Flyboy76

My Feedback: (14)

Hi, i just upgraded my TX battery in my Optic 6 from a 600mah NiCad to a 2100mah NimH. Just wondering can i still use my Wall Charger that came with the Radio for charging it?

Geoff

BarracudaHockey

My Feedback: (11)

You can but you'll never reach a full charge. You want something like an Accucyle or Triton if you're going to start playing with larger batteries. A transmitter wall wart is 50 to 100mah output.

wswanepoel

I agree.

If you want someting cheaper, look at this:

http://www.hobbycity.com/hobbycity/s...pair&cda=36317

or

http://www.hobbycity.com/hobbycity/s...ells&cda=36317

Both will get you on your way.

Rodney

Yes you can, it is again a simple matter of physics, if you put more energy in than leaks out (self discharge) you will eventually reach full charge. If you have an ammeter just check to see how much current you are putting into the battery with your wall wart. If you then divide the battery capacity by that value and multiply by 1.6 you will have the approximate time it will take to fully charge the battery from a fully discharged state. Edited to add the following: if that current is more than 0.1C then the 1.6 multiplier may be to high a number but it should be close.

BarracudaHockey

My Feedback: (11)

Thats great in theory. In practice however I think you will find electrical losses and inefficency means you could put that on charge for a week and it would probably never reach full capacity.

guver

My Feedback: (325)

If the rate is slower than c/10 then the multiplier goes up as well. 100 ma should charge a 2100 mah battery in about 4 days.

Flying Geezer

My Feedback: (14)

You can also dig a basement with a teaspoon!

guver

My Feedback: (325)

That would take longer than 4 days. []

wswanepoel

or cut the lawn with a nailclipper

Flyboy76

My Feedback: (14)

I have a Triton jr. that i can use. What setting would you reccomend for charging and discharging

Geoff

guver

My Feedback: (325)

If it's a newer version that can have the safety timer disabled then use 1/2 amp max for chargeing. Discharge is not recommended.

Flyboy76

My Feedback: (14)

so 500 mah max for charging. the safety timer can be disabled and just let it go?? does it stop when it is charged on it's own???

guver

My Feedback: (325)

Yes, it is an automatic "peak" charger that stops when the batts are full. Disable timer or set it to 4 hrs if possible because it would take 4 hrs to do the batts if they were dead.

rlmcnii

My Feedback: (3)

500ma should cook those new 2100 AAs to well-done in short order. High-capacity AA NiMH cells do not tolerate charge rates above C/10 too well. And, unless you are in some huge hurry, there is no reason to charge them at a greater rate.

NiMH need about three cycles of form-charging: 16 to 18 hours @C/10 followed by discharge @ C/5. This method will get your cells to the rated 2100 mAh capacity.

There is a real good tutorial about NiMH batteries at the Hangtimes Hobbies website. Also, read the note about high-capacity AA cells for Tx packs. It is some good information.

Flyboy76

My Feedback: (14)

I'm sorry but what is C/10 and C/5???

Geoff

rctrax

These are charge rates. C/5 is capacity divided by 5 or 420 mills for the 2100 bat, C10 is capacity divided by 10 or 210 mills for 2100 mill bat

guver

My Feedback: (325)

C/10 is capacity divided by 10 or C/5 is capacity divided by 5 . C is a 1 hr rate.

Your 2100's would be 210 ma and 420 ma respectively.

Recalculated , thanks geezer

Flying Geezer

My Feedback: (14)

Better calculate that again.

Flyboy76

My Feedback: (14)

Ok so if i'm reading this right then i should disable the timout on the JR, set the charge rate to 210Mah and let it go until it stops.... then set it up to discharge at 105mah and do this about 3 times. I believe i can set it up on my charger to do that automatically. It says it has a cool down period set in before it begins the next phase? I appreciate all the advice, i am pretty unsure of myself when it comes to batteries and charge rates and such. Which means i'll be hanging around here lots asking questions!!

Geoff

Flying Geezer

My Feedback: (14)

Charge at 210 mAh for 15-16 hrs. Discharge at 420 mAh with a cutoff voltage of .9 volts per cell.

If you were to discharge at 105 mAh it would take 21 hours to discharge. Industry standards for testing for capacity is to discharge at a rate 1/5 the capacity of the battery pack.

