+Eric Gee : Actually, no - as far as I can tell, EEVblog is about excessively opinionated rants that may have something to do with reality or nothing at all. And before you ask, the only reason I watch is because EE stuff is mighty scarce on TH-cam.
+Eric Gee I'd really like to use more than one 'thumsUp' to emphasize how much I agree. The internet rly needs a 'handsUp-' or fistbump-type of agreement, not just binary :|
+Attila Asztalos --- Hmmm, so what are you saying with that ? That you selflessly contribute to likes/views of the MOST PROMINENT channel featuring EE. instead of helping some less prominent channels ?! Don't rly get your motivation/implication here.... pls help us with that.
Ha! I was shouting at the screen like a sports fan at one point, "you're schematic isn't complete!!!" Great video, Dave - with lithium charging getting so much attention, the lowly NiMH is at risk of being totally ignored. As someone working on a project that incorporates multi-cell charging, I found it quite entertaining and informative. BIG thumbs up!
I think Dave gave the poor charger too much hate on the voltage measurement. Remember the weird short pattern that the channels were displaying during charge (14:15)? I think this is where it actually measures the cell voltage. It first disconnects all the batteries to get the out-of-circuit voltage for each cell that is actually displayed on the screen. Then it gives full charge current to or each, one by one, to test if charge voltage is still within safety I guess. I think Dave should've used the scope to measure battery voltage and trigger on the drop to get the cell voltage. I'm not an experienced engineer by any means, but just gave my 2cents.
+MrZhilvinas Agreed. The charger does not deserve that poor verdict. 4-pont voltage measurement would not have worked for a battery charger. They have to shut off the charge current to get accurate voltage meqasurement, and guess what, it is exactly what they are doing. IF the charger had used 4-point voltage measurement, then it would have deserved the poor verdict!
HI Dave. @30:32 in your video. You talked about a major discrepancy in the voltage on your meter and what was showing up on the charger. That's not because the charger is off cal. It's because the charger is measuring the voltage when the charge circuit is off. The charger is measuring the voltage of the battery in-between those short off pulses on your oscilloscope, Your meter is measuring the voltage while the charger is on and that 200mV discrepancy is cause by the battery internal resistance.
+Charlie Pechiar Yes it certainly is. But it's still very sadistic how they push the cells. I would not recommend these 8A chargers to anyone. And I also do not recommend to charge cells in them unattended!!!
+EEVblog - Well I still think my idea of discharging exactly reverse of charging is more elegant! (posted in part 1) Less parts required and variable discharge rates with ease. Also, the higher than expected charging voltage is required to push the higher than standard charge current. Disconnected voltage would still be under max battery charged voltage. Great video!
We had someone demonstrate an I-prober at work, but my boss never bought one... It would be so useful sometimes, there's always that one moment when you need it
Yet again, another awesome video... BTW - Dave, you could get the LAN/VGA add on unit for your scope - DSOXLAN. That way you can do split screen and the scope screen would be nice and clear with still being able to have the test device in view
So does it have reverse polarity protection ? Or is it imposible to place cells wrong ? Because if i see it right, then it would toast the mosfets via the parasitic diodes right ?
+Martin Stránský-Krtek Right person would put them in reverse. I know that some people have skill to even put RAM in reverse and fully lock them in place. So i think no mechanical protection would help it :D And cells are cylindrical, so not much you can do mechanically. I hope it has reverse protection...
That "inaccurate" voltage is so much lower for a reason! That short pulse you see when it stops charging is there to measure the battery voltage without the extra voltage caused by the charging current making a drop in the resistances. This way the charger gets a better idea of what the actual voltage is without being screwed over by the varying internal resistance of different batteries and the possibly changing contact resistance.
Every time I watch one of these Dave videos, I end up needing to win the lottery to pay for all those probes- Oscilloscopes- signal generators, and fancy electronic do da's!
Grouse work chief, really enjoyed this one. Bonza! On a more serious note, it was great to see the gadgets come out and using more of that Agilent scope's feature set. I love how responsive it appears to be in all scenarios... Unlike the Tek MDO
The voltage on the cell was so high because the current is very high and the cell reaches it's voltage very fast. But the controller is measuring the cell voltage when the charging is temporarly disabled, so the voltage is much lower on the display of the unit. It actually shows the unloaded resting voltage of the cell.
Hey Dave, thanks for the 2nd Video. Even if I also like Your Product Presentations, these Teardowns/Reverse Engineering Videos are why I subscribed to Your Channel. Thumbs UP! Richard.
