RADICAL RC
NiMH F.A.Q.
See "Your New Battery Pack" below

Everybody is curious about NIMH cells.  Just as there is a "best" glue  for every job in a kit, there is a best battery pack for every application.   NiCad technology has been around for a long time and is very highly developed.   New larger size NiCads don't come out very often.  However, NiMH is still  fairly early in its development.  Every few orders I place come in with  slightly higher ratings.  If you look carefully at most written opinions  about NiMH VS NiCad, you will quickly see they almost always are comparing  good well proven Sanyo's to Panasonic.  Hydri-Max is Panasonic.  Well, to  me that is like comparing apples to oranges.  92.2213% of all RC'rs  would not consider using anything but a Sanyo Nicad for a TX or RX pack.   If you would not choose a Panasonic NiCad for your ship, why would you use  a Panasonic NiMH pack?

I am sure Panasonic makes a very fine product.  But, I feel Sanyo  has probably "earned" its position with RC'rs for a very good reason.  Have you noticed how much they spend advertising to us?  Zero!  We use them  because they have generally proven to be the only wise choice (SR excepted)  Currently the Top Sanyo AA NIMH is 1650 mah.  The Top Panasonic AA NIMH  is 1400 mah.  Now, who do you think is at the Apex of the technology curve?   Simple, Sanyo is at the top.  Probably they always will be.  All my following  comments are about Sanyo NiMH cells.

Hopefully at this point you will agree that most of the previous press  and modeler comment on NiMH is questionable for sure and dated at the very  best.  Often I will get an email asking me which is better, Nicad or NiMH.   Well, there is no answer to that question.  It is like asking what is better,  apples or fig leaves.  If you hungry, an apple is pretty good, but if your  naked, maybe you need a fig leaf.  So, which is better depends on the  job you are trying to do.

Strengths and weaknesses.  There is no such thing as a perfect battery.    All chemistry's have good and bad points.  Most modelers have a reasonable   understanding of the personality of NICADs.  NiMH has a slightly different   personality.

Advantages of NIMH over NICAD
1. Same weight NiMH will have 1.5 to 3 times the capacity of a Nicad.
2.  Same capacity NIMH will come in a much smaller lighter package.
3.  No memory worries.

Advantages of NICAD over NIMH
1.  Nicads can "dump" their power quicker.   Thus, they "can be" better ultra high drain applications like electric motor  power packs.  Note, were talking about dumping a pack in 20 minutes or less here, not RX and servo loads.
2.  More tolerant of abusive overcharge.
3.  Your current quick charger will charge it for sure.

Special considerations for NIMH and NiCad batteries.

1.  Overnight charge rates must be at Capacity / 10 or less.  So, no more than 72 mah for a 720 AAA pack.  This is true of NiCad batteries as well.  But, a Nicad will tolerate a slightly higher charge rate for a longer period of time without damage.
2.   A fast charger must be rated to detect the much shallower peak of NiMH.    If you are considering a new charger of any kind, make sure it is NiMH  rated.  Anything else is a dinosaur!  Make  sure you invest your money in  a tool that will work well into the future.  Even if you don't try NiMH  now, you will before too long.
3.  Don't expect them to perform exactly like Nicads in high drain applications like  motor packs.  In most cases adding one more cell will allow a similar weight NiMH pack to outperform a NiCad pack.  Those who don't use the extra cell will be disappointed.  Two years ago I considered all NiMH motor packs purely experimental.  Now, all the way up to Speed 400 there are superior NiMH choices as long as you are not running super hopped up motors.  For a transmitter, receiver/servo or ignition  pack,  the drain rate is modest and NIMH compare very favorably to Nicads often with a slightly higher voltage (were talking 1/10's here) under drain in these  applications.

