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Sep 21, 2015, 02:23 PM
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Choosing capacity for lipo receiver pack


I am starting the assembly of a Hangar 9 Valiant, weight will be ~ 8 kg. I am in doubt which receiver pack to choose. Going for redundancy so two packs, a Jeti Max BEC 12A and two leads from BEC to receiver. Servo's will be Savox SC-0254MG servo's (7 pcs).

Hangar 9 recommends a 2200 - 3000 LiFe pack, but I want to go with regular lipo's. Since I also have added a BEC and since I am going to use two packs, I might save some weight on the capacity, but I want to be able to fly at least 4 times before I have to recharge the receiver packs, preferably 6.

Options:
- Turnigy nano-tech 2000 mAh 2S1P 20C receiver pack = light but maybe too small in capacity
- Turnigy nano-tech 2200 mAh 2S1P 25C regular lipo = heavier, little more capacity, but also thicker gauge wire
- Turnigy nano-tech 3000 mAh 2S2P 20C receiver pack = heaviest, most capacity, two separate discharge leads..?

I'd rather go with two 2000 mAh packs if going for the weight and size, but they feel a bit small too (capacity-wise). The 3000 mAh packs are definitely adequate, but heavier and.. what's up with the two discharge leads? What is the intended use for them and can I just add the red and black wires in pairs and solder them to one connector? And what's the advantage in going for a receiver type pack? Weight? Because the wires aren't as thick, but I will replace the connector anyhow to suit my default connector type and charge leads.

What would you choose?
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Sep 21, 2015, 03:29 PM
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tacx's Avatar
Why would you need 3000 to 4000 mah for just a receiver pack ??

Or, is this battery supplying more than just a RX ?
Sep 21, 2015, 03:55 PM
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It will supply both the receiver and the servo's. Hangar 9 recommends 2200 to 3000 and I am in doubt whether to go with a 2000 or 3000 receiver pack or with a regular lipo (higher gauge wire and in between other options regarding capacity). Don't need 4000 indeed.

(The two packs I mentioned will be redundant, not parallel or series!)
Sep 21, 2015, 07:32 PM
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So you are going with two batteries with one bec? Not very redundant. Why not use Hv servos and no bec? If you have servos which are not Hv rated use life batteries. Two 2000mah batteries would be plenty. That is 33% more than the recommended battery.
Sep 22, 2015, 01:55 AM
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I think why using a BEC is a whole different topic, but I would rather use lipo instead of life, I do not have HV rated servo's and I like the fact that it can switch between packs if one fails. I agree that the bec is a single point of failure, but it has two input leads and two outputs going to the RX, so all leads are redundant and it is a brand I thrust, high quality stuff (jeti). It also indicates the battery state and it lets me regulate output voltage.

You say 2000 mah is plenty and 33% more than recommended. Mind that in my setup the batteries are redundant so you cannot add the milli amps into one figure. Or do you mean a different recommendation?

Guess my question should be, without all the other fuzz around it: would 2000 mAh be enough for a 8 kg 30cc size plane with 7 digital servo's?

And question two: what's up with the duplicate leads on the rx battery from Turnigy?
Sep 22, 2015, 09:38 AM
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Quote:
Originally Posted by roberthabraken
I think why using a BEC is a whole different topic, but I would rather use lipo instead of life, I do not have HV rated servo's and I like the fact that it can switch between packs if one fails. I agree that the bec is a single point of failure, but it has two input leads and two outputs going to the RX, so all leads are redundant and it is a brand I thrust, high quality stuff (jeti). It also indicates the battery state and it lets me regulate output voltage.

You say 2000 mah is plenty and 33% more than recommended. Mind that in my setup the batteries are redundant so you cannot add the milli amps into one figure. Or do you mean a different recommendation?

Guess my question should be, without all the other fuzz around it: would 2000 mAh be enough for a 8 kg 30cc size plane with 7 digital servo's?

And question two: what's up with the duplicate leads on the rx battery from Turnigy?
For near bullet proof receiver power on 30 CC gassers, my club members are using a pair of 2S1P 2500 May A123s, each with their own switch and each with their own connection to the receiver. No regulator is required. Simple, and it works.
Sep 22, 2015, 11:46 AM
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Originally Posted by vollrathd
For near bullet proof receiver power on 30 CC gassers, my club members are using a pair of 2S1P 2500 May A123s, each with their own switch and each with their own connection to the receiver. No regulator is required. Simple, and it works.
Sounds great, but not applicable for me. Thanks though! Too bad I cannot find a 2500 mAh battery in the series I'm looking, that would pretty much solve the dilemma between 2000 and 3000
Sep 22, 2015, 01:29 PM
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vollrathd's Avatar
Quote:
Originally Posted by roberthabraken
Sounds great, but not applicable for me. Thanks though! Too bad I cannot find a 2500 mAh battery in the series I'm looking, that would pretty much solve the dilemma between 2000 and 3000
Don't know where you are located. Tower Hobbies has several 2500 Mah LiPo receiver batteries.

