Turnigy Graphene batteries: calculating the internal resistance
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- čas přidán 20. 03. 2016
- How do you measure the internal resistance of a high performance lipo battery like the Turnigy Graphene series? In this video I show you the theory and practice behind making such measurement.
Using this technique it was determined that with a resting voltage of almost 15V, the 4S 1300mAH 60C Graphene battery has an internal resistance of around 0.0435 ohms (43.5 milliohms)
This significantly better than the 45C Turnigy Nanotech 1300mAH 4S pack which measures 0.056 Ohms (56 milliohms).
Next up will be the 25C Nanotech and the 75C Tatu batteries.
Interestingly, both my Turnigy chargers gave different (and quite a bit lower) internal resistance figures but I suspect these tests are done at a much lower current and internal resistance does tend to vary, depending on the current at which it is measured. - Věda a technologie
I can listen to you speak for hours. So much info but you keep it interesting. Thanks for the video. Busy deciding on what packs to buy for my long range FPV plane.
Thanks for uploading another fantastic and much anticipated video Bruce! Its a great feeling we get when you release a new video! Kind regards and greetings from the UK!
Brilliant work Bruce, I am well versed in a lot of science aspects of the hobby but I learn something new each time I watch one of these kinds of videos of yours. Keep it up.
Bruce once again.. I feel I should thank you and love your work.
Thank you from across the world
Thank you Bruce! Never stop making these videos :)
Bruce, nice job! Good solid treatment of the topic. I have been a fan for a while now. I was so impressed I went over to Patreon and signed up!!! Keep up the good work mate!
+Paul Langenkamp Thanks Paul, I appreciate the support and will do my best to justify it.
Nice testing there! :D Very in depth explained as usual! Waiting for the heads up test agaist Turnigy nano-tech 1.3Ah 45-90C! :)
Thanks again for the knowledge you help share with the community!
Been waiting for this video.
Thanks , I've been waiting to learn how to do this. I had already bought some ,1 s graphene 's and they have out performed the other batteries I have by a significant amount in just casual flying.
Great video! Here on this channel you realy could see stuff that matters and get knowledge all in a cool package! I am very gracefull that you didnt close this channel when you had the troubles with the officials.
Thanks Bruce:) As usual, you're like the handbook of rc tech nitty gritty, but for the newest stuff ! =GREAT!!
I think everyone has been waiting for you to do these tests! Nice work Bruce :D I'm also interested to hear your thoughts when flying them. They seem to be on par to the Tattu when flying but are slightly heavier. So that's another factor that needs to be taken into consideration. Interestingly the prototype we received is still going strong and no puffing at all but, the prototype 1300 4S Graphene is actually smaller and lighter than the production ones we purchased. Many things to factor in
Graphenes are blowing tatto away by a long shot the bolts and revos both the high voltage versions are the only packs giving these any competition whatsoever. Check out the 2 threads on the rcgroups forum. The graphene thread and the battery comparison thread both show the real deal results.
I've actually stopped following those threads because I'm learning the hard way that some times real world performance and testing is what counts. Much like a racing car, you can do all the scientific testing you like but at some point you need to test them in real life. When I purchased our thrust stand I thought it was the best thing ever. I made a prop selection for a race based on what I had tested on the thrust stand along with the Watt meter. My son completely disagreed with me! In the end we did lap tests and both of us produced better times on his prop selection not mine.
So real world testing is without a doubt relevant. For Thomas and myself we already know the Graphene offer us the best value for money hands down.
+BMSWEB Do you still feel this way after the SMC battery?
Tim Fulford It's hard to say, because we have only the one pack and that's pretty much it. So when we go for a fly, we compare the one flight on SMC vs the 16 or so on Graphene. SMC are a good pack without a doubt. My gut feel is they are better but the Graphene are still cheaper for us in Australia.
If I had heaps of cash I would without a doubt buy a heap of SMC Packs, but I don't and they don't have them in stock in Australia anyway :D
Thanks Paul. I bought 2 graphene packs and SMC are the same price. I may just stick to graphene since they are supposed to last so much longer.
lovin this Bruce ...cant wait for Part 2 Lets see those numbers :)
Yes! This is what people want to know. Thanks Bruce.
