Lipo discharge q
 

Check out the Amp Draw:

http://i212.photobucket.com/albums/c...rols/flux2.jpg

And the voltage drop

http://i212.photobucket.com/albums/c...rols/flux1.jpg

This is one ONE pack out of two in my Savage Flux (30C 5000mah packs), Speed controller set to 3.2v/cell cut off. Packs read 3.3v/cell on end of run with a small lipo monitor. Pack temp was 90f and took charge no problem (4200mah)

At this cut off, the LVC did NOT kick in although the vehicle performance did drop off significantly


So should the LVC be set a lot higher, or does it only kick in on a packs resting voltage, not voltage under amp draw?

..slightly confused!

I to would like to know more about this. I run the cheap chinese packs $60 and want to know what kinda performance im getting from them. true Discharge rating, I run my packs @ 3.2V cut off and they never get over 95f with hard running. Motor never seen 140f ESC 125f Mamba Monster 2200kv

4s1p 25c 5000mAh but they charge up damn near 6000mAh

http://www.hobbycity.com/hobbycity/s...8850135U-4.jpg
http://www.hobbycity.com/hobbycity/s...R4900-4-25.jpg

What packs are you running?

hobbycity specials.

Turnigy,Rhino,Zippy

4s1p 5000mAh 25C and 20C packs @ $60 bucks each

http://www.hobbycity.com/hobbycity/s...8850135U-4.jpg

http://www.hobbycity.com/hobbycity/s...R4900-4-25.jpg

http://www.hobbycity.com/hobbycity/s.../5000-4-25.jpg

Sorry Mentat, I was asking the OP. Anyway I seen in another thread what he is using.

Thanks for caring anyway:great:

If I can get voltage drops like this on a 5000mah 30C pack, it'd probably be worse for those on the 25C packs.

But without the Eagle Tree many ppl wouldn't see that even before the LVC on a MMM kicks in (at 3.2 v a cell) under amp load, the pack is being pushed down to 2.6/2.7v a cell.

This was running two identical packs, bought at the same time and both only ever used in the Savage Flux at the same time, so they each have an identical number of cycles.

Wow, that's pretty bad, especially towards the end there. I know the MMM LC works, but maybe it either averages out those really low v dips and /or samples every X amounts of seconds.

Hmm, not sure about those zippy/tunigy/etc packs. 118A on a 5Ah pack is 23.6C, and if they can't even hold 3v/cell at that rate, I'd hate to see a real 150A (30C) draw. Personally, I would rate these 15-20C continuous and 25C burst. Once again, this really shows the value of standardized ratings.

I have some Elite 3.3Ah 30C 3s packs that hold 3.3v/cell at 133A (40C), but that is burst. Yeah, they are more expensive, but maybe you DO get what you pay for?

I.... **hangs head in shame**

On the upside, I run my packs in parallel, so Im safe... for now.


EDIT: these arent hobbycity lipos, they're harris lipos right?

I wish people would list the brand/ model when posting stuff like this :rules:

The OP said they were Harris Lipos in another thread, but then the pictures got added and the topic turned somewhat.

Can you verify the Brand of Lipos in the discharge graph please?

Yes they are harris rc lipos

see here:

Harris RC 5000mah 30C hardcase


http://www.harrisrc.com/lipo1.htm


Curious thing is when I emailed them re these discharge graphs, I get no answer. Strange yes?

Regardless I will reset the MMM esc to a cut off of 3.5v / cell, if it's averaging or taking a sample based on the packs resting voltage, it "should" cut off around the 15min mark on this graph which is what I want.

PS, a Reedy 5000mah 20C hardcase lipo dropped to 5.89v on a full charge amp burst and the lvc didn't trip there either.

Define "full charge amp burst"- you didnt list the current draw so the *true* C rating can not be determined...

Wouldnt mind seeing some eagle tree graphes of Zippies though, there must be some around somewhere.

Yikes, those Harris packs are way overpriced.

Yeah, I would love to see some Zippy flightmax eagletree graphs. So if anyone has recorded a zippy session, then come on and post er up!

I can't see them performing very well, I wouldn't hold my breath about the idea that they are overrated packs for a great price.

I have a cell logger setup on the way that works with a program called Logview. It's not exactly an eagletree, but should be interesting to monitor cell voltage under a load. It hooks up to the balance lead and records individual cell voltage. Handy for spotting troublesome cells I would think.

ZPB, I wouldn't sell the flightmax or the Turnigy short. I've ran both.

My E Revo is set up this way.

