NiMH 10X / discharge rate?

[3daviator]

I replaced the oem battery in my 10X with a NiMH. Charges up and holds a charge for a day ok, but if I charge it and let it sit for a few days, when I turn it on, it's down to 9v or less in a matter of min's. Is this normal for NiMH or do I have a problem??

[WangoTango]

3D,
I have 1650 Sanyo dark green cells in both my 10X's and they do the same. They bleed down over a few days but after a charge, I can get more hours of run time than I can stand. You might want to check your pack. I don't think I ever have fallen below 9.6 volts.
WT

[XJet]

What capacity are your NiMH cells?

If they're the ultra-hi capacity cells (2200mAH or higher) then your observations are not unexpected.

That's why I only use 1650mAH packs, they have a *much* lower self-discharge rate.

I'd also ask, if these are 2200mAH+ how you charged them?

These ultra-hi capacity NiMH cells are *fragile* and will not tolerate fast charging (ie: more than 1/10 C) or over-charging.

RadicalRC recommend only ever using your Wall-wart charger for these packs since even 1/10C can cause problems if the cells don't peak and cause your charger to shut down.

1650mAH is *more* than enough for a full day's flying (in my experience) and (just to check) I have just turned on my JR9XII (9303) which has these cells in it. They were last charged six weeks ago and the transmitter still reads 10.3V.

[3daviator]

Thanks for the replies.

They're 2500mah, I've been charging with a triton charger set to "nimh" .6amp charge rate. My JR factory nicad wall chargers output is 65mah.

[Gus155]

got 2200mah nimh in my 10x. last charged 2weeks ago, still @ 10.3v.
Will peak after charging around 10.9-11v, but drops down to 10.4 fairly quickly, but will remain there for a long time.
Charg at 1/10c using hyperion charger, usually over night.
If it drops down to below 9v, think you might have a dud cell.

[Scott Gerber]

Just a side question related to this... are some of you guys not getting a full day's flying on the original 1100 mah size battery and needing to move up to higher capacity...???


Scott

[Gus155]

	Quote: Originally Posted by Scott Gerber
	Just a side question related to this... are some of you guys not getting a full day's flying on the original 1100 mah size battery and needing to move up to higher capacity...??? Scott

Mine was toast, but also wouldnt cut 4hrs on the slope a day.

[WangoTango]

	Quote: Originally Posted by Scott Gerber
	Just a side question related to this... are some of you guys not getting a full day's flying on the original 1100 mah size battery and needing to move up to higher capacity...??? Scott

Scott,
I just changed mine out because they were two years old. Now the TX can go for eons and its the RX batts I worry about!
I see you changed your avatar..... Ya must have had a falling out with the YAK and fell FOR Shania!! LOL!
WT

[Scott Gerber]

	Quote: Originally Posted by WangoTango
	Scott, I just changed mine out because they were two years old. Now the TX can go for eons and its the RX batts I worry about! I see you changed your avatar..... Ya must have had a falling out with the YAK and fell FOR Shania!! LOL! WT

No falling out with the Yak, it 's doing just fine. The change was for the benefit of T.bob on another thread...


Scott

[Four Stroker]

The new Sanyo Eneloop cells are perfect for a transmitter. An honest 1800 mAh, they retain their charge for a long time - I let them sit for three months and lost less than 10%. I peak charge them at 300 mA NiMH on an old Super Nova. That's the lowest charge rate. 9V either means you TX meter is broken or you have a bad cell as previously mentioned.

[Scott Gerber]

	Quote: Originally Posted by Four Stroker
	The new Sanyo Eneloop cells are perfect for a transmitter. An honest 1800 mAh, they retain their charge for a long time - I let them sit for three months and lost less than 10%. I peak charge them at 300 mA NiMH on an old Super Nova. That's the lowest charge rate. 9V either means you TX meter is broken or you have a bad cell as previously mentioned.

http://thomasdistributing.com/shop/s...irvviv4f0n2m40



Are the batteries in the JR 10X carrier solder tab style or button top...???


Scott

[alec taylor]

i use eneloop 2000 in my futaba 8. i get 6 hrs between charges. i use a wall charger @ 150 milli amp. alex

[Troy Newman]

I think you are focusing on the cells that are being used.

XJET is correct nd gives good advice.

I think the issue really is the charger. The NIMH cells tend to kick off or false peak when charged with some of the "fast field" chargers the Triton falls into that slot. The charger sees the voltage "peak" and stops. yet it might only be a 70% charge even though it comes off the charger at 10.7-11v When you get the pack fully charged the top voltage will not change much. The newer nimh cells will hold their voltage longer while discharging. So a fully charged one might come of the charger at 11v but a 70% charge might be 10.7 or 10.8V. The fully charge one will be at that 10.7 volts still after 2-3 flights but the 70% charge that started at 10.7V might be down to 10V after those 3 flights.