Nice Bruce! I know others have pointed out that you're not subtracting the load resistance from the total resistance, but it shouldn't matter as long as you continue to use the exact same load on all the batteries. One thing that is worth mentioning is that IR is very heavily dependent on temperature. If the packs vary even by a few degrees it can make a dramatic difference in the IR. Ideally all the packs should sit at the same temperature in the same environment before testing.
Also I just got my ESR meter in the mail from Wayne Giles today and ran some quick tests on my 1300mah 4S 65C Graphenes I've been bashing about for the last few months. Cell IR measured about 4.7-4.9 mOhms at about 75deg F, with pack voltage around 26mOhm. They're at about 30 cycles or so, but I've accidentally overdrawn a couple of them down to below 3v per cell, and there's been no measurable increase in IR.
+Ryan Harrell (QuadMcFly) That's exactly what most of the test are lacking: a controlled temperature environment. I experimented with my lipo heater box and came of with some stable ESR readings. My reference temperature for testing is much higher though (40°C). It simply the temperature I found out is best for winter flying in terms of performance.
Another test I did, verifying the temperature dependence: Discharged on of my packs at constant 70 A for about 30 seconds. This will heat up the pack nicely already (1800 mAh, 4S). Killing the load and start measuring IR will give you a rapidly increasing resistance when doing multiple IR measurements as the pack is starting to cool again (without the load). But as you said: As long as you keep all your variables (load type, temp) constant even those manual measured DC-IR values are very well usable for comparison between different packs. :) For general comparisons between different testers the ESR meter seems to be our best bet. Not just because it seems to be pretty accurate, but it is the only platform out there for measuring IR that has a relatively high "market share" and therefore takes out the variables "load type" and "test setup".
You don't need to worry about the load resistance. The only point of the load resistance is it determines what the current is, but since you are measuring the voltage only across the battery, there is no subtracting the load resistance
@@aeroscience9834 You're measuring the voltage across the load as well. It is directly connected!
Really interesting video! Thanks Bruce! :D
very cool lesson Bruce! I was interested in the graphenes by myself as well (ordered the 1800mah 4cells since I want some more flight time with the vortex).
since I have 3 different batt types now (Nanotech 2200mah 4cell, Tattu 1300 and graphene 1800) I did one practical test:
use a fresh battery, hover at 0m alt (well kind of) and apply full throttle and stop the time you need to gain 150m alt (max allowed height blabla...)
also with recording the OSD in my DVR I can look at the VOLTS and AMPS while ascending fast.
the voltage drop (not sure how accurate ezOSD in vortex is) is quite different.
and now with your video I know the theoretical stuff to my practical test - this add's up so nice.
I add a link to my little test-video seperatly - Bruce please get it out of your spam folder (where it will land for sure)
Great video as always.I would like to ask you if instead of a lightbulb, use my charger to discarge a battery by 1C for 10 seconds. Will the results be also accurate?
I've been watching a lot of your videos lately and trying to learn a lot of this stuff. So much to wrap my head around, but you're a very good teacher and great presenter.
I would love to see you do the same test on a 4S 2200mAh Turnigy Heavy Duty pack to see how it compares to the Graphene. I have a couple of these 4S Graphene packs and I've been using them in my ME-163 from HK along with the above mentioned 2200mah. Not a huge difference in performance as far as I can tell, but what I did notice is the low voltage alarms don't work too well with the Graphene packs. Basically, they start beeping right when the battery dies and I've been caught a couple of times with no power left to land. I guess the Graphene packs hold voltage really well as they should, but the THD 2200mah feel like they're on par as far as performance.
Thank you for the great, educational videos. 👍🏼
+Aussie RC Playground same here.. i run 2200mah i suspect they are truer to a 2200mah battery...
Whats a good rule for battery voltages whilst flying? I generally land when the voltage is at 14v whilst hovering/ flying slowly - Can I get any more out the battery? How about voltages under load - punchouts etc ? I have a constant OSD voltage display to keep an eye on things but I think I'm paying too much attention to it !
Does anyone know what a respectable range for internal resistance should be? How do i know if i have a bed cell other than charge being limited on said cell?
What if I do the following: Fully charge the lipo battery and wait 3 hours before I take measurements. Put a load of 4.36A for 20 seconds and then measure the voltage. Then turn off the load and measure the voltage. Could I do this and accurately calculate my IR for my batteries?