I was wondering about the 8A and the mosfet on-resistance from the last video, and now I know :) ~0.29W power dissipated by the mosfet with 10V Vgs Nice
The periodic switch off each mosfet is to detect if the battery is still there and what is it own voltage. Sure, you could measure the lack of current on shunt resistor, but you would not know which cell was taken out (or is broken). You need to do that even if you have single cell. The staggered signal, is there probably to measure current per cell. If you know a total current per cell 1 and 2, and you switch off the cell 1 and 2, measure voltages of 1 and 2, then switch on cell 1 back (but not 2), and measure current, you could calculate in software individual currents. That is my guess. Very smart. There is only one limitation of this setup. You cannot discharge and charge different cells at the same time. Same with refresh. If you are refreshing 4 cells, the device will most likely wait for all 4 to be discharged, and only then switch to charging.
The voltage discrepancy when charging is because the charger takes the voltage readings at OCV during the pauses during charging. If you captured the voltage at the cell during the pause, you'd find it would measure a lot closer to the readout voltage display, I suspect.
Regarding the series ammeter that causes charge to stop - I always understood these "fast charge" cells had a chip inside for identification, accessed through some one-wire like protocol, maybe that's to do with some of the pulses that are seen, would be interesting to scope the actual battery terminal instead of the MOSFET gates to see if any communication is visible. If I'm right it's possible the ammeter breaks the communication. I have the "old" charger, and when any normal cell is inserted it will charge it with the usual C/5 current. Only when it detects a Varta fast charge cell will it switch to 8A charging. I could be wrong and it might be based on internal resistance measurement but I doubt it, because once my Varta cells became worn it would still charge them fast. By the way I can confirm the cells don't like the treatment - mine became nearly unuseable after maybe 20 cycles, with terrible self-discharge rates and barely half of the capacity. Hopefully they've made progress, the old ones weren't eneloop-like.
Can you do a ghetto measurement of current by using a standard oscilloscope probe with a loop of wire, essentially making a current transformer? How do those clamp meters work, and how can they measure DC?
+Power Max I think the current probe is actually using a Hall effect sensor, not a simple coil. How could it measure the earths magnetic field otherwise?
I bought one of these chargers a couple of months back, and was a bit concerned about how hot the cells get. It's interesting to have an investigation like this, and confirm my suspicion that Varta are pushing the envelope quite a lot here. (I try to put four cells in at a time, to get the charging current down to slightly less insane values. It is a pity that it isn't user-settable to a lower rate.)
+boggisthecat Yeah, they should have included a 1/2/4/8A setting at least and just disable the 8A setting when more than 2 batteries are in. The hardware is clearly capable of doing this.
+KX36 Everything over 700 mA is stupid and insane. I recommend the BC-700 charger from various reseller brands. AAA should not be charged with more than 200 mA and AA not with more than 500, in urgent cases you can use 700 mA. This will increase the lifespan of quality cells quite a bit. I am only using Eneloops now, threw away all other NiMh cells because they were a pile of garbage. Fully charged and then empty the other day. LOL If it happens that you need full cells instantly, just go ahead and buy some alkalines. There is no use for this VARTA charger. Being said by a German. ;)
I know nothing about it but the datasheet shown in part 1 gave specs at 2A charging, so it sounds like up to 2A would be OK rather than anything up to 700mA. I just plain don't use rechargable AA batteries as they last nowhere near as long per charge as the life of even a cheap single use battery so I just get those. These videos have got me wondering what the charging current on my cordless drill is though since that charges a pack of 5x 18650 lithium batteries from the point of no movement on the drill to what the charger calls "full" in about 20 minutes.
You should test the Panasonic Eneloop cells. They are as good as any alkaline. You can even put them into a remote, lasting very long. Use Eneloop Lite for remotes, self-discharge rate almost zero. Never trust data sheets, every cell manufacturer wants you to wear your cells as fast as possible to buy new ones. So do not charge them with more than 1A... 500mA is better for AA and 200mA for AAA.
I agree with you Kyodai. Having used a Rayovac 15 minute fast charger manufacturers CAN (and did in one case) build robust high quality fast charging NiMH batteries. Unfortunately Rayovac discontinued this amazing system 8 years ago (I think) probably because it was too successful. It was a proprietary battery and charger system that actually charged their AA and AAA batteries in 15 minutes or less and they did get hot. But they lasted forever. I had used them daily for years (400 to 600 cycles on most of them) and they worked under very high drain conditions. In fact I still have a few batteries that are still working (easily 10 years old) albeit at lower capacity. I'm going to get the Varta and test it on my Eneloops b/c it's the only charger that actually monitors the individual cell temperatures with active cooling. We'll see if it actually works like my Rayovacs did...
