PDA

View Full Version : Lower mAh than advertised.


RFick73
2014.03.25, 09:50 AM
Hey Guys.

So, I went ahead and bought 5 sets of the R1 Wurks Competition 990UHO batteries.
I was a little dissapointed at the result of my first break-in run.
As you can see below, I got on average of like 780mAh.
I had expected that to be a lot closer to 850 or so.

I decided to run them through 6 cycles of the Break-in setting on my chargers. (That took forever!!!)
The results with 000's are from a battery charger that doesn't display the proper ending mAh, it always showed somewhere around 1500, apparently it was a complaint others had too. :(
I then ran them through a normal Charge/Discharge/Charge Cycle in case the Break-In wasn't calculating properly.

Anyhow, do these numbers look right to everyone else?
I only noted down mAh this time & not the Voltage as I decided to match them by mAh.

Batt#_C#1__C#2_C#3__C#4__C#5_C#6____AVG____FullCyc le
01____774__792__000__000__803__802____792.75____86 5
02____767__791__000__000__796__796____787.50____86 3
03____757__774__000__000__784__780____773.75____82 3
04____782__796__000__000__801__801____795.00____85 8
05____784__798__000__000__818__812____803.00____86 3
06____786__797__000__000__808__804____798.75____84 8
07____763__778__000__000__795__790____781.50____83 6
08____786__800__000__000__809__803____799.50____85 1
09____782__802__791__800__801__803____796.50____79 6
10____767__792__785__788__791__792____785.83____78 8
11____769__788__779__788__786__791____783.50____78 3
12____780__795__758__799__797__800____788.16____79 1
13____797__816__826__828__000__000____816.75____90 5
14____773__781__786__783__000__000____780.75____86 9
15____781__796__804__804__000__000____796.25____85 6
16____782__796__802__803__000__000____795.75____87 4
17____790__809__812__818__000__000____807.25____81 4
18____751__770__773__777__000__000____767.75____77 2
19____764__780__784__787__000__000____778.75____78 3
20____779__798__803__809__000__000____797.25____79 6

For now I've matched them from highest to lowest mAh:
13, 16, 14, 1
2, 5, 4, 15
8, 6, 7, 3
17, 9, 20, 12
10, 11, 19, 18

Thoughts?

TheSteve
2014.03.25, 11:42 AM
What discharge rate did you use? Many times the capacity of a battery is spec'd with a discharge rate of C/10. The higher the discharge rate you use the less capacity you will get.

Traveler
2014.03.25, 12:23 PM
They seem kind of low. In addition to the discharge rate, what charger did you use? Some chargers measure charge capacity and others measure discharge capacity. Discharge capacities are always lower.

ChiMiniRc
2014.03.25, 12:59 PM
If you are concerned about matching the label, than a 100mah discharge would be what you are after and this would be after a 100mah trickle charge overnight. Even then, I've rarely had labels match real word results. It's gotten to the point where I find the label meaningless.

In practice I haven't used the 990 version. The regular R1's tend to be high 700's on a 1amp (1000mah) discharge.

chad508
2014.03.25, 10:14 PM
you also have to take into account that you are not completely discharging the battery. it still has .9 volts and voltage will go back up after discharge is done. If you have a battery that is charging to its labeled voltage i suspect that battery to be bad or charger to not be charging correct.
and a side note is to not match by charge mah. you always match by average discharge voltage then discharge mah as thats what matters not how much goes in but how much comes out and how fast.

chad508
2014.03.25, 10:16 PM
i also never match batteries before i have ran them 4-6 cycles on the track.

RFick73
2014.03.27, 10:04 AM
What discharge rate did you use? Many times the capacity of a battery is spec'd with a discharge rate of C/10. The higher the discharge rate you use the less capacity you will get.

The manual for one set of chargers says the break-in cycle charges at 0.1c for 16 hours, rests for an hour, discharges @ 0.2c, then recharges @0.1C for 16 hours again.

When I did my final cycle, I set it to charge @ 1000MA & discharge @ 500MA

RFick73
2014.03.27, 10:06 AM
They seem kind of low. In addition to the discharge rate, what charger did you use? Some chargers measure charge capacity and others measure discharge capacity. Discharge capacities are always lower.

2x Powerex Maha MH-C9000
2x SkyRC NC2500

Traveler
2014.03.27, 12:30 PM
2x Powerex Maha MH-C9000
2x SkyRC NC2500

The SkyRC displays the discharge capacity and I believe the Maha does too, although I only have the LaCrosse and SkyRC charger. This is probably why the capacity numbers are lower than expected.