Hi I've been flying for over a year now on my emax night hawk and I'm looking for an upgrade what frame and motors do you suggest it has to be strong and look good but not break the bank :) thanks
good work Bruce - now I understand
This is the first time I have ever gotten an ad on this channel. Finally!!! You need to git sum revenue!!!
It's like a patreon for him but we are paying for it with time!
John Mcdonald lol I never watch the ads, I just scratch my self for 15 seconds
+Kick Goldenrod & then there's the cheeky buggers that run AdBlock in their browsers. =^/.~=
ZZ Cat I dont run adblock but I might buy premium ad block and donate $5 to all the youtube channels I watch. Spend about $50 and have all the chores done
So how do I know what the normal IR range of a particular battery is supposed to be?
Hello, what are the internal resistances of the 4S lipo battery? I have a 5200mah 50C battery, which shows 7 ohms.
Do you think it is normal?
If the internal resistance of a 2s lipo (lipo A) has 21 and 22 ohms and another 2s lipo (lipo B) has 26 and 27 ohms and both battery are exactly the same, which lipo would perform better?
I own one graphene battery. It's a Dinogy 1300mah 80C batt. I have literally drained this battery on the bench down to destruction levels while it was connected to some little experiment I was performing. That was 6 months ago. I just went out today and flew a 6 minute flight on an AlfaRc Monster V2 frame w/ old eachine 2205/2300kv motors with the same battery. These things are well worth the extra few bucks you'll pay for them. Old video yes. Up to date reply....priceless ;)
Great video! So once you have the resistance, is it possible to work out what the max reasonable discharge rate is?
Would be interested to know what the actual load is that is used to eliminate the Ionic charge, floating or resting voltage. Also guidelines for testing other batteries based on Capacity and Voltage. Also, use of AC impedance measurements to perform this?
Well explained Bruce. May I suggest you try a PWM driven MOSFET into a short circuit to really give the packs a workout :) Oh and no mention of pre and post test pack temperatures or the totally BS C rate figures manufacturers slap in these packs. It is high time someone named and shamed the biggest liars.
Can't wait for common graphene batteries!
Hey Bruce, could you review Flite Test's Versacopter? It looks quite sturdy to me, but I've never flown it.
Great video. Thank you
Thanks for this video very useful and fun
Thanks Bruce!
could it be that the graphene is a bigger rated battery than 1300mah ? hence why it doesnt discharge so quickly.
Doesn't that Internal Resistance you measured include the resistance of the light globe you used to take off the floating voltage?
Thanks, interesting review :)
I got the Tundra plane from Hobby King. it said to use 3s. 11.1v 2200mAH min30c. some one told me on a plane don't go higher then 2200mAH.. is it OK to? like Go up to a 2500mAH?
as long as the cg is right and the planr is not underpowered it doesn't matter wich size battery you take. so 2500 will be right for sure
Great work Bruce. I'm going to put my own whiteboard up. :-)
Where is the other video you mentioned will be released after this?
Bruce did you like the Graphene packaging
very fancy box and soft bag for the lipo
awesome thanks for another informative video. Can you test the turnigy a spec battery 1300mah..
Bruce, when you go over the battery that you are hammering, would you do an internal resistance test on that battery again? I am very curious to see if the value changes with cell age.
+John Brewer I think thats what he is doing, and will extrapolate the IR increase. Would give a fairly accurate indication !
Looking 4ward to the tattu tests!
Broke one today flying my 250 in a quarry! Punctured one cell:(
So I blew it up!:D Got to see the positive in things!
This is great! I knew this was the way of calculating the IR, but I didn't know about the parasitic load you needed to put on the battery to get reliable values. I guess that's why chargers don't get it right?
Another thing you can do here is calculate the parasitic power draw of the battery itself! Using the example in the end of the video: 40A and 1.7V voltage drop, then the power P=V*I --> 40*1.7=68W (wow that's really high!?). This is why the battery gets warm during flight, and why batteries stay cooler if the IR is lower.
did you ever do the 25C tattu battery?
You didn't show where in the circuit you placed the 12v globe as small load ...? across pos and neg to the left (in the diagram) of the switch and the
ammeter? so it'll be on permanently (nope, probably not), or on pos right of the switch and on neg left of the ammeter?
