Flip and Fly

I will be using two Hitec receivers, and 3 5955s and 2 5945s on the control surfaces of my next giant project. I am using two Expert PRO 2700 Sanyo Ni-MH batteries. Should I be concerned on the ability of the 2700's to handle the current loads, I have heard that the 2700 NiMHs cells may not be capable of high discharge rates.

Any one using a similar setup.

Thanks.

JoeAirPort

My Feedback: (41)

Try the NoBS 1950 FAUP NiMh. The pack has a super high discharge rate (40 amps) and low internal resistance (4 milli ohms). The best NiMh batteries out there IMO. Hangtime hobbies has them.

Nogyro

My Feedback: (10)

I'm using one 5 cell 1950 FAUP NiMH pack with 2 leads and 2 switches in my 28% WH Extra. 5-5945's and one std on throttle. No problems at all. Great pack.

3D Joy

I also use this pack at 6V. I use 2 of them directly into the single receive for my 33% Extra. These cells have an internal resistance of 4.5 uohms. From your 2 receiver setup I think you will use 2 batteries so just make sure the cells in your packs have NO MORE than, say 6-7 uohms. If you use only 1 pack, then you have no choice of having the least internal resistance pack you can find.

In my setup, I use 7 coreless digitals including 1 5955 and also 2 coreless analogs for the engine. Works great!

Flip and Fly

Thanks for all the replys.

Joe AirPort and Nogyro,

where can I get the packs from. Do you have a E-mail address for Hang Time Hobbies. I have never heard of those packs, anyway I already have the new Expert 2700 packs so will give them a try.

Hi 3D Joy,

Yes I am using 2 packs, this is all new to me, how do I check the uohms in my packs, with a uohm meter! I need to get up to speed on all this stuff []

Thanks all.

Rcpilot

My Feedback: (78)

Radical RC has high discharge MH batteries.

www.radicalrc.com

I bought some of them for my next project. They are 6V and 1100mah. They have some crazy discharge capacity like 10amps or 15amps.

I'll bet they have larger capacity sizes. Call them and talk to Chris. He'll hook ya up.

Darrinc

My Feedback: (5)

You will blow up your meter if you try to check for ohms. A meter uses a small voltage, or current as a known to figure out your resistance, so the voltage of your battery would be a bad thing to the meter.

Volts/Amps=Resistance

A 2 Cell Li-Poly would work very well for what you are doing and they are very high output. If you fly foamies, you probably already have these lying around.

Flip and Fly

I don't want to rush out and buy more batteries if the Expert packs will work. I just want to be sure that they will not fail. So what I need to do is learn how to check the cells/pack for discharge capacity.

I would go with Li-Poly packs but I don't want to spend extra on chargers, testers, and so on. I have this setup and will use Ni-MHs for the time being. Li-Poly looks great, one day I just may get into foamies Its all a matter of time!

aegis

Flip and Fly - Below is the contact info for NoBS Batteries (Hangtimes Hobbies). I've gotten my last couple of packs from him (and, no, I'm not affiliated in any way). Contact Steve at NoBS and ask him about your batteries and if there will be a problem. He has given me advice in the past even when it was about something I didn't purchase from him.

Dan

http://www.hangtimes.com/nobsbatteries.html
631-610-5169 9-3pm eastern M-F
E-mail: [email protected]

RTK

My Feedback: (1)

I have been running 2 of these in a 2.6 comp-arf, 8611's all around, 1 rx with 4 leads from the battery. These probably are the best choice in Nimh. Soon I will be changing to straigh Li- for weight savings.

Flip and Fly

Aegis

Thanks for the web address to Hangtimes! Lots of info there I looked around and this is what he says about 2700 Sanyo Ni-MHs, these are the cells in the Expert pack.

NOTE: Yes!! We still carry the NiMH Sanyo 2700 AU packs! However, due to their high internal impedance (20 mOhms), they are listed on our 'sport packs' page. If you are considering using the 2700's in your 25% or larger IMAC bird with digital servo's we recommend you run them in Parallel with dual switches to get the impedance of the system down to 10 mOhms.


Interesting, I think I will give them a call, the price on the packs is good and the construction also looks good.