I would say put them all through a charge cycle at 1A and let them rest a few hours or a day, then discharge them at 1A on the SkyRC and record discharge capacity and IR (Bat. Res. in App pic below). I would consider matching based on IR. Lower is better.

I'm not sure if Voltage in App above Bat. Res. is actual voltage or average discharge volts. If its the later, that would be the best way to match cells and how I do it when using the TurboMatcher8.

If you haven't tried these cells on the track, I think you'll be pleasantly surprised. :)

http://mini-zracer.com/forums/attachment.php?attachmentid=34177&stc=1&d=1395941150

xmodcanuck
2014.03.27, 05:05 PM
I'm going to throw my $.02 in here.

I think you've gone a little overboard. We're not racing for money or pink slips. It's all about having fun.
Your first break in cycle got you capacities ranging from 751-797 (only a 6% variance). You could have done ONE break-in cycle and matched them with the ages old classic "52 pick-up" method and likely gotten the same end results. I'm not very educated in the terms of batteries and electricity but (I think) if you have a 1000mah battery and you draw 1A from it, it should last 1 hour. (under perfect conditions) Your capacities should give you 45-47 min of run time. (those who know more, feel free to correct me if I'm wrong)

cowboysir
2014.03.27, 06:32 PM
I'm going to throw my $.02 in here.

I think you've gone a little overboard. We're not racing for money or pink slips. It's all about having fun.
Your first break in cycle got you capacities ranging from 751-797 (only a 6% variance). You could have done ONE break-in cycle and matched them with the ages old classic "52 pick-up" method and likely gotten the same end results. I'm not very educated in the terms of batteries and electricity but (I think) if you have a 1000mah battery and you draw 1A from it, it should last 1 hour. (under perfect conditions) Your capacities should give you 45-47 min of run time. (those who know more, feel free to correct me if I'm wrong)

Thats for guys like us who run 70T motors....Ryan is a "mod motor so get out of my way" driver but he should have plenty enough of run time. I don't think Ryan is out to be uber racer guy (since we all know the truth about him:D) but it is kind of fun to organize cells to acheive a better performance from them.

JesseT
2014.03.28, 01:42 AM
I would say put them all through a charge cycle at 1A and let them rest a few hours or a day, then discharge them at 1A on the SkyRC and record discharge capacity and IR (Bat. Res. in App pic below). I would consider matching based on IR. Lower is better.


http://mini-zracer.com/forums/attachment.php?attachmentid=34177&stc=1&d=1395941150

Note that the resistance number is about double from the actual value on the SKyRC and can not be compared with other testers very well. Also, it measures the resistance only at the time of inserting the cells and shows that value constantly.
The voltage on the other hand shows the latest value.
So, to use it to match batteries. There is no really good way besides having a paper and pen and taking voltage numbers up at a few mAh values. If someone ever invents a way to extract the curve out of the device, please tell me.

RFick73
2014.03.28, 09:37 AM
Ryan is a "mod motor so get out of my way" driver

Actually, All my cars are now "stock". My Mod class is actually just my brushless. :p

cowboysir
2014.03.28, 12:37 PM
Guess we'll have to see what you consider "stock" Ryan....what motor and tires make your view will be interesting. :D

Any improvement on cells since the start of this thread?

RFick73
2014.03.29, 01:14 PM
Any improvement on cells since the start of this thread?

I havn't bothered to run them through their paces yet again.

I've decided to run um all this upcoming Sunday. I'm just gunna run um for 20-30mins or till I notice a significant performance decrease then toss them in the chargers on a low amp discharge.
When I get um home I'll charge them again & then discharge them on a low amp draw once again & annotate their discharge mAh.

I figure that's good enough for me, I've just had the last set of batteries now for 2-3 years so I figure it's time for a swap out to make sure I'm getting the most performace outta my cars.

Move outta the way boys, here comes the yellow bulldozer! :cool:

RFick73
2014.03.31, 08:50 AM
Well, I didn't get to run much yesterday at our local GTG. I seem to lean more to the "social" aspect of the hobby. :)

I did run through two sets of the batteries, I cannot say they seemed to be any punchier then others I have run, but they did seem to have good run times. I think I ran both sets for at least 25-30 mins before just swapping them out as to make sure they didn't just die during a race. =)

Maybe if I actually pay attention to what I'm doing I'll start using the up timer on my radio to pay attention to running time.

Thanx for all the help & suggestions all, they were muchly appreciated!