One question about the solder loaded traces that should carry more current: Why is that solder interrupted periodically? Doesn't that defeat the purpose? I mean if you have just the trace on that 1 mm where the solder is interrupted, isn't the extra solder just useless?
Regarding the difference between the built in voltage display and that measured by the meter, could it that it's measuring the battery voltage during the dips when the charging current is bypassed/off?
I did a quick Google search on the Varta and only found a eBay link to your part of the world , no US availability ? Dave you mention the lack of accuracy on the charger , my 1st thought was its a battery charger , not a piece of test gear , is it that critical , and if so , could we find a better unit ? Thanks again John
At 14:13, only one charge FET is on at a time, all others in bypass: it must be measuring individual cell voltages during this time, then returning to muxed charge. But why does the D0/D1 cell measurement take ~6 times as long as the others?
+FlyingShotsman maybe it is doing something else during that cycle, not only measuring cells' voltages. Maybe checking temperature sensors or something else.
20:50 Where the meter can't measure current properly, is it because it's in auto mode? I've had issues with my meter messing with the device on current mode because its auto was switching the shunt or something, where it worked fine if I disabled auto and switched to a higher range and left it there.
if you could physically place a couple batteries in series; and hipotetically the charger went to 3.3v: ¿could they be carged in series and enjoying the same voltage, 1/2 * VDC?
Now this is off topic, but as I think almost everyone use it, it should be mentioned. How many of you are using Adblock? I do, but I have dave's channel in the whitelist. The least I can do since he's been doing this for ages. I hope you do the same, peeps.
Go to settings and tick "Allow whitelisting of specific TH-cam channels" Go to specific channel and press the adblock button and select whitelist 'nnnn' channel
+Christian Ivarsson Sorry, I can't see how to do that. I've just got Options. Using Chrome and Adblock Plus (and a great little tool called tabs outliner).
+Christian Ivarsson I have ABP but whitelist youtube because there's so many good channels I want to support. With patreon and YT red it seems like there are now alternatives, but the ads here are mostly unintrusive (except on vevo channels).
discharge is half watt right? what if you discharged one cell for an hour then got out the flir cam would that show you if mosfets or current sense resistor is passing that 400 ma?
+marty mure - Well it would be about 400mA x 1.5V = 600mW... close enough depending of the battery's state of charge. I think you might be able to see it in IR but it's only 300mW per resistor and there are likely other parts that are getting hotter. IDK maybe!
Maybe they are discharging by applying PWM to both MOSFETS at the same time, Thereby controlling the rate EDIT>NOPE. guess not Can't escape Dave! He'll figure it out with all the awesome tools :)
+nikotwenty But then how do you measure the current. Plus you cant control the rate because of the battery esr. I have some AA that give 5A+ when shorted, but other with more charge cycles that barely give 2A
+Eviltech why would the battery company sell something that makes you buy batteries more frequently? hmm. I don't know. ;-) I think they probably can push the specs *a bit* because of the fan cooling and presumably safety monitoring and that they will have tested in house with their own batteries, but yeah it does seem very dodgy.
+Coolkeys2009 I can recommend the BC-700 charger, it's not from a single brand, in Germany it is reselled by Technoline. It can charge with 200 500 and 700 mA adjustable, can discharge, can test, also refresh and costs only ~$30. BE CAREFUL, THE SOCKET ON THIS THING IS A 12V SOCKET BUT IT IS DRIVEN WITH ONLY 3 VOLTS! Carefully take a look which power plug you stuff into it's back before putting in the power plug / wall wart...
+Eviltech I deleted my original comment about my Maha charger when I realised I may have been over discharging some of my batteries damaging them. However I've just discovered that as well as refusing to recharge older higher impedance batteries, the discharge test when set to 100ma also tells you the batteries have 0mah capacity which has caused me to throw away many batteries. These batteries can supply 1 to 2amps+ of short circuit current and light a 200ma+torch bulb for hours. From the reviews I read on Amazon it looks like all the chargers(intelligent ones) suffer from similar issues, definitely causing people to throw away batteries with plenty of usable capacity.
