Anyone interested in a graphene battery test?

[T.S.Davis]

Yeah, Giant Power. Maybe he doesn't have them in stock yet. These were prototypes.

I'll ask Bob about it on my commute. He'll want to hear how they ran this past weekend anyway. I still have a 10s set I haven't picked up yet too. Need a place to race them though.

[kfxguy]

Have 6 on the way. Too bad I ordered before noticing the HV435 packs.

I wouldn't worry about that. I've found that even though they are rated at 4.35v, if you constantly charge them to that they get squishy or puffed prematurely. Stick with a 4.20v charge is my recommendation even if you have 4.35's.

[Erroneous]

Yeah, Ive been charging the 435s up to 4.27. I had the same thought on lifespan. Just like the idea of headroom. So the consensus is less heat with the graphenes. Sounds good so far.

[Erroneous]

So.. Generating fuel tables for the new packs.image.jpg. On a Powerlab8. IRs are a little higher than the HV packs.... Will see after a couple cycles what happens. This IR reading is on the 3s go packs 2600mah 70c. image.jpg Will need a bigger granite slab soon

[jim82]

Don't forget about the Turnigy Bolts!

[Erroneous]

So after two cycles, IR is down to 1.8, 1.6, 1.7.. All good.

[kfxguy]

I was gonna tell you I cycled mine 5 times and the ir is super low. (Gohan)ran his new graphenes yesterday in his zelos, got 75mph out of it and said the batts took a beating and didn't get warm. He said he's impressed. Furthermore it's the fastest by far his boat has gone. Good stuff.

[RaceMechaniX]

Come September their will be two new batteries available in ~5000mAh sizes, one 60-70C and the other an extreme 80C battery. Myself and several others have been testing the samples and I can confidently say these are better than anything else on the market. We have tested these against HK Graphenes, Bolts, Hyperion HV's, SLS, GenAce and others. The vendor has got the chemistry and the mechanical construction correct.

If you want to compare IR values off a charger they are coming in around 0.5-0.6mOhms. When tested with a proper ESR meter, values are around 0.6-0.75mOhm.

More info to come with the first batch of production cells are ready for distribution.

[longballlumber]

I have a couple dumb questions (still learning)...

I am assuming that everyone (other than Tyler because I know he has an ESR meter) is posting IR numbers based off of their chargers...

1. Are your IR numbers coming from the charge cycle or a discharge cycle?

2. Again assuming; taking the number from the discharge would make more sense. Is anyone tracking the heat of the battery when getting these IR numbers. won't the number fluctuate based on battery internal temp? (warmer/hotter = lower)

3. My main question; Will a an applied load give you largely different IR numbers i.e. 40amp load vs. 2amp-5amp load (speaking discharge)?

4. At what IR value difference will you actually see a performance difference? I am certain that number will be different for SAW vs. Heat Racing vs. bashing

4. Last one (for now); With all of these numbers getting tossed around are we REALLY comparing "apples to apples"?

[kfxguy]

Come September their will be two new batteries available in ~5000mAh sizes, one 60-70C and the other an extreme 80C battery. Myself and several others have been testing the samples and I can confidently say these are better than anything else on the market. We have tested these against HK Graphenes, Bolts, Hyperion HV's, SLS, GenAce and others. The vendor has got the chemistry and the mechanical construction correct.

If you want to compare IR values off a charger they are coming in around 0.5-0.6mOhms. When tested with a proper ESR meter, values are around 0.6-0.75mOhm.

More info to come with the first batch of production cells are ready for distribution.

When you get some in, send me a pm. I'd like to try a pair of 4s in my Rivercat.

[RaceMechaniX]

Mike,
As we have discussed I use both methods for measuring IR.
With a new battery I will charge to 3.85V/cell and starting at room temp measure the IR with a good ESR meter. I use the Wayne Giles ESR meter, you can get them at PRC here: http://www.progressiverc.com/univers...sis-meter.html I highly suggest getting one as it separates the good from the bad.
I continue by slowly heating the cells from room temp up to 50C and take IR measurements of every cell every 5Deg C. This plots a consistent IR over temp at a known voltage. IR should drop with temperature. Be careful at the higher temps and it goes without saying, never leave the area when you are performing this testing.