NiMH has come a long way in the last two years and is a good choice in  my view.   I use both NiMH and  NICAD packs with great results.  I absolutely use what I sell.  Most modelers  that use my NiMH packs fall into one of two categories.  Many want to change out an existing AA Nicad that is 600 or 700 mah and are replacing it with  a "AA" 1650 NiMH of the same size so they no longer have to quick charge  it the field. The largest "A" size NICAD battery you can buy is a 1700 (1400  is the common size).  The same a size cell in NiMH is 2700 mah.  This 2700  mah pack weighs about the same as a sub C 1300 pack that most everyone has  seen.   Others, are using the "AAA" 720 and 2/3 AAA 280 in 1/2A, HLG, Combat and  other space or weight critical airplanes.  Think of it,  AAA size battery  with 720 mah!  That's outstanding. Weighs the same as the typical 270 mah  1/2A pack.   I've used the  720  and 280 packs in my combat ships with from 3 to 5 servos.  The 720 gives me the weight advantage of a 1/2A pack  (I need all the advantages I can find!) with better capacity than any standard  AA pack without any short flying session disadvantage or hassle. The 280 gives me a weight reduction and is what I am currently concentrating on.   One of  my good flying friends uses one of my 2700 packs in a 1/3 scale Aircraft International Extra with  9 JR coreless servos.  He has about $4000 in this ship and is one of the most respected  pilots in the club.  With NiMH, he has a huge capacity reserve and a light  weight pack.  He loves hoverbatics!

So, if you have a ship that could benefit from a lighter pack or if the  space you have available won't carry a high enough capacity Nicad or if  you just want to get away from having to quick charge at the field and want  to up your capacity a great deal, give NiMH a try.  Also, it is the latest RC worthy technology.  That in it's self makes it an interesting choice.  I think you will like it.

"Will my standard wall charger charge it?"

Here is how you calculate charge times for NiCad and NiMH packs. (MAH Capacity X 1.4) /  Charger  MAH = Charge time in hours.  For a little safety margin you might replace  the 1.4 figure with 1.6  .

So, 1650 TX pack would work like this:  1600 x 1.4 = 2310.      2240 / 50 MAH = 44.8 hours.

If the answer is less than 14 hours, then the charge rate is too high to be left unattended or too high to be used without proper peak detection.

Keep in mind, you won't be running down a 1650 TX pack in a day of flying!  So, you will only charge it from dead one time most likely.  Most cyclers have a 120 charge setting.  This is a better overnight rate for this pack.   2310/120=  19.25 hours.  But, your 50 mah wall charger will work just fine as long as you keep the pack full and allow enough time to charge.

Never charge a NiMH pack at a rate over C/10 unless the charger is designed to properly detect and shut down when the pack is full.  At a rate above C/10, all packs (NiMH and NiCad will begin to heat up after they are full.  A NiMH pack will heat up very quickly and excessively.  As long as you are using the correct chargers or rates, this is never a worry.

"What fast chargers do you recommend?"

I suggest the SIRIUS Chargers or the Ace Super Smart Charge.  Either charger is of excellent quality and will properly detect NiMH cells as well as NiCad.  I sell the Ace Super Smart Charge for $70.  Runs off your 12V field box battery, will charge two packs from 4 to 8 cells simultaneously.  One side of the Ace SSC does 4 and 5 cell packs and the other does 4-8 cell packs.

As of this time (10/19/2000) there are no Hitec chargers that properly detect NiMH packs.

"Can I use my RC Car pack charger to charge this TX or RX pack?"

Some RC electric car people who move into RC Airplanes or Gas Cars or Gas Boats want to use their car motor pack chargers on their TX and RX packs.  Almost without exception, the use of RC Car battery charger to charge any TX or RX pack is a terrible idea.  You will incinerate your packs.  These type chargers are made to charge very large (sub C) high charge/discharge rated cells.  Not delicate AA cells.  Remember, your TX and RX packs are very important.  If one of your packs fails from your abuse, the airplane won't just stop and a gas car or boat won't just quit racing ahead.  It will crash!  How often does an electric RC car pack get flaky and need replaced?  Pretty often.  If you use one of those chargers on your TX and RX pack, which is very tiny compared to you RC car packs, the abuse will be even more severe.  Kind of like Mike Tyson against a 6th grader.  Your TX and RX packs will fail at a faster rate than your car motor packs did.  Can you afford to destroy a models with even great regularity?  A charge rate of Capacity X 2 is the maximum that should ever be considered for any RX or TX pack and then ONLY with proper peak detection.  Preferable Slope or Delta Peak detection.  I use the Ace Super Smart Charge and much less of a charge rate. "Yea, but shouldn't it be ok with my Super Wiz-Bang XLT Charger?"  NO!  Invest in the right equipment for the job so you don't have bad day with your model or hurt anybody.  You might get away with it for a little while, but pretty soon you are going to crash.  I hope nobody gets hit with your airplane or boat that you were pinching pennies on.  Besides, I have always found penny pinchers spend 2 or 3X as much in the end.  How much are your models worth?   My strong opinion on this matter comes from desire to see the sport grow without black eyes from accidents that could be avoided and to see all succeed..  For the good of us all, try to be safe by doing things right.