Nice analysis Dave. Would the FLIR like Oscar and James suggested a week ago detect the higher current paths albeit thicker tracks? does it detect a 1 or 2 degree change? Keep up the Great work :)
While it is really convenient to rapid charge one's batteries. Doing so will drastically reduce battery life. I have a US version of this charger made by Energizer and it charges fast, but the batteries are so hot after you can hardly touch them. I wouldn't use this fast charge very often, only when needed. 90% of the time I slow charge my batteries at .200 MA.
I did got why they have the 4 bypass mosfets. Can someone tell why they could not have the 4 charge mosfets in parallell? Why do they need to drive one the second, third and fourth mosfets through the bypass instead of driving them in parallel with the first?
30:30 I'm total noob but for me charger do constant current, and shows voltage of cell not charging voltage. (measured during for few ms break in charging)
So, if this is multiplexed, does that mean it'll take 30 minutes to charge four batteries? Also, don't you hate it when the fast battery charger you bought keeps charging your batteries too quickly. ^-^
I do not get it... that little MOSFET + the 6.2||6.2 resistors cannot handle the 500mW discharge, and survive for that long ... MOSFET is a SOTx, and the Rs are maybe 0.10W each? Those three components would be burning hot if they are the discharge path.
+Ivan Kocher Not a problem for the mosfet as it would be wide open and dissipating little power. All the dissipation happens on the resistors. Maybe warta did push the specs a little there too :D
+DolganoFF The mosfet is not the one I really worry about. If all 1206 resistors are dissipating .25W each, such a small volume will heat up. But as you said, varta is pushing the specs a little, if they do that to the batteries, who cares about a little resistors ;)
![ILLSLICK - KILLSHOT REMIX [FULL VERSION]](http://i.ytimg.com/vi/RIK8RrqIAzE/mqdefault.jpg)
When Dave says a quick follow up you know your in for a mini movie. Yay
This is what the EEVblog is about. Nice one Dave,
+Eric Gee : Actually, no - as far as I can tell, EEVblog is about excessively opinionated rants that may have something to do with reality or nothing at all. And before you ask, the only reason I watch is because EE stuff is mighty scarce on TH-cam.
+Eric Gee
I'd really like to use more than one 'thumsUp' to emphasize how much I agree.
The internet rly needs a 'handsUp-' or fistbump-type of agreement, not just binary :|
+Attila Asztalos --- Hmmm, so what are you saying with that ?
That you selflessly contribute to likes/views of the MOST PROMINENT channel featuring EE. instead of helping some less prominent channels ?!
Don't rly get your motivation/implication here.... pls help us with that.
Ha! I was shouting at the screen like a sports fan at one point, "you're schematic isn't complete!!!"
Great video, Dave - with lithium charging getting so much attention, the lowly NiMH is at risk of being totally ignored.
As someone working on a project that incorporates multi-cell charging, I found it quite entertaining and informative. BIG thumbs up!
Nice one. Discovering that return path has put my brain back into equilibrium. Thanks.
It's nice to see that you genuinely enjoy talking about this stuff.
"The trick is stopping him..."
I think Dave gave the poor charger too much hate on the voltage measurement. Remember the weird short pattern that the channels were displaying during charge (14:15)? I think this is where it actually measures the cell voltage. It first disconnects all the batteries to get the out-of-circuit voltage for each cell that is actually displayed on the screen. Then it gives full charge current to or each, one by one, to test if charge voltage is still within safety I guess. I think Dave should've used the scope to measure battery voltage and trigger on the drop to get the cell voltage. I'm not an experienced engineer by any means, but just gave my 2cents.
+MrZhilvinas Yeah, it's doing something like this.
+MrZhilvinas Agreed. The charger does not deserve that poor verdict. 4-pont voltage measurement would not have worked for a battery charger. They have to shut off the charge current to get accurate voltage meqasurement, and guess what, it is exactly what they are doing.
IF the charger had used 4-point voltage measurement, then it would have deserved the poor verdict!
HI Dave. @30:32 in your video. You talked about a major discrepancy in the voltage on your meter and what was showing up on the charger. That's not because the charger is off cal. It's because the charger is measuring the voltage when the charge circuit is off. The charger is measuring the voltage of the battery in-between those short off pulses on your oscilloscope, Your meter is measuring the voltage while the charger is on and that 200mV discrepancy is cause by the battery internal resistance.
Glad you found the discharge path eventually, would have suggested using the FLIR to find the hotspots had you not.
+James Lamb i was all the time thinking "get the damn thermal thing!"
