I have a pair of hand held vhf radio's that I need to look into replacing the rechargable batteries for.
The NiCd batteries have a wider operating temperature where the NiMh batteries have a longer run time and don't display the same "memory effect"

What say you?
What have been your experiances with these types of batteries?
Keep in mind this is a battery pack that has is made specifically to fit the radio, so I can't just chose the cells ***** nilly.

 

I have never been a fan of NiCads.
I am rapidly becoming a fan of Li-Ion batters.
No experience with NiMh batteries.

I use NiCads in my field radios, but after teh day is done, I leave the radio on till the batteries are completely dead and swap out with a fresh set the next day.

 

I would just stick with whatever was intended to be used with the radio, mainly due to the charger. Nickel cadmium and nickel-metal hydride batteries have very different charging properties. Most Ni-Cad chargers will eventually ruin Ni-MH batteries. Ni-Cads also are more suited for high-current drains, and longer shelf life between charges- Ni-MH have a lower internal resistance. However, Ni-MHs do not develop the "memory" problem Ni-Cads do, and typically have longer run times in the absence of high-current draining (cellular phones are a perfect example).

If you do have your choice, it depends on the usage really- each has it's advantages and disadvantages.


AJ
Electrician,
Electrical Instructor,
Amateur Radio licensed

 

We have NiCads in our radios as well. They don't last.

 

I race professional R/C vehicles. In electric R/C racing, NiMH packs are the only choice. The largest ROAR legal capacity is a 6 cell, 7.2V 3800 MAH pack. Sizes of NiMH packs can go up to nearly 5,000 now, and matched 6 cell NiMH packs can go for $100+ in price for high quality packs. NiCD packs are pretty much a thing of the past, they are no longer used in racing, and are the "Cheap" choice for the n00bs who are just getting started.

NiCD packs in R/C are all Sub C sized, but the capacity stopped growing at 2400 MAH. NiMH packs pick up at 3,000 and go up from there. A NiCD pack will have less fade during run time, but won't last as long. NiCD packs will take a faster charge, and have a lot of punch off the line, but they have less punch after the peak wears off. NiMH packs are powerful and punchy to drive. You can feel a lot more pull, but they have a tiny bit of fade due to heat. They also require slower charge rates to sustain cool tempuratures. R/C NiMH packs also require a Peak Detection charger. Peak Detect (AKA: Delta Peak) detects the point at which a battery has fully charged. At this point, the voltage of the pack drops a TINY bit... the charger must be able to detect this and slow the charge rate so the pack doesn't overheat. Delta Peak in R/C is highly adjustable, along with all the other aspects of charging race packs. NiCD packs do not require a delta peak charger, because they do not take current beyond full capacity. A NiMH pack will act as a resistor after it has been fully charged. It will keep taking current and convert it into heat, whereas a NiCD pack will just stop accepting current.

NiCD packs will have a memory effect. Years ago we used to carry around dischargers which were just strips of automotive brake lights attatched to a common rail made from steel or copper. This would serve as a discharger after the battery was used... You discharge it completely then store it, or recharge it again. NiCD packs SHOULD NEVER be stored with much voltage. Reduce the voltage to about .9V per cell if you use NiCD packs and standard voltage cells. NiMH packs still benefit from the occasional discharge, but should be stored WITH VOLTAGE as to keep the electrolytes inside the cell active. Inactive NiMH electrolytes will decay. NEVER LEAVE a NiMH pack for more than a day with less than .9V per cell in them. Always leave them with some voltage to protect them from decay. Both types of batteries will have a break in period that will determine the quality of power delivery and reliability from the get go. Make sure that you follow all instructions to the T for the first 4 or 5 charges.

If you have any other questions feel free to ask. This hobby is WAY more complicated than what I just unloaded on you, so if you're confused I can clear things up. Good luck in your decision!

Many years ago my father was a HAM radio operator... He had the same thing you speak of, and knowing what he did with his batteries I would say go with NiMH packs. They are a lot more forgiving, and if you are charging them slowly like with a wall charger then overcharging shouldn't be a real problem. If the charge rate is 3-7A a NiMH pack will overheat, but several hundred MAH won't cause a lot of heat build up.

 

I guess I should have mentiond their use as well....
Once a week for a day, once every two weeks or more for a day. They really are only casual use. The maintaince and storage characteristics are a factor as well. I understand NiCd batteries are best stored in the frig. Although the ones I have here didn't really wase any time discharging themselves in this enviroment either...

 

Unless you want to discharge the packs and charge them again for every day of use I suggest going for NiMH batteries... They're less overall maintnence. I understand you don't have to maintain these batteries like we do for competition, but it's still nice to have a good reliable pack that you don't have to worry about all the time.

 

Thanks for the replies,
I have no idea what kind of charger I have other than the factory kenwood charger that has minimal circutry inside it.
I know I can't leave the NiCd batteries (7.2V 1100mAh kenwood KNB15A) in the charger for much more than 2.5 hours. I am guessing it is some sort of a rapid charger. Talking to the local kenwood dealer he suggests using the same charger for NiCd as for the NiMh packs. (Apparently kenwood doesn't make NiCd Packs anymore but they are still freely available else where) At $75 a pop (from the dealer ) I want to know what I am buying.

Everything I have read has indicated the NiMh packs are the way to go. It's just the operating temperatures that has me wondering... (it can get cold here in Canada.)

 

What voltage is the pack? I recall my father going to a local Radio Shack many years ago and picking up a toy 9.6V 1100 MAH pack for his Kenwood handy talkie. Now remember, these are the toy department store/Radio Shack R/C cars, the REAL ones can run into the thousands, so if you see anything about R/C Racing Pack on it, please don't think it has anything to do with my hobby... It's like REAL Amature Radio equipment versus a Police Scanner or a CB Radio... If that makes sense.

 

It's not amature radio, it's commercial radio (automatically double the price and add 50%) It's a kenwood tk-2102 (four channel) with a 7.2 volt 1100 mAh battery part KNB15A
I suppose amature would have worked, but these came along used at a good price. and since the frequencies I want to use are in the commercial band....