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Old Oct 26, 2007, 08:08 PM
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Build Log
LI FE PO4 battery pack build.

This is my first LI FE PO4 pack build for GWS sized planes. I bought 4 of the 1200 mah cells WITH solder tabs. Their built packs ALL have a built in current limiter built in, that is below the 15C rating of the cells.
4 cells and a 4 cell .5 amp CC/CV charger is $67.03 delivered.

www.batteryspace.com .....Li-Ion Batteries section.

These are the VERY safe LIPO's. No fires due to any screwup you can do to it.

I Will do some photos when I start.

Charge and sleep again.
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Old Oct 26, 2007, 11:09 PM
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Quote:
Li-Fe-PO4 battery must be cut-off at 3.8V/cell condition when charging
You must limit discharging rate below Max rate
Please see our damage test report to understand our specs and limit your application within specs

I took this off their page, I like the part about keeping the draw below 15C. I think the weight is going to limit your flight to just puttttting around.

Challenger413
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Old Oct 26, 2007, 11:22 PM
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I just love the specs... on the page (http://www.batteryspace.com/index.as...D&ProdID=3737)...
Quote:
New Generation Li-Ion Battery ( Li-Fe-PO4): High discharging rate, non explosive, lighter weight and much safe
Then further down the page it says:
Quote:
Wrong type of charger used will cause explode. Batteryspace.com will not be resposible for damage.
So which is it.
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Old Oct 27, 2007, 10:13 AM
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Valence holds the patent rights with M I T on LI FE PO4 technology and has had their electric car batteries shot with bullets to get D O T approval. It passed.

Want to shoot 1,200 lbs. of the biggest RC LI PO's with bullets and get D O T approval for car use ?

As i understand it. The FE part is rust of Iron. That is the key to the NO hazard ability. Lower power density, but everyone does not go to the Burn Center in a crushed battery occurence.

Simple trade off.
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Old Oct 27, 2007, 10:19 AM
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Why would any of us believe any sales P R hype, good or bad, without going to a really accurate source ?
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Old Oct 27, 2007, 10:28 AM
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Dickinson, Tx.
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Quote:
Originally Posted by cyclops2
That is the key to the NO hazard ability. Lower power density, but everyone does not go to the Burn Center in a crushed battery occurence.
Simple trade off.

When has anyone gone to a burn center with Lipo's? I know of house fires...

If these explode, how is that not a "Hazard Liability" ?????

Challenger413
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Old Oct 27, 2007, 01:34 PM
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I should be using more smiles in my posts.
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Old Oct 27, 2007, 01:44 PM
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Does anyone have a news clipping of a LIFE PO4 causing injury or loss of property ?

Or did the store PR person make up a "Guesstimate" about the safety, or risks.
Go to the www.valence.com site for the facts. Not some retailer.

I was told way back, that all the stories about LIPO's going off like a road flare were lies started by stores with loads of NICADS & NIMH batteries to get rid of.

Word of mouth is great in a armchair with a beer.
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Old Oct 27, 2007, 09:51 PM
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Uuuuh Perhaps I'm not understanding.. But one can Buy a pack of Nimh's for errr Less coin which weigh roughly similar and CAN discharge 30 amps.. What am I missing here??
IF significant lightness is not the advantage then What Exactly IS the advantage.? Higher Price? Bragging Rights?
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Old Oct 27, 2007, 10:17 PM
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Quote:
Originally Posted by Bare
Uuuuh Perhaps I'm not understanding.. But one can Buy a pack of Nimh's for errr Less coin which weigh roughly similar and CAN discharge 30 amps.. What am I missing here??
IF significant lightness is not the advantage then What Exactly IS the advantage.? Higher Price? Bragging Rights?
Okay, let's compare apples to apples:
http://www.batteryspace.com/index.as...OD&ProdID=3737
vs.
https://01836cd.netsolstores.com/ind...ROD&ProdID=267

LiFePO4, 1200mah, 3.3V, 15C, 36g, $6.95
Nimh, 1400mah, 1.1V, 15C, 23g, , $2.49

But because of the voltage difference, three Nimh cells are equivalent to one LiFePO4 cell. So, Nimh is 1.9 times heavier, the price is about the same and Nimh has a bit more capacity.

Additional benefits:
LiFePO4's will hold a charge unlike Nimh.
LiFePO4's don't need to be warmed up to perform well unlike Nimh.
You're likely to get much longer cycle life from LiFePO4's (some are rated up to 2000 cycles) vs. Nimh (high capacity Nimh die quickly; especially if you charge and discharge them at high rates and they heat up.)
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Old Oct 28, 2007, 09:44 AM
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My PR spokesperson does it again.

