4.8V - 1700MAh RX battery, all I have is the Hobbico quick field charger. I have no wallwart to do the initial slow charge so I'm setting the quick charger to 0.2 amps (200mA? Just over the 1.70mA that would be 10/C for a long slow full charge. ???) Because the battery doesnt reach full charge in two hours the charger shuts off. I just keep resetting the charger and it runs for another 2 hours. I've done this about 5 times. The last time the pack was a little warm to the touch.


Tomorrow I fly again. If I feel I have to quick charge at the field I should not go above 1.0 amps setting, max?

My TX was on charge over night and the screen shows 5.2V I took out the Spektrum 1500mAh AA rechargables and put in Alkaline AAs and I get 6.2V on the TX.
The Alkalines dont give a mAh number. Are they ok to use? I have a regular quick charger for the Spektrum AAs, 'll see if they come up to 6.2 in the TX.
Keep 4 Alkalines in the flight box and They will power the TX in a pinch???


About the wallwarts: I have 20 or so of these devices saved over the years from various electronic equipment.
If I have one that puts out 150 mAh could I splice the appropriate connector and use that????
I doubt I have one thats 4.8 volts though?? most will be 6V or 9V????
I know they are not expensive but would these work?

Thanks

Steve

Not in any particular order.
You can use Alkaline batteries, but DON"T TRY TO CHARGE THEM. Alkaline batteries have a higher nominal voltage than NiCad and NiMH at 1.5v per cell vs 1.2v for the rechargables.
So don't expect a fully charged NiCad to have the same voltage as an Alkaline.
DO NOT use a charger that is not rated for the voltage of the pack you are trying to charge.
What you really need is a good charger.

The Hobbico quick field charger is a good charger. A slow charge is best for a new battery, but you should be able to quick charge the battery at 1.5 to 2.0 amps without any harm to the battery.

If anybody makes a wall wart well suited for trickle charging a 1700 Mah NiCd/NiMH pack, I sure haven't seen it. Wall warts generally can't provide enough current to charge that large of a pack sufficiently. You need 170 Mah or so for the charge rate, and most wall warts typically charge at 50 or 75 Mah.

A more advanced charger might be a good investment. I bought the Super Brain 989 about eighteen months ago, and it's amazingly flexible. It can charge at rates from 100 Mah to 10 Amps, can handle NiCd/NiMH packs from 1 to 25 cells, can discharge and autocycle NiCd/NiMH packs, can handle LiPo packs from 1 to 8 cells, works well with a variety of balancing modules, can charge 6v to 24v lead acid batteries, and comes with its own 10 Amp AC power supply.

The SB 989 has so many features that I couldn't adequately explain them all. It was not inexpensive, but I constantly use it for cycling receiver packs and balance charging LiPos.

The 100Mah charge rate is low enough to be appriopriate for slooooow charging a brand new receiver pack, even if it's only 600Mah or so in capacity. It can be increased 100Mah at a time and be set to exactly how fast I want it to charge.

The $144.99 price tag may seem ridiculous at first glance, but you can knock $25 or $30 off the cost if you hit the right Tower Hobbies discount code. I caught it on sale back in Jan '07 and got one for $110 delivered. I use the charger so often now that I've never regretted a nickel of the money I spent on it. I can't imagine ever using an RC battery of any kind that the 989 won't charge. I just don't have to worry about it.

Hmm....

I regularly charge my plane's packs up to 4000mAh 6V on a lowly 4.8v 50mA to 100mAh stock JR chargers.

I may leave the charger on the plane for a few days or so, but my Accucycle shows that the battery does put out faily good capacity.

1700mAh packs?

At least half of my planes have 2000mAh packs or greater and all charge just fine with the "trickle" charge rate of the wall wart.

I don't have to worry about leaving the charger on too long too.

( For safety I also use an extended range meter with load at the field... ).

BTW: Most wall warts put out a higher voltage than the targetted pack...

That's C/10 not 10/C.

CGr

That's cool. One of the advantages of large capacity packs is that they don't have to be at peak capacity to fly. I was particularly thinking of peak charging the battery to full capacity and maximum voltage, but I didn't clarify that in my original comments. Many pilots might lack the patience to leave a battery pack on the charger for two or three days, which would also be a consideration. "Be sure to charge it overnight," is usually good advice, but probably not when using a wall wart to charge up a 2000 Mah pack.

Using your method of charging, opjose, I'd expect your receiver batteries to last darn near forever!

Probably a typo but with a 1700mah pack C/10 would be 170 ma or 0.17 amp. This would be a "trickle or slow charge" rate. To charge an empty battery in 2 hours you would need to set it to 850 ma or higher. This shouldn't hurt anything but if charging at home I'd use a lower rate or a wall wart charger. A 6 volt wall wart should be OK at 150 ma. They will take a lot longer than a Quick Charger though but are easier on the batteries.

Thanks for telling me what you are using. All I have to charge now it the TX and RX so I will just use the hobbico fiels charger. When I go into Electric planes I will invest in a better charger with all the bells and whistles..

C/10, whats the C stand for?


Steve

"C" stands for the battery Capacity measured in mah or milliamp hours.
ie.... 1700mah battery C=1700ma or 1.7amps

Exactly.

The 4000mAh packs might night be charged up to the full 4000mAh capacity, but even at 3400-3700mAh ( which is what I usually read off when I test the charge ), what me worry? Heh. Usually the Accucycle doesn't take the cell voltages too far so capacity is oft less than stated.


Knocks on wood, knocks on wood again... knocks on wood a third time....

So far so good.

I doubt I'm straining the batteries at all even when I forget and leave the plane charging all week. [X(]

And with the bigger packs I don't worry about the servos overloading the batteries...

FlyRC had a good article on the power draw rates of servos.

Quite compelling info... no 800mAh packs for me!

Well, with a 1700 mah battery, C=1700 milli-amp hours (mah) or 1.7 amp hours (Ah). An Amp is a current, not a capacity.

If you have a 1 Ah battery, then if you pull 1 Amp of current off the battery, then it will theoretically last for an hour before it is empty.

True and I should have written it the other way but when doing the math C/10 for example the desired result is not capacity but charge rate in Amps.
I should have said C= 1700mah on a 1700mah battery and the desired charge rate is C/10= 170 ma for 10 hours + (+ is due to the inefficiency of battery charging so add about 10% to 20% or so or about an additional 2 hours)

My experience has been that how I charge isn't so important as that I charge. I've got the usual collection of wall warts, and when I know my schedule I'll use them when I can. When that's inconvenient for whatever reason, I use an MRC SB969 to charge my NiCads and NiMHs. My LiPos only get used with an FMA Cell Pro.

More important than the charging, I think, is the checking. Get a loaded voltmeter. I've gotten into the habit of checking my batteries before each flight. It hasn't saved me any trouble yet, but I have no doubt that it will at some point. With a good charge-switch, it's very easy to do. I got tired of the cheap little switch harnesses, so I bought a bunch of decent ones for about $12 each.

What kind of switch was it?

Steve

I've been using EMS's heavy duty ones. They're a little larger than most switches, but I haven't found that to be a problem.

Yeah, but we usually don't run them all the way down so charging efficiency doesn't become an issue.