Anyone have the SkyRC NC2500 charger?

[Norm]

After waiting almost four weeks my charger has finally arrived, just playing with it now with some new Eneloops and some older Aldi LSD batteries (two of each).

Norm

 

[samgab]

After waiting almost four weeks my charger has finally arrived, just playing with it now with some new Eneloops and some older Aldi LSD batteries (two of each).

Norm

Cool: Do you have an iPhone to link to it?

 

[Norm]

Cool: Do you have an iPhone to link to it?

Yes, there's a lot more info available when using the app.

Here's a graph of an Aldi AA LSD after ding a refresh = charge - rest 1 hour - discharge - charge.

Norm

 

[Planz]

After waiting almost four weeks my charger has finally arrived, just playing with it now with some new Eneloops and some older Aldi LSD batteries (two of each).

Norm

I ordered from rcmart on Sep 13 and it's still nowhere in sight even though rcmart claims they have shipped it on Sep 15th.
I was given a tracking number and when I checked with the Hong Kong post office, they said the tracking number is not in their system.
Anyway, paypal is now handling the case and rcmart has just given them another new tracking number.
Let's see whether I get my hands on one eventually.

 

[shelm]

Nice charger!!

:huh:

 

[Planz]

After waiting almost 6 weeks, I got the charger.
The first thing that surprised me was the high internal resistance of a relatively new battery.

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So I tried with another set of old batteries and the internal resistances seemed ok




I also measured the pulsed charging current: 3A

 

[samgab]

Wow, the thermal images are fantastic thanks Planz... Can you possibly post some more, perhaps of them both side-by-side like you have them above, but filled up with 4 AA cells each, and at various charge/discharge rates and states of charge/discharge? That'd be cool. I wish I could afford a thermal imaging camera, or could talk work into buying one...

 

[Norm]

After waiting almost 6 weeks, I got the charger.
The first thing that surprised me was the high internal resistance of a relatively new battery.
So I tried with another set of old batteries and the internal resistances seemed ok

If you have a cell that seems to have high internal resistance, give the cell a few spins to make sure you have a good connection.

Norm

 

[Planz]

Yes, I did notice when I first install the battery, it did not sit in fully and then I pushed the battery in a second time. Not sure if that is the problem but will spin it next time. I also messed things up and thought I'd share what I did.
I originally wanted to record the resistance of each battery and used that to track the value over time.
However, when I removed the batteries, I forgot to do that and they all got mixed up. So next time round, I'm going to write down the value on the batteries while the batteries are still in the charger.

 

[Norm]

I forgot to do that and they all got mixed up.

Must admit I've been guilty of doing a refresh on 4 cells then forgetting to note the results

Norm

 

[Planz]

Wow, the thermal images are fantastic thanks Planz... Can you possibly post some more, perhaps of them both side-by-side like you have them above, but filled up with 4 AA cells each, and at various charge/discharge rates and states of charge/discharge? That'd be cool. I wish I could afford a thermal imaging camera, or could talk work into buying one...

Unfortunately, I ran out of batteries. I might be able to salvage 4 at most.
Meantime, here's a couple which I took the first time round.
Observations:
1. Maha slot 2 seems to be hot even though there was no battery.
2. The NC charger fan is generating just as much heat.

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[Planz]

I managed to find some batteries to do refresh and analyze.

Setup for NC Charger

4 AAA 750 mAh eneloops (less than 1 year old) taken from weighing machine. Found to be totally depleted to 0.2V.
Voltage recovered to 0.9V the next day except for 1 which reads 0.7V
All 4 batteries put into NC charger for refresh and analyze, 400mA charge and 200mA discharge.
Slot 4 contains the 0.7V battery.

Observations:
The readings for the int. resistance for the batteries read
Slot 1 265 mOhm
Slot 2 267 mOhm
Slot 3 269 mOhm
Slot 4 274 mOhm

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There was no change in int. resistance even after spinning the batteries in their holders.
I guessed I have 'ruined' the batteries by letting them over discharged.
As expected, slot 4 took longer to terminate as it has the highest resistance; about 10 minutes longer.
The batteries started discharging in about an hour, as per the manual.

