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Old Apr 15, 2015, 06:24 PM
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Question
Spektrum with Eneloops charging question - keep stock charger plugged in?

I have a Spektrum DX7 (not the DX7 S) that I purchased used about 2 years ago. The battery is the stock 9.7 volt 1500mAh NiMH battery. I keep the battery charged with the stock Spektrum110mA charger. The battery has gone bad and will not hold a charge very long. It ran out of power on me this past weekend after about 5 hours having it on only during flights which totaled around 2 - 1/2 hours of actual flight time.

I have ordered 8 Sanyo Eneloop NiMH AA 2000mAh batteries to replace the stock battery and a Radio Shack style battery holder. I will use the connector from the stock battery to plug this new battery set into my DX7 transmitter.

My question is how I keep the batteries charged. I have been keeping the transmitter charger plugged in all of the time. I unplug it to go flying and then plug it back in when I get back home. I fly each week or every other week. The unit is plugged in 24 hours a day between flying sessions. Is this what caused the stock battery to go bad? Will it be OK if I do this with the Eneloops? If this is not OK, what is the best practice to use for occasional flying that ensures that the TX batteries are ready to go with a full charge when I go flying?

Thanks.

Freddy
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Old Apr 15, 2015, 06:32 PM
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Yeah, should be fine to leave it plugged in. You're going to be charging the new ones at an even slower rate than the stock batteries. It's not the ideal solution, which would probably be to plug it in for a day or two after flying and then unplug it. But you're talking still a lifespan of likely years not ruining them in months.
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Old Apr 15, 2015, 06:58 PM
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IMO, I'd go with the "plug it in for a day or two after flying and then unplug it."
Since the eneloops have an extremely low self discharge rate, the potential for excess current is high and that excess energy has to be dissipated as heat. How much will that degrade the pack...got me. Some recommend a C/40 trickle rate.
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Old Apr 15, 2015, 07:09 PM
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To leave on a charger, it should have been one that charges and then shifts to trickle charge.

With the eneloops, charge and then remove from the charger as they will remain charged between flying sessions.
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Old Apr 15, 2015, 07:19 PM
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Quote:
Originally Posted by AA5BY View Post
To leave on a charger, it should have been one that charges and then shifts to trickle charge.

With the eneloops, charge and then remove from the charger as they will remain charged between flying sessions.
+1

mw
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Old Apr 15, 2015, 07:23 PM
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Thanks for the advice. It is appreciated.

I forget that the eneloop's hold a charge for a long, long time. The old battery lost charge in around three weeks of being unplugged.

Since these eneloops will hold a charge, I will opt for the "plug it in for a day or two after flying and then unplug it." I am sure my run time on the TX will be much improved. And the unplugging part will not be a problem.

Freddy
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Old Apr 15, 2015, 08:08 PM
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For starters the endloops are 2300 mah opposed to the 1500mah loose the charge Spektrum batteries,so all being equal you start with 25% more capacity.
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Old Apr 15, 2015, 11:47 PM
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The Eneloops you want to use in a TX are rated at 1900mAh "minimum", 2000mAh typical. There are Eneloop Pro XX cells with 2300-2500mAh capacity, but they have a higher self-discharge rate and they're only good for about 500 charge-discharge cycles vs. 1500+ cycles for the standard Eneloops.

Pete
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Old Yesterday, 01:43 AM
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Most reputable brand NiMh are now low self discharge, Enerloop lost hold of that marketing bit a long time ago.

I use Grundig NiMh of 2300mAh and have old Futaba M chargers of 50mA rate. They stay plugged in continuous to my Tx's. My Grundigs are well into 3rd year and get hard use as well. My Tx is left on once or twice a year to discharge to its Low voltage alarm and still now - I get over 9hrs before it sounds. My alarm is set with still good margin left.

For when I need quick charge - I have a Prolux Smart Nixx charger that whacks out near 1A - not recc'd to leave connected past its auto point as most Tx sockets are not designed for such loads.

1500 cells on a 110mA charger ? I'm not surprised if you left plugged in continuous that your pack is now damaged. At 1/10th rate you are advised not more than 14 - 15 hrs. Your charger although less than 1/10th is still in the range that you should not leave continuous.
My way to calculate is : battery capacity / charger rate gives perfect charge time, which is impossible. Therefore add ~30% to the time ... up to 40% depending on charger etc,

The only continuous rate I would be happy with on your new batts of 2000 mAh would be similar to my 50mA chargers. If 100mA - then I would calculate the charge time needed or best is invest in a NiMH delta peak auto charger such as the Prolux.

Nigel
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Old Yesterday, 10:28 AM
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Most say they are, some are quite good, many are crap. Eneloop are the only ones I've seen that are made in Japan, the rest are China. Given the cost difference is less than 20% in most cases I use Eneloop almost exclusively. I've been burned too many times trying to save a bit of money buying something cheaper only to have to go back and buy the better one anyway. I can go buy a pack of Eneloop AA's and KNOW they will perform as specified, why chance it?
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Old Yesterday, 10:32 PM
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Quote:
Originally Posted by James_S View Post
Eneloop are the only ones I've seen that are made in Japan, ...
Beware: Some generation-4 Eneloops are made in China now and they're not as good as the Japanese ones. But please note that some generation-4 Eneloops are still made in Japan and they're better than ever, so don't believe the rumor that all gen-4 Eneloops are junk. Unfortunately it's impossible to tell the Japanese Eneloops from the Chinese version without reading the small print on the cells, but the Japanese cells do say Made in Japan on them and the Chinese cells do say Made In China.

Probably the most comprehensive discussion on the topic can be found HERE IN THE CANDLEPOWER FORUM. There are even photos of the Japanese and Chinese cells in posts # 158 & 160.

Pete
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