Hope this helps.

guver

My Feedback: (325)

I made mistake on the c/5 rate, it is 420 ma. The charge rate can be 210 ma and the timer should be disabled or set to 15+ hrs.

rlmcnii

My Feedback: (3)

F76,

The charge rate is 2100/10 = 210(or close to it) ma. The discharge rate is 2100/5 = 420(or close to it) ma load.

I do not know how your charger works. However, for the forming charges you do not want it to cutoff automatically. You want to go 16 to 18(it can be as long as 24) hours at C/10. The forming charges are TIMED charges. C/10 will not damage your cells.

Discharge the cells to .8volt/cell (that would be 6.4 volts for your eight-cell pack) and re-charge atC/10. Do this THREE times.

If your charger records mA discharged when cycling you should be very close to, or even a little above, the 2100 rating after the third discharge. You may even get there after the second.

Once formed, many people seem to be very happy fast-charging their AA packs. Unless you must do so it is probably best to avoid the practice. AA cells tend to have high internal resistance and a high charging current just produces heat (Joule's law???, long time ago!) which will shorten the life of the cells.

Fast charge? No fast charge? Make your choice and pay your money.

I have a 2100 pack in a little used Tx. The cells were formed as described above. It will stay above nominal voltage (9.6) for months without recharging. Perhaps the high self-discharge rate attributed to NiMH cells is partly caused by overly exuberant charging!!

?????

Good luck.

P.S. FG's discharge to .9 volt/cell is undoubtedly fine. That would be 7.2 volts for your eight-cell pack.

Flyboy76

My Feedback: (14)

thanks very much guys. I will set it up and run it the way you have suggested. Much appreciated

Geoff

SilverFoxCPF

Hello Geoff,

Keep in mind that a big killer of NiMh cells is overcharging. When you charge at high rates, you need to be sure you send a strong termination signal to your charger so that it will properly terminate the charge and not overcharge.

At the 0.1C rate, this is not a concern, and you simply set a timer and you stop the charge. You are the terminating factor. If you happen to go a little over, very little damage occurs at this rate. By now you know that for your 2100 mAh cells, the 0.1C rate is 210 mA.

It is when you charge at a higher rate that you can run into problems. With NiMh chemistry, it is not recommended to charge in the 0.2 - 0.4C range if your charger uses -dV termination. With your 2100 mAh cells, this would be charging in the 420 mA - 840 mA range. Don't charge in this range if your charger terminates using -dV. The reason for this is because the -dV signal is not reliable or strong enough in that range to properly terminate the charge. The recommended charge rate is 0.5 - 1.0C. This means charging in the 1050 mA - 2100 mA range. This goes for both consumer and hobby cells. Keep in mind that if your cells are in a battery holder, the holder may not be suitable for charging in this range, so you are stuck with 0.1C timed charges.

If your charger uses a change in cell temperature, or the rate of change in cell temperature, you want to be charging at 1C to produce a strong end of charge signal.

Now, if your charger terminates when a peak voltage is reached, you can charge at any rate you want to.

So, you first have to determine how your charger determines that the charge should be terminated, then you have to determine if your cells and holders can handle a certain charge rate, and finally you need to monitor the charge progress to make sure your back up termination works if the main termination is missed for some reason.

I find that I get better performance from my packs and cells if I do a 0.1C charge for 16 hours every 20 - 25 charge/discharge cycles when I am charging at high charge rates. I would suggest that you start with discharged cells before doing the slow charge to limit the amount of overcharge.

People say that fast charging reduces cycle life, and they are correct. When you are charging at 2 - 5C, you get a reduction in cycle life.

If you have the time and can figure out how much you have used from your pack, 0.1C charging is the best way to go. The problem is figuring out how much you have used and adjusting your charging time accordingly. Overcharging at this rate is not all that bad, so you don't have to be exact, but if you leave your pack constantly trickle charging at this rate, you will ruin your cells in a little over a year.

Charging is pretty straightforward once you figure out how your charger works. Take some time and get to learn all you can about it.

Tom

Flyboy76

My Feedback: (14)

Tom, thanks for all the info. I charged up the battery this weekend and i was able to fly all weekend without having to charge it up again. All the flying only brought it down to 9.7V on the TX. Should i leave the TX on until it reaches around the 8.8 V range before charging it or is it ok to just charge it up from this point??

geoff