"What is the highest rate I can charge a NiMH pack with proper peak detection?"

Though all manufacturers recommend a maximum charge rate of C X 1, I have had good luck up to C X 2.  Above Cx2 is strongly discouraged. Any charging is ultimately up to you and in your control and consideration.  Just remember, the higher the charge rate, the higher the risk to the pack.  C/10 is considered the safest charge rate for NiMH or NiCad packs.

"What are some examples of good NiMH motor packs?"

Speed 480 or Twin 280 and below:

The RRC-1000 is an awesome cell that replaces the 600AE and 500AR in most normal applications.  It is the exact same size so no worries about fitting it in.  As long as your load is 12 amps or less I know you'll prefer this cell over your 600AE.  You'll find the discharge curve is very very flat, she'll pull hard until your down to the last 20% of the pack.  In this regard, it is a stand out head and shoulders above the 600AE.  For most applications, you want to order 8 or 9 cell RRC1000 packs.  Available in popular shapes and yes and there has been lots of good feedback on them.

The AA 1650 works well too but is too heavy for most Speed 400 applications.  I've had good reports and it's popular in the Zagi 400X.  But remember, the Zagi has lots of wing area and tolerates a few ounces extra weight well.

Speed 280 and below:

For loads at or below 6 amps the 720 cell works great.  7 cells for an MG-1, 7 or 8 cells for a GWS ICS motor or speed 280 motor.   At or below 6 amps using packs with 1 extra cell the 720 will beat the 270/350 Nicad in any application you have.  Also great for the GWS motor line.  I've heard many like this pack in a flat 7 shape for the Pico/Cub/Lite stick for outdoors.  Awesome with 7 cells on the MG-1 motor.  The AAA720 cell weighs just slightly less than the 270 or 350 Nicad.

RRC300 Cell

This cell is great for loads at or below 4.5 amps.  YES you can use it on a Speed 280 but it is most generally used on motor sizes below this.  This is a very popular cell in packs of 7 or 8 for the GWS ICS motors due to the reduced weight these ships fly much better on this pack.  Generally anteing you'd use a 110 Nicad for the RRC300 will do a great job.  Without a doubt, this NiMH cell will out perform the 110 NiCad in any motor application you have 3 amps or less and has some applications up to 4.5 amps.  I've even used it at 6 amps with careful throttle control.  The RRC300 weighs about the same as the 110 Nicad.  You still need to add one additional cell.  The RRC300 is not a Sanyo cell but still of high quality.  Sanyo does not make a cell in the 2/3AAA size range at this time.

RRC120 Cell

This cell is well liked in applications up to 1 amp.  Some like it up to 1.4 amps.  The DC17-17 when propped within this cells range is very happy for example.

"What charger can I use to get an appropriate C/10 charge rates for overnight charging my odd sized pack?"

Without a doubt, the ACE Super Digipulse is an excellent choice for small to medium sized packs.  With it you get 6 charge ports.  Each charge port can be programed from anywhere from 10 to 150 mah.  Digital readout and simple keyboard entry make it a modern high quality tool.  It is a great overnight charger for 100 mah to 2000 mah packs.  There is no peak detection as it is intended to be used for overnight or trickle charge rates.  It charges continuously at the rate you set it at. $85

For an even wider mah output setting, the ACE Super DDVC is the way to go. 2 ports that can be programmed from 5 mah to 500 mah.  Great for overnight rates on 50 mah cells all the way up to 5000 mah or larger packs.  Digital readout makes it a modern high quality tool.  It charges continuously at the rate you set it at. $85

You will find many other manufacturers charge a great deal for a NiMH pack.   With Radical RC, you get the brand cell you want (Sanyo) and a price that  beats the off brand cell.  It is my view that Nicads will always be with  us, but over time more and more people will be converting to NiMH.  Sanyo  is producing fewer and fewer Nicads and more and more NiMH cells.  So, it  is happening already.  Even if you don't decide to try NIMH now, make sure  all your future charger purchases have this capability.  You won't be sorry  you planned ahead.

