F5J/LMR batteries for 7 cell competition - RC Groups
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Dec 20, 2003, 12:45 PM
Registered User

F5J/LMR batteries for 7 cell competition

what is the best new cell on the block for this style of competition? i am currently running a hacker with 4.4:1 gear box and a 14x9.5 prop. cells are cp1700scr at about 35 amps. ken
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Dec 20, 2003, 01:46 PM
sloping addict
Protocooler's Avatar

Sanyo HR 4/5 1950 FAUP actually rule. With those you could allow proping up to 700W (limit for the maxxon gearbox).
That's 39g / cell.

The smaller 1700 AUP cells (34g/cell) could also take it but they'll loose a good share of volts compared to the FAUP at same amps.

Another option is Lipoly (Thunder power or IRate) in 3S2P provided they fit in the fuse...

Dec 20, 2003, 02:18 PM
sloping addict
Protocooler's Avatar
Additional notes: for actual competition, Lipo are out

Speed 400: brushed, ferrite magnet 400/380 can motors using no more than 8 NiCd or NiMh cells with a maximum 60 second motor run (motor timing adjustment ok)

Seven cell: restricted to 7 NiCd or NiMh cells with a maximum 40 second motor run

Unlimited: no restrictions on motor or number of NiCd or NiMh cells with a maximum 20 second motor run
(for that one you'd need GP3300 I suppose)
Dec 20, 2003, 02:35 PM
Motorless Wing Nut
Since you are in the US, check with the contest director of any competion you are thinking of prepping for. If it is an F5J contest, the above info is fine. If, however, it is an AMA event, the rules are different.

Class B is up to 30 cells but only allows NiCDs and they must weigh less than 2oz each which leaves zapped CP1700SCR's. There probably won't be a Class A event but there might be a NEAC Sport Sailplane event that is essentially an electrified RES event for planes under 100".

Dec 20, 2003, 02:40 PM
Registered User
MikeC's Avatar
Agree with Proto.

The CP 1700s are fine for what you are doing. The FAUP 1950s will save you an ounce or so and have less resistance, they are the best of the three. The AUP 1700s will save about 3 ounces but have the highest resistance of the three batteries mentioned. I have been using the AUPs 1700s at over 60 amps this past autumn and they are still doing fine, although I get a slightly better climb rate with the heavier CP1700s. It is really a matter of how far you can see with any of these batteries launching a competitive F5J type sailplane.

With a Hacker B40 6, 7or 8L some of us are using 18X10, 17X13 or 18.5X12 props. Climb rates with these props are much better than with the 14X9.5.

For the best performance with the two NIMH batteries mentioned they should be used HOT off the charger (120+ deg f).

Dec 20, 2003, 05:05 PM
Tragic case
davidleitch's Avatar
the most powerful battery is the GP3300. Offers the most volts at a given amp level. If you want to get into the 100 amp plus range they are the way to go. In Australian 7 cell comps where each second of motor run counts a negative point, 100 amps are required.
Dec 20, 2003, 06:52 PM
Registered User
dave...i am not familiar with the NAEC res class. something new? where can i find info? thanks,ken
Dec 20, 2003, 08:24 PM
Motorless Wing Nut
Sorry, I meant NEAC. It's call 'Sport Sailplane'.


Dec 20, 2003, 11:27 PM
Registered User

NEAC is the SIG for the AMA in electrics. I'm the Pres and we are responsible for running the Nats and promoting electric competition. Go to www.electricaircraft.org for info. Or go to ezonemag/ AMA/NEAC to post questions. Or just ask me and I'll try to help. We've been around for a while, but have been very silent. I'm trying to revive it so everyone knows who we are.

Ric Vaughn
Dec 21, 2003, 01:29 AM
Electric Airplane Junkie
bhchan's Avatar

Re: F5J/LMR batteries for 7 cell competition

Originally posted by ken troxell
what is the best new cell on the block for this style of competition? i am currently running a hacker with 4.4:1 gear box and a 14x9.5 prop. cells are cp1700scr at about 35 amps. ken

Hacker What motor? And what plane set up? I have a "7 cells" set up on my Graphite, lehner motor and 8:1 gear box, turning a 23x12 prop with 7 x 2400zap, will go to GP3300. The set up pulls about 75 amp. For most of the LMR event, the capacity is not an issue, but bigger cells maintain higher voltage with high current draw. At 35 amps, CP1700 are fine for current level that you are pulling. Actually, the new motor I will be using should pulls about 90-100 amp, hopefully!

Bria, an EAJ

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