Turnigy LiFEPO4 packs

[thzero]

JThiessen, well said. IMO too many people see the prices from "HobbyKing" and automatically assume all other battery vendors are shafting them and absolutely refuse to turn the argument around and say "wait a minute, why are they the only one that is so low"?

Everyone wants to demand accountability from MaxAmps, ThunderPower, SMC (anyone see the latest Epic, cough Trinity, ad that has the red letters SMC throughout their advertisements?), Hyperion (they are in HK), etc. But I've yet to see any call, except my own of course, for "HobbyKing" to be held accountable.

It'd be nice to see for each LiPo back the exact specifications of each cell in the pack. Along with testing methodology and performance charts. Then again, you'd still have to take those with a grain of salt, unless they could be backed up by independent testing, as they'll go through the marketing machine and get fudged anyways.

[himalaya]

Keep this great thread going on Lutach. I love science fictions but better not from our battery vendors.

[lutach]

Originally Posted by himalaya

Keep this great thread going on Lutach. I love science fictions but better not from our battery vendors.

The places I know that makes lifepo4 cells are having a blast reading there stuff. The place that actually makes the lifepo4 soft prismatic cell that are 2250mAh said they don't have many rejects and there's no such thing as "top grade cells or Seconds and Thirds". If there was, they would have to stop production. Quality in Asia is changing or should I say, "has changed". You probably know this as well, you're closer to the factories than I am. As for as I know this 25C or 30C lifepo4 cell is not fully mature. There are other capacity as well ranging from: 1100-3600 for 25C and 1900-3600 for 30C. As for lipos, I know for a fact that 25C is mature and anything above it has not fully matured yet, but are showing good results. To be honest, I could've been making some nice change if I sold lipos or lifepo4 at the same price as Hobbycity, but the liability batteries have are very high.

[himalaya]

Here in China soft pack LiFePO4 cells has been around for some time, I would say two years at least. Due to its higher IR and the long exsisting superstition to "genuine" A123 cells, they are not selling too well in RC market, but it's pretty successful in electric bikes. Bigger steel case cells for automotive use has also came out.

I have to agree with you that Chinese products quality has been tremendously improved. I still rememeber when I was around 10 years old making my first 6-transistor radio I have to scratch all transistor legs with a knife to get them solderable, now my company has automatic pick&place machine and multi-temp-zone reflow soldering oven making BEAUTIFUL PCB assemblies.

One of my friends is a competitive RC boater, he spoke to a LiPo factory to get the finest cells to win the game. What he was told is they do "filter" their products to several grades, usually called A, B1 and B2. 5Ah 28C cell as an exmaple, they draw a line at 1.9mOhms. In other words, You may get a 1.8mOhms cell with twice the price of a 1.9mOhms cell. There are difference between A and B grades but not heaven to earth, if there are such huge diversity, the production line MUST be stopped to check what has gone wrong.

[lutach]

Originally Posted by himalaya

Here in China soft pack LiFePO4 cells has been around for some time, I would say two years at least. Due to its higher IR and the long exsisting superstition to "genuine" A123 cells, they are not selling too well in RC market, but it's pretty successful in electric bikes. Bigger steel case cells for automotive use has also came out.

I have to agree with you that Chinese products quality has been tremendously improved. I still rememeber when I was around 10 years old making my first 6-transistor radio I have to scratch all transistor legs with a knife to get them solderable, now my company has automatic pick&place machine and multi-temp-zone reflow soldering oven making BEAUTIFUL PCB assemblies.

One of my friends is a competitive RC boater, he spoke to a LiPo factory to get the finest cells to win the game. What he was told is they do "filter" their products to several grades, usually called A, B1 and B2. 5Ah 28C cell as an exmaple, they draw a line at 1.9mOhms. In other words, You may get a 1.8mOhms cell with twice the price of a 1.9mOhms cell. There are difference between A and B grades but not heaven to earth, if there are such huge diversity, the production line MUST be stopped to check what has gone wrong.

The only grades I know of are the ones that sit in stock for longer then expected. As far as fresh cells go, yes they'll vary in resistance and capacity a little, it happens to almost if not everything as it's hard to have two of the same exact thing made. If a pack builder gets a lot of cell, he may choose to check the resistance and capacity on all of the cells to have them match as close as they can and maybe the price increase of some brands is due to that. Now the question is, how many of the pack builders have the machines capable of doing such a job? Most materials used in the lithium battery manufacturing is as pure as 99.99% and I bet the factory will not have other production lines using 85, 90 or 95% pure material just to cut cost and have a grading sytem going. I like to wait and see what's working for everyone and if I feel the need for more lipos, I just go through the ones that are working good.

[sikeston34m]

OK, back on topic here.

Just received my packs, and they look good.

All cells are right at 3.33 volts and are within .003 volts of each other.

After soldering a few connectors on, I'm running a limited discharge test.

My MRC Superbrain 989 will do lead acid. Well it just happens that is a 3.6 volt per cell cutoff, just like the Lifepo4 chemistry.

These packs were nearly charged upon receipt, but I went ahead and topped them off until the charger dropped to .5 charge amps.

It's already dark outside here, so E Revo runs will have to wait until tomorrow, but I can tell you this.

On a 10 amp constant discharge, cell voltage at the balance lead, drops to 3.25 volts per cell at the beginning of the discharge cycle.

I'm using an Extrema Balancer with PC Software for voltage reporting.

Discharge at the 1000mah mark sees volts per cell at 3.21 volts after 7 minutes.

