heli4me
Heliman
Location: Springfield MO.
| This should answere your QuestionRADICAL RC
NiMH F.A.Q.
See "Your New Battery Pack" below
I
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!
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.
"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.
" 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.
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