Battery capacity at end of discharge:

Slot 1 684 mAh
Slot 2 734 mAh
Slot 3 712 mAh
Slot 4 697 mAh

Setup for C9000

4 AAA 750 mAh eneloops (less than 1 year old) taken from 2 remote controls
Voltage found to be about 1.28V each
All 4 batteries put into C9000 for refresh and analyze, 400mA charge and 200mA discharge.

Observations:

According to the C9000 manual, the battery should discharge after one hour of rest.
That did not happen. It took almost 2 hours before the batteries started to discharge.
In between the 2 hours, the voltage maintains at around 1.49V.

Battery capacity at end of discharge:

Slot 1 766 mAh
Slot 2 761 mAh
Slot 3 766 mAh
Slot 4 763 mAh

Observations between C9000 and NC charger

When the C9000 did not discharge after more than 1 hour, I took a few thermal images.

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Even though the charger say it is resting, it does not look like it is. The charger seems to be still 'on'.
Compared with thermal image of the NC charger, when it rests, the temp drops fast and the charger seems to be 'off'. The voltage dropped to around 1.42V compared with C9000 which maintains at 1.49V

As a side note, the day before, I did a quick measurement on the NC charger discharge of an AA battery
At 1A discharge, the pulse current was 1.25A
At 0.5A discharge, the pulse current was 1.25A

So it seems like the discharge current is 1.25A pulsed as compared with C9000 which IIRC, is 2A pulsed.
The thermal image shows the batteries in C9000 are hotter than the batteries in NC charger in discharge mode.
In fact, the temp profile for C9000 is higher in discharge mode than it is in charge mode.
However, in charge mode, the thermal image shows the batteries in NC charger are hotter than the batteries in C9000.
The NC charges at a pulsed 3A and IIRC, C9000 charges at 2A pulsed?

Conclusion

Strictly speaking, this exercise is a partial characterization than drawing of conclusions. I do not have sufficient knowledge to draw meaningful conclusions. There are pros and cons of each charger but one major feature that I like so far is the ability of the NC charger to display the internal resistance. Under normal usage, I do not monitor the voltages of the eneloops. I normally only charge them after a device gives a low battery warning or until a device no longer works due to low battery voltage. This can be seen by the over discharged batteries in two of the devices that I use. If indeed the over discharged batteries resulted in high resistance, then the ability to conveniently measure/display the int. resistance is useful in reminding me to be more conscious of monitoring and not allowing the batteries to go into an over discharged state. There's probably quite a bit more to do and go back and check/verify the condition of the high resistance batteries but I'll leave it for another day when time permits.

 

[samgab]

...the temp profile for C9000 is higher in discharge mode than it is in charge mode.
However, in charge mode, the thermal image shows the batteries in NC charger are hotter than the batteries in C9000...

Thanks for the extra thermal photos, interesting stuff. It makes sense that the C9000 is hotter when it is discharging than when charging, because the energy of the cells discharging is being dissipated as heat inside the unit; whereas when charging, the cells themselves only start heating up when they approach 100% SOC, and the charger isn't producing as much heat when charging as it isn't having to dissipate all of the heat from the discharge process. I think the voltage regulator on the underside of the PCB puts out a fair bit of waste heat, which would occur when charging or discharging, but when discharging you have the additional heat of the power of the cells dissipating. So that would be highest if you were discharging 4 cells at the max rate 1A each. That's about 4-5.6 Watts of waste heat.

...Even though the {C9000} charger say it is resting, it does not look like it is. The charger seems to be still 'on'.
Compared with thermal image of the NC charger, when it rests, the temp drops fast and the charger seems to be 'off'. The voltage dropped to around 1.42V compared with C9000 which maintains at 1.49V...

