scott282

My Feedback: (7)

I’ve been using Futaba and Airtronics 72MHz electronics since the early 80’s and just recently made the plunge into 2.4GHz.

I purchased 3 AR7000 receivers to go with my new Spektrum Tx and need to purchase receiver batteries (I understand the current 4 cell 600mAh are too small). I will be installing these receivers/batteries in a 60 size glow powered H9 Hellcat, 60 size glow powered Sig Astrohog, and a 60 size glow powered Bridi Utter Kaos. I will be using the servos that came with the Spektrum in the Hellcat and standard Futaba servos in the other two. I will use only 1 receiver battery/switch in each airplane.

Would I be better off purchasing the 4.8V NiMH 2000mAh or the 6.0V NiMH 2000mAh batteries? Is there a better choice than these? Also, if I purchase the 6.0V batteries will the wall charger that came with the Spektrum fully charge them?

Thanks,

Scott.

DadsToysBG

My Feedback: (35)

I Would use the 6v, and no the wall charger will take forever to charge. Find a good fast charger such as a the Hobbico Quick Field charger HCAP0290. Dennis

pilotpete2

Hi Scott,
While I still fly on 72Mhz I have followed the battery issue closely, I'm a retired electronics tech and have flown E-powered sailplanes since the late 80's
So here are my 2 cents. Four or five cells? I gave up flying 4 cell packs years ago, I prefer 5 cell packs. Capacity, this is important, but not as important as their ability to hold voltage under a high current load, for example if you were to use a pack made up of AA cells of the max Nimh capacity of 2800mAh, in my view this would be the worst case scenario, as these cells are very high resistance and will not maintain voltage under heavy loads, if using AA sized packs I would probably only go up to the 1650mAh capacity Nimh and with 5 cells. Now if you happen to put many flights on only one or two planes you will have to monitor your battery very carefully with a loaded ESV. Whoa there, what am I saying, you always have to do that
The "wall wart" charger is a bit of a problem, since if you use 2000mAh cells with a 50mAh charger for example, to fully charge them it theoretically will take 64 hours for a full charge, and that's for 4 cells, add about 25% more time for a 5 cell pack[X(] not a good situation. The only charger on the market that is designed strictly for 16 hour timed charging of radio batteries at C/10 that I'm aware of is the Ace Digipulse which has six timed outputs that charge from 1 to 10 cells, even this unit only has a max rate of 150mA per output, fortunately two outputs can be paralleled, so that if you want to charge at 200mA rate you can set two outputs to 100mA in parallel to fully charge a 2000mAh pack in 16 hours. I know I'm outa step with the times, most are using peak detecting chargers, personally I only resort to fast charging radio batteries on a "need to" basis, like when the switch got hit on[:@] loading the ATV (airlplane transportation vehicle).
If you really have the need for high capacity in Nimh cells I would be inclined to use a pack made of physically larger cells that are normally used for powering motors in E-flight setups.
Again these are my 2 cents, others mileage may vary
Good luck,
Pete

scott282

My Feedback: (7)

Thanks for the responses –

Being that I can only fly on weekends, I’m ok with a really long charge time with the wall charger and will simply charge the batteries during the week. I never run the batteries down where it would actually take that long to charge anyway. It sounds like the 5 cell batteries are the way to go. I have the Hobbico Quick Field Charger and love it. I use it to keep my batteries charged up in between flights. I have never lost an airplane due to a low battery (knock on wood here) and I don’t intend to have it happen in the future with this new system.

Pilotpete2 - On the 5 cell batteries – are you saying I’m better off purchasing the 6.0V 1400mAh NiMH 2/3A instead of the 6.0V 2000mAh AA? I don’t get it.

I’m looking at the Tower Hobbies Tower Talk magazine and probably don’t have all the options here.

Scott.

pilotpete2

Scott,
The high capacity AA cells (long & skinny) are great in applications where the current demand is low and steady state, like in a transmitter. In the airborne receiver, particularly with digital servos momentary spikes in current demand can and will result in a momentary drop in voltage to the receiver with these cells, as they have a rather high internal resistance. 2/3 A cells can maintain the needed voltage under a heavy momentary current demand. In the good old days a momentary severe negative voltage spike would go unnoticed, but with receivers such as the Spektrum, if there is a very short term drop in voltage to the receiver, it will reboot, resulting in a fail safe lock out for about 3 seconds, not good if you're doing a low knife edge over the runway[&o]. Our old tried and true PPM receivers just kept on truckin. I fly at a very well controlled AMA field, shoot downs have not been a problem, but just recently we did have a trainer shot down, turns out a kid was trying to fly a foamie in a nearby school yard and crashed that same afternoon. The only reason this event was proven is because our El Presidente is a crossing guard, he talked to the kids with the wrecked plane and noted the channel they were on, well no surprise when 2 and 2 were put together, that the kids were on the same channel as the crashed trainer. So there is another way to look at the situation as more fliers "dump" 72Mhz we'll hold outs on 72 will have friendlier skies, I'm not so sure less of a wait for a pin sure, but what gets pawned off, may just come back to bite you[:-]
Cheers,
Pete

DadsToysBG

My Feedback: (35)

Many of the "toy" are coming out in 72. These kids may be across the street and you'll never know it. Dennis

scott282

My Feedback: (7)

Based on Pete's and Dad's comments -

I'm going with these

http://www3.towerhobbies.com/cgi-bin...?&I=LXRJT9&P=0

Scott.

RCBANDIT85

Hi there i use 2cell 7.4volt 2100mah flightpower rx lipo pack they are great

pilotpete2

That can be a very good solution too, but I hope you are also using a regulator or external BEC to bring the 8.4V (fully charged) lipo down to at least 6V.
Pete

Ed

Hey Scott, for more battery options, why don't you visit these two web sites first. And when you get to the No BS site, scroll down the left side and read their FAQ's. It should help.

http://www.hangtimes.com/

http://www.radicalrc.com/shop/index.php?cat=1&shop=1&

Both are battery specialists, and I've enjoyed excellent service from both.

Jim

RCBANDIT85

I was told there was no need for a regulator as the AR7000 can take up to 11volts and will only pull 6volts i have been using it for a few months now and had no problems (i hope its true) but i will get a regulator to be on the safe side. thanks

pilotpete2

Yes, the receiver is OK, but servos are a different story.
Pete

RCBANDIT85

ok my servos will all run on 6v i checked this out, was it true that the AR7000 will only pull 6volt?

pilotpete2

OK, no device pulls voltage, voltage pushes, devices draw or pull current. Receivers generally have a lower internal operating voltage than the voltage being supplied by the battery, there is an internal voltage regulator for the receiver circuitry, though this does not regulate the voltage on the power buss, so the servos see the full voltage of the battery.
Pete

RCBANDIT85

S#%T, thanks mate i will get a regulator today i dont want to cook my servos.