Anyone use 3s LiFe-Po's

[arevir]

Hi guys it seem there not a lot of talk about them.
I remembered when they where coming out all the good stuff about them.

Only negatives weight more and less Volts per cell.

So are they required to have LVC?
Is everything bad about regular lipo a thing of the past with lifepo?

I have some zippy life 4200 3s coming to replace 2s lipo pack. 3s lipo are too much, roll over are not fun after a few of them.

[Johnnysplits]

You can use life packs for crawlers, but they don't have anywhere near the punch of lipo's. Not good for high power situations. They have a very low discharge rate compared to lipo (tried one in a brushless slash...not happy) They're really great for powering your transmitter. And no, you don't need to use lvc...life's can be totally discharged.

[arevir]

Thanks, yes forgot to mention it would be used on a crawler.
That why I made the comment of roll overs with 3s lipo. But it seem that a 3s Life would be a good balance of power in between a 2s and 3s lipo.

How do they discharge slow 30c is good I believe and the 2c charge would that mean a 8amp rate.

[Johnnysplits]

I've used only a 2s life battery. In a go fast, I wouldn't use it. My slash ran a lot slower with the 2s life compared to a 2s lipo. But for a crawler, you're good!

[beomagi]

Which LiFe did you use?

A123s should supply more than enough on low geared vehicles so you'd never notice. I run A123 2s2p 23650 cells on a buggy of mine, and there's enough punch to rely on wheel weight to flip it over when it's on it's top.

The only downside I found with these were the size of the cells vs capacity. Weight is actually fine given the power density, but the overall energy stored (mAh) is low.

I've got some interesting LiMn Sony VTC5 cells (smaller 18650, 2600mAh, 30 amp discharge, safe cell). Looking forward to testing those. They're apparently big in the e-cigarette world and started showing up in electric scooters/bike forums too - though scooters and bikes tend to rely more on higher volts lower amps than we RC guys use.

[Johnnysplits]

Originally Posted by arevir

Thanks, yes forgot to mention it would be used on a crawler.
That why I made the comment of roll overs with 3s lipo. But it seem that a 3s Life would be a good balance of power in between a 2s and 3s lipo.

Are you talking about the weight of the battery itself causing roll overs?

[stelerzman]

I can say that a 3s lipo and nano-tech lipo's are the way to go for powering your rig, they give the best power and the longest run time. Now when you get into LiFe batteries you get a really long run time for low power draw applications such as RX's
Ie: I've noticed a great improvement in battery life in my Futaba 4pk with the LiFe battery compared to the factory battery. I used to have to charge the ni-mh battery 3 times compared to a single charge of the LiFe battery.

So, in my experience, the LiFe battery is a great choice for a transmitter and standard lipo & nano-tech lipos are better suited for higher output applications. The nano-tech are a great battery for super high powered electric boats. I have several nano-tech batteries with a C rating of 40C to 135 C ratings, there very impressive.

[infodragon]

There is a lot of misconception about LiFePO4 vs LiPo.

All the ratings mean the same thing... 2S is two cell, 3S three cell...

A 20C discharge is 20x the mah of the battery. A 1000mah 3S LiFe will produce 20,000ma @ 9.9v nominal. Conversely a 4000mah 4S LiFe will produce 80,000ma @ 13.2v nominal.

The main differences are...

LiPo is 3.7v/cell nominal
LiFe is 3.3v/cell nominal

LiFe has most of it's energy very close to 3.3v, so you have a much more consistent voltage over the discharge cycle of the batt.

I much prefer LiFe as they are safer, and much more consistent. You just have to be careful of the voltages. A 4S LiFe is slightly more voltage than a 3S LiPo max changed.

For more information check out these links
http://www.cse.anl.gov/us-china-work...0for%20BMS.pdf
http://liionbms.com/pdf/huanyu/HYP-3.2V-100Ah.pdf
http://liionbms.com/pdf/goldpeak/GP18EVLF.pdf

EDIT: You don't have to have a LV alarm or cutoff, however you will extend the life of the LiFePO4 by not discharging below 3v/cell, not overcharging over 3.6v/cell and balance charging. Also charging at 1/2 the published rate will extend the life as well. In summary abuse a LiFePO4 and you shorten it's life span, abuse a LiPo and you get a fireball.

[arevir]

Originally Posted by Johnnysplits

Are you talking about the weight of the battery itself causing roll overs?

I mean the power of a 3s Lipo causing it to roll over during bashing sections.

I receive the 3s Life a few days ago and like you guys mention they have less power but still plenty. Roll over are not as bad now due to the decrease in power/wheel speed.
Im liking it so far. I will upload some pic next to a hard case 2s Lipo later

[Bhilliy82]

It's not that they have less power the have less voltage. Get some good tamiya brand life packs and you will not say they don't have the punch. You have to gear up with them. 7.4v vs 6.6v on 2s.

