catspaw

Has anyone converted their "stock" hobby lobby P-38 to li-poly batteries? I'm talking about speed 400's (6 volt version, I think I've got), and Jeti 30 amp speed control that they sell as a package with the 1900mah ni-cad battery.

Should I get a 7.4 volt, or can this setup handle the 11.1 volts? (I don't think so, but I'm not gonna experiment either!).

John

Greg Covey

Using either a 2s or 3s pack on the P-38 is a close call. In part, it would depend on wheather or not you feel it needs a little extra power for take-offs and loops. Also, can you make use of throttle management so that full power is used very little on the first half of the flight.

I would design a pack for at least 20amps continuous current delivery. A 2s2p configuration of Kokam 1500 cells would work well here and provide 50% more flight time than the stock 1900SCR pack.

Good luck!

catspaw

Greg,
I was thinking of one of those 2200ma packs, or something in that neighborhood. The only li-poly capable charger I have is the Triton, so I'm "limited" to 2.5 amp charging rate, for now anyway.
With each motor drawing 10 amps, the 2200 would be enough, but if I go with 3 cells, I'm drawing more amps...hmmm...I think I gotta go reread that article in MA about li-poly batteries and see what he says about discharge rates.

I note that the 2s 2200 pack is $39 from batteries America (have not looked around for other prices yet), which is cheaper than the 1900ma nicade pack from HL.

John

Peter Khor

My Feedback: (4)

Remember it's a tight fit in there (the JandR P-38), some LiPo's will barely fit; the ThunderPower 2100's are a natural fit, 2s2p or if you change out to Long Can 400's, you should be able to go 3s2p and swing ~5.5x4.4 props.

Matt Kirsch

My Feedback: (21)

The 2200mAh Tanic pack, which is what I assume you're thinking about, won't fit in the P-38. I do believe the Kokam 1500s will.

A 2S pack of Kokam 1500s is a steal right now. Low price is $35 on a Kokam factory pack, and I believe Troy at Bishop Power Products sells his own house-built packs for $33. Two in parallel will take about an hour and a half to charge on the Triton, but for 10-15 minute flights... I wouldn't even worry about it. You'll need 90 minutes to calm down

catspaw

I decided to order a couple of Kokam 1500 packs. I'll probably have to shift some stuff forward to get the balance right.

John

Peter Khor

My Feedback: (4)

John, have you had a chance to try out the packs yet? iirc the 1500 packs are a little wide, and getting even a Sub-C pack into the P-38 fuze is tight ...

catspaw

Peter,
I've been on vacation this past week, and they arrived while I was gone. I'll get the connectors soldered on, a parallel harness made, then charge em up, and see how they fit. I'll also want to make a tow hook and block, and move stuff around to get the balance. Whew!

'course, I'll probably just stick them in there just to test fit first.

John

catspaw

Trail fitted the kokam 1500 packs. Dang, there is LOADS of room. I could have gone with the larger packs after all.

John

Peter Khor

My Feedback: (4)

Thanks for the update ... now how about a flight report? (fwiw I've only flown one with S400 and 8 cell CP1700, loads of fun!).

orectolobus

John,

I have a scratch built Ryan P38 with two 6v speed 400's and would also like to get some lipos
for it. I am very interested in hearing how your flys so I would have a good report of success
before buying a couple 2s packs.



Any report appreciated.

Terry

Matt Kirsch

My Feedback: (21)

2S2P Kokam 1500s, for sure.

Jason W M

My Feedback: (6)

I really love those Ryans P-38s! Ive wanted to build one for years, but never got around to it. Will you custom build another? Just name a price

Your Ryan P-38s are begging for some of the new Thunder Power 12C 2100s. These feature the same narrow footprint that made the current 2100s so desireable in many applications (same width as 2/3 sub A packs like Sanyo 500AR/600AE/HeCell/Kan), but with double the discharge capability! A 2S pack weighs only 3 ounces with 2100 mAh. Initial tests have shown the voltage is on par or better than most 7 cell packs which means theyll be a great alternative power pack for 6v Speed 400 motors. I plan to test some of the new 2100s in my 6v 400 powered MicroJet next week! Testing so far using mostly 3S packs and larger brushless motors has proven very impressive (21-25 amps continuous on 2100 mAh cells!).

These new cells/packs will be available next month. You can call and pre-order some of the new packs now directly from TP:

(702) 228-8883

These would also be a perfect fit in the Hobby Lobby P-38 (about the same weight as Kokam 1500s, but with 40% more capacity and higher voltage under load)!