Discharge at the 2000mah mark sees 3.19 volts per cell at the 15 minute mark.

At this point my discharger is getting hot. LOL It has tapered back the amps of discharge to 7 amps. Dang it.

At 2300mah's of discharge, it tapers it back to 5 amps. The discharge side of this MRC is wimpy. LOL

At 3000mah's of discharge, 5 amp draw shows 3.15 volts per cell.

Even though it's a small discharge rate, the discharge curve appears to be pretty flat.

Spin the Clock forward to the next afternoon.

I just took my E Revo for a run. MMM ESC, Medusa 36-60-1500kv geared 22/40, being powered by 4S Lifepo4.

When I sat the truck down and stabbed the throttle, it charged off, then just stopped. I was already on the LVC, because it was still set at 3.2 volts per cell for the Lipo..........dang!

I quickly unplugged the ESC and plugged it back up. It beeped 3 times and told me that it was now counting 3 Lipo cells for the LVC.

Hmmm..........9.6 volts Total LVC = 2.4 volts per cell. Perfect!

These packs are punchy! The truck wasn't as anxious to backflip like it was on Lipo, but alot of time was spent on the spoiler and it would point the front end to the sky almost at will.

Top speed was much better than I expected, even though no gears were changed.

I zipped around the yard, pulling wheelies and slinging dirt for 20 minutes, before it got on the LVC of 9.6 volts.

At the end of the run, the cells had settled back up to around 3.2 volts per cell and were all within .004 volts of each other.

Pack temperature was barely warmer than when they were put in the compartments.

I have ran 4S2P A123 cells in the past, on similiar setup. I believe these are holding voltage better under a load.

Plans are to hook these up 4S to a lead acid charger I have. Then test their fast charge ability, while monitoring individual cell voltage.

A Typical Lead acid charger has a 14.5 volt charge cutoff. This is perfect for 4P!

Then I can charge at 20 amps. I will report more as testing continues........

[lutach]

Not bad for rejects.

[sikeston34m]

Originally Posted by lutach

Not bad for rejects.

I'm not "giving" that "other" company any of my money, but I would just about be willing to bet, these ARE the same cells.

Identical size and weight!

[Unsullied_Spy]

Originally Posted by sikeston34m

Identical size and weight!

Yeah but what about the ratings? The MA ones are rated better so they must be superior. Oh yeah, they're also factory fresh cells and made to order. And water proof

[lutach]

Originally Posted by sikeston34m

I'm not "giving" that "other" company any of my money, but I would just about be willing to bet, these ARE the same cells.

Identical size and weight!

What are you F****** serious, I said they were factory rejects and will never perform like my packs....Now go buy my packs (I'm in Jason's mode btw).

So, does anyone here have the other life pack from you know who?

[suicideneil]

I believe a few mugs on the trx forum have some, and I think on rccrawlers too- good luck getting an intelligent answer about test results out of them; people who pay $300 for a $70 batt tend not to know remotely about anythign too technical, they just believe everything they are told/shown.

As a rapper once said; dont believe the hype...

[himalaya]

Originally Posted by lutach

The only grades I know of are the ones that sit in stock for longer then expected. As far as fresh cells go, yes they'll vary in resistance and capacity a little, it happens to almost if not everything as it's hard to have two of the same exact thing made. If a pack builder gets a lot of cell, he may choose to check the resistance and capacity on all of the cells to have them match as close as they can and maybe the price increase of some brands is due to that. Now the question is, how many of the pack builders have the machines capable of doing such a job? Most materials used in the lithium battery manufacturing is as pure as 99.99% and I bet the factory will not have other production lines using 85, 90 or 95% pure material just to cut cost and have a grading sytem going. I like to wait and see what's working for everyone and if I feel the need for more lipos, I just go through the ones that are working good.

I failed to find ANY CLUE to verify that they really do the "IR and capacity matching" job when building a pack as they claimed. I mean the big names, their triple or quad price tag that customers have to pay is only for the name, the service and much of their pocket, IMO.

Here's what I found between a cheap Turnigy 5000mAh and a big name hot product 4200mAh. These are the last 1/4 ending section of the discharge curve taken from a same charger and the packs are both brand new. Can anyone say it has tighter capacity tolenrance than the much cheaper one?

Turnigy:


a hot big name pack:


Also, at 3.2A discharge(due to 80W discharge limit of my charger) my Turnigy 5000mAh delivers 5184mAh while the big name 4200mAh delivers 4043mAh. And there come many complaint the Turnigy packs are heavier than SIMILAR RATED packs.

Interesting information on those graphs.

I love RC Monster, it's very educational.

[thzero]

And many also said; 'you get what you pay' for or another one is 'its too good to be true'.

I'm curious as to why other vendors, such as Hyperion, aren't producing lower price packs themselves.

Then rhetrotric on both sides of the fence is equally off putting.

Originally Posted by suicideneil

people who pay $300 for a $70 batt tend not to know remotely about anythign too technical, they just believe everything they are told/shown.

As a rapper once said; dont believe the hype...

[lincpimp]

Originally Posted by suicideneil

As a rapper once said; dont believe the hype...

A rapper also said " I've got that fire, holla at a nizzle if you want that oscar mayer"

Good advice to live by if you ask me!

I only bought 1 of the 2s2p 4500 packs, but I plan to test it in situations that would easily outclass a maxamps pack. Thats right, not 1 but 2 tamiya silver can motors and a 8lb truck that is geared for 5mph! And no lvc!!! Lets see any maxamps pack stand up to that abuse. My jugg2 will conquer all, after I overnight some parts from japan.