Lumenier RB2205C-12 2400KV SKITZO Ceramic Bearing Motor
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Old Apr 21, 2006, 10:08 AM
taekwondo is offline
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BEC 4s1p made from 2 cell packs


Everyone:

I have a question regarding using BEC on a 4s1p made from 2 cell packs. I purchased 4 two cell packs with the intention of making 2 4s1p packs. I later found out I needed to use a BEC so as to not burn out the receiver because of the higher voltage. Question is, which BEC would you guys recommend, where can I get it and do they all work basically the same? I'm planning on using this in my larger planes, I have a electric telemaster with 6' wingspan and I am using an axi 2826-12 with an apc sf 13" x 6.5 pitch prop. I don't have access to moto calc. Thanks for your help in advance.

Henry
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Old Apr 21, 2006, 10:10 AM
taekwondo is offline
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Sorry, I forgot to mention. Obviously, I will be wiring them in series.
Old Apr 21, 2006, 11:41 AM
dave morris is offline
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Ubec and Parkbec are a couple. Ubec is made by Koolflight, and the parkbec is dimension engineering.

One thing to watch out for is the chance for interference from the switching BEC, just be sure a do a very good range check, if if fails you can try rearanging the wireing and placement of the BEC.

BTW your Rx will not burn out, but the BEC built into the ESC can.

Besure to disable the built in BEC before using an external power source.
Old Apr 21, 2006, 11:42 AM
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opps Charles beat me to it.
Old Apr 21, 2006, 12:26 PM
taekwondo is offline
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Charles:

Thanks for the info. Based on what I read here briefly,

If you are using a speed controller with a built-in BEC, it will very likely have only a limited ability to supply power to your receive and servos without overheating, if you have a relatively high-voltage battery pack or have high servo loads. Consult the speed controller specifications to determine what the stated recommendations or limitations are. In general, if you are using a 4S Lithium pack, or more than a 12-cell Nickel based pack, you should consider using the UBER-BEC

The ubec would be the way to go if I decide on 4s1p. But really, in thinking about it, I should find out if it is at all possible to use the batts in a 2s2p configuration. They are Polyquest 12c 3100 mah, capable of about 36 amps draw each. If I'm not mistaken, this means 72 amps together in the 2s2p configuration. Do you have a link to pcalc or motor calc or some free software so I can check if this would work or do you know yourself?

The park bec said it wouldn't work on 2s so that's out. I flew this plane twice on the 3s2p configuration at 1/2 power with a friends batteries. If I used a 2s2p configuration, would I use a bigger prop? Thanks for your help in this matter.

Kindest regards,
Henry
Old Apr 21, 2006, 12:29 PM
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Quote:
Originally Posted by dave morris
Ubec and Parkbec are a couple. Ubec is made by Koolflight, and the parkbec is dimension engineering.

One thing to watch out for is the chance for interference from the switching BEC, just be sure a do a very good range check, if if fails you can try rearanging the wireing and placement of the BEC.

BTW your Rx will not burn out, but the BEC built into the ESC can.

Besure to disable the built in BEC before using an external power source.
Dave:

Thanks for the information. You said 'Besure to disable the built in BEC before using an external power source.' how do you disable it, with a software programming code? Sounds like the bec/park bec methods are going to be complicated for me. I just ordered 2 3s1p batts which I can use in the 3s2p configuration and utilize these batts else where or if I can get it to work, then I will have a 4s1p configuration possible as well. Thanks for your help.
Henry
Old Apr 21, 2006, 12:34 PM
ImaBiggles is offline
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Quote:
Originally Posted by taekwondo
Dave:

Thanks for the information. You said 'Besure to disable the built in BEC before using an external power source.' how do you disable it, with a software programming code? Sounds like the bec/park bec methods are going to be complicated for me. I just ordered 2 3s1p batts which I can use in the 3s2p configuration and utilize these batts else where or if I can get it to work, then I will have a 4s1p configuration possible as well. Thanks for your help.
Henry
Pull the red wire out of the connector going to the RX and tape/shrink wrap it.
Old Apr 21, 2006, 12:46 PM
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https://www.rcgroups.com/forums/showthread.php?t=326226

Start reading at post #90. It's tough to beat a $1.00 UBEC

Brad
Old Apr 21, 2006, 01:41 PM
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Dimension Engineering
Quote:
Originally Posted by taekwondo
Dave:

Thanks for the information. You said 'Besure to disable the built in BEC before using an external power source.' how do you disable it, with a software programming code? Sounds like the bec/park bec methods are going to be complicated for me. I just ordered 2 3s1p batts which I can use in the 3s2p configuration and utilize these batts else where or if I can get it to work, then I will have a 4s1p configuration possible as well. Thanks for your help.
Henry

A parkBEC disables the ESC BEC automatically if you follow the installation instructions. It installs inline between the ESC and RX.

On 2s you almost certainly don't need a switching BEC. The heat generated by the linear BEC in your speed control is a function of the difference between the input and output voltage. On 2s, thats only going to be about 2V. On 3s, its about 5V difference, so 2.5X the heat. With 4s, its more like 8 volts, so 4X the heat.


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