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Rhondas
12-06-2005, 05:25 AM
I have been reading up on Nimh batteries and they recommend that you charge them for a long time say at 50Milli amps on a 750 MAH 7 cell pack for about 15 Hrs with a wall type charger like the one we use on our radios.Now after I do this long charge do I fly my arplane with this pack then do the faster delta type peak charging and from then on I can always fast charge the pack on my peak charger;)

slipstick
12-06-2005, 09:30 AM
The recommendation is that you use a current of C/10 (one tenth of the capacity) for around 15 hours. So that would be 75mA for a 750mAh battery or 200mA for a 2000mAh battery etc. You then need to discharge it and going flying is certainly one of the easiest ways to do that.

Ideally you should do 3 or 4 slow charges and discharges like that before you start fast charging but it won't really hurt if you only do that first slow charge and then go straight for it. Your battery will carry on getting better for the first few charges so don't worry if the first flight or two seems a bit down on power/duration.

You can then keep on fast charging but, if you can be bothered, it's better for the battery if you give it a slow charge like the first one every so often, say once every few months. It stops it getting out of balance which robs you of power and causes the battery to go bad faster.

Steve

Rhondas
12-06-2005, 10:29 AM
The recommendation is that you use a current of C/10 (one tenth of the capacity) for around 15 hours. So that would be 75mA for a 750mAh battery or 200mA for a 2000mAh battery etc. You then need to discharge it and going flying is certainly one of the easiest ways to do that.

Ideally you should do 3 or 4 slow charges and discharges like that before you start fast charging but it won't really hurt if you only do that first slow charge and then go straight for it. Your battery will carry on getting better for the first few charges so don't worry if the first flight or two seems a bit down on power/duration.

You can then keep on fast charging but, if you can be bothered, it's better for the battery if you give it a slow charge like the first one every so often, say once every few months. It stops it getting out of balance which robs you of power and causes the battery to go bad faster.

Steve
tHANKS ,i ONLY HAVE MY FUTABA WALL WART THAT PRODUCES 50ma mY PACK IS A 750maah DO i HAVE TO MATCH THAT WITH A 75ma CHARGE?

Matt Kirsch
12-06-2005, 01:13 PM
Not necessarily, but you will have to modify the charge time to match the charge rate. Divide the mAh capacity by the mA charge rate, then add about 40% for that first "break-in" charge.

Are you using the transmitter or the receiver side of the wall wart? The receiver side is 4.8V, for a 4-cell pack, and will never charge your 7-cell, 750mAh pack. The transmitter side is 9.6V for an 8-cell pack, and charges at approximately 100mA. It will work on the 7-cell pack, but it will charge faster than 100mA. I wouldn't charge on the transmitter side for more than 10 hours, and I would start feeling the pack to see if it's warm after about 6 hours. If it's warm, take it off the charger

Tallyho88
12-06-2005, 05:06 PM
I have been charging Ni-Mh packs with a MEN pulse charger designed for 4 & 8 cell packs. So far (About 1 year) I see no problems. If not fully discharged I can usually reach 80 percent full in 15 to 20 mins or less!!!Anyone have other experiences???
Norman

kuzikood
12-06-2005, 05:25 PM
or ya can just do it the way i do ...buy cheap nmhs fast charge them till they croak put some change in a jar everytime ya fly them then by the time the batterie is dead you have saved enough to buy a new one ...works for me

-kuzi-

freddings
12-06-2005, 05:57 PM
I have been charging Ni-Mh packs with a MEN pulse charger designed for 4 & 8 cell packs. So far (About 1 year) I see no problems. If not fully discharged I can usually reach 80 percent full in 15 to 20 mins or less!!!Anyone have other experiences???
Norman

MEN chargers...I have 4 and I also think they are great chargers. Too bad they stopped making them. I've used mine for Nicad for at least 20 years. Works well on NiMh also.

FRED

John Hill-Tout
12-11-2005, 06:10 PM
I have been using a GWS MC2002 charger for about 1 1/2 years. It charges ni-cds great at 3C but ni-mh need at least 5C. I have read that they don't like it but it works.

John

Still travelling at the speed of dark.

qban_flyer
12-11-2005, 06:38 PM
Interesting comments.

My Supernova 250S won't allow me to go over 1C charge rate on NIMH packs, so that's what all of mine get charged at. :)

slipstick
12-11-2005, 10:08 PM
I have been using a GWS MC2002 charger for about 1 1/2 years. It charges ni-cds great at 3C but ni-mh need at least 5C. I have read that they don't like it but it works.
I have seen the dead NiMH packs that didn't like being charged at anything over 1 to 1.5C. I've even killed a couple myself before I learned better.

Can you please give details of exactly what makes and sizes of NiMH pack you succesfully charge at 5C ?

Steve

Rhondas
12-11-2005, 10:15 PM
I have been using a GWS MC2002 charger for about 1 1/2 years. It charges ni-cds great at 3C but ni-mh need at least 5C. I have read that they don't like it but it works.

