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HomeScaleAircraftScale HeliScale Helicopter Main Discussion › Century E640 > Jet Ranger Project (10S3P A123)
09-02-2013 03:45 PM  5 years agoPost 1


Elk River, MN

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Hi Folks

First new project in years. Just got my E640 into the air and I like it so far.

- NEU 1915 1.5y
- CC 110 HV - cutout @ 21 volts
- 10S3P A123
- 13 lbs
- Flight time 14 plus mins
- Slant cut main and drive gear
- Brass tubing adapter 5mm NUE to 6mm slant cut
- Stretched to 700mm
- 3300mAh receiver battery

Any ideas to get more flight time on this setup? A am using the A123 for rapid charging without removing packs. I have been using the A123 for some time now and have confidence they won't go up in flames.

Temperatures after 14 minute flight

- Motor temp = 136 degrees F
- ESC temp = 89 degrees F
- Battery temp = 78 degrees F

Seems like the power system is running with reasonable efficiency.
Plenty of collective response. Running low rotor-head speed (need to tech).


- 2 Dell DPS-500CB power supplies in series for 24 volts
- Revolectrix Cellpro PowerLab 8 (v2) 1344W Workstation
- Rapid A123 parallel charging

Once I have all testing completed it will be a Jet Ranger

I inadvertently did a redundant posting, is there a way to combine and delete the previous post?

Logo 14/24 (Agusta 109A-MKII) (MH-6 Little Bird) (OH-58A) Navy - Retired

09-02-2013 05:00 PM  5 years agoPost 2
Peter Wales

rrElite Veteran

Orlando Fl

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there is a problem with using paralleled A123 batteries which you may not be aware of, but I am half the it set my 300 C on fire.

The problem is that when an A123 battery fails, it fails short-circuit. This is fine if you only have a "1 P" pack as it will simply drop the output voltage and the helicopter will keep flying.

When you parallel them up and charge them in parallel, if one or more cells in one particular pack have got short-circuit then that pack is going to be seriously overcharged. I used to run my 47G on a 2P pack and was forever trying to find the one cell which had gone short-circuit and reduced my flying time. It was obvious one had shorted as the head speed dropped rapidly during the flight by about 100 RPM. Then I had to open up access to the batteries and probe each cell for a terminal voltage of 3.3 V. When I found one significantly less than this I had to cut it out and replace it. After doing this four or five times, I ended up replacing the batteries with liPo's.

From the looks of your helicopter you have one pack separate from the others and I am hoping that the other two are also split so that you can charge each pack separately. That way you will be able to tell which pack has gone faulty should one go bad, and you will not be stripping the entire helicopter apart just to find one faulty cell. Nor should you be using a fire extinguisher!

Peter Wales

09-02-2013 05:34 PM  5 years agoPost 3


Elk River, MN

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Hi Peter

Great information!

I may have been just very lucky with the A123s so far.

I would like to develop a monitoring strategy to avoid the issue you identified.

I currently have 2 (5s3P) A123 packs that are in series for flight. I monitor the cell voltages while charging every time using the Revolectrix PowerLab 8 software.

The two packs seem to track very similar. Maybe I should charge them separately on a periodic basis. This would show any difference in pack performance and total energy used to achieve a full charge.

The Revolectrix PowerLab 8 software also provides cell internal resistance graphs while charging.

I still have two older 5S2P packs that have been used for many years and they are still tracking each other. I have never charged without balancing.

I am also start looking at getting 2 5S 8000mAh lipo packs to experiment with.

Logo 14/24 (Agusta 109A-MKII) (MH-6 Little Bird) (OH-58A) Navy - Retired

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