carbunkle

I am trying to get my nose & total weight down so I'm wanting a small lipo that I will have spares of ready to swap out. I'm running 8 JR 8711 servos (4 used for flt controls) , a gyro, and 2 jetronic air valves via JR DSM R1221X2.4 with regulator. I fly about 7 minute flts. Anyone have any good experienced advice, as far as 2s or 3s, mah, watts , c#, mfg, etc.?

gooseF22

Twin 2100 2S packs.. could go 1800s, I wouldn't go any lower tho.. 30C minimum... fly twice, swap.. Size for one battery, for half the MAH, then double it.. thats my way.. In other words, add a second regulator.. 1 -2 ounces of insurance,, preference? Fromeco sahara or Spektrum 6007

David Gladwin

I can give you some very precise figures after flying my AW Hawk yesterday. It has 7 8711s plus 3 8411s plus 2 small digitals on nose doors, plus 3 Jetronic devices. Weatronic 12-22 reciver with 3 gyros and GPS. M
3 6 minute , airborne , flights took 1100 Ma to top up the primary battery (use an Orbit Micro Lader) which is a Thunderpower 3800 Ma pack, The standby is 2,300 Ma Hacker Lipo ma and is not normally used. Idle current on the ground is just over 1 amp. rising to around 3 amps in flight with flaps up, gear doors closed and gyros active. V short spikes at around 7 amps. (less than 1 second).

Primary battery start voltage, 8.1 ends at 7.9 v. and after 3 flights was still passing the Weatronics auto battery check (7 amps for 1 second). Batt 2, the standby, remained as expected at 8.2 v

I need to lose weight for the next JWM ( the model, well me, too, I suppose) so to reduce weight I will use a 1500 Ma primary and 1000 ma standby and charge after each flight, comfortable I the knowledge that I have a considerable reserve of battery capacity. Anyway, the Wea. telemetry will advise me if the voltage drops below a set level or has switched batteries.

Hope this helps as its REAL data not just guesswork.

Regards,

David.

Dave Wilshere

The regulator system you use has a big influence too! Some use too much capacity just regulating...

Dw

erbroens

Just say no to lipos..

Andy Aldridge

Sorry, know nothing about wiggly amps; but your Hawk David was the most realistic model I have ever seen.
The taxi, t/o and flt were superb. Well done me ol'.

David Gladwin

Thank you SO much for your kind comments , Andy, all I was doing was enjoying flying it like I was in it !

Its thanks to you guys who do the work which allows us to have so much fun at Classic jets, thank YOU all.

Regards,

David.

carbunkle

I'm going to go with these-> http://dreamworksrc.com/catalog/lipo...mah-p-869.html
I will have 4 of them 1 for rx, 1 for ecu, and 2 for spares. All can be used in either position.
And I will jump start the turbine with my big lifepo. Anyone see a problem with this plan?

kev-o

My Feedback: (1)

I use 2 a123 2300 mah packs and fly3-4 flights and top them up quick. No need to swap. I know you posted lipos but I tend to bury the packs so I like the safety of a123 chemistry leave Em in and charge.

Just my thoughts

gooseF22

Car, you will need to answer for yourself if you want to run a redundant battery/regulator.. I for one, always use two main batteries especially with a regulator.setup. you are only as good as the capacity thruput of the reg.. alot of guys fly one, alot fly two.... Its a personal choice..

Yes the spektrum 2000 works fine.. I see them on alot of planes.. but its not a high C rated pack, so it will be slower to charge, it has plenty power tho.. I would recommend a 30C or more pack, so that the pack is quicker to balance charge with a quality bal. charger at 2C..

By the way, if you investigate A123's, they are 6.6 ounces per 2300 pack, but you can put them anywhere in the model buried, and just balance charge them using an extension balance tap, or a servo lead.. again a personal choice.. but no regulator needed

I dont want to start a discussion on the merits of each, there is plenty of info in RCU.. good luck..

David, I am hoping to be able to support JWM as US helper/caller/not sure.. I look forward to seeing that hawk..

carbunkle

I got the spectrum 2000mah lipos so I have to try them out. They came with a slight charge of 7.6v, which is what the directions said they should be. I charged up 1 to 8.4v. and put it on the rx, did a sim flt for 8 mins. It dropped to 8.1v after the flt asper my onboard volt "gauge" (which is turned on with rx switch on and does not load, other than 8 servos not moving - 6 digital and 2 analog). After a 2nd sim flt it dropped to 8.0. So I am about to do a 3rd and see how much more it will drop. I'm using a 6v regulator. The volt guage onboard is before the reg. The batt directions just say no charge below 6.2. My questions now are- What should be my min volts before no more flts? And should I use my other (hand held) volt "meter" that puts a 1 amp load or a .5 amp load to check it? I believe my charger shows the total mah it puts in during each charge, so I may need to use that info in figuring no fly number/s.
Forgive my electrical ignorance and allow me more of your knowledge kind sirs.

gooseF22

You dont use voltage as a charge trigger.. you figure out how many MAH each actual flight uses, and never use more than half the capacity of the battery.. so on your flights, you have to fully charge after each flight, to determine how much the typical flight uses, then round up.. most jets use around 300-500 MAH for a 7 min flight for example, so if you are using 1 2000 pack, you get 2 or 3 flights.. if you have 2 packs, which I recommend for safety, you can fly 4 times... I never fly more than 4 times without charging ever anyway, because its easy to lose track..

FenderBean

Ions weigh less plus jets dont seem require high c ratings like 3D planes

gooseF22

Yes, thats correct, however they take alot longer to charge.. another good reason you use Hi C rated lipos or A123's are because you can charge 2+ C with them.. If you go with Ion batteries, you need a larger capacity because they take longer to charge..

Example..

Kingcat has 2X 5200 ions w regs.. usually charge one time per day total

Elan, 2x2300 A123.. charge after 4 flights, but only takes about 15 min, so can charge during fueling.. Both have same battery weight

Bandit, 2X2100 45C Lipos.. keep an extra set or pull and charge at 2C

I would not under any circumstances use a 2600 Ion by it self on a jet because its still high impedence.. A Single A123, maybe, but Im a big redundancy geek.. but a single 2600 will power a jet because I lost a battery connector once in flight. .the other one did fine.. didnt' notice it until just before shutdown..

fwiw..