The C9000 follows the main charge with a 100 mA top off charge for 2 hours, then supplies a 10 mA trickle charge. The top off charge and trickle charge rates are not displayed, and the trickle charge continues until the cell is removed.

Edit: sorry, the above is for when a charge completes, not for when it is "resting" in the middle of doing a refresh & analyze cycle... I've never checked what the C9000 does when doing a refresh/analyze because I very rarely use that particular function; however the manual I looked at does say the "rest" period (whatever they mean exactly by that) is 2 hours long:

"First recharges the battery, rest for two hours, discharges, rest, then recharges again. Charging and discharging rates are programmable. "

I suppose it's possible that the C9000 follows its usual end of charge trickle charge process when "resting" after the initial charge in the middle of the refresh/analyze cycle?

FYI, the C9000 uses 2A pulsed for charging at all selected charge rates, and 1A pulsed for discharging at all selected discharge rates, just varying duty cycles of these rates. I had tested this previously, but I'd forgotten the figures, so I just retested on my C9000, using a Fluke 87V.

 

[Planz]

Thanks for the extra thermal photos, interesting stuff. It makes sense that the C9000 is hotter when it is discharging than when charging, because the energy of the cells discharging is being dissipated as heat inside the unit; whereas when charging, the cells themselves only start heating up when they approach 100% SOC, and the charger isn't producing as much heat when charging as it isn't having to dissipate all of the heat from the discharge process. I think the voltage regulator on the underside of the PCB puts out a fair bit of waste heat, which would occur when charging or discharging, but when discharging you have the additional heat of the power of the cells dissipating. So that would be highest if you were discharging 4 cells at the max rate 1A each. That's about 4-5.6 Watts of waste heat.

Makes sense. Strange thing though the NC chager seems to cool down in the discharge mode. When I put a piece of tissue paper under the fan slots, the paper got sucked toward the slots so I presume air gets in from below. The exit path cannot be felt with the hands nor a piece of paper. Doesn't seemed like the ventilation path is well designed. Could be due to design constraints. If you look at the thermal image of the bottom case above, the hottest region in around M1. Not sure if it's design constraints that don't allow them to put the fan there instead.

however the manual I looked at does say the "rest" period (whatever they mean exactly by that) is 2 hours long:

You are right. I was reading from the manual revision A03-3713420-496 which says rest for one hour.

FYI, the C9000 uses 2A pulsed for charging at all selected charge rates, and 1A pulsed for discharging at all selected discharge rates, just varying duty cycles of these rates. I had tested this previously, but I'd forgotten the figures, so I just retested on my C9000, using a Fluke 87V.

Thanks for the clarification on the discharge rate.

 

[shelm]

the new firmware version was posted today.
you can download and install it.

Updated
October 28, 2013

Size
2.2M

Installs
500 - 1,000

Current Version
0.9.8

Requires Android
2.3.3 and up

Content Rating
High Maturity

 

[Norm]

the new firmware version was posted today.
you can download and install it.

From where?

Norm

 

[shelm]

From where?

From your iphone/android smartphone app search , search term < skyrc >

From PC, things are more complicated i guess.

check also:

https://play.google.com/store/apps/details?id=com.revogi.smartcharge

 

[Norm]

OK an upgrade to the App or a firmware upgrade for the charger? My Iphone Apps upgrade automatically and that hasn't happened yet.

Edit : Looks like the Iphone App hasn't been upgraded since May 10 2013.

Norm

 

[shelm]

the new app contains the new firmware. it is hidden inside the app. so there is no separate firmware download needed/possible.

as soon as the app is downloaded/updated/installed and you connect smartphone with the nc2500, the app informs on screen that the app can transfer an updated firmware to the nc2500 device.

i am on android with activated automatic app updating. the automatic app update worked fine on my android. then the new firmware is not automatically transferred, one has to confirm with YES / NO once the nc2500 is paired up.

 

[Norm]

Thanks shelm, must just be android.

Norm