+David Clark The globe was placed directly across the battery terminals so the current that flowed through it did not affect the reading on the ammeter. The current itself was very low -- in the order of 120mA so will have had little or no bearing on the overall results -- whereas the effect of the ionic charge on the voltage readings could have had a significant effect if it wasn't bled off.
Does that include the connector? I had issues with the connectors on my graphene batteries due to shoddy soldering which would increase IR if measured with the connector.
didn't know Putin was into rc flying.
I like to airlift my attack bears in with a taranis. Really scares scummy capitalists.
+Vladmir Putin you should check out Bruce's UHF system shootout. Now you can bomb Europe from the comfort of the Kremlin :) Who would have thought RCModelReviews was assisting the Russian air force...
Bruce, it would be interesting to repeat this test with various different load currents. I suspect that the ESR is not quite linear. You can also avoid the need to compensate for charge accumulation by calculating the resistance based on the difference between two loads, i.e. R = (V1-V2)/(I1-I2). I think this method would be more accurate.
Would be interesting to see a comparison between the bolt atteries and the graphenes. My subjective observations with my mini quad suggest similar power near full charge. The graphenes seem to hold onto that power all the way through the charge whereas the bolts sag a little. However the bolts definitely fly longer. Internal resistance measured on my charger shows lower for the bolts interestingly. Both very good batteries.
You've done a wonderful job of accounting for ionic charge, and the charge state as it discharges. I notice you used the voltage it recovers to, not the starting voltage, which makes sense for the 1st order model over 10 secs. For a static or slow changing usage case, it is nearly perfect. Although it might eventually recover to the initial voltage if you remove the small load.
What about the 2nd order model? The one with 2 different resistors. One for current spikes or short bursts, and another resistor for extended current draw, like when it's hovering or moving forward at a constant speed without turning. There are 2 different ways to draw the model circuit. You have not taken into account the other resistor and capacitor. This is relevant when the typical usage is in short bursts like during a race. IR can be measured with an AC signal or a DC signal. Both are relevant.
Some say a resistor or light is different from a MOSFET/ESC. I disagree.
Temperature is important. A horrible Lipo at warm temps beats a quality Lipo that is cold every time. This is especially true in the winter when the cells never reach a desirable temperature due to the 100mph freezing wind. Even a few degrees matter on the bench.
Perhaps the Graphene is great at room temperature, but it stays cold due to its initial low IR. And another Lipo warms up until the IR beats the Graphene.
www.ncbi.nlm.nih.gov/pmc/articles/PMC3247723/
I didn't want to be a jerk and ask for part 2 the day after you posted this... but it has been over a month... Can we have part 2 please? Also i would think bigger batteries can take a load better so they likely have lower resistance.
This is useful for setting up battery monitoring on Pixhawk and other FC. if you want to get more accurate battery info on the ground station software.
Hey Bruce, I made some videos on these and found that they do have much more punch than, for example the multi star 'race spec'. I do find them quite large and heavy in comparison. They have a piece of fiberglass on each side to protect them which is nice. The other thing is that when you fly them,they are punchy until the very end, then they drop out of the sky :)
+Nils Rohwer Yep, that's my experience too. This is because the IR doesn't change much right up until the battery capacity is virtually exhausted. Other batteries tend to see a more noticeable increase in IR as they discharge. This was one of the reasons I measured the IR at a storage-charge level (about 35% remaining capacity) because this is where the Graphenes will show the biggest difference against other packs.
Nice video! I'm preparing to make a similar video on my channel, but I'm trying to figure out a way to SAFELY produce run a load of ~75-100 Amps so it's more relevant for my 100+ mph RC speed run application. Do you mind if I share this video on my Facebook page?
Please also test the Dinogy brand lipos they are told to Be awesome.
you probably dont care but if you guys are bored like me atm then you can stream all of the latest movies and series on InstaFlixxer. I've been binge watching with my girlfriend for the last weeks xD
@Raylan Camden yup, been using instaflixxer for since november myself :D
It would neat to test an actual 40a load and see if the voltage drop you calculated holds up.