I charge my TX battery with the c/10 chargers. I also have a JR 2500mah TX pack that I have retrofitted into the 10X TX cartridge case. If you charge it at 250mah for 16hrs the charge will last many days of flying.

Nimh cells are more critical when it comes to the fast charging stuff. They don't like it...Yes they can do it but false peaks and shorter battery life is the result.

A false peak means the charger shuts off and says the pack is charged when it really is not. To begin with the peak detection chargers don't go to 100% anyway for safety. They will stop at 90% even if they sense the peak properly. So you are already on the down side of the curve.

Also the Nimh cells like to have the slow charge especially when they are new. I usually do the first 4-5 cycles on my nimh packs both TX and RX packs with a slow charge rate. If you abuse them with the peak detection chargers early on sometimes they never come back to life.

using this slow c/10 charge rate for 90% of your charging needs will make the packs last longer both in "on" time between charges and also number of cycles too.

Get a good charger that allows you to set the charge current, and not a peak detect charger. I have several that have had for many years. These are really the Best chargers for Nimh packs.

JR also makes a special wall wart charger just for the 2500mah TX packs. I have one and use it as well.

http://www.horizonhobby.com/Products...ProdID=JRPC223

When the Nimh packs start to get warm they are getting close to charged. SO I tend to monitor the charge like that. Just put your hand on it to make sure its not getting hot. The NIMH cells have this property they start to get hot when fully charged. So I keep an eye on them to make sure they get warm, but not too hot.

Usually c/10 so 250mah for a 2500mah battery will only start to get warm after about 10-12hrs of charging.

If you treat your batteries nice like this then the occasional field quick charge is not as damaging to the batteries.

Next issue is self discharge. Yes the Nimh packs will self discharge at a faster rate. However if you are getting them fully charged with a c/10 charge they stay up much better over time. Int he summer I fly a bunch, 4-5 days a week at least. But I can have a fully charged 10X pack sit for about 10 days to 2 weeks and it still has above 10v and can handle a normal day of 3-5 flights.

I think you are only charging the pack up to 70% in the first place and its falling off faster as a result.

Some will argue this but I'm sharing my experience with you on it. By the way I just flipped on my 12X has not been charged since July 24th was flown 4 flights at the Nationals on July 25th, and then I have done some programming and playing with the system but not more than about 20mins of on time since the 25th of July. Its battery voltage is 10.1V and it runs a 2200mah nimh stock 12X battery. It gets the wall charger that is included in the 12X system. Think I have field charged it 3-4 times since I got the system in May. The battery life to me is very good even just sitting.

I suggest try changing your charger and your experience will be much better. Start with a couple slow 16hrs charge cycles at 250mah. Or get that 270mah charger from JR its cheap. At 270mah it should charge a little quicker than 16hrs....maybe 13-14 on a pack that is mostly discharged "9V"

Troy Newman
Team JR

[dick hanson]

NiMh can fool a lot of us --
I had at one time, a dual charger -a Hobbico which I really thot was handy - but my NiMh were obviously NOT charging -then supplying what they should.
I bought an EFlite charger which charged then discharged Nimh/NiCad.

I then measured capacities of charged cells .
This is the only way you can really determine what is happening with cells -- ANY cells.
To cut to the chase - I found that the crummy NiMh I was using ,had high internal resistance -- causing the cellsto indicate they were charged - long before they were actually fully charged.
I also have a little test stand I designed a few years back ( someone now markets a clone of it) which uses an electric motor , an amp meter and a postage scale . The setup permits a quick look at actual power output of any battery pack under various loads .
Most older NiMh are worthless -really

Any good ones will charge/discharge and recharge and read the full RATED ampere hr .
The cycling type chargers will show this.
The caveat is that you must charge slowly -on new cells - to permit correct cell forming.
Before I sold my 10X radios --I had new packs I fitted into the battery holder - these EXPERT packs from Horizon-worked well but the charge rate had to be kept low -
My 2.4 9303 and DX7 use ony piddling amounts of power - so I just charge with the wal warts -leaving them on charge a day or two - no harm to them at all.
keep yer mitts off the quick chargers - the stock cells and wall wart is the best setup for your TX.
Each time I help sort out a tx problem - the chances are that someone has attempted to "speed things up"

[Four Stroker]

The Sirius Pro (500 mA model) will consistently false peak large capacity NiMH cells at about 40% as Troy says. There is general agreement that they should only be charged at C/10 as here:

http://www.hangtimes.com/txpacks.html

I have been very successful charging Sanyo 2700's at 300 mA (C/10 = 270) and Eneloops on an old Super Nova peak charger on the NiMH setting.

The Sanyo 1600 cells don't mind fast/quick charging at 500 mA and don't false peak.