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Old Nov 14, 2004, 01:40 AM
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Joined Sep 2003
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Help needed for large NiMh packs...

For use with very large motors, many battery packs are described as having 24, 30, or more cells... I need to know if these batteries are hooked up in series, i.e. 30 cells times 1.2 volts = 36.0 volts... OR are they 3 packs of 10 each for a total of 12.0 volts..., or some combination...??
I have noticed some of the medium size motors require 14 cells, could these be 2 ea 7 cell packs for a total of 8.4 Volts, but twice the amperage..??
I have never had a chance of a need to have a pack of over 8 cells (9.6 V), pretty simple stuff up to now...

I have looked the catalogs from one end to the other, and did not find the maximum voltage some of the larger brushless motors can take...I would be surprised if the large motors require 30-40 volts...

I would like to someday make a 60 size aircraft ( warbird ) and wish to know a bit more about battery packs of this maginitude...

Thank you for your time and consideration..
I realize this is probably one of the most basic questions that could be asked,
but I have to start someplace...LOL
Thanks again....
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Old Nov 14, 2004, 03:40 AM
know it all
Miami, Fl
Joined Nov 2003
2,949 Posts
if you need a 29 volt pack, then you can use two 12 cell packs wired in series.. voltage adds in series, amps add in parallel.. 2 12 cells packs wired in parallel would give you 14.5volts but the pack would be able to deliver twice the rated amps of each cell.

You can have both series or parallel packs with nimh or nicads, but they must be charged only in series. Lipos can be charged in parallel.

I use 24 cells in my large planes, two packs of 12 cells in series, I also use a single pack in smaller planes.

If I wanted I could parallel 2 12 cell packs, then I would have the twice the capacity and amps delivering ability for my smaller planes..

Parallel or series depends on you selecting high voltage or high current, and also if you speed controller is limited to a max number of cells or voltage then you have no choice but to increase amps. watts is amps times volts, so if you want to increase power one of the two has to increase.

There are also limitations of how many cells you can use, once you start going over 40 volts DC then you start increasing the risk of electrocution, so giant scale flyers will start to parallel blocks of 36 cells to increase ability to deliver amps and increase capacity of a pack.

A 36 cell pack delivering 30 amps produces as much power as an 18 cell pack delivering 60 amps.. thus you configure your packs in series or parallel to get your desired configuration.

Sermos, anderson or powerpoles are very useful connectors for reconfiguring packs.

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Last edited by hermperez; Nov 14, 2004 at 03:43 AM.
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Old Nov 14, 2004, 07:11 AM
Southern Pride
everydayflyer's Avatar
Haralson County GA. USA
Joined Oct 2004
34,848 Posts
This is perhaps a good place to start.

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Last edited by everydayflyer; Nov 14, 2004 at 07:15 AM.
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Old Nov 14, 2004, 10:51 AM
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Joined Sep 2003
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Again fellows, thank you very much for your description and the link...Most helpful...
I am sure that a good salesman, such as someone at Hobby Lobby might be able to answer some questions when that day arrives..., but til then at least I have a better basis from which to ask further questions..
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