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Old Nov 10, 2011, 04:15 AM
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Lancair's Avatar
near Byron Bay, Australia
Joined Sep 2002
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Li-Po Versus traditonal power source for gliders ?

Ive been away from the hobby a few years and on my return I find everyone talking about using Li-Po's for glider power source.

Whats the advantage other than the potential for long flight times between charges ?

To my perhaps uneducated eye, it seems to be needing extra circuitry and more potential for accidental release of magic smoke from incorrect connection and for post impact damage to Li-Po ?

Ive been replacing my old NiCd flight packs for new NiMh. 800mah is more than enough for a 4 servo glider to fly for a few hours. Way more than Ill do in a typical day at the slope with that one model.

Lancair
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Old Nov 10, 2011, 07:12 AM
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Mark Wood's Avatar
United States, CA, Bear Valley Springs
Joined Feb 2000
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The only advantage to me would be weight. That said, I use only quality Nimh or LiFe for my radio systems in gliders.

mw
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Old Nov 10, 2011, 07:58 AM
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Woodstock 1's Avatar
Ireland, County Kerry, Kerry
Joined Dec 2005
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The advantages are mainly:

LOW SELF DISCHARGE!!

This makes for a huge, life-changing difference. Charged planes can be stored or left in the car for weeks or even months on end, and will still be instantly ready to fly. No more charging every plane the night before hassles. This is particularly important for me, as I travel with some gliders all the time, and I often don't know when I am or not going to fly. Whatever, my planes are ready to go!

I do not now have a single NiMh battery in a plane. I DO have a box full of NiMh's in very good nick. Mark, you wanna ?
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Old Nov 10, 2011, 09:50 AM
Flagstaff, AZ
dawsonh's Avatar
USA, AZ, Flagstaff
Joined Mar 2003
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Another advantage to LiPo and LiFe batteries is that they have tremendous "C" ratings and thus are very resistant to brown outs.

2.4 receivers are their cpu-based. If you have a low voltage situation (low pack, a stalled servo... or just big servo drain), the receiver stops working and may take several seconds to re-boot.

I am starting to convert to LiFe in my larger gliders (many servos) for this reason.

LiFe has the advantage over LiPo in that it is compatible with most 6 volt servos... and does not have the "fire" issues. Lipos are nice because they are very inexpensive and come in small sizes for light weight gliders. Most 2.4 receivers and some servos, like the Dymond 4.7 and 6.0, have no problems with the high (7.4 v) voltage.
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Old Nov 10, 2011, 11:26 AM
TD- F3K- Slope - What to fly?
Dale Thompson's Avatar
Cupertino CA
Joined Aug 2005
1,503 Posts
I only use Li-Po's in my DLG's for the weight advantage.
If you forget to turn off the plane and drain the Li-Po too far down then you must replace it. So far I've only had to replace 2 packs in 4 months.
I'm getting much better at remembering.

I perfer Eneloop's where ever possible. Costco is now selling 10 Eneloop AA's for $19.99. Good deal.
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Old Nov 10, 2011, 12:21 PM
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Carlsbad, Ca
Joined Mar 2007
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Sanyo Eneloop AA & AAA's at Costco
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Old Nov 10, 2011, 01:34 PM
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flyzwell's Avatar
So Cal
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Eneloops and other off the shelf "pre charged" batts seem to have a low self discharge rate similar to Lipos.
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Old Nov 10, 2011, 02:24 PM
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Mark Wood's Avatar
United States, CA, Bear Valley Springs
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True, but they don't do as well as Nimh or Li at high discharge rates in operation.

mw
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Old Nov 10, 2011, 02:36 PM
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Daemon's Avatar
Lakewood, Colorado
Joined Aug 2002
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But very few slope planes generate a high enough discharge rate for that to matter.
If I need to run 6 digital servos in a big plane, I'll just use a 5 cell Eneloop pack.
The heavier NiMH pack in a slope plane is rarely an issue since we're typically adding
lead to the nose anyway.

Over the years I've seen enough NiCAD and NiMH battery packs smashed on rocks
to take the risk of fire by smashing a Lipo pack very seriously. We highly
discourage their use on our local slopes, as the first fire started would likely
be the last time we ever get to fly there. Not always a popular decision
with the newer pilots.

ian
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Old Nov 10, 2011, 02:41 PM
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Woodstock 1's Avatar
Ireland, County Kerry, Kerry
Joined Dec 2005
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Lets's put this fire risk thing into perspective: not everyone on this planet lives in a semi-desert or high fire risk zone, and last time I looked this was an international forum. If my LiPo - powered planes caught fire after crashing (and such a thing has NEVER happened to me - and I crash a LOT), we'd be glad of the spot of warmth !
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Old Nov 10, 2011, 02:52 PM
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Carlsbad, Ca
Joined Mar 2007
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I'm closing my eyes and picturing lush rolling green hillsides,...

.....and not the 6month old dead dried weeds that make up the So Cal masses

Point taken
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Old Nov 10, 2011, 03:04 PM
weisenflymanheimer
snakecrew's Avatar
Crested Butte, Colorado
Joined Dec 2007
1,193 Posts
what about these cr2 lithium(photo cell) for lightweight dlg types.

should I solder the unrechargebles then replace them when they go dead or get the rechargeble kind?

it is hard to get snow, dirt and ice, and rocks to catch fire up here.
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Old Nov 10, 2011, 03:26 PM
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Warwickshire, England
Joined Sep 2006
5,507 Posts
nimh, lipo and life are all workable.
each type has pros and cons that suit a particular plane or person, but they can all be used if they are, importantly, used correctly.

In terms of the "C" rating of lithium types, as most lipo types will be regulated, say to 5amps (AA nimh cells are about 7amps max discharge) they are not particularly special. A lot of LIFE (e.g hyperion) packs actually have a lower max discarge then nickel types. e.g a 1450 hyperion life has a max discharge of about 7 amps/hr whereas a 2/3a nimh pack could easily have a max discharge of 15mps.

nimh has a bit of self discharge and small cells are a bit weedy, lipo needs a regulator, LiFe is hard to measure the capacity (and might need a regulator).
Take your choice. Lipos have a potential fire risk as well.
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Old Nov 10, 2011, 06:41 PM
Just Toss It !!!
MATIN's Avatar
Australia, NSW, Sydney
Joined May 2004
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Quote:
Originally Posted by cvanscho View Post
Lets's put this fire risk thing into perspective: not everyone on this planet lives in a semi-desert or high fire risk zone, and last time I looked this was an international forum. If my LiPo - powered planes caught fire after crashing (and such a thing has NEVER happened to me - and I crash a LOT), we'd be glad of the spot of warmth !
I other words I guess you are saying (and far from me to put words your mouth!) that everyone should look out of the car window before deciding on battery type?.....Hell, I can live with that!

Matin
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Old Nov 10, 2011, 08:07 PM
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Lancair's Avatar
near Byron Bay, Australia
Joined Sep 2002
733 Posts
Hey thanks guys for the answers. I think Ill stick to NiMh. I dont mind charging planes, it's all part of the sloping experience getting everything ready the night before, or that morning as I usually am doing.

Lancair
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