If after reading this long winded article you still have a question, feel free to ask it.  I will add the answer to this page.

Happy Flying All!
Dave

Your New Battery Pack

Here are the basics for getting the best out of your new battery packs.

First and foremost!  NEVER NEVER put ANY new battery on a Peak Predictor / Delta Peak or any other type of fast charger without giving it a break-in charge at C/10.  Capacity 10 is the overnight un-terminated safe charge rate for NiCad and NiMH cells.  You can plug it in and forget it.  If you have a 280mah pack of any cell count, the C/10 rate is 28mah.  This rate or less is what you need to break in the pack.  A 1400 mah pack needs a charge rate not over 140 mah for its first charge.  The charge rate can be less than C/10 but should not be over.  Your charge time will be (Capacity X 1.6) / charger output in MAH.  This will give you the time to full in hours for a first charge.

If you take a new pack and put it on a Delta Peak or Peak detect charger or any other kind of NiMH rated fast charger it will not be filled up.  I don't care what the instructions say.  I'm sure they say to never charge a new un-conditioned battery on them.  If they do not tell you not to charge new packs on them then they are wrong.  The voltage curve is measured and calculated by these chargers in order to predict the peak.  The voltage curve is not normal on a brand new pack.  It needs one slow conditioning charge before the curve becomes stable.  Try as you may, you can't fill up a new battery on one of these chargers.  After it's first C/10 charge, it will work fine.

We've had many customers write us saying "I've cycled this pack 3 times now and it has not come up anywhere near where it's rating is."  I remind them to put one slow overnight charge on the pack, they always write back and say "You were right!  It cycles perfect now."  So, we've been there many times.  Don't suffer the frustration of trying to fast charge a new pack if you want the best out of it.  After it's initial break in charge you can fast charge all you like.  In fact, this is almost all I do with my personal packs.

Any TX or RX pack should never be charged above Cx2 at any time in it's life.  These are mission critical packs and capacity X 2 is has high as you want to go for the best reliable life out of the cells.  Never under any circumstances charge a NiMH pack above Cx2.  Not even a motor pack.  Always use a NiMH rated charger for either kind of battery.  The Nicad only peak detect chargers are Dinosaurs and put a pack into a state of deep overcharge before it has figured out that the pack is full.

In order to service your Nicads, you need these basic tools.  If you are missing one of them then you are handicapped in some way.  Everybody wants you to think their one tool will "do it all".  You will find you won't have versatile charging options until you have all these tools.

Variable rate charger:  Everybody needs a variable rate charger so they can break in a new pack and set overnight charge rates for times when fast charging is not necessary.  The ACE DDVC has two ports that can be set from 5 to 500 mah in 5 mah increments.  The ACE Digipulse has 6 ports that can be set from 10 to 150 mah in 10 mah increments.  Both are excellent choices, I am sure there are others.

Cycler:  You can't tell when your batteries are near the end of their life without a cycler.  This tool will run a pack down at a fixed rate and over a timed period.  From this information the capacity can be determined.  FMA Einstein, ACE Digipace, ACE Smartest, SIRIUS Test, etc....  With such a tool you can cycle a pack down after a flying session and be sure you are using a large enough pack.  For instance, if after a normal flying session you only have 15% of the batteries capacity left you will know you are dancing on the line of a crash.  Also, many cyclers have higher rates of charge available making some odd sized RX packs a little bit easier to get charged overnight.

Fast Field Charger:  Some type of charger that is NiMH rated for charging from 12V.  Adjustable charge rate is nice and the lower the range the better so you can charge the smaller packs without damage.  Avoid anything much over 500 mah.  For E-Flight, look at the Aster 110D, 112D, MA Super Nova 250 and I'm sure there are others.  For fuel fliers, consider the Sires and Ace Super Smart. Diamond also make almost
exclusively NiMH rated chargers.
 
 



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