7XL 0r 9L with BK 9920 on LIPO? - Page 3 - RC-Monster Forums

squeeforever · 08.15.2006, 09:30 PM

I don't think you will need to change your motor at all.

coolhandcountry · 08.16.2006, 08:36 AM

If you change motors as well as the batts. How do you know what makes more power? If the 9L don't work out put the 7xl on. I think it do better on heat issues.

standard_63 · 08.16.2006, 09:52 AM

If you're not going to use lipos, 14 cells, 9920, 7XL will be perfect. I do use a UBEC, and geared so the motor only hits 155f I can run for about 6-7 minutes before I thermal. Given the abuse my ESC has seen I do not think this is bad. The problem seems to be the constant high current and long runtimes make things heat up too much...

Serum · 08.16.2006, 11:30 AM

the 7XL on my 9920 doesn't thermal at all with 14 cells.

coolhandcountry · 08.16.2006, 02:19 PM

I had a 7xl on a 18.97 with 18 cells on it. I could run a whole pack with no thermal. The motor would be hot.

standard_63 · 08.16.2006, 02:24 PM

I know, I think 14 cells is a good match for 9920 and 7XL. I think though that 4s lipo is more like 16 cells. I know they are 14.8v, but that is almost at no charge. Fully charged pack seems to be more like 16.8v? And it puts out higher constant voltage than nimh cells, nimhs start to drop off very quickly and loose a lot of punch into a run, where lipos run strong till they dump.
More avaliable current over longer duration equals more heat for longer time.

I think I've weakend my 9920 anyway by thermalling it really hard when I first got it trying to run a 6XL, I shorted it once too and metled the shrink off it! I didn't even think it would work anymore, so much smoke came out. Maybe that's why I have thermalling problems?

squeeforever · 08.16.2006, 04:34 PM

Yes. It sounds like you fried a few fets and thats why it thermals. 4S LiPo is more like 14 cells actually. Hippie, don't worry, you shouldn't have ANY problems with 4S LiPo and a 7XL if geared correctly.

rchippie · 08.16.2006, 09:01 PM

Quote:

Originally Posted by squeeforever

Yes. It sounds like you fried a few fets and thats why it thermals. 4S LiPo is more like 14 cells actually. Hippie, don't worry, you shouldn't have ANY problems with 4S LiPo and a 7XL if geared correctly.

Squee right now im geared with a 12-51 mod 1 setup with a 9L on my EVO. My racebomb has a 16-51 mod 1 setup with UE diffs. On my EVO i have got 12 minutes of runtime in a race on 14 3300's, before i broke & still had 5 minutes of battery left when i dumped them on my integy 30 amp dumper. I have'nt raced my RACEBOMB yet. I just got offered a deal on some NIMH cells. My buddy jeremy (BOMB PROOF PRODUCTS partner) offerd me 40 IB 3600 cells for $100.00. They are brand new the only time they were used was at monster maddness this year. They have maybe 2 or 3 runs per pack.

coolhandcountry · 08.16.2006, 09:15 PM

That is a good deal. Hard to pass it up. Deals like that it is hard to go lipo.

rchippie · 08.16.2006, 09:23 PM

Quote:

Originally Posted by coolhandcountry

That is a good deal. Hard to pass it up. Deals like that it is hard to go lipo.

Leroy i think thats agood deal also. I know they were built right because i built 2 of the packs for him . 20 of the cells are promatch & 20 of the cells are smc.