Newbie - Frying my Batt with Endoplasma. Help? - RC Groups
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Jun 20, 2003, 08:58 AM
Registered User

Newbie - Frying my Batt with Endoplasma. Help?


I'm new at the electric game, and am trying to build a PBF using an Endoplasma motor, geared 3:1 (GD-600) with a 12x8 APC. Currently using 8 cell 1350 NiMH pack. Here's the rub. When testing this setup, running the motor full out, the battery pack became very hot, very quickly. Seems I may be trying to pull too much current (I guess). Too much prop? Perhaps go to an 11x7? Not enough cells? Change gearing? (I do realize that prop unloading in air might help with load)

Can someone give me a quick tutorial? I'll be looking into getting Motocalc to learn, but I just don't want to fry things.

Thanks for any help.
Gray
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Jun 20, 2003, 09:26 AM
Fixed Wing Fanatic
Jim Walker's Avatar
You need to see how many amps you are pulling. They sell some reasonably priced clamp on amp meters or the best way would be with an Astro Flight super watt meter. Another way would be to simulate your setup in motocalc. That should give you a ball park idea on your amp draw and what your cells are capable of.

Off the top of my head, I would say you are wayyy under geared/over propped with that setup. I was swinging an 11-7 on ten sub C cells and pulling 30 amps with 3.8:1 gearing. How many cells are you running? What are the physical dimensions of your cells? I'm not familiar with your 1350 nimh's, but I'm pretty sure that the smallest cell that will handle an endoplasma's current needs are the CP1700 nicads or the 5/4FAUP 1950 nimh's. If your cells are not equal to these cells I've mentioned then for sure you are pushing them way past their limits and toasting the poor things. Once again, at least download motocalc for a free trial and get an idea of what's happening.
Jun 20, 2003, 11:34 AM
Rehab is for quitters
LuckyArmpit's Avatar
Those nimh batts you have won't be able to handle the amps that the endo will pull. You need to run SC or SCR batts. The endo likes 10 cells. So, I would run 1900 or 1700 SC or SCR batt packs. The 12x8 prop is fine as I have (3) models running with 3 to 1 gearing and 12x8 folding props.

Dave...
Jun 20, 2003, 03:51 PM
Registered User
You can't just use any old rechargeable cell and expect it to work. Every cell has a limit as to how much current it can produce. In general, the larger the cell, the more current it can produce. Be wary of AA NiMH cells intended for digital cameras and children's toys. These are designed for maximum CAPACITY, not power, and have extremely low current producing capability.

In other words, don't use crap cells then ask why they're getting really hot...

At 3:1 gearing on 8 cells with a 12x8 prop, Motocalc says 48 Amps. That's too high. The motor will burn up in a few minutes.
Jun 20, 2003, 05:28 PM
Registered User
Thanks to all for your assist. Clearly I need to put my head in a book and learn something!!!
Gray
Jun 21, 2003, 08:05 AM
AMA 697691 / FAA 13675
Hi Gray,

Check out the Endoplasma setup on my Graupner Monsun Trainer at the bottom of my Trainers page.

Notice that my gear ratio is higher than yours for even an 11x7 prop and I am drawing 35amps on 10 cells. This will be less for 8 cells but the Endoplasma can handle short bursts up to 40amps.

To spin a 12x8 prop, you need the so-called "E3D" setup from Gary Wright and the 10T pinion gear. Do a search here for E3D for more information.

Finally, pick a cell that can deliver 40amps like the CP1700, CP2400, or HR-SC2600.

Good luck and welcome to the E-Zone!
Last edited by Greg Covey; Jun 21, 2003 at 08:08 AM.
Jun 21, 2003, 05:45 PM
Registered User
Take a look at building your own just test it 200 times
on nicads voltage above the others.
http://www.national.com/catalog/AnalogRegulators.html
Jun 21, 2003, 06:39 PM
Addicted to Feigao...
Kidknight's Avatar
I'm suprised nobody has mentioned the HR-4/5FAUP cells yet. You can get them atedogfight. They are supposed to be very good cells, even the pylon guys are using these things. They say that they break them in at 70amps, weeding out the bad apples(not my words, just some other guys). Most people think 40amps is the limit to these guys.

Like everyone else said, get yourself an Astro Wattmeter. The best 60 bucks I have spent yet.
Jun 21, 2003, 07:07 PM
Registered User
Bill Glover's Avatar
Quote:
Originally posted by mkirsch1
At 3:1 gearing on 8 cells with a 12x8 prop, Motocalc says 48 Amps. That's too high. The motor will burn up in a few minutes.
I'm running my Endo on a 2.8:1 gearbox (pretty close to 3:1) and 8x2400 cells. A brief test with an Aeronaut 10x8 folder gave 45A static, so IMO a 12x8 would be way too much. I fly with a 10x6, that pulls 37A.