PLEASE SIR WERE DID THE 0.02VOLT COME FROM? I REALLY ENJOYED THE PROCESS THANK YOU AND GOD BLESS U
While I find chalk talk interesting, the real proof in the pudding are flight times and pack life. While we're at it Bruce, you mentioned something about the IR measurement included on some chargers. In your experience, how accurate are they, what are they really indicating and how would you use that data. Currently (pun intended), I use those figures to show health of the pack and quality of the pack (lower is better) and I keep an eye out on retest for individual cells creeping up in resistance which shows as the pack ages. Any insight on this?
+Aerial Adventurer Thanks, I did understand that, but my question is more of what can they be used for, if anything at all? My practice has been to record internal resistance numbers on each battery when new and periodically check them for cells creeping upward as they do. I've had packs I unwisely drew too much current from and then wouldn't charge correctly. A quick check of their IR with my charger tells the story. I'm not sure supreme accuracy is what I'm after in that regard.
In the last example, the voltage drop is 1.74V, and that is when 40A is being pulled from it. Since P=IV, that means the voltage drop represents 1.74V*40A = 69.6W. Where does that 70W go to? Is it what's heating up the battery? If so, I can see how a lower internal resistance can prolong battery life.
Would love to see the A-Spec batteries that you got a few not so weekly news ago.
Why do you not use the measured voltage at the time when you disconnect the load and the unloaded battery voltage after the test ? In that case its not needed to compensate the discharge of the battery. (14.85v-14.66V)/4,35A = 43.678mOhm
+Peter Kis Because I wanted to be double-sure I got the numbers right and prove that the discharge curve was accounted for.
+xjet With both methods, the calculated values are very close to each other, i expected more difference between the single and the combined calculation results. I think for a beginner easier to understand my calculation but both methods are acceptable. Have you plan to do some advanced measurements with a microcontroller based dummy load ? (discharge curves and internal resistance with different load currents) I think also a good video topic to measure and plot brushless motors current/thrust, current/efficiency curves.(Maybe with different props?) Its so obvious to measure these things for brushless motors but i haven't seen any videos about this subject on youtube.
Looking forward to the results, but I had no idea it would be this complicated. I anticipated the use of a load such as a heating element, with an ammeter and voltmeter appropriately connected. I do see one obvious difference between the batteries: the Nano-Tech has 14-gauge leads while the others have 12-gauge, meaning approximately a 1m𝛺 penalty per foot. I know that's old scale but I figure you probably have about 1 foot of wire between the two leads.
YAYAYAYAY Bruce Reviews!
A video about the influence of the temperature and why pre-heating of the battery in higher load scenarios especially on those colder days improves both power (due to less voltage drop) and service life would be a good followup to this.
5:54 The voltage goes up, because you have stopped drawing current over the internal resistance , so the new voltage is the no-load voltage, which is higher. Then your multimeter has a low-pass filter (especially in the DC setting) and so you have this effect of the voltage seeming to slowly go up (or down).
Floating charge will affect it as well, but I bet it's mostly the dynamics of your voltmeter. If you use an oscilloscope to track the voltage without the lowpass filter, you'll be able to see the difference.
can you do the turnigy multistar batteries
+Hoggdoc There are some 65c multistar 1400mah 4s batts available. My mates have some and love them
+flapflapflap88 I use the 40c discharge 1400 4s batts, and they seem fairly comparable to the dronelabs batteries (UK), and seem better than the nanotechs I've borrowed (the multistars have 2x burst c rating than continuous). IMO they are VERY good for the money
Thanks for this video Bruce, you are awesome. Have you heard of SMC battery packs too? You should try to get your hands on one of them for testing. They have been reviewed very positively. And well I have a selfish reason for wanting you to do that as they are my main packs! Take care
Smc are some great packs. If you want some great info get on the rcgroups forum in the batteries and chargers section go to the load comparison thread. Great info on all the packs. Smc are among the elite.
+Jacob Hendrickson Cool thanks for the helpful info. I will definitely be checking it out
If you could do the test with a Turnigy bolt 4s 1300 65C it would be really nice to compare
odd. almost all other tests i have seen indicate the internal resistance per cell as in the single digits milli ohms. for the graphene ones.
over 10 mohms is actually quite bad.
Hi Bruce, would you consider doing a video about breaking in LiPo packs: whether it is necessary and the best procedure? Manufacturers recommend it but many say it is hocus pocus. What's the truth?
