I posted this in the battery forum, I don't think it gets as much traffic as this one....

Couple questions..

1. I have a Futuba 6EXA radio. It has a digital voltage readout. I understand that the battery should be discharged to a certain point to prevent memory. What defines discharge? How low to go? Is it OK to just leave the radio on until that point is reached?

2. Could someone please give an explanation of charging levels... 10C etc... I have a field charger and want to understand what to set it at.

The C in the forumla referes to the Capacity Usually measured in Mah (milli amp hours)

Here is an example my charger uses Amps to measure its output

To fast charge my 300mah Nimh pach at 2C (most people agree that charging NiMh packs at more then 2C is not a good thing) the charger needs to be at:

Formula 2(300) /1000 = .6 amps

you Divide by 1000 to convert to amps

BTW I'm not sure about your 10C capacity I've always been told to fast charge Nicads and NiMh batteries at no more then 2C I believe the charger inculded with your radio charges the batteries at 1/10C or about 50/60Mah

Crashem is right on. In theory, a 1/10C rate for 10hrs gives you a full charge. But things aren't 100% efficient, so you usually take 12hrs at 1/10C to account for energy lost as heat, etc.

10C will toast off most batteries used for TX and RX packs. There are some high current nicads used for the larger motor packs that might handle that rate, but the AA size cells in your TX won't.

As for memory in your TX pack, don't worry about it. It's a non-issue. Especially since just about every TX these days has a meter right on the front to tell you what's going on. Just charge it up and go fly.

On the RX side, memory is also pretty much a non-issue. You're more likely to damage a cell in a dozen other ways, causing the capacity to go down than you are to actually see measureable "memory". But if you want to cycle your pack, you can just leave it on and wiggle the sticks for a while.

By the way, you don't want to discharge the pack below 1.1v per cell on a regular basis. Once in a while, when you accidentally leave things on over night may or may not be a problem, but don't do it regularlly.

Moden NiCds don't really suffer from memory problems that would effect batteries of a decade ago. In short, don't worry about memory issues. While it doesn't hurt the battery to run the full discgarge cycle, it is a waste of time IMO. The only reason I run full discharge cycles is to verify battery health. I typically only do this two or three times a year. Don't leave the radio on. If you forget, you could possibly over discharge the battery. If you want to cycle the pack, get a battery cycler.

Batteries are charged with respect to the cell capacity. The cell capacity is called "C". A slow charge is 1/10 C. All this means is that if you have a 500mah pack, a slow charge would be 1/10th that, or 50ma. Some cells tollerate faster charge rates of 1C or higher. In general it is best to avoid high charge rates unless your cells are designed to handle the faster rates. The high charge rates will shorten battery life somewhat. Discharge works the same way. A 1C discharge on a 500mah pack is 0.5 amps or 500ma.

Hope this helps.

Thanks much for the answers... my 10C comment was just from memory, must have been 1C.

So.. my 600mah NiCd can be charged at a .6 setting on my field charger, or 1C. At this setting, if the pack were dead, it should take 1 hour to charge. Right?

Also.. I am all ears.. so any other battery tidbits are appreciatted.

Thanks again,

J

Yep, you got it. Actually, slightly more than an hour, since you loose some energy in the process, but close enough.

Check your field charger out if it is a peak charger it will automically shut off when the charge peaks

I found this site it covers almost evrything you could want to know about batterys go and check it out.
http://www.rcbatteryclinic.com/

The above comments on not worrying about memory are correct. It has really never been a real problem, even in the old days. Since you appear to be new to the game, do check out the rcbatteryclinic.com, it is very good with accurate info being distributed. Also, refrain from running your batteries down by just leaving the system on. One cell (the weaker one) will always be discharged faster than the others and can become reverse charged and destroyed by the current from the still functioning cells. It will not hurt a cell to be discharged to zero but NEVER reverse charge it. The reason for the "only discharge to 1 volt per cell" rule is to prevent the inadvertent reverse charge of that weakest cell. Ror NiCads if you were to monitor each individual cell, you could discharge the pack until that weakest cell reached zero volts with no damage to any cell. Since this is difficult at best to do, just stop the discharge when you get to the 1 volt/cell point.