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Old Oct 16, 2014, 02:45 PM
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yorkshire UK
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Why don't the manufacturers of all the RC gear ie speed controllers cater more for lifepo4 batteries ?
If they supplied life batteries with new models instead of lipos it would be a LOT safer and would get newbies started right away on the safer technology.
My guess is they don't really care about the safety and actually like the fact that lipos only last a fairly short number of cycles so they can keep selling more lipos ,
I bought some lifpo4 cells some 4 to 5 years ago and they All work fine still, apart from one pack which I stupid ly over charged by toping a 2 cell pack up on 3 cell setting without the balance lead in, all that happened was the pack stopped working , no fire , no drama, I dread to think what might have happened if that was a lipo!
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Old Oct 16, 2014, 04:20 PM
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Two words: energy density.

mw
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Old Oct 16, 2014, 04:53 PM
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Two word's, lipo fires.



The argument for both has been going on and obviously its a personal choice, for me safety and longevity win over run time, for others lipos give the performance required.
What we need is some new tech that gives us both and even longer run times would be good,
Too much is made of C rating these days, who really needs a battery that can be drained in 30 seconds flat?
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Old Oct 16, 2014, 07:08 PM
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C rating is more important when it comes to keeping the voltage from sagging. It's not as much about how fast it can be drained.

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Old Oct 16, 2014, 08:48 PM
Heli's rule!
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Midvale, Utah, USA
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There are lots of problems when switching to life packs. IMO, The main problem with life is its higher weight about even with that is the lack of flexibility in form factor. being round metal cells, there are only so many configurations you can have. You also get a lot less mah for the same weight vs lipo. The other big issue is the voltage, you have to choose a whole other KV motor when switching to life packs, or deal with significantly less power vs lipo (or too high voltage)... Also, they can confuse the LVC on your ESC's, and confuse chargers while they are at it, which leads to ruined packs... You cannot depend on the voltage of a life cell to tell you how much capacity you have left like you can a lipo. You have to balance charge a life pack EVERY charge, as charging through the discharge lead could easily lead to the pack being mistaken for the wrong cell count, which can wreck it.....

These are the things no one tells you about life packs.... all you hear about are the good stuff, the bad stuff gets pushed aside... you can NOT fully discharge a life pack without consequences like many people think..... They can handle it a lot better than lipos can, but it does damage them....
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Old Oct 17, 2014, 02:14 AM
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Letchworth, Great Britain (UK)
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I fly a mixture of LiFe (A123 and Saphion) and LiPo, but I'm gradually going towards LiPo because of the extra flight time I get, and because LiPos have become cheaper and more reliable. For instance, in one particular model I use either 5S A123, which is nominally 16.5v 2300mAh, or 4S 3200mAh LiPo which is nominally 14.8v. I chose the LiPo size because it's the same weight as the A123, so I don't need to re-balance the model when changing packs, though I do change the prop from 12x6 to 11x7 to keep the amps the same -- and watts increases with the LiPo due to less voltage sag. With the LiPo I get 9 minutes flight time compared with 5 minutes for the A123. So you don't have to change the motor -- just pick a LiPo cell-count which matches the A123 voltage as close as possible, then check the amps and adjust the prop size if necessary.

My ESCs are mainly older Jeti models which set lvc at a certain percentage of starting voltage, so they don't get confused by trying to determine the cell-count. I time my flights anyway to leave 20% in the packs, so lvc is not an issue for me.

As for lifespan, I've just discarded my first 6S 2600mAh LiPo after 6 years, due to falling performance. My oldest A123, a 5S pack, is now 7-1/2 years old and still going strong, but I have had individual cells die in a couple of A123 packs, and have either replaced them or cut the pack size down for use in a different model.

As for charging, most quality balance chargers these days have a LiFe program.

Oh, and the biggest advantage of A123s is that they're about half the weight of the equivalent NiMh packs The model I mentioned above started out using a 12-cell 3300mAh NiMh pack.
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Old Oct 17, 2014, 02:33 AM
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yorkshire UK
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Even new ESCs have a NiMH setting so this can be used for lifpo4, chargers have a life setting so USE it rather then relying autodetect.
4 cell life is so close in voltage to 3 cell lipo under load it makes almost no difference to motor / prop combo.
But a123 cells are expensive and have less capacity and form factor is limited so will only work in certain models and give shorter flight times.
I bought my cells really cheap off eBay years ago for about 1 each so they were cheaper then buying lipo at the time, if I was buying new now though I would be undecided.
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Old Oct 18, 2014, 02:08 PM
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Greenland, Qaasuitsup
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Quote:
Originally Posted by nigelsheffield View Post
........ for others lipos give the performance required.\
6S Lipo fire (0 min 40 sec)


performance unleashed
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Old Oct 19, 2014, 04:07 PM
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United States, OR, Portland
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Quote:
Originally Posted by dacaur View Post
There are lots of problems when switching to life packs. IMO, The main problem with life is its higher weight about even with that is the lack of flexibility in form factor. being round metal cells, there are only so many configurations you can have. You also get a lot less mah for the same weight vs lipo. The other big issue is the voltage, you have to choose a whole other KV motor when switching to life packs, or deal with significantly less power vs lipo (or too high voltage)... Also, they can confuse the LVC on your ESC's, and confuse chargers while they are at it, which leads to ruined packs... You cannot depend on the voltage of a life cell to tell you how much capacity you have left like you can a lipo. You have to balance charge a life pack EVERY charge, as charging through the discharge lead could easily lead to the pack being mistaken for the wrong cell count, which can wreck it.....

These are the things no one tells you about life packs.... all you hear about are the good stuff, the bad stuff gets pushed aside... you can NOT fully discharge a life pack without consequences like many people think..... They can handle it a lot better than lipos can, but it does damage them....
LiFe packs are not restricted to metal cells. I have one right now that is a 2s and it looks exactly like a LiPo, flat foil wrapped "bags" in a plastic outer wrap. I think it is A123 that are only in metal cells.
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