. Li-ion batteries however run at about 3.6 volts per cell instead of 1.2 like nicad/nimh's so you usually have to have a regulator. They don't have problems with self discharge though.

Bytehawk

Panasonic rechargeable batteries are engineered for use and reuse in today's high drain digital consumer electronics. In fact, recharging them puts absolutely no strain on the memory, so they can be charged hundreds and hundreds of times. But best of all, they can last over 2-2.5 times longer than standard nickel-cadmium batteries, giving you much more power while saving you money.

From panasonic website.

Strykaas

Hum...

sizam

My Feedback: (6)

Lithium Polymer are the best, better then NiCd, NiMh, or Li Ion, as I've posted elsewhere allow me to enlighten. They are lighter then all three, have as much (if not more capacity then Li Ion), and have a better discharge rate then not only LiIon but many NiMh's as well. I'm going to be using a Thunder Power 1350 2S pack for my Funtana which weighs 1.9oz, has 1350mAh, and can put out 6C in Amps (8.1A) continuously and higher peak draws, costs only $32+. Or (if I can't wait to order from Horizon) maybe a eTec 1200 2s at 2oz, 1200mAh, 6C (7.2A), and $26. In my 27% Extra I'll be using a Tanic 2200 2s pack which will weigh about 3oz, have 2200mAh and put out 10C (22A!) continuous and 15C (33A!!) peak, costs around $40!! These batteries have no memory effect, and a very very long charge retention (for sitting on the shelf), not to mention maintaing their voltage until the bitter end. The only down side is they take more care in charging and use, you can't abuse them. So, in my Funtana the 1350 (even with the .2 oz regulator) weighs less then my 600mAh NiCd pack, and half as much as my 1450 NiMh pack.

tiggerinmk

Capacities in nimh are going up too, I wouldn't bother buying a 1450mh or 1650mh battery as now you can get 2100mh and possibly better.
A short while ago, I bought a pack of Enegizer batteries for my camera. They were AA size and 2100mh, so I assumed you should be able to get something similar made into an airplane battery pack. Sure enough, 2100mh batteries have appeared on ebay. I 'won' a 4.8v 2100mh pack last night for the extortionate sum of $8.99!

My airborne pack of 4 DS811's and a 537 in my Funtana would drain my 1100nicd in two flights, so I hope this will improve the situation....

sizam

My Feedback: (6)

That doesn't make any sense given my previous discussion on choosing enough mAh for digital servos:

http://www.rcuniverse.com/forum/How_...1274512/tm.htm

The guist was each digital servo drew about 4-5mA/minute/servo so in my 5 servo plane a 10 minute flight will cost me 250mA, sounds like you were drawing a lot more.

tiggerinmk

There's a fair amount of specific info in that thread you gave the link for, thanks.

Up to now, I've not been very scientific with my estimates... OK, maybe I can get 3 flights on the Funtana but no more than that, and that's just flying around; no 3D or extreme maneuvers. I use a Hobbico Voltwatch and that shows red after 3 flights, with the voltage reading around around 4.8v on my H9 DVT.
My other planes which use 4 standard servos and a 600mh pack just seem to last a lot longer....

Volfy

My Feedback: (23)

Fact is, not all NiMH cells are made the same, even if they claim the same capacity. Same thing for NiCd. Also, Sanyo and Panasonic don't necessarily have the best chemistry anymore. They are both, by and large, high quality cells, but others are formulating better chemistries all the time.

I have had several different brands of 1800mAh cells a while ago. Some of them won't take take even 2C charge rate without getting real hot. A few can charge at 3C safely - at least when new anyways. If you're using them for low drain rate TX/RX purposes and charge at 1C or so, pretty much all of them will work fine. For high amperage electric-powered planes and cars, however, you'd better sticking with high quality cells.

J.Paul Saure

IMHO Red B. hit the nail!
Nice post.

Rodney

A very good post Red B. Lots of accurate info in a succinct manner.

JPMacG

My Feedback: (2)

.... 10% of its capacity in the first 24 hours for NiCds... Very interesting! I never knew this. This may explain problems I have had in obtaining repeatable capacity measurements on my NiCd packs.

Is there more information on this subject? I don't believe Red S. covers this on RCBatteryClinic.

Thanks!

ivangriesemer

The people at my local hobby shop are telling me that you can't charge nimh 4.8 flight pack with the standard wall charger that comes with most radios. they say that those chargers are for nicds only. is this true or do you just have to charge longer? please help i don't want to loose a plane because of a battery pack not charging.