Thanks for clearing up my thoughts in a great way.

Many thanks, Rich.
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Old Oct 28, 2007, 11:53 AM
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Well that's certainly abetter explanation than I've seen so far.. thanx

There ..are.. however slightly 'better' Nimh batteries available :
1400 mah ..with a ..proven ..30 amp ..discharge (wee bit better than the 15 c nonsense) 23 grammes and a $2.50 price
http://www.cheapbatterypacks.com/?si...ells&chem=NIMH
So assuming a 9 volt pack one saves little less than 3oz.. certainly worthwhile

BUT also at the cost of half the output rate.. a Significant.. tradeoff IMO.
Unless one is entirely into Park fliers.. where typically amp draws are v low.. that's a pretty high price to pay perf wise.
Also have No idea what yr on about re life cycle arguements .
I for example have a Venerable (bought in '88) 8cell pack of Sanyo 800 AR' s that Continue to measure out at their "as New' rates .. True.
Heavy though, but lotsa Amps.. on demand.. darn near 20 years and "many" Cylces later.

Also there'sthe First on the Block aspect.. Remember all those who bought Lipos's.. to be First .
Lucky Them
I have Lipos as well ..But my old Nicads and Nimh packs remain my First choice (Yeah! Still) in models with hi amp performance needs.
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Old Oct 28, 2007, 04:00 PM
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Quote:
Originally Posted by Bare
There ..are.. however slightly 'better' Nimh batteries available :
1400 mah ..with a ..proven ..30 amp ..discharge (wee bit better than the 15 c nonsense) 23 grammes and a $2.50 price
http://www.cheapbatterypacks.com/?si...ells&chem=NIMH
So assuming a 9 volt pack one saves little less than 3oz.. certainly worthwhile BUT also at the cost of half the output rate.. a Significant.. tradeoff IMO.

Unless one is entirely into Park fliers.. where typically amp draws are v low.. that's a pretty high price to pay perf wise.
Sure, and there are also better LiFePO4 cells as well... I tried to compare equally cheap/bad cells.

Also, I know from experience that those Nimh cells will not sustain 30 amps unless you use them hot of the charger and keep them nice and toasty. And if you use them this way, they won't last very long before they really start to fade (e.g. <50 cycles is not unheard of.)

A123's are actually a type of LiFePO4's and nobody would say those cells are whimpy or the chemistry is inherently bad... just like other chemistries (Nicd, Nimh) there are good cells and bad cells. Given that generic LiFePO4's are not yet very popular (but they will be because of their use in consumer power tools, etc.) they are still catching up in the discharge rate game.

For me, if I need ultimate performance, I'll stick with Lipos as they're still lighter and higher performance. I think the appeal of round cells is for sport flyers anyways where you want a more robust cell and you're willing to sacrifice some performance. For example, I don't push my GP1100's (very robust 2/3A nimh's) beyond about 15 amps, so 15C LiFePO4's would be a fine replacement.

Quote:
Originally Posted by Bare
Also have No idea what yr on about re life cycle arguements .
I for example have a Venerable (bought in '88) 8cell pack of Sanyo 800 AR' s that Continue to measure out at their "as New' rates .. True.
Heavy though, but lotsa Amps.. on demand.. darn near 20 years and "many" Cylces later.

Also there'sthe First on the Block aspect.. Remember all those who bought Lipos's.. to be First .
Lucky Them
I have Lipos as well ..But my old Nicads and Nimh packs remain my First choice (Yeah! Still) in models with hi amp performance needs.
I was comparing cycle life to modern Nimh cells which die rather fast when pushed (I know from experience.)

My experience with Lipos are that they seem to have good cycle life, but they have a fixed calendar life.

I agree that old Sanyo Nicads like the AR800 were very robust (unlike most Nimh cells or even Lipos) ... but now you're comparing apples and oranges in that they are low capacity vs. weight and size.

The promise of LiFePO4's is that they are just as robust as old NiCd's but don't have any toxic chemicals in them and that they have a better power to weight and size ratio.

Also LiFePO4's have been around for a while now (e.g. A123's and Saphion's) and they're proving themselves to be very robust from all reports. So I don't think there is a first on the block problem anymore with the name-brand cells. A question does remain with the generic LiFePO4's. Time will tell if the generic LiFePO4 cell manufacturers can produce a cell that is close to as good as the A123's.
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Old Oct 28, 2007, 04:26 PM
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Dumpster diving!!

Bare.
I had the identical cells for 15 -20? years. They originaly had 125% capacity!! I threw them out 3 years ago.

You found them. Good old days. Mine had a bright shiney orange wrapper on each cell..........Enjoy them.
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