John

Still travelling at the speed of dark.


what are you setting your charger on in amps not milliamps say for a 7 cell nimh 950mah Kan or other name, battery pack oooooooooooooooooooooooooooooooooooooooooooo
here are the spects on that charger notr auto cut off so you cant over charge ooooooooooooooooooooooooooooooooooo


Controlled Quick Charger
[MC2002]$49.00http://www.allerc.com/images/pixel_trans.gifhttp://www.allerc.com/images/Pictures/gwscharger.jpg
http://www.allerc.com/includes/languages/english/images/buttons/image_enlarge.gif (javascript:popupWindow('http://www.allerc.com/popup_image.php?pID=160&image=0&osCsid=ccab244343f4b6efa6a4ff88dd829390')) images/Pictures/gwscharger.jpg&image=0
includes/languages/english/images/buttons/image_enlarge.gif (http://www.allerc.com/images/?osCsid=ccab244343f4b6efa6a4ff88dd829390)
Input Voltage range:9~15V DC.
Step up-down converter, 4~12 cells of 50mAh~3000mAh Ni-Cd or Ni-MH pack can be charged rapidly.
Automatic Delta-peak cutoff prevents battery overcharge.
Output port polarity and short protection.
Maximum charge time: 90 minutes safety cutoff.
Charge current: 0.25~6A continuous. Large scale current-meter. Sturdy aluminum case and heat-sink for maximum heat dissipation.

cyclops2
12-13-2005, 05:23 AM
Any battery will ALWAYS give more full cycles if charged at 1C. I do not care WHAT IT is made of. 1C charge and 1C discharge give the longest life. Anything else shortens life and capacity. There is a very good reason for a 1C anything. -----------Now who will be the first to live on a 1C diet?

Rhondas
12-13-2005, 05:55 AM
Any battery will ALWAYS give more full cycles if charged at 1C. I do not care WHAT IT is made of. 1C charge and 1C discharge give the longest life. Anything else shortens life and capacity. There is a very good reason for a 1C anything. -----------Now who will be the first to live on a 1C diet?

I agree with you cy, how ever most guys want a quick charge at the field , so they do a 2 C charge and maybe you get 700 charges out of the pack instead of 1000 charges:eek:

qban_flyer
12-13-2005, 04:06 PM
I agree with you cy, how ever most guys want a quick charge at the field , so they do a 2 C charge and maybe you get 700 charges out of the pack instead of 1000 charges:eek:

The old Sanyo (RED) 500ARs were and are still being charged at 3C :eek:, though I have never charged mine any faster than 1.5C at times :). NiMHs I have never charged at over 1C because my Supernova 250S charger won't allow me to go any higher.

One more thig, never charge batteries at the field. Regardless of what type they are, they get charged at home the night before being used. :)

slipstick
12-13-2005, 05:37 PM
I still charge my old (1998) RED 500ARs at the field and at anything up to 2.5A (5C) depending on how impatient I am. But those are a really exceptional NiCD cell. The only ones I know which take a higher charge rate at Sanyo's tiny 50mAh cell which you can happily charge at over 1A (20C) and mine are still going strong after I'd guess 2000+ cycles.

BTW if you really need the maximum performance out of NiMH cells they MUST be charged, or at least topped up, at the field. They work best when they're still warm off the charger ;).

Steve

qban_flyer
12-13-2005, 08:32 PM
I still charge my old (1998) RED 500ARs at the field and at anything up to 2.5A (5C) depending on how impatient I am. But those are a really exceptional NiCD cell. The only ones I know which take a higher charge rate at Sanyo's tiny 50mAh cell which you can happily charge at over 1A (20C) and mine are still going strong after I'd guess 2000+ cycles.

BTW if you really need the maximum performance out of NiMH cells they MUST be charged, or at least topped up, at the field. They work best when they're still warm off the charger ;).

Steve

YUP!

Those ancient RED 500ARs are something else. I still have two eight cell packs that I use in my Zagi. Nothing can touch them when it comes to delivering raw power!

Absolutely incredible cells! They are still taking charges upwards of 520 mils six years later! :)

cyclops2
12-14-2005, 03:36 AM
For a sport flier. Anything but LIPO. Speed or competition, GO LIPO.:)

qban_flyer
12-14-2005, 11:43 AM
I have switched to Li-Po packs on everything except my older models. Everything I have put together in the past three plus years is powered by
Li-Pos exclusively. :)

lindart aviation
12-18-2005, 01:57 AM
radicalrc.com (Dave Thatcher) One of the best sites for charging info.

rocannon
01-24-2007, 12:26 AM
hi,
i see reference to 1C, 3C, etc.

does that mean charging at some multiple of rated capacity?

frank

kuzikood
01-25-2007, 01:47 AM
thats it exactly so if its 3C and its a 1700mah pack that means 1.7 amps X 3 so that = 5.1 amps:) or 10C = 17.0 amps or 20C 34.0 amps and so on