Opus with 80mm fan showing lower discharge values

wimpie007

wimpie007

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Apr 8, 2017
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Hi guys,

Since one of my opus chargers had the fan slowly dying (and making lots of noise while doing so), I modified it with a 80mm fan I had lying around.
Funny thing is that since I've done this, the discharge capacities measured are lower than on the other two units (which are pausing the discharging every now and then).

Samsung 26F cell, measured 2666 mAh on a "regular" Opus, only shows 2472 mAh on the 80mm Opus.
Same goes the other way around, a samsung 26F measured at 2304 mAh on the 80mm Opus shows 2657 mAh now.

The fan I used came out of a power supply and it's a 12V 0.19A fan. I just hooked it up to the internal fan header.

Did I just solve the problem of the Opus showing 10% inflated/optimistic values?
While it's always more fun too see good test results, this might lead to a more 'realistic' estimate about total capacity when building the powerwall...
 
Yup, congratulations, I'd say you've fixed it :D
To be a bit more scientific we need to know what the results of the now modified unit were before the modification. There might have been a difference before and it has nothing to do with the mod.
 
Now the next mod would be to solder a wire from the post to the Neg connector where the spring holds the cell in place. This is the major cause of misreadings on the IR.
The wire would also help eliminate some of that 10% misreading on the mAh ratings as well as the wire wouldn't be dissipating heat like the spring most likely does.

Do a few more tests with the cells, and make the wire mod, then test the cells again and see what ya come up with :)
Then, after all that, we await your mod video of the opus ;)
 
Results from 8 cells tested:
Standard opus -> 80mm Opus
2644 -> 2472
2660 -> 2481
2676 -> 2497
2636 -> 2514
2657 -> 2304
2641 -> 2254
2615 -> 2271
2624 -> 2288

I'm a bit lost in how to go further now. If we assume the lower values are "more realistic" I'd have to mod the other two Opus charges that I have as well.
Probably best to get all the same fans for them then, instead of something out of the parts bin.

@Korishan, you mean putting a wire in parallel with the spring? I guess I could try that, but I don't measure IR values right now.

I'll cycle another 8 cells through both chargers to see what results I come up with.
Cell temperatures have dropped from the 40 - 48C range to about 28 - 30C while discharging (measured with an IR thermometer).
 
Yes it's best to mod the other two to get the name information. now the number is only good as the test equipment so try and make it the same conditions. Also with pausing of the current draw the battery will rebound and rest. Not that your gaining capacity just there must be errors in how the opus calculates capacity and the start/stop inflates those numbers. With my RC chargers, my 2 hyperion pause for 5 seconds every minute to check the health of the battery to get a better idea of it's rest voltage. the charger does calculate the capacity the same as my turnigy that runs a constant discharger but only because the hyperion are way more sophisticated than the opus
 
Since you now have a reference for the unmodded Opus you can mod it and compare before and after. You should definitely go for the most realistic results as possible.

Lower cell temperatures are an issue though, you can't properly tell which ones get very hot while discharging (or charging if you use the Opus to charge them).
 
Funny I was planning to do the same mod, the fan on my Opus only lasted 2 days :|

I bought the fan suggested here which also found the same phenomenon:http://budgetlightforum.com/node/54728 Unfortunately as the new fan moves more air it's also quite a bit noisier. It's hard to say how the capacity values changed before/after the fan mod, values do seem a bit lower but not by a huge amount. I'm trying to measure cells on the Opus and my other 2 analyzers to be able to correlate the valuesgotten between them, which of course are ~5-10% lower on my "good" MiBoxer analyzer.
 
DarkRaven said:
Since you now have a reference for the unmodded Opus you can mod it and compare before and after. You should definitely go for the most realistic results as possible.

