Turnigy LiFEPO4 packs

[V0RT3X]

Might aswell post here.

http://www.hobbyking.com/hobbyking/s...idCategory=218

What LVC do you run on a 4S pack in MMM? How much of a difference would I notice when using 4S lipo or life? For ERBE. (3S doesn't fit)

[BrianG]

IIRC, A123s LVC around 2.5v. But really, you will notice the loss of power at the end of the cycle so an LVC is not really needed. 4s LiFe is gonna be 13.2v (3.3v/cell), whereas 4s lipo is 14.8v, so right there you will lose some speed. And if you gear up too much to compensate, the current will go up, which might exceed the pack's capacity. It says 30C (135A), but I'd like to see some ET graphs before I believe that.

[lutach]

Originally Posted by BrianG

IIRC, A123s LVC around 2.5v. But really, you will notice the loss of power at the end of the cycle so an LVC is not really needed. 4s LiFe is gonna be 13.2v (3.3v/cell), whereas 4s lipo is 14.8v, so right there you will lose some speed. And if you gear up too much to compensate, the current will go up, which might exceed the pack's capacity. It says 30C (135A), but I'd like to see some ET graphs before I believe that.

Brian,

What do you think MA will do when more people find those packs? I was going to buy some to make it 1P (2,250mAh) for my applications, but like you, I want to see some graphs on them as well.

[Unsullied_Spy]

Originally Posted by lutach

Brian,

What do you think MA will do when more people find those packs? I was going to buy some to make it 1P (2,250mAh) for my applications, but like you, I want to see some graphs on them as well.

I don't know about you guys, but I smell a bunch of BS coming from MA about how their cell chemistry is superior, pack construction, "factory fresh, made to order" as if they were a sandwich...

[lutach]

Originally Posted by Unsullied_Spy

I don't know about you guys, but I smell a bunch of BS coming from MA about how their cell chemistry is superior, pack construction, "factory fresh, made to order" as if they were a sandwich...

Question is, could they really be going through so many packs that the cells they use don't actually sit on a shelf? How many of you have actually seen the "Factory"? I know Castle Creations makes their own ESC and we've seen pictures of the factory. When MA had a somewhat decent price, yes I bought 2 packs, but almost paid the real price.

[V0RT3X]

Are they sensitive to wet conditions? (snow) Probably gonna order a pair tomorrow.

[lutach]

Originally Posted by V0RT3X

Are they sensitive to wet conditions? (snow) Probably gonna order a pair tomorrow.

Most batteries will not perform very well in cold weather. There could be a very large voltage drop and it could hurt how they perform and if drained too far, you might damage them.

[JThiessen]

With the A123's I ran, the discharge rate seemed to me to be as good as the Lipo's - but that was just by seat of the pants on my part. They ran well with my Novak, and even a little better with the MMM/Castle. However, when run on a stock E-Revo, they did not seem to perform as well as the Nimh batt's my in laws had.

[suicideneil]

Pre-warm them in your pockets/indoors to around 100*F, then dash outside to use them; the longer you wait, the more they will cool down- dont store them in a gargage or shed either, store them in your nice warm bedroom.

Anyway, I would use 2 of those packs in series, say 6s2p to replace a 5s lipo, or 4s2p to replace a 3s lipo, or 5s2p (3s + 2s packs) to replace a 4s lipo.

But... $120 vs $25 (2s2p 4500packs, direct comparison)= MA are toast- spread the word brothers!

[BrianG]

MA packs may be using the same cells, but maybe they are weeding out the "bad" ones/matched better? Remember, I said "maybe".

[lutach]

....I know one place that makes similar cells, but the problem is the MOQ they have. The word will spread fast and MA better have a good back up plan to explain how different their pack is .

[himalaya]

A123 or similar soft pack LiFe are good 10C ~14C cells if comparing voltage holding capability with LiPos. They surely can be 30C discharged, if you don't care about how much voltage under load left and how hot the pack gets.

[snellemin]

I wonder how those softpacks really compare to A123's.
Fresh A123's can discharge at 36C cont. They are good up to 160F or so. Voltage drop is very high, but you use the Amps to your advantage rather than the Voltage like in lipo's.

[sikeston34m]

It's probably time for me to buy a data logger.

I have some of the 2S2P packs on their way and should be here the first part of next week.

Many of the questions you guys are pondering, I've been asking myself too.

I've ran A123 packs before and wasn't really impressed with them, due to the extreme voltage drop under a load. Lipos are famous for holding the voltage high during discharge.

I wonder if the flat poly form of the Lifepo4 will hold loaded voltage better than the cylindrical form?

In comparing the cylindrical form to the flat form, won't surface area of the anode and cathode material have a big impact on performance?

It stands to reason the flat form should be superior.

I will do side by side run tests to compare the 4S Lifepo4 to 4S Lipo.

4S 30C 5000mah Turnigy Lipo versus 4S 30C 4500mah Turnigy Lifepo4

My testing will be done with an E Revo.

MMM ESC and a Medusa 36-60-1500kv geared 22/40 using Mod 1 gears.

I want to see the differences in performance with no changes to the setup.

Then I want to alter gearing to compensate for the greater voltage drop of the Lifepo4 cells. I may even swap the 1500kv motor out for a 36-60-2000kv version.

I can either change the gearing, change the kv of the motor, or both to make up the difference.

[Thomas]

Originally Posted by sikeston34m

... In comparing the cylindrical form to the flat form, won't surface area of the anode and cathode material have a big impact on performance? ...

As far as I know, all batteries are just thin films stacked, no matter if they're arranged in a cylindrical or a prismatic case or just wrapped in aluminium foil. But of course, the one with a hard shell will be heavier for the same performance.