BuschBarber

My Feedback: (2)

That is absolutely NOT true. Actually, a NiMh pack likes a slow charge better than a fast charge. Wall Chargers (also known as Wall Warts) typically were designed to charge the 600Mah NiCad packs, that used to come with Tx's and Rx's, at 1/10th C or 60Ma, for 18 hours. I haven't checked lately to see what the output of a modern Wall Wart charge is but I am guessing it is around 100Ma. If you take the time to look at Red Shofields' Battery Clinic (a column by a noted expert on batteries) you will find that he has no problems with anyone using a Wall Charger on NiMh batteries.

Actually, some battery manufacturer's, like NOBS Batteries, publish instructions on their website, instructing you to use a process called Forming the Cells, with brand new NiMh battery packs, where you cycle them 3 times, using low Charge and Discharge rates, before using them in a model.

I personally like to use a Cycling Charger that Anticipates Peak, thus helping to prevent OverCharging. At some point during the charge, the charger Pluses up and down rather than charging at a constant rate. This type of charger gives you more information on the state of a battery's true capacity than a Wall Charger.

049flyer

My Feedback: (18)

My experience indicates that Nicad batteries are MUCH more robust than Nimh batteries. Nicads tolerate repeated fast charges while Nimh batteries often do not fast charge very well at all. In addition I believe the lifespan of Nicad batteries is much greater than Nimh batteries.

I recently had a reason to cycle test over 50 different batteries of different ages used in RC vehicles, transmitters and planes. The batteries were anywhere from 3 years to 10 years old and had been in storage.

Almost ALL of the Nimh batteries were bad and almost ALL of the Nicad batteries were good.

There is speculation that the Nicad battery manufacturers are very tightly regulated due to environmental concerns resulting in a higher quality product. Nimh batteries are manufactured in much greater quantities and don't suffer from intense regulation so their quality is inconsistent.

After having changed over to Nimh batteries for the increased capacity and reduced weight, I am now switching back to Nicad batteries.

BuschBarber

My Feedback: (2)

I agree that NiCads lose less of a charge just sitting around than NiCads and NiCads can take a Fast charge better than NiMh. NiMh tend to false peak the chargers when trying to fast charge.

I switched exclusively to 2cell LiPos for Rx batteries and 3cell LiPos for my Tx. I have to use a 5v or 6v voltage regulator on the Rx batteries and no regulator for the Tx batteries. LilPos hold their charge for months. I can go out an spend the day flying and come back weeks later and the battery voltage has not changed. It only takes an hour to charge LiPos. Some of the newer LiPos coming out next year can draw 45C rates and charge at 6C.

If you are afraid of LiPos, the voltage of A123 cells is closer to NiCad/NiMh so you do not need a regulator. They are a bit heavier than LiPos, but lighter than NiMh.

It is best to get a charger like the FMA 4S or 10S, for balancing chargers, however, you could use a Triton. There are other chargers that support LiPO, LithIon, or A123.

I see no reason to stay with NiCad or NiMh.

wcmorrison

My Feedback: (2)

Another characteristic not mentioned is that the NiCd seems to have a more consistent/flat discharge rate while NiMh seems to have a knee in the middle of the discharge curve. The knee leads to a more rapid decline to fully discharged state. I lost an airplane due to that knee, it had a not fully charged NiMh that died in flight and I watch gradually climb in a nice wide circle until it ran out of fuel, then into a large lake. Never recovered the machine. And for that reason I tend to not use NiMhs, though I have recently gone to 2000 to 2500 MAH NiMhs in the 6 volt variety.

Cheers,

Chip

jaka

Hi!
All electrical power tool equipment over here in Europe uses (or has used) NiMH cells for years, two decades or more.
It's just one or two year ago most manufacturers went over to LiPo cells in their power tools.

Like wise in 1/10 car racing , it was decades ago that 7,4-8,4V NiMh cells took over from Nicad cells.
We haven't seen an NiCad cells in our stores (both hobby and others ) for more than 15 years.

All fliers over here use either NiMH cells in their radios or recently LiPo cells.
NiCad cells are something of the past!

Here are the 850 mAh GP NiMh cells I use in my pylon racers and in my DC-3

vasek

My Feedback: (4)

hi Solo,

Personally I didn't like NiMHs (used NiCads) until the Eneloop came along. Keeps the charge much longer (UP TO 80% of charge for one year, if my info is correct)

much more user friendly!

switched this year, so far no problems