[Johnnysplits]

Originally Posted by arevir

I mean the power of a 3s Lipo causing it to roll over during bashing sections. Roll over are not as bad now due to the decrease in power/wheel speed

That's a throttle finger problem, not a more powerful battery problem. Learn to drive.

[realsickclown]

I disagree about not needing a LVC with a life pack. I have run a life-po packs in my savage and forgot to turn off the rig and unplug the pack, went back few days later, the battery was completely dead and wont charge. My charger wont even see the balance plug its just dead. Nothing could bring it back, so I thnk you would want to set a custom LVC. Thats my own experience

[realsickclown]

Originally Posted by arevir

I mean the power of a 3s Lipo causing it to roll over during bashing sections.

I receive the 3s Life a few days ago and like you guys mention they have less power but still plenty. Roll over are not as bad now due to the decrease in power/wheel speed.
Im liking it so far. I will upload some pic next to a hard case 2s Lipo later

you can also try turning down the current limiter

[JohnRobHolmes]

Lithium iron is a great chemistry when shelf life is a concern, or when it offers a voltage profile not possible with lithium cobalt or manganese. The drawback is poor charge/ discharge speeds and almost twice the weight and size per watt hour.

I only use them in transmitters because of the voltage profile. Otherwise they perform poor compared to lipo and cost more, so you won't find them in my rigs. I do use liFe on some ebikes, but that was the only stuff available a few years ago and as they wear out I'm going liCo to shed pounds from the battery.

[arevir]

Originally Posted by Johnnysplits

That's a throttle finger problem, not a more powerful battery problem. Learn to drive.

lol I know but since I dont race having that extra punch have not come into play so I think is a waste if you cant even use it. As the vehicle is top heavy. There for the 3s Life seem to be a good alternative.

Originally Posted by realsickclown

I disagree about not needing a LVC with a life pack. I have run a life-po packs in my savage and forgot to turn off the rig and unplug the pack, went back few days later, the battery was completely dead and wont charge. My charger wont even see the balance plug its just dead. Nothing could bring it back, so I thnk you would want to set a custom LVC. Thats my own experience

I will set it the venom LVC to 3.0V and see how much I can put back in the battery

Originally Posted by realsickclown

you can also try turning down the current limiter

I believe I have hear something like that but no clue how to do that.

Originally Posted by JohnRobHolmes

Lithium iron is a great chemistry when shelf life is a concern, or when it offers a voltage profile not possible with lithium cobalt or manganese. The drawback is poor charge/ discharge speeds and almost twice the weight and size per watt hour.

I only use them in transmitters because of the voltage profile. Otherwise they perform poor compared to lipo and cost more, so you won't find them in my rigs. I do use liFe on some ebikes, but that was the only stuff available a few years ago and as they wear out I'm going liCo to shed pounds from the battery.

Are this hobby king also considered poor as far as discharge/charge rate?
the weight is true heavier, cost seem to have come down well at least this HK brand.
So if this one still safer as far as fire then I thing is still a win but if not hmm I should have stayed with lipo.
But again 2s lipo in my case dont have the punch, that when the 3s Life come in as the 3s Lipo have to much.


here are
Red weight 233g with wire
blue weight 358g



On the front of a wraith


On the front and back of the SCX10 the yellow is a 3s 2200 for comparison
never mind the wiring

[JohnRobHolmes]

Fire safety depends on much more than the chemistry. There is still an extremely flammable solvent inside. I've seen LiFe battery fires, and LiCo packs that wouldn't catch fire with the worst abuse.


Use a 2v per cell low voltage cutoff, 2.5v if you want to be on the safer side. There isn't much usable energy after 2.5v anyway.

[beomagi]

I've never really looked into other LiFe packs other than A123 18650s. The A123s are definitely lower in power than lipo but they take a hell of a beating.

John, do you have any information on LiCo? What pack/brand/oem are you using? Only found these.
http://lygte-info.dk/review/batterie...k%29%20UK.html


Edit: Am I looking at the same thing with LiNiMnCo? Does this include the Sony VTC5? I bought some of those a couple weeks back and will be playing around with them.

LiNiMnCoO2/NMC:http://www.electricbike.com/lithium-cobalt-manganese/

[JohnRobHolmes]

LiCo is basically all lipo. LiNiMnCo and LiMnCo are great variations that are just coming to market with Lico power and runtime densities but better life cycles and thermal stability. In a few years we might see most lipos switching over as the production secrets trickle down, but right now they are just low discharge rate stuff.

[infodragon]

What caused the LiFe fire? I'm very interested in this and I have not been able to find an instance in which they primarily catch fire. The worst I've been able to find is the LiFe starting a secondary fire due to a short and that fire igniting the LiFe.

[JohnRobHolmes]

A puncture that caused the organic solvent to flame up, on a a123 20ah cell