MMM ESC
Medusa 36-60-2000kv geared 18/52

I know this setup doesn't draw as much as the Castle Neu does, but it has allowed me some comparitive testing.

They're not bad at all. :yes: I will be able to do some comparitive cell voltage reports under a load when my cell logger gets here.

I have several different brands that will be put to the test.

It's just that I have never seen a discharge graph for one...

I would like to contact many of the mainstream manufacturers of RC packs to get them to give up one of each of their different C rated packs, then do exhaustive testing and to determine a standard performance rating, like we mentioned in the other thread. I would love to do this myself, as I have some good equipment already, and would only need a few pieces here and there, and I have a professional test setup.

What is amazing to me is:

It seems each Lipo manufacturer is playing around with the slurry "recipe".

I've ran the cheap slurry compounds. They tend to not hold voltage well under a load and toward the end of the run, you know the end is coming. It's still running but it's starting to get tired. This lasts for a few minutes.

The better slurry compounds, higher "C", behave somewhat differently. They hold their voltage well under a load, quite high. When the end comes, it's like falling off a cliff. One minute, you're running strong, and then it's on the LVC.

Pack Temperature often gives you some indication as to how hard you are pushing the pack. This "rule" doesn't seem to hold true for the flightpower compounds. They have some incredible punch, but seem to run warmer than the rest of the herd.

Not sure what you're wanting, I charged the 5000mah pack at 1C on my balance charger, then hooked it up to the logger and another identical pack (no logger) on the otherside of the Savage Flux

Powered it up took it for a bash

Downloaded graph as above.

Was hoping some of you lipo gurus would have answers! :rofl:

I am thinking maybe we need to set the LVC at :gasp: 3.5v a cell to avoid these below 6v drops near the end of the cycle but before a 3.2v / cell cut off kicks in. Because as I said before, LVC did not kick in.

Maybe their Coulombic efficiency is not very high? I am still wondering if this efficiency is converted into heat, or if I am off base with this..?

I have seen one video on youtube where they test a flightmax 20/30C 2200mah pack and the voltage drops to 3.05v/cell @ 26C, which I guess isn't too bad, and might actually be on target for a 20C rating... but I would like to see the same kind of test for the 30C packs. Cuz don't get me wrong, I am very interested in these packs, I just have not seen any data showing they deliver as advertised.

Where as I did a bit of research on the Hyperion G3 35C packs I bought, and on RCGroups, and helifreak forums they did some good tests and they really do deliver amazing power, and just a touch off the 'ultimate pack' Thunderpower 40C batteries, but for almost 1/2 the cost of the TP.

Like you said Sike, these G3's are delivering the power right up until the end, much like A123's in fact. From the few tests I did of my own, I found they would deliver around 3.35v/cell at 35C discharge, maybe higher. The one temp reading I ever took was at the track, someone else's gun (lost mine), the temps were only ever 5F above ambient temps... that's impressive.

I suspect Flightpower is using the same cells in their EON X30 packs, as they state VERY similar benefits for their 'new' packs over their old ones. Neu I think might be using these cells as well, along with CTech batteries.

If I were you, I would double check everything. Make sure you have the latest firmware version uploaded to your ESC. I remember issues with the lvc on previous versions.

Looking at your graph, the run really started at about the 3 minute mark. The pack wasn't doing too bad until about the 15 minute mark. (12 minutes into the run).
It was at this point, it really began struggling to keep up with the load. Only 3400mah spent at this point.

Based soley on this graph, IMO, this isn't a 30C pack and it probably isn't a full 5000mah pack either.

What is this pack's size? Dimensions? What does it weigh?

Maybe your eagletree logger is not calibrated/inaccurate?

Pack measures 137mm by 46mm by 25mm

Weight 320 grams

ESC is running V1.21 (Beta) firmware and has been for weeks.

It's an Australian site (I'm pretty sure), so stuff like that is a bit more expensive here usually, but manly it's in AUS$, which got up to 97US cents around this time last year, but is down to a bit under 80US cents now.

I wonder what types of cells the 30C packs use. I remember hearing a while ago that some of the 30C packs didn't hold voltage quite as well as the older 25C cells of the same brand.

You said you did another run with the Reedy pack hooked up and produced a voltage of 5.89 under load, but you didnt post the graph for use to look at & determine the C rating, nor did you say what the load was that produced that voltage drop, thats what I was wanting. If you posted the graph elsewhere, then a link would be handy :yes: (my psychic powers arent what they used to be....).