ECO 7 and LiPo Batteries

[ethomas999]

Hi all,
I'm looking for advice on LiPo batteries for the ECO 7 (Sport). I've seen the "Poly Quest 3700XP" (3 Cell 11.1V 3700 mAh LiPo Pack 6 x 1-7/8 x 7/8", 10.4 oz.) mentioned in another post, and I've found one USA-based site carrying it: http://www.hobby-lobby.com/polyquest.htm
Anyone know of other sources for this battery or have other battery recommendations?

Thanks
--ET
http://www.lexthomas.com/etheli

[ethomas999]

Hi all,
I figured out a really good solution for LiPo (Lithium Polymer) batteries on the ECO 7: Wire two or three smaller LiPo batteries in parallel. Two $28 E-Power-1800mAH-3S batteries provide lots of power; they are available here (and elsewhere):

http://www.helidirect.com/product_info.php?products_id=614

The batteries are rated at 10C, so in parallel they provide 20C, or about 36 amps of current (20C x 1800mah). Three of the $19 E-Power-1300 mAH batteries can also be used (though they provide less current). An adapter harness can be made using two or three JST-female connectors and a battery connector that mates to the heli. (I've converted my ECO 7 to use a Deans connector, which is much better.) Just solder all the red wires together and all the black wires together. See the links below for charger options.

The increase in power and agility that you get moving from the NiMH to the LiPo batteries is really quite amazing. With more power and less weight, the heli jumps right up when you hit the throttle. On top of that, the flight time is about twice as long. Once you fly the LiPos you'll never want to go back.

Once slight thing with the LiPos is that when you let off the throttle quickly the tail tends to swing out a bit. I expect this is because the specs in the Gigatronic are tuned to the weight of the heavier NiMH battery. If anyone knows how to compensate for this in the Gigatronic Control program setup, please let me know.

JST connectors with wires:
http://www.helidirect.com/product_info.php?products_id=1466

Dean connectors:
http://www.helidirect.com/product_info.php?products_id=582

AC LiPo balance charger:
http://www.helidirect.com/product_info.php?products_id=1038

DC LiPo balance charger:
http://www.helidirect.com/product_info.php?products_id=1146

Cheap but effective balance charger:
http://www.helidirect.com/product_info.php?products_id=615

I've updated my heli website with this information and a few other sections that may be of interest to ECO 7 fliers: http://www.etheli.com

Regards
--ET

[AlphaPapa]

Hi ET,

"Once you fly the LiPos you'll never want to go back." That's exactly the problem ;-)

The swing out of the tail comes most probabely from the steep throttle curve you have in hover mode. If you can (means if you have the additional switches Phase and Mode installed) please try again in flight phase Acro. There the throttle curve is much flatter and should not influence the tail that much.

Regards,
Andreas

[ethomas999]

Hi Andreas,
Thanks for that tip; I tried it and it does help. Also wanted to note, regarding LiPos:
I use the "HRPoly-X low-voltage warning device" from customidea.com to monitor the battery level to make sure that it doesn't get too low. (Draining LiPo batteries too low can damage them.) I wired a JST-female connector to the points on the E7 Powerboard where the batteries leads go in, and wired a JST-male connector to the leads of HRPoly-X device, which I attached (using velcro) just above where the boom goes into the main body of the heli. The HRPoly-X comes preconfigured with a low-voltage limit of 3.0V per cell (setting #6, 9.0V). I configured its low-voltage limit to 3.1V per cell (setting #7, 9.3V), which I found works better in that the early-warning beeping from the device happens sooner, allowing time for a non-panicky landing.
The website for the HRPoly-X is here: http://www.customidea.com

--ET
http://www.etheli.com

[mestdaght]

[ QUOTE ]
The batteries are rated at 10C, so in parallel they provide 20C, or about 36 amps of current (20C x 1800mah).

[/ QUOTE ]
I have some comment on your calculations !
You cannot make 20C out of two 10C batteries.
the correct formula 10Cx(**mAh + **mAh ) of course because the double mAh you can get the double of the current of a singe pack.
5C means -> fly at least (60/5=) 12min or you destroy your batterie
10C means fly at least 6min or destroy your batt.
20C means fly at least 3min or destroy your batt.

[Ransom]

[ QUOTE ]
I have some comment on your calculations !
You cannot make 20C out of two 10C batteries.
the correct formula 10Cx(**mAh + **mAh ) of course because the double mAh you can get the double of the current of a singe pack.
5C means -> fly at least (60/5=) 12min or you destroy your batterie
10C means fly at least 6min or destroy your batt.
20C means fly at least 3min or destroy your batt.

[/ QUOTE ]

I think I understand the 10Cx(**mAh + **mAh) part... but ya kinda lost me with the say "10C means fly at least 6min or destroy your batt."... :confused: Are you saying you must fly for 6min or you will destroy your Battery, or if you fly for more than 6min you will destroy your Battery???...:confused:

[AlphaPapa]

Hi all,

the correct statement is: 10C for a 2000mAh battery means this battery can spend 10*2 Ampere = 20 Ampere continously.