Volfy

My Feedback: (23)

Flip and fly, to answer your original answer, the Expert Pro 2700mAh packs are made with Sanyo 'A' cells, which are not exactly super high current drain devices like sub-C (generally used in power tools) and 3/4A (used a lot in mini electric car racing), but it does put out quite a bit more than the typical AA cells. You can find the datasheet for the Sanyo 2700mAh NiMH here (as well as many others):

http://www.robotcombat.com/store_batterypacks_pdfs.html

It is plenty sufficient for powering your system, assuming the rest of your wiring and switches are up to snuff. Sanyo makes some of the best NiMH cells available (some latest GP cells are arguably better).

I use these cell too, but I build them from loose cell I buy bulk. It is a nice size and package - right between my other two personal favorite - GP 1100mAh 3/4A and GP 3700mAh SC.

Flip and Fly

Oh good grief, the mystery of it all. Thanks Volfy for the clarification, and tables.

After looking at all the data I am thinking I will be fine with the 2700 packs if I run two packs and two receivers. Actually I have been running the same setup in my big Ultimate with 6 5645s and 1 5945. Have not had any issues with it and always have plenty of power left even after 7 flights.

Because I am using the 5955s and the higher curent draw I was a little concerned.

Nogyro

My Feedback: (10)

FWIW, Radical RC has the same 6 volt 1950 FAUP pack for less than NoBS. Both companies assemble great packs.

Volfy

My Feedback: (23)

While your concerns about current draw with the high power digitals is perfectly justified, IMHO the internal resistance issue has been overblown out of proportion (by factions whose motives are not always altruistic). It is true that a cell having higher internal resistance will likely have lower maximum continuous current rating, it only relates to the heat produced (and the slightly higher voltage drop) due to the higher internal resistance under SUSTSAINED peak current draw. The typical RC system load is far from SUSTAINED. Rather, servos (even digital ones) demand high current draw for very short bursts. I've yet to see somebody bang on the sticks enough to cause any appreciable heat build-up. As for the voltage drop, the battery pack actually acts as a great big capacitor such that it is able to produce short burst of large current without the voltage drop associated with continuous high current draws.

In any case, you're better of with your dual 2700mAh packs - peak current delivery-wise - than having to suck juice out of LiPos through regulators.

RTK

My Feedback: (1)

In my next project I will be using Li-ion no regulators

Flip and Fly

Volfy, I think you are correct from what I have seen in my other setup. I will just use the 2700s and keep a good eye on current draw!

3D Joy

You can test the voltage drop by plugging a voltmeter into the receiver and work the servos with the radio and see the actual loaded voltage. I did this test with 1 servo stalled and measued voltage drop either at the receiver and at the servo after a 48" extension. Results are very interesting to say the least. With 2300 mah AA cells, I got voltage drops of the order of 1 volts and more. With the 4/5 FAUP's the voltage drop was reduced by 5 times and actual loaded capacity was better than with the AA cells as the 1950 mah were not heating at all.

hope this helps.

Banche

if you are gonna go 5955 you might as well go Fromeco!

Nogyro

My Feedback: (10)

Interesting test...........There has always been speculation that the Hitec servos are susceptible to going into lockup with a voltage drop. One volt may be enough to do it. Your pack get down to 5.9, do a snap or something and the current drops 1 or 1.5 volts, and there you go, lockup..........The rest is history[:@]

Flip and Fly

Well we are only talking a few more dollars. Why take a chance, I think I just might get the 1950s FAUPs. I will try that test 3D on my 2700 packs. If the drop is 1 volt or more, well!


Thanks.

Darrinc

My Feedback: (5)

Humm, we could add the big caps the car audio guys are using in our planes.

You heard it here first!!!

Nogyro

My Feedback: (10)

I think you'll be fine with the 2700 packs. Before I switched to the 1950, I was running 2-5 cell KR1100 Sanyo packs. There impedance is like 20 or 25. On several occasions I had forgotten to turn one of the switches on and my flight was glitch free. Just find out for sure what the impedance on your packs are.

Flip and Fly

Well I would probably be fine with the 2700s but there is very high current draw with the 5955s. I can use these packs in other planes, why chance it. I will be going with the 1950s.

No system is foolproof because fools are so ingenious

JoeAirPort

My Feedback: (41)

You will be amazed how long these batteries will last on a charge. Especially two of them. You might be able to fly two or three days. I have flown two days on one of those ((4) 5945's (1) 8611, a mini for throttle). It was just above 6 volts at the end of the second day.