And as noted above, those A123's are also 2500 Mah.
Sep 22, 2015, 05:27 PM
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Quote:
Originally Posted by vollrathd
Don't know where you are located. Tower Hobbies has several 2500 Mah LiPo receiver batteries.

And as noted above, those A123's are also 2500 Mah.
Located in the Netherlands, Europe. I can order some products at TH but not all, not sure about lipos. Found a good one though, from ThunderPower, 2700 mAh, will look for something like that around here.
Sep 22, 2015, 06:28 PM
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Pretty sure both batteries are being used to power the plane. If one fails the other takes the full load. You don't fly on battery A and battery B is just along for the ride just in case something happens.

The plane is advertised as basically a 30cc high wing trainer. It would be fine weight wise with 2x 3000mah receiver packs.
Sep 22, 2015, 06:47 PM
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Also there is no reason to limit yourself to rx batteries. You can use any 2s pack. Rx packs are usually low c rated and lighter than other "flight" packs. The extra connectors are typically servo connectors rated at maybe 5amps. The batteries are capable of much more so you can double up. The LIFE brand from towerhobbies has 4 connectors. Two servos, one high power dean's type and the balance connector. I started using the two servo leads with dual switches and fast charge through the deans connector and balance port.
Sep 23, 2015, 01:16 AM
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Quote:
Originally Posted by lrb75
Pretty sure both batteries are being used to power the plane. If one fails the other takes the full load. You don't fly on battery A and battery B is just along for the ride just in case something happens.

The plane is advertised as basically a 30cc high wing trainer. It would be fine weight wise with 2x 3000mah receiver packs.
I think you are right about that indeed, but the instructions do not explicitely mention that (or I missed it). So it is a backup but not a cold one. That's even better because then the consumption out of one pack is lower, so although it could carry the weight, two 2000 packs would be more than enough in that case. Thanks!

Quote:
Originally Posted by lrb75
Also there is no reason to limit yourself to rx batteries. You can use any 2s pack. Rx packs are usually low c rated and lighter than other "flight" packs. The extra connectors are typically servo connectors rated at maybe 5amps. The batteries are capable of much more so you can double up. The LIFE brand from towerhobbies has 4 connectors. Two servos, one high power dean's type and the balance connector. I started using the two servo leads with dual switches and fast charge through the deans connector and balance port.
Thanks, good point, that increases the number of options.
Mar 17, 2019, 05:05 PM
Still diggin' holes...
You don't need a lot of battery in a high wing trainer... You'd have to fly pretty long to consume 200mAh in one flight.

So a 2000mAh pack will probably last longer than you care to fly on sunny afternoon.
Mar 18, 2019, 03:12 AM
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Quote:
Originally Posted by Cometlover
You don't need a lot of battery in a high wing trainer... You'd have to fly pretty long to consume 200mAh in one flight.

So a 2000mAh pack will probably last longer than you care to fly on sunny afternoon.
Thanks for your reply Cometlover. But the thread is close to 4 years old and I'm flying this plane for a while now, so I'm good ;-). Nice time to get back and add my experience to this thread.

I eventually chose two of these: Hacker - 2S 2400mAh, controlled by a JETI MAXBEC2 12A (two packs for safety / failover, not for capacity).

The Valiant isn't exactly a high wing trainer though, of course being large and having a high wing is easier to fly, but it's not trainer-like in the setup (no dihedral, and power, lots of power with the Power 160 in it). Please note that this plane is 8,5 kg with a 275 cm span. It's more like a very big high wing acrobat. Goes straight up on full throttle. Hence the digital metal gear servo's. It only has 7 of them, but that influences the required power most (note that this thread is ONLY about the receiver battery). So yeah, your estimate of 200mAh isn't far off, I'm actually using ~ 225 - 250 mAh per flight and can fly 7 times without hitting the safe bottom level of 30% battery charge. One flight roughly takes 15 min. I tend to fly somewhere in between 2 to 5 times on an afternoon, so it suffices quite well. Wouldn't go any lower though.
Last edited by roberthabraken; Mar 18, 2019 at 03:18 AM.


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