Following the baseline test, I cycle three to five times on an icharger with a 1000W load. At the end of every charge/discharge event I record the cell IR from charger and plot this in excel.

The iCharger is not as accurate as the ESR meter, but it is fairly consistent. I typically see readings 0.15 to 0.25 lower on the charger compared to the ESR meter.

Following the cycle test, I will balance store to 3.85V/cell and repeat the IR test with the ESR meter over the temperature range.

There is a difference between testing at 5A and 20A. Hence the reason the ESR meter is a little more accurate, it uses a higher pulse current to measure the voltage drop across each cell.

For SAW racing, the lower the better. Period. The mechanical construction is as important as the chemistry. One nice feature of the iCharger is it will differentiate between the cell IR and the pack IR which includes the cables and interconnects.
For 1P heat racing cell values should be lower than 1.5mOhm to have the best performance. In 2P racing, 2-3mOhm is OK.
For bashing, it is more important that the cells are balanced across the pack for IR values. If you have one poor cell it will work this cell harder leading to a potential failure.

[RaceMechaniX]

I would also highly recommend using heat sensitive labels for measuring battery pack temps. Most of you will remember the thermometer strips used to measure your forehead temperature. Stick one on each battery and keeps tabs on you battery temp. Simple and easy to use.

McMaster sells them in 10 packs in a perfect temp range. http://www.mcmaster.com/#59485k21/=13nfmqs

59485k21p1-c02a-digitall.jpg

[kfxguy]

I have a couple dumb questions (still learning)...

I am assuming that everyone (other than Tyler because I know he has an ESR meter) is posting IR numbers based off of their chargers...

1. Are your IR numbers coming from the charge cycle or a discharge cycle?

2. Again assuming; taking the number from the discharge would make more sense. Is anyone tracking the heat of the battery when getting these IR numbers. won't the number fluctuate based on battery internal temp? (warmer/hotter = lower)

3. My main question; Will a an applied load give you largely different IR numbers i.e. 40amp load vs. 2amp-5amp load (speaking discharge)?

4. At what IR value difference will you actually see a performance difference? I am certain that number will be different for SAW vs. Heat Racing vs. bashing

4. Last one (for now); With all of these numbers getting tossed around are we REALLY comparing "apples to apples"?

I'm checking it on my powerlab. I'm only doing it for my own personal comparison to my hv batts. In my case I feel like I'm comparing apples to apples. But me comparing mine to what someone else is coming up with May or may not be the same. Does the final number really matter? To me, not so much. It's just the fact that they are indeed lower than my other batteries. Also the fact that I'm running them in stuff that normally gets my batteries warm and the the graphenes aren't getting warm. That means something too. I'm not checking the temps during my charge cycle, 1) I don't have time to do that 2) it's meaningless to me 3) I doubt at 5-7amps it generates much hear anyway. I have felt them and they are always about room temp

My powerlab charger starts taking the ir at the beginning of the charge cycle. It takes 2-3 minutes to check it. I guess it's as accurate as a powerlab is. They are said to be really good chargers and I love mine. I'm actually considering selling mine and upgrading to the next highest one.

[kfxguy]

I would also highly recommend using heat sensitive labels for measuring battery pack temps. Most of you will remember the thermometer strips used to measure your forehead temperature. Stick one on each battery and keeps tabs on you battery temp. Simple and easy to use.

McMaster sells them in 10 packs in a perfect temp range. http://www.mcmaster.com/#59485k21/=13nfmqs

[ATTACH=CONFIG]145092[/ATTACH]

The revo packs come with thermal labels.

[kfxguy]

I would also highly recommend using heat sensitive labels for measuring battery pack temps. Most of you will remember the thermometer strips used to measure your forehead temperature. Stick one on each battery and keeps tabs on you battery temp. Simple and easy to use.

McMaster sells them in 10 packs in a perfect temp range. http://www.mcmaster.com/#59485k21/=13nfmqs

[ATTACH=CONFIG]145092[/ATTACH]

I do like those better. Question. Say I wanted to use a label on a motor. Can I cut it shorter to the temp range I need and it still work? If so, this would be great for sticking on a motor and esc for at a glance temps.