rheauljj

Can you recommend a quicker way to charge the batteries on my new Spectrum DX7? Seems to take an awful long time using the supplied wall charger.

alan0899

G'day Mate,
Charge them using the wall charger, then I don't have to charge mine again for about 3 or 4 weekends.
1500Mah batteries last a looong time in a TX.
But I use an ACE smart charger for all my RX batteries.

rheauljj

Thanks for the advice. I will visit a local hobby store to see what sort of battery charger is available for my TX (there seem to be dozens available).

Is there a website or a book you can recommend that I can review that explains the basics of batteries. The idea seems simple enough...pump juice in them and hope they hold...but having a better understanding should make my efforts less of a gamble.

alan0899

G'day John,
Have a look here, http://members.aol.com/davthacker/balancecharging.htm]
& here, http://www.rcbatteryclinic.com/
They should answer all your questions.

rheauljj

Thanks for the information. It is much appreciated.

alan0899

G'day John,
No problem, have a great weekend.

Semi Retired Aviator

Post deleted. Information found.

Zeeb

My Feedback: (41)

Alan gave you a couple of good links, just watch the charge jack you use and make sure it's for JR rather than Futaba or Airtronics or Hitec. The reason being that the JR and Spektrum transmitters use a center negative polarity on the charge jack where Futaba and the others use center pin positive polarity...[8D]

rheauljj

Here's another question(s) for the experts...

After quick charging my new DX-7 Receiver pack (1100 mAhr, 4.8 volt) the best I can get is 5.3volts on my Volt Meter...after two 12 minute flights my reading drops to 4.8 volts. I've probably flown it only a dozen times with the new radio system.

Does this seem odd?

I'm flying a basic 40 size stick plane (nitro) with what I would venture to say is reasonable servo action, as I'm still in the early stages of intermediate skills development. I've re-done my linkages to rule out friction.

I would think a new pack would yield me better results.

What would be considered unsafe remaining voltage?

leyland384

Did you slow charge the pack the first time to "Form" it? The first charge must be slow, followed by a slow to moderate drawdown. If you fast charged the battery right out of the box you may have done permanent damage to it. Just use the charger that came with the radio the first time or two.

My battery did the same thing on the first charge, even with the stock charger. I cycled (discharged it down to 4.5 volts, then charged it back up) and it is now working at full capacity. I get about 5-6 12 minute flights with plenty of juice to spare (over 5 volts on ground check on last flight of the day) on my .46 size Sig Somethin' Extra.

If you have any more problems, there are lots of forums here on RCU that explain batteries in detail, and how to "Form" them when new and cycle them to get the most out of them.

Adam

Edit:

Also, you should almost never need to fast charge your TX. The spektrum uses so little juice, that I charge it overnight about once every 2 weeks or so. I generally fly about 2-4 hours at a time, and about 4 times a week, and it's still over 10 volts when I finally do plug it in. Save your money on fast chargers and buy more planes...

alan0899

G'day Mate,
Be aware, the nominal voltage of the battery pack is, 4.8 volts @ 1100Mah, meaning it should deliver 1.1amps for 1 hour, or 2.2amps for 1/2hour, or 550Ma for 2 hours, so it will have a higher voltage straight off the charger, but will drop down to it's normal or nominal voltage 4.8volts pretty quickly, under load, & stay at that voltage, until it is almost flat, then will drop off quickly. That is the way nicad's behave.
This is normal behavour, & is only valid, if the battery was balance charged, slowly, until full, & then cycled a few times, as Leyland384 stated.

rheauljj

OK...I think I'm starting to understand. A 4.8V pack should drop from the high I get of 5.3v to 4.8v quickly as 4.8v is the "target" voltage of the battery. Like the link you sent me the other day...(http://members.aol.com/davthacker/balancecharging.htm)..."Also bear in mind you need to put in about 140% of an empty cell’s capacity to fill it up."...from . If I understand this quote, the initial 5.3V my volt meter shows me is a residual of this "140% capacity"?


For the first three weeks, I used the supplied Spectrum wall charger. First charge was 40 hours...and subsequent charges were in the 24 hour range... so I don't think I killed the batteries.

Here's what I bought from the local hobby store...Hanger 9 - Double Vision Fast Field Charger



The Double Vision features two independent charge circuits: one for charging 9.6-volt transmitter packs and the other for charging 4.8-volt (4-cell) and 6-volt (5-cell) receiver packs. Both circuits fast charge at a constant 800mA and automatically trickle after a fast charge at 80mA. I've been charging on 4.8 Volts and have the correct polarity set for JR/Spectrum.

I hope this was a good buy.

Your help has been extremely valuable to me.

Thank you!

rheauljj

Here are some stat's I got yesterday... tried to use the servos as much as possible.

Full charge ... volt meter 5.3V

After first 12-minute flight - volt meter reading 4.8V
After second 12-minute flight - volt meter reading 4.7V
After third 12-minute flight - volt meter reading 4.6V

I seem to be losing .10 V per 12 minute flight

At what point would you recommend a re-charge?

leyland384

The number for your full charge voltage looks okay, but then it looks like things drop off pretty fast. There must be something wrong with your pack. When I fly, the voltage is usually 5.4 for the first flight, then about 5.2 for the second, then 5.1 for the 3, 4, 5 or so. When it drops below 4.9 I start to really watch it close, and recharge at 4.8.

As Alan said earlier, the nominal voltage is 4.8v. It will be higher just after you unplug it from the charger, and it will drop a few tenths of a volt. The voltage should not drop down to 4.8 volt until the pack is nearly dead. Fully charged batteries should always be higher than the nominal voltage. (For an example, 12v car batteries are usually at 12.5 to 13v).

Flying your plane below 4.8v is asking for trouble. Below that voltage, Nicads and NiMH packs drop to almost nothing very quickly.


See if your new charger has a discharger/cycler function. You need to discharge the pack under controlled conditions, then fully recharge it. This formats the chemistry of the battery. Cycling (also known as exercising) helps the battery maintain it's peak capacity.