Bad choice if terms for Internal Resistance (IR), Bruce. You easily confuse the punters as you then immediately talk about the V:I:R triangle which also uses the terms I & R!!
Hi, over 10seconds, so 0.019v/4.36A = 4.35 mOhms, is this correct, or is 10seconds the standard?
+dasraiser The time doesn't matter. The only reason I took the reading after 10 seconds was so that I could factor in the discharge curve of the battery. By allowing 10 seconds, the actual amount of voltage drop due to the discharge of the battery is large enough to measure and subtract. If I'd only waited a second or two then it would have been too small a number to accurately factor into the results.
that's fair enough, but if you could accurately measure 1s you would get a 1/10th the answer you have, unless I have misunderstood your video, which is more likely.
+dasraiser No, the time is irrelevant because we're subtracting the effect of the battery discharging. By allowing 10 seconds we're simply letting things stabilize (ie: the load resistance/current stabilising and the internal resistance stabilizing). Because we subtract the effect of the discharge on the voltage we could use *any* time and get the same results because the internal resistance remains pretty constant.
Can you tell me roughly what temperature you are doing these at?
+Reuben Horner It was 21 degrees C in the studio when I made these measurements.
***** Cheers, might test my batteries
Interesting results, but I wonder how well the manufacturers claims of C rating stand up?
You're missing one factor here Bruce. In a closed circuit, the total resistance is the battery's internal resistance + the load resistance. You use the the ammeter and the voltmeter to measure the actual current and voltage drop within that closed circuit.. Now that you know V and I, you will now get the Rt (Total Resistance) through Ohm's Law. Now, to get the Internal Resistance is just a matter of subtracting the load resistance from the total resistance. In your testing you didn't consider the load resistance
+Jan Bobis He's actually right. The load resistance gets canceled buy subtracting the two measurements. The whole formula is (U1-U2)/(I1-I2)
because I1 = 0 he just dropped it.
+Jan Bobis He isn't using the direct figure off the multimeter which would like you said give you the total resistance. He is using the difference in voltage between open circuit and closed circuit, which gives you the voltage drop from the resistance of the battery and the discharged voltage from the battery as he mentioned and accounted for in the video. The total current is the same as the current going through each component in series so the internal resistance is the voltage drop over the total current drawn during the drop.
Can you show us some other batteries like your truck battery.
Does every milliohm difference matter? How does 12milliohms difference matter?
crashed on my 1st flight of my new plane....lost all control at the 5 min mark and was in close range, but near the ground , and there was no chance to recover...........checked voltage on my very old 3S 2200mah lipo right after the crash and it read 3.80 per cell......this seemed OK but all indications before the crash were a loss of control ( brown out due to a LVC ) ....now searching for a simple way to check IR on all my LiPos .....thanks for the video..
One of the most important factors in battery longevity is max and min states of charge, that is, how full you charge (usually 4.2V/cell) and how far down you discharge (usually 3.3V/cell). What the electric vehicle manufacturers have found is that using the middle 70% of the battery capacity can dramatically increase the charge cycles to over 3000. Take for example the Chevy volt which has a 150,000 mile battery warranty (in california) proves this, and is what has made the EV practical. The other important factor is battery temperature under use and charge, as well as storage state of charge (~30-60% is best). Its all about the $/(kWh*cycles).
0.0435 Ohms x 1.3A x 65C = 3,68V Voltage drop under 65C
Minimum Voltage => 3V per Cell => 12V
12V + 3,68V = 15,68 V -> Minimum Voltage to deliver full 65C ?
+David Kaden Not sure that is true. The cell minimum voltage is really the off-load resting voltage, that's what gives you the 'state of charge'. Measuring the cell voltage under load is never a very accurate way of judging the state of charge, because it varies significantly with the amount of load current.
There might be an issue because light bulbs do not have a constant resistance. As far as I remember, the resistance tends to increase with the temperature of the filament, which increases with the current. So I think that your experimental setting is somewhat wrong if you want to perform absolute measures. For comparative purposes, it might be still OK if the "resistance" increases monotonically with the voltage.
It sounds weird but I think it is actually called an "ammeter" rather than amp meter
Where is the load resistance hiding in your calculation? It's not present with the switch off.
cheers brusey! not too hot on the old electronic theory. I can't believe I got an a in school and all I can remember is ohms law and red is live or brown in the uk if your colour blind lol.
