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Best way to charge a RX pack

Old 09-13-2009, 04:45 PM
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dufault
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Default Best way to charge a RX pack

Hi there,

I have a Nicd 4.8v 700mah pack and Im wondering whats the best way to charge it. I have a wall trickle charger as well as a quick charger. After flying, should I discharge the cells to a certain amount before charging? Also, Whats the rate I should be charger at? I usually set it to 0.3 which I know is pretty low. Thanks.
Old 09-13-2009, 05:09 PM
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mclina
 
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Default RE: Best way to charge a RX pack

I have always used my wall chargers for all of my packs. I plug them in the day before I go flying, regardless of how much I may have used them since the last charge.
Old 09-13-2009, 05:33 PM
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sportrider_fz6
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Default RE: Best way to charge a RX pack

I will normally decide which planes are going to the field a few days before, I'll put one on the charger on Saturday morning and switch it out before I go to bed and let the second plane charge overnight. If I bring a third plane it goes on the charger friday night. if I only bring one I'll charge it overnight. I use a wall charger. I have a buddy that charges his RX packs with a super brain the morning he goes to the field. I guess whatever works, works.
Old 09-13-2009, 05:37 PM
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GaryHarris
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Default RE: Best way to charge a RX pack

Rule of thumb is to charge slow for longer run time. I discharged my RX pack last night with my car charger at 1 amp. It took 29 minutes to discharge after a few short flights the week before. And for charging, I just used the Footaba supplied Wal Wart overnight.

Cycle your packs.
Old 09-13-2009, 06:06 PM
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dufault
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Default RE: Best way to charge a RX pack

So what should I cycle the pack down to? I have to choose a voltage per cell on my charger. 0.9V? or even lower?
Old 09-13-2009, 06:13 PM
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tschuy
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Default RE: Best way to charge a RX pack

For nicads you should never go below 1.1V per cell or you'll damage the battery.
Old 09-13-2009, 06:35 PM
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RCKen
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Default RE: Best way to charge a RX pack



With modern battery chemistry the only reason you need to discharge a battery back is to determine the capacity of the pack. You won't get any performance benefit from discharging them before you charge. And unless you have a battery charger/discharger that is designed to discharge the battery properly you could actually damage the pack if you discharge it too far. You best bet is to simply recharge the pack fully before you use it. If you are using the wall wart that came with the radio then you'll want to put the pack on charge for approximately 14-16 hours.

As I said above, the only real reason to discharge a pack these days is to check it's capacity. I will run a new pack through 3 charge/discharge cycles in order to determine it's initial capacity (never ever trust the capacity on the label of the battery). Then about once a month I'll cycle the pack to check it's capacity. When the capacity of the pack drops to approximately 80% of it's initial capacity I'll take the pack out of service and replace it.

Ken

Old 09-13-2009, 06:49 PM
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Default RE: Best way to charge a RX pack


ORIGINAL: tschuy

For nicads you should never go below 1.1V per cell or you'll damage the battery.
Not true.
Old 09-13-2009, 07:01 PM
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GaryHarris
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Default RE: Best way to charge a RX pack


ORIGINAL: RCKen



With modern battery chemistry the only reason you need to discharge a battery back is to determine the capacity of the pack. You won't get any performance benefit from discharging them before you charge. And unless you have a battery charger/discharger that is designed to discharge the battery properly you could actually damage the pack if you discharge it too far. You best bet is to simply recharge the pack fully before you use it. If you are using the wall wart that came with the radio then you'll want to put the pack on charge for approximately 14-16 hours.

As I said above, the only real reason to discharge a pack these days is to check it's capacity. I will run a new pack through 3 charge/discharge cycles in order to determine it's initial capacity (never ever trust the capacity on the label of the battery). Then about once a month I'll cycle the pack to check it's capacity. When the capacity of the pack drops to approximately 80% of it's initial capacity I'll take the pack out of service and replace it.

