Thread: Build Log The Flying Eye
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Old Dec 27, 2013, 04:57 AM
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Australia, NSW, Avoca Beach
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Turnigy nano-tech 300mah 45-90C batteries

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Carrying a camera is already a big task for such a small frame, lets keep the battery as light as possible. The 300mah 45-90C nano-techs have the most power in the sub-10g class to date (end 2013), and HK sells them for less than $3 (or less than $1 if you are in Australia).

I do the following to get the most out of these cells:

I set a counter on the transmitter: Without payload to 4:30min, with ~10g camera: 3:00min. I want the remaining voltage to be 3.7-3.8V. There is still a decent amount of lift available at that voltage, but a drop in performance is noticeable, and recover maneuvers are getting more difficult.
3.7-3.8V is a safe storage voltage, so I dont need to charge packs after flying, potentially for weeks.
If all packs from a flying session are discharged to the same voltage, they can be parallel charged at the same time without prior balancing.

Store them at 3.7-3.8V. Storing LiPos fully charged (4.2V) or fully discharged (3.0V) can shorten their life.
I made a habit of storing the majority of my packs at 3.7V, and only have a few ready to fly. When I then start flying, I put more packs on charge.

If you care about your batteries, throw away those USP-LiPo chargers. They are bad! Get a quality charger!
requirements to charge 8 300mah flight packs in parrellel at 2C: (1S) 3.7V, 4.8A
requirements to charge the 9XR battery pack at 1C: 3S (11.1V), 2.2A
Most hobby chargers will do that, you dont need to get a high end one.

I am using a Duratrax ICE for charging my batteries. Its not charging them better than any other good charger, but it has the following advantages:
- up to 10A discharge rate (the whole housing is a massive heatsink). I use this a lot to test battery packs. The charger shows the voltage to what each pack a battery drops when drawing the given current, and it measures the discharged mah. Very useful to weed out bad batteries. Some of these 1S packs dont last long. Battery testing = more consistent flight experience.
- a motor test program. This basically applies a given voltage to the outputs, and displays the drawn current. This is very useful to test and weed out bad motors.

Charge them as slow as possible! 1C is usually a very conservative charge rate. If you have a 1Ah battery pack, a 1C charger rate is 1A. The 300mah 45C's are rated at 2C max charge, e.g. 0.6A
I prefer to charge them at no more than 1C, e.g. 0.3A. A 1C charge from 3.7V to full takes about an hour. To have a non-stop battery supply, I use a parallel charging adapter for 8 battery packs.

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8x300mah, that is a total capacity of 2400mah. 2.4A charge current corresponds to 1C.
With 2 sets of 8 packs, you can get a constant supply of 8 packs per hour with a conservative 1C charge rate. You can safely double the rate. However, if you plan ahead, charge your packs gentler and they will last longer.
Maker sure all packs have the same voltage when connecting them to the parallel charging lead. Connecting packs with big voltage differences might damage them. I havent seen problem when connecting pack with +-0.1V.
I use an adapter to connect 6 single cell packs to a 6S balancer. This allows a quick voltage check for multiple packs, but also pre-charge-balancing if needed.
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Last edited by benedikt; Jan 03, 2014 at 04:38 AM.
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