Lower cell temperatures are an issue though, you can't properly tell which ones get very hot while discharging (or charging if you use the Opus to charge them).
Click to expand...
DarkRaven, since the Opus itself heats up, it causes the cells to heat up more because they can't get rid of their heat. Out of ehe second batch of cells, some ran hotter, 37C max at a 21C room temperature. I would think that cooling the Opus better allows me to more accurately spot which cells are heating up, instead of throwing out false positives...

Discharging the second batch now... Stay tuned for results :)
 
You did great doing this mod for two things:

1. At higher temperatures, lithium ion cells can release more energy than their cooler counterparts in exchange for lower cycle life, and lower stability.

2. At high temperatures, the resistance of any resistor, current shunt, wire, increases. Meaning that the Opus, as an example, instead of drawing 500mA at 25C, it could be drawing 350mA at 45C, meaning the capacity will actually be higher than it actually. This is especially important as we are working with low currents, and current shunts at low currents aren't very accurate to begin with, meaning high temperature will accentuate the problem.
 
Bugger, it seems my results for the second batch never got posted here...

Anyhow, I ran another batch of Sanyo UR18650Y's (1850 mAh nominal):
Standard opus <-> 80mm opus
1835 <-> 1775 (+ 3,3%)
1835 <-> 1768 (+ 3,7 %)
1839 <-> 1776 (+ 3,5 %)
1881 <-> 1817 (+ 3,5 %)
1814 <-> 1758 (+ 3,2 %)
1788 <-> 1725 (+3,6 %)
1822 <-> 1783 (+ 2,1 %)
1830 <-> 1753 (+ 4,4 %)

Seems like a pretty consistent deviation across the board.
Added % off for the first batch:

Results from 8 cells tested:
Standard opus -> 80mm Opus
2644 -> 2472 (+ 7 %)
2660 -> 2481 (+ 7,2 %)
2676 -> 2497 (+ 7,2 %)
2636 -> 2514 (+ 4,8 %)
2657 -> 2304 (+ 11,3 %)
2641 -> 2254 (+ 17,2 %)
2615 -> 2271 (+ 15,2 %)
2624 -> 2288 (+ 14,7 %)
Click to expand...
Quite a larger variation here. These cells were heating up more, possibly throwing the results off more... (Or it could be that the results are different between the first and second cycle since these cells were quite deeply discharged)
 
Do you think the power consumed by the fan can be affecting the #'s?
 
No, as it is only discharging the power from the cells, and not counting the fan's power consumption.
 
I know this is an old thread and mostly everyone knows the reason by now but the higher readings on a standard cooled Opusbecausethe standard Opus fan is insufficient for cooling. This causes the charger to pause during the test and each pause results in a higher mAh rating.

For Opus chargers that have proper cooling and never pause, they provide a fairly accurate mAh reading.

I discovered this the hard way and had to retest many cells after getting a proper cooling system built.
 
jm1 said:
I know this is an old thread and mostly everyone knows the reason by now but the higher readings on a standard cooled Opusbecausethe standard Opus fan is insufficient for cooling. This causes the charger to pause during the test and each pause results in a higher mAh rating.

For Opus chargers that have proper cooling and never pause, they provide a fairly accurate mAh reading.

I discovered this the hard way and had to retest many cells after getting a proper cooling system built.
Click to expand...

This is indeed the case. I choose to test at 500ma. That way the Opus does not pause. Even with stock cooling. I never test cells in hot conditions, only in cooler winter months.
 
I test them at 700mA. And if it's too hot, I just put the Opus on one side, so the air flows better and it doesn't stop discharging.
 
I took to setting them on their sides when discharging too. Last summer I ran a test on two Opus' to check thermal shutdown / capacity differences - 700mA on one , 1000mA on the other, both with 4x cells. They have the stock fan but I did add the wires like Korishan mentioned.

The capacities were all close to what they had tested at before, and the 700mA took 1hr longer to discharge. I thought the 1000mA would go into thermal shutdown as I've seen it do, likely take longer and show higher capacities, but nope.

After that test I thought maybe it's more of a problem when dicharging multiple batches, but didn't get to testing that far.
 
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