Ken


Ill have to dissgagree with you Ken. A Nicad is still a Nicad. There is no new chemistry in Nicad tech. They still develope a memory if not fully cycled. As far as being discharged too far, I have seen many world class car racers dead short their packs.
Old 09-14-2009, 08:26 AM
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Default RE: Best way to charge a RX pack

I have to disagree with Gary and almost agree with Ken.
There is no need to frequently cycle Nixx batteries.
What they have changed in them I don't know.
It could be something as simple as an alloy percentage.
However, I believe the engineers when they say the problem is gone.
In addition, if a pack has been unused for a month or more it may need reforming,
especially if it is a NiMh.
I do believe in cycling but I only do it about twice a year.
In California we fly year round.
Also, when I discharge I do it to .9 volts per cell.
Good Luck,
KW_Counter
Old 09-14-2009, 09:07 AM
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Rodney
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Default RE: Best way to charge a RX pack

I also have to agree with most of what RCKen said. Gary is in error in several points. First off, NiCads will not be damaged by discharging to zero volts, in fact, NASA recommends that they be stored with a shorting bar across their terminals. What will damage them is a reverse charge or discharge at a rate so high it raises their internal temperature over limits. As long as the discharge rate is kept to .3C or less, no damage will occur. Also, as we use them, NiCads do not exhibit a memory. Under some circumstances you can get voltage depression (also happens to NiMh). An occasional deep discharge and recharge at 0.1C for 16 hours tends to recover from said depression. For long life, your batteries (NiCad and NiMh) will give you longer life (more charge/discharge cycles) if you always use a slow charge (0.1C) rather than a peak charger. Heat is the biggest factor in lowering the lifespan of Nixx batteries as the separator deteriorates faster at higher temperatures. While fast charging is convenient, it definitely decreases the lifespan of the batteries.
Old 09-14-2009, 10:38 AM
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Default RE: Best way to charge a RX pack

Garry I am sorry but you are wrong.
Nicads do not develop a memory. The older ones did but not anymore.
I discharge a pack once a year and only to test the battery.
never had any problem at all.
Old 09-14-2009, 11:18 AM
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Rodney
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Default RE: Best way to charge a RX pack

Here are some very good sources of factual information on batteries if you want to take the time to read them.
http://www.hangtimes.com/redsbatteryclinic.html

http://www.camlight.com/techinfo/techtips.html

http://www.whenshtf.com/showthread.php?t=2153

http://www.srbatteries.com/nimh.htm

http://dansdata.com/gz011.htm

http://users.frii.com/dlc/battery.htm
Old 09-14-2009, 05:06 PM
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GaryHarris
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Default RE: Best way to charge a RX pack


ORIGINAL: Rodney

I also have to agree with most of what RCKen said. Gary is in error in several points. First off, NiCads will not be damaged by discharging to zero volts, in fact, NASA recommends that they be stored with a shorting bar across their terminals. What will damage them is a reverse charge or discharge at a rate so high it raises their internal temperature over limits. As long as the discharge rate is kept to .3C or less, no damage will occur. Also, as we use them, NiCads do not exhibit a memory. Under some circumstances you can get voltage depression (also happens to NiMh). An occasional deep discharge and recharge at 0.1C for 16 hours tends to recover from said depression. For long life, your batteries (NiCad and NiMh) will give you longer life (more charge/discharge cycles) if you always use a slow charge (0.1C) rather than a peak charger. Heat is the biggest factor in lowering the lifespan of Nixx batteries as the separator deteriorates faster at higher temperatures. While fast charging is convenient, it definitely decreases the lifespan of the batteries.
I didn't say discharging Nicads to zero volts was bad. In fact I pointed out that some racers "Dead Shorted" their packs allthough I never did. And I allways dropped off at 0.9 volts.

And Ill dissagree with the comment that Nicads will NOT develope a memory as we use them. Nicads are like muscles. They require exercize to remain flexiable.

Sorry guys, unless some new majic nicad tech has sprung up within the last two years, I think I know what I'm talking about. Or Ernie Provetti lied to me. [>:]

Ken, Your in Lawton. Go to the race track and look up Dave Alford. Tell him Biff sent ya.

Love this forum! We can agree to dissagree, without flaming!

Thanks
Old 09-14-2009, 05:08 PM
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GaryHarris
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Default RE: Best way to charge a RX pack

ORIGINAL: Missileman

Garry I am sorry but you are wrong.
Nicads do not develop a memory. The older ones did but not anymore.
I discharge a pack once a year and only to test the battery.
never had any problem at all.
What equipment do you use?
Old 09-14-2009, 07:38 PM
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dufault
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Default RE: Best way to charge a RX pack

Well I think I have it sorted out for the most part. I did do a discharge just to see my capacity. Looks like Im around 770 mah. Thanks for the help everyone

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