If you connect 2 of such batteries in parallel, you can draw 40 Amperes at the voltage level of one battery.

If you connect 2 of such batteries in a row, you can draw 20 Amperes with double voltage level.

Andreas

[Ransom]

Hallo Papa,

"the correct statement is: 10C for a 2000mAh battery means this battery can spend 10*2 Ampere = 20 Ampere continously"

So I assume that in a perfect world you could draw 2amp continously for 1 hour or at 10C discharge rate 20amp continously for 6 minutes before the battery was completely drained...but this is not practical in the real world due to losses as no battery that I know of is 100% efficient.

"If you connect 2 of such batteries in parallel, you can draw 40 Amperes at the voltage level of one battery."

Double the mAh capacity, but not double the 'C' discharge rate... is this correct?

"If you connect 2 of such batteries in a row, you can draw 20 Amperes with double voltage level."

(a row) as in series wired, double the nominal voltage but still at the same 'C' discharge rate... is this also correct?

Best regards,

[AlphaPapa]

Hi Ransom,

of course the world is not perfect not even for batteries ;-)
All calculations assume a perfect environment but real life is a bit different. Anyhow we should start with our calculation based on a "perfect world assumption" and than take into account that we finally can expect less.

Row and series has more or less the same meaning in German language. I'm talking about series wired of course. Batteries wired in series doubles the voltage, parallel wired doubles the current. The C factor of every single battery is not affected by the wiring. In case of parallel wiring every battery still has e.g. 10C but as you draw the current from both batteries in parallel, you can see the parallel wired batteries as one batterie with double C factor.

Best regards,
Andreas

[Ransom]

[ QUOTE ]

Row and series has more or less the same meaning in German language. I'm talking about series wired of course. Batteries wired in series doubles the voltage, parallel wired doubles the current. The C factor of every single battery is not affected by the wiring. In case of parallel wiring every battery still has e.g. 10C but as you draw the current from both batteries in parallel, you can see the parallel wired batteries as one batterie with double C factor.

[/ QUOTE ]



Yep! Makes perfect sense now that you've explained it to me... I always seem to have a booger of a time getting my head around that 'C' factor stuff and parallel wiring for some reason... :D

Kind Regards,
Ransom

[Heliman888]

Put a sock in it, Ransom.

Andreas was doing his best to be helpful, and in a foreign language at that, so quit taking the piss - try doing the same yourself.

[ QUOTE ]
I think I understand the 10Cx(**mAh + **mAh) part... but ya kinda lost me with the say "10C means fly at least 6min or destroy your batt."... Are you saying you must fly for 6min or you will destroy your Battery, or if you fly for more than 6min you will destroy your Battery???

[/ QUOTE ]

MaH stands for Milliamp per Hour - that's what the battery can deliver (Capacity). So a 2000Mah pack will theoretically deliver 2A for 1 hour, or 1A for 2 hours, etc.

The "C" part refers to the demand the heli is putting on the battery. So 10C, as in the above example, means the heli is demanding 10 times the "C"apacity, or 20 amps per hour.

The battery can deliver 20A, but not for one hour - more like 6 minutes (10C = 1/10 of the rate per hour time, or 60 minutes divided by 10).

Regards,
Sebastian

[Ransom]

"Put a sock in it, Ransom."... /ubbthreads/images/graemlins/crazy.gif Ah Geez! Do I have to...snif, sniffle, boo hoo hoo!... /ubbthreads/images/graemlins/grin.gif

"Andreas was doing his best to be helpful, and in a foreign language at that, so quit taking the piss - try doing the same yourself."... I thought Andreas did a great job of explaining it and was very helpful, and I thank him for his effort.

The quote below was in response to Mestys' post, and I was just razzing him a little bit as I really wasn't sure what he meant for certain the way he worded it... So There now!

Quote:
--------------------------------------------------------------------------------

I think I understand the 10Cx(**mAh + **mAh) part... but ya kinda lost me with the say "10C means fly at least 6min or destroy your batt."... Are you saying you must fly for 6min or you will destroy your Battery, or if you fly for more than 6min you will destroy your Battery???
--------------------------------------------------------------------------------

Best Regards

[Heliman888]

[ QUOTE ]
And this is for You!!!

http://images5.theimagehosting.com/albums/2201/raspberry.1.th.png


[/ QUOTE ]

Well, now you mention it, that was the attitude I was referring to.

However, on re-reading the posts, it appears that it was an educational experience for you, and that I mis-read the 'poking your nose' symbology as a reference to Andreas' comment about the translation for series and parallel into German. Of course these are "not" the same, in electrical terminology.

Apologies for the misinterpretation. I'm sure you're a good guy, raspberries notwithstanding.

Kind Regards,
Sebastian


Anyway,

[Ransom]

ROFL...Hey, No Worries Mate... /ubbthreads/images/graemlins/grin.gif

I'm sure your one of the good guys too!

Best regards,