Bumped up from $1 a month to $5 :)
+Sonic Orb Studios I noticed Bruce is getting some decent money out of that patreon thing.
neclovekSK yeah, I should have jumped on that site years ago for my channels.
for me the most exciting thing is the high C charge rating if you could charge at 4 or 5C and drop your charge time down to 10 or 15 minutes you could buy way less batteries and just stay out flying all day
agreed. the higher resistance is what kills charges time: at low amps while it's trying to balance near the end of the charge. this is where most of the charge time is wasted. if the resistance is significantly lower on these, it should charge quicker.
***** no I'm talking about the battery charge specs. They say 10 and 15c charge
+Nathan Knight and replace more often..
Xava they say charge at 10c and 900+ cycles is the lifetime of the battery. 4 or 5 c is significantly less than their recommendation.
they lie as always
1:40 - an *upside-down* stack of cells.
(Yeah, I know, there is no polarity marked on that schematic. But up is positive, or you're weird!)
Would love a video on the questionable "C" rating on lipos.
The is no need as video can be 4 seconds long with "Hello and this is RCmodelreviews and today: everybody lie about their C rating. Good bye"
are these graphene or is that a marketing ploy?
+m ej Its a bit of a marketing ploy really - they are essentially just "posh" LiPos using a very small amount of graphene to reduce the internal resistance. Tests show they do seem to perform very well though from what I have read on various forums.
Shame, I thought it was a leap forward in battery tech, like what happened to lipo's over the old nicad's
I would be interested in seeing the test run with a real resistor of a known value in series with the battery to validate the method and the results
what was that voltage again? 14.sexsex V
:-)
oww and thank you for your efforts in the RC hobby
What can you say, that’s how New Zealanders speak
I know I'm a bit picky, but I don't fully agree with your method because in fact you measure the internal resistance of the lipo parallel to the little light bulb. If the bulb draws say 1A then its resistance is approx. 15 ohms which is completely negligible (parallel to 45 milliohms). But I'm complaining about the method, not about the results ;-)
I would divide the voltage diff by the current diff which results in a slightly worse internal resistance. But the difference is just a few permille.
+Martin7182 It's most unlikely the test equipment is calibrated or very accurate, so the absolute value of the internal resistance won't be accurate. The number is really only valuable as a comparison with other batteries, and so long as the setup remains the same it should be good enough for that.
+philDotCom Thanks for that. I'm not complaining about accuracy but about the method. Not taking the parallel load into account will affect the outcome. The small bulb (15W?) is definitely a small load, but you shouldn't repeat this test with a very heavy load. Unless you use a better method, e.g. like I described above.
On the other hand, Bruce seems to like Occam''s Razor, which is a good thing taken into account the mixed group of viewers of this channel.
+Martin7182 The point I was trying to make is that the objective here is to compare different batteries, so any small inaccuracy introduced by the small bulb is irrelevant if the same inaccuracy is present for each and every battery tested. The relative differences between them is still accurate.
I was also trying to point out that the resolution and inaccuracy of the meters will far outweigh the inaccuracy introduced by the small bulb anyway. The small bulb was drawing 120mA, and through roughly 0.0435 Ohms equates to a voltage of 0.00522 Volts which wouldn't even register on the meter being used.
You are correct, but the difference in method would be immeasurable without much better equipment.
Thanks +philDotCom. I got your point although I didn't hear him say that the current was 120mA. But even it is 12A then it will affect the outcome just marginally
The graphene batts are good stuff, a bit heavier than the A-spec G2 but certainly a class above.
The A-Spec G2 are total crap,the first A-spec were good so they've managed to stuffed it up trying to improve or reduced cost.
Bruce how did you break your glasses? lol
+David Smith I walked into a door. I figure that if I didn't see the door, these glasses were already buggered so it makes no difference that now they're cracked :-)
Lol I wasn't sure what I was seeing at first....
Are those doors the same as the trees that jump in front of planes? lmfao
+David Smith magnetic doors :-)
Uhmm, your train went totally off the tracks. Measure the voltage of each cell at the balance plug with and without the load on the discharge leads. Then you can calculate the IR of each cell..