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Old 08-21-2019, 08:13 PM   #1
NEW222
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LiFe Battery Size For 40 Size Plane


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Hi. So, I have made the decision to get back into flying again using a glow powered plane. I will be buying a new battery pack to power the airplane, and am really thinking of going to a LiFe battery. Now these are new to me, so would like to seek the advice of those here that would know what size would be best for my needs.

The basics I will say is that for the next near future, I will be flying a trainer aircraft, and possibly a sport style aircraft after that. Largest would be .40 size, and as small as possibly a .15 size, but realistically, the smallest would be a .25 size plane. Also again, I will be using 4 standard servos and possibly 3 if I get a 3 channel trainer. Thanks, and ready to learn!
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Old 08-21-2019, 08:28 PM   #2
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Re: LiFe Battery Size For 40 Size Plane

I use these for 25 to 60 size and have never discharged them more than 15% in three or four 5 minute flights.

So I'm going down in capacity to these for anything below the 40 size planes.

A couple things about LiFe:
- The ONLY way to know how much they have been discharged is to recharge them and look at how much the charger put back in. Those little meters that work great for LiPo percentage sometimes report LiFe percentage but it is to be ignored.
- They will be a bit over 6.6V off the charger so make sure your servos can deal with that. Almost all 6V servos are fine but I have found one 6V servo which is not ok with anything over 6.0V.

I highly recommend them for flight batteries but I always fully charge them at the beginning of the day.
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Old 08-22-2019, 01:02 AM   #3
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Re: LiFe Battery Size For 40 Size Plane

The 1100's above will do the job and have done so for many of our club members but due to the small cost involved most of us use anywhere from 1400-2500mah packs now. It also means you can use them for the onboard glow devices that 6.6 volt is acceptable for. Remember we used 700 and 800 mah nicad packs. Certainly 6.6 volt packs may mean a little more current drawn but more than adequate for more than one flight. One of our former active members used to fly much larger than .40 size on those 1100's and had 2 or 3 flights normally.
LIFE has a weight advantage so other than cost no disadvantage to carrying a little more!
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Old 08-22-2019, 08:09 AM   #4
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Re: LiFe Battery Size For 40 Size Plane

I switched to LiFE for both flight packs and transmitters several years ago and have not looked back. They can easily supply me with a full day of flying with little fear of alarms. My charger lets me know how much was used, but I have enough experience now to pretty much estimate if need to rewind.

The advantages are many: Far better current output for their capacity and weight, with far less chance for voltage drop when pushed hard.

LiFE store charge for much longer and are ridiculously quick to rewind, (my 1500MAh Tx packs can take less than 5 minutes after a full flying session). I can be confident of coming back to something stored all winter to find still almost fully charged. To get anywhere near the same current feed rate a NiMH pack would need to be of a MUCH larger capacity and weight and I found to be comfortable I needed to ensure full recharge no more than the evening before a flying session.



The only disadvantages are that your charger needs to be able to work with that chem, but all modern types I have seen have that capability. Also, when replacing a NiCad or NiMH transmitter pack the onboard voltage monitors or meters do not work.

Lastly, if still running 72MHz the much lighter packs will not balance the transmitter like their much heavier predecessors. Definitely a minor nit pick.

There are systems and monitors now that can pretty accurately read charge states. The picture shows one I adapted to remain onboard one of my planes. It plugs into the balance lead on the battery and there is a momentary pushbutton in the negative monitor lead. When not pressed the monitor is off and draws no power at all. In fact, the flashing LED I also install with most new builds to show the AC is powered up is the only other non-flight related draw.

The reasons I add this is it removes the need to plug in a remote battery monitor and gives instant read of both peak voltage and, more importantly, cell balance.

You will see a 2S LiFE shows 6.6V. That is a no load voltage and I find it drops to approx 6.2V immediately after switching on the flight switch. This is remarkably close to and possibly even less than what a fully charged 5-cell NiMH pack will provide. After a test with some 20A Castle PRO BEC's on the first few builds I opted to run these straight into the flight system. In 4 seasons I have had only a single analog servo failure and that had a dubious history.

Although he also builds Eneloop NiMH packs and at 2500 mAH they may be a bit much for a 4-channel trainer, stegl here provides excellent LiFE flight packs:

https://www.rccanada.ca/rccforum/sho...d.php?t=578085

I have purchased these and his earlier packs of slightly less capacity. All are well put together and reliable. The AC in the pick is currently running one of his 2500's.

There is one warning I can relate regardless of battery tech: If your craft or transmitter has had a flight pack plugged in for storage you should seriously look at replacing switches and extensions and have a very close boo at any remaining electricals. You can get what is called "Black Wire Disease" where the negative wiring and any connections can corrode. This can be hidden withing switch cases and under wire insulation and may not be easy to spot. The problem is you may be able to power up the system and it seems fine, but under load it can and will rear it's ugly head. Some radio systems being far more vulnerable to voltage drops.


ps. Welcome back. The new tech may seem intimidating at first, but in most cases it has become more reliable and less expensive to boot. Don't hesitate to ask questions. That's what we're here for.
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Old 08-22-2019, 09:29 AM   #5
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Re: LiFe Battery Size For 40 Size Plane

I guess I will bring up what the OP stated and that is 25-40 size aircraft is what he is planning on using. I remember back in the days and Gary probably does too, that we used to run 500-600 mah Nicad receiver packs in many aircraft right up to 60 size. I used to fly 6 plus flights a day and still have battery left on my 40’s and now we are down to 2-3 flights. Wonder what has changed ?
For 3 to 4 channel aircraft the Eneloop 2000 4.8v should fit the bill very well and use original chargers. Agreed ,the Life A123 packs are the way to go with large high drain aircraft. Also most of your newer “smart” chargers are also an improvement over some of the older chargers with just about any battery chemistry available today.
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Old 08-22-2019, 04:16 PM   #6
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Re: LiFe Battery Size For 40 Size Plane

I agree with Mike. I use 1100-1450 mah packs and get at least 10-15 flights. I also have a battery monitor on each plane. When I turn it on it always shows state of charge and they do not loose charge when not flying. As Mike said you have to learn how may mah they use per flight. I like them.
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Old 09-12-2019, 08:36 AM   #7
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Re: LiFe Battery Size For 40 Size Plane

The main thing with 2.4 is does the battery have enough ability to supply the amperage needed for four servos operating in flight to still maintain a minimum voltage to run the receiver?
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