30C Continuous(ish) Lipo Discharge
 

interesting...especially the last paragraph.

if the testing equipment he is using is right...then sweet. proves a point....


as for the last paragraph...hes saying bashers pull 3c?
thats like saying " you bought a 500hp car, but its about the about 200 your typically gonna use" and dropping a 250hp motor in it instead

I think that he means that us bashers are harder on our batts. than racers. That's what I took out of it any way.

i bet it was maxamps or smc.

that battery did not like 30c at all.

I think he's referring to the average amp draw that we pull. Bashers and Racers alike.

If you've ever really looked at an Eagletree graph, they turn out to be alot of spikes.

Average amp draw is surprizingly low. Although, Amp Spikes for 1/8 scale can easily hit 150 amps.

These spikes only last for maybe 1/4th of a second.

ahh that makes sense. i really need to get myself a eagle tree...it sounds fun :yes:

as for the brand, i think it may be maxamps, my packs had the same yellow tape holding it together...but again i dont know if any other brands use that tape:neutral:

Yeah, average amp draw is around 6 -7 times lower than the spikes, and "running" amperage is ~2X lower than the average. Of course, this depends on how it is used, gearing, etc, but pretty typical.

Hi Brian. I'm glad you stopped into this thread. :yes:

Remember the home brew battery discharger? That would have been turning alot of lipos into goo. LOL (Testing of this nature isn't something you would want to do in your home.)

Although, if what I suspect is correct, it wouldn't be fair to judge all Lipos by the one in the video.

I also suspect that a 30C continuous discharge (even to 3.0 volts per cell) would substantially shorten the life of just about ANY Lipo pack on the market.

Oh I know. That's why I had said any donated packs may not survive the testing. It would just be nice to define a set of criteria (like v under load, duration, temp, duty cycle, etc) and then see what kind of C rates the pack can really deliver under those criteria.

I think we can all agree that constant discharging at anything approaching 30C is not representative of 99% of car users. At best, we can usually assume that higher C rate batteries will maintain a higher voltage under a given load, which is better for cell longevity.

Looking at the numbers they tested a good 5-8C pack , it never really made 30C. The pack should've been done at around 10C or so. It is customary to progressively go higher until one reaches the point of "max C" so that the other tests aren't lost.

Brian, do you think there might be a way to develop a theoretical amp draw calculation, and thereby use that data to select battery requirements? I know there are a lot of variables, but we already input most of them into the calculator already...

Yes....your 500hp motor that you operate at 40% of its capacity is going to last much longer, and should be more efficient than a 250hp motor operated at 90-100% of capacity.

IMO, this video means nothing without stating the brand name, lol, simply calling it a 'name brand' pack doesn't tell us anything.

As for efficiency, can't really say that, depends on displacement, forced induction or not, whether it's a high speed/low torque, or low speed/high torque, anywhere in between, etc.

LiCoO2 , whose pack is this? Venom perhaps? flightpower or a mis-print?

Why is that?

True - shouldn't have thrown that in there.

Don't you think it matters what brand it is? Is it just me?

I think the point of this whole thing is that the "C" rating is total BS and im sure it is on all prands of lipo. If you did this same test on 10 different brands of lipo you would probably get the same results. Some would take 3 seconds to drop below 3v/cell and some of the better ones might take 2 or 3 times that long, but none would likely stand for a true constant discharge at the C rateing printed on the sticker.

Its all marketing BS.

Maybe so, but I still think it means nothing when they don't state what brand they are using. I could go get a crap brand LiFePO4 cell and test it to the rated C rating and get much lower volts than the manufacturer would provide, does that mean A123's are crap?

So that's exactly the type of thinking that they were trying to avoid. If you put a name with it, people will focus on that, and not on the data.

What I read into it, was that we are being fed a C rating number, and being told its important, kinda like Hp ratings. But this one particular experiment shows that a battery can not in fact handle running at its C rating. Just another feather to put into the "use your C rating with an asterik" hat....

Even if they don't want to publish the names of the lipo brands it would be interesting to me to see them do this same test on a few more different brands and see what results they got. Just to understand how much difference there is from one brand to the next.

I can guaruntee that "another" brand would be much more accurate in it's labeling. I have enough experience in watching voltages at differing currents to label this pack as a "cheap, generic, e-bay type" pack. There are really some that will deliver very close to what they are rated.

My guess is that this was a hard pack to start out.

It definately matter which brand it is, but without comparitive testing the reult is pretty meaningless regardless of the brand- I think they didnt name the brand because of this very reason + the possibility of the test & results being called liable/ slander ( picking on one brand instead of several ). Indeed, if most packs performed like this you'd know the ratings system was just bollocks, but if this was just a cheapo pack & high-end packs performed much better/ closer to rated spec, you'd know your money was well spent or not..

It is an exception rather than a rule that businesses correctly state their product's capability unless specifically directed to do so. I think that's pretty much all they were trying to say. Without industry standards and independent testing we have no idea if we are actually getting what we paid for.

Yeah, I would have to say either state the brand AND test several brand packs, or don't do a single pack test at all, means diddly squat! It doesn't tell anyone anything.

Agreed that C ratings should be changed to a more real world and easily understandable term as pack Ri, have a standard test for a pack take the Ri at the middle of the discharge? At a standard C discharge, say 10-20C.

Besides, you can't draw the currents from a 30C pack from wires and deans plug anyways, the losses are so great in the wire itself, the solder might have melted, especially if the pack was larger.

hoober, I would agree with you that this pack is obviously a low end cheapy pack, no high quality lipo pack drops that much voltage in 10 seconds.

everydayflyer over at RCGroups forum has tested Hyperion G3 packs, both 35 and 45C EX packs at near their limits, they always do fine throughout the discharge.

http://www.rcgroups.com/forums/showthread.php?t=1242354

Thanks ZP - that was good data. I've bookmarked his thread (especially since I'm now converting to Hyperions...!)