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After only one week waiting for the order delivery (thanks David for support), my new flightpower lipo packs are there.

My selection is 3s 1P 3700 EVO 20.

Main characteristics are :

Nominal voltage11.1 V

Nominal Capacity 3700 mA

Max. constant current: 74 A

Max. Peak current 111 A

Size (mm): 48 x 22 x 152

weight : 300 gr

As you can see, building of the packs is really well done. Batteries are protected on each extremity by additionnal material and the complete pack is reinforced by a gold/brown colored armed adhesif . All is then packed in a thermoretractable plastic cover.

Only one point that looks no so good to me, the batteries are sticked together and then, there's no space in between for cooling. Lets see later if this has an impact on performance (my main concern is cell unbalancing during discharge as the middle one will get higher temp. than the others).

Packs are delivered with 10 cm wires with no connectors on the extremity (each user can then select the appropriate connector for his application).

In my case, i'm using only 4mm PK gold connectors.

Good idea, packs are delivered with already wired balancing connector.

Bad news, the connector is specific to Flightpower. I'll need to build an adapter to connect to my balancing system.

This is not difficult to do but user must take care: Usually, there's only one Red wire (positive of the pack) and all the other wires for balancing are black. With Flightpower packs, there's only one Black wire (Minus of the pack) and all the others are Red.

After checking with a multimeter, it appears that all wires are connected in the order of the cells. Last red wire located at the opposite side compare to the black one is the positive (+) of the pack.

PK connectors being now soldered, it is time to jump to serious things:

Checking of the balancing of the batteries packs directly after delivery

Pack 1: 3.852 Volt, 3.851 Volt et 3.851 Volt =>Perfect !

Pack 2: 3.851 Volt, 3.850 Volt et 3.851 Volt =>again perfect !

I'll be able to pass on a complete charge/discharge without having to balance the pack before (thank you Flightpower for saved time).

Before that, let's verify the security instructions of the manufacturer and especially the limits not to exceed. Here, no risk to loose instructions, it is sticked inside the pack.

Min. low level voltage by cell: 3 Volt

Max Voltage by cell : 4.25 Volt

After first charge on separated packs, a 'slow' discharge (1.75 A) is made to verify the complete pack and the real battery capacity (this time discharge is made on both packs in series).

For security reason, low voltage limit is fixed to 3.15 volt /cell (in case of unbalancing during discharge).

Result: 3682 mA . This is perfectly in line with the announced capacity (the low voltage stop level being higher than the real pack limit).

Few minutes after discharge was completed, Cells were giving following voltages:

3.305, 3.306, 3.305, 3.312, 3.310, 3.314.

The differences in values are due to the two packs that have been charged on a different charger (time saving). Each packs has good balancing value anyway.

Let's charge the batteries packs again and go to real environment tests...

EVO 20 packs have been tested on a 'Boxed' Logo 10 (1st flight of latest realease with +/- 12 ° Pitch) and connected as a 6S pack.

A special support made of 2mm Carbone plate has been prepared. The packs are attaches to this mounting platform via 3M dual lock strips (heavy duty Velcro).

This solution has the advantage of allowing fresh air to flow around the packs (It is necessary to prepare in advance next hot summer time).

Current winter température being only 3°C , the lipo packs should normally have problem to give all their power.... but even in this case ....

Video

As you can see in the video, power is already there.

In the recorded flight measurement; we can see following points:

Max. peak power used : 1157.48 Watt ( 54.87 Amp. under 20.02 Volts after about 4 mn flight).

Taking into account the very low ambiant temperature, (about 4°C during the flight) , it is a very impressive result. It gives 3.336 Volts / Cell under 15C !

For comparision, a flight the next day with another logo equiped with Kokam 3200 8S Lipo gave 3.227 Volts /Cell under only 41 Amp. after 4mn flight.

EVO 20 batteries gave 3.425 Volt/ Cell under 41Amp. after about 4 minutes flight.

Another réference to show the impact of ambiant temperature: a X-400 helicopter with Align 2000 18C lipo gave under 17 Amp. a voltage of 2.8 volt/cell instead of 3.2 /cell under normal conditions !

Average pack voltage in Statio. is about 22.6 volts under 18 Amperes (4.9 C). It is a very good 3.76 volts/cell..

A second flight has been realised the day after and shown exactly same excellent results.

I'm now waiting for higher ambiant temp. to get the additionnal power... But it is already really giving a lot.

Soon, new measurements will be made on new ordered 3700 Flightpower packs. Thanks to the power i can get from them, i've decide to use only those packs in my Logo.

That's all folks...

PS: In case of question, feel free to contact me directly :bruno.bosso@free.fr

LIPO Packs Review Bruno B. Déc 2005