I love it when you say, "It's just a quick follow up video...", and it lasts for 40 min )))
Absolut fantastic how Dave take all out and share this with us. I have learned a lot of this video. Thanks Dave.
For some reason my fucking brain blew when he wiped the ink off...
+Jeff Schefke lmao same
+Jeff Schefke Same here :) He's using overhead projector transparency stuff
+Jeff Schefke Sorry for the trauma!
+Jeff Schefke At least I'm not alone. My mind went totally blank for a second when he did that ;-)
+Jeff Schefke Same here :) At first I thought: "I want that pen!" :D
Glad you nailed that ladder! Well worth the re-visit.
Excellent video!
I love how complicated a simple battery charger is.
I guess battery voltage during charge is measured during the cuttoff time, which would be reasonable.
I think so too :)
+Charlie Pechiar Yes it certainly is. But it's still very sadistic how they push the cells. I would not recommend these 8A chargers to anyone. And I also do not recommend to charge cells in them unattended!!!
+EEVblog - Well I still think my idea of discharging exactly reverse of charging is more elegant! (posted in part 1) Less parts required and variable discharge rates with ease. Also, the higher than expected charging voltage is required to push the higher than standard charge current. Disconnected voltage would still be under max battery charged voltage. Great video!
Even if a bit late: reverse engineering at its best! Kudos Dave!
More like this please. Finally understanding the circuit. Hate you make it look so easy ;)
Always love your reverse engineering and repair videos.
Brilliant Video, Dave!! You really should start a ReEE segment, in where you explain/inspect some EveryDay tech stuff!
+TubiCal
Yes! I love these types of video's!! Thanks Dave!
Glad for the follow up really enjoyed both videos. Well done and thank you
"Hi, just a quick follow up" and 37:48 min later we're done
Btw: the quick follow up is longer than the main video :)
We had someone demonstrate an I-prober at work, but my boss never bought one... It would be so useful sometimes, there's always that one moment when you need it
Yet again, another awesome video... BTW - Dave, you could get the LAN/VGA add on unit for your scope - DSOXLAN. That way you can do split screen and the scope screen would be nice and clear with still being able to have the test device in view
Fun stuff even when I understand half the stuff I still feel as if i can follow what you're saying and still learn.
felt like i was in a movie trip. the tension built up till the end and bamm!.. happy ending. :)
This is what Dave is all about. Detective stories go on...
"Just a quick follow up..." 38 mins later... :)
Just messing Dave, we all love your ramblings! Keep it up
So does it have reverse polarity protection ? Or is it imposible to place cells wrong ? Because if i see it right, then it would toast the mosfets via the parasitic diodes right ?
+Martin Stránský-Krtek Right person would put them in reverse. I know that some people have skill to even put RAM in reverse and fully lock them in place. So i think no mechanical protection would help it :D
And cells are cylindrical, so not much you can do mechanically. I hope it has reverse protection...
That "inaccurate" voltage is so much lower for a reason!
That short pulse you see when it stops charging is there to measure the battery voltage without the extra voltage caused by the charging current making a drop in the resistances. This way the charger gets a better idea of what the actual voltage is without being screwed over by the varying internal resistance of different batteries and the possibly changing contact resistance.
Why is this unlisted o-O?
Every time I watch one of these Dave videos, I end up needing to win the lottery to pay for all those probes- Oscilloscopes- signal generators, and fancy electronic do da's!
Grouse work chief, really enjoyed this one. Bonza!
On a more serious note, it was great to see the gadgets come out and using more of that Agilent scope's feature set. I love how responsive it appears to be in all scenarios... Unlike the Tek MDO
Thanks Dave, always learn so much from your videos...
If only I had all of those neat tools that Dave has when I'm doing hardware debugging/investigating...
Definitely one of your best videos yet Dave. Really great job! Whoever downvoted has trouble clicking. ;)
Fantastic presentation, "please sir, can we have some more".
The voltage on the cell was so high because the current is very high and the cell reaches it's voltage very fast. But the controller is measuring the cell voltage when the charging is temporarly disabled, so the voltage is much lower on the display of the unit. It actually shows the unloaded resting voltage of the cell.
Hey Dave, thanks for the 2nd Video. Even if I also like Your Product Presentations, these Teardowns/Reverse Engineering Videos are why I subscribed to Your Channel. Thumbs UP!
Richard.
quick video...37 mins later.....love it.....
I was wondering about the 8A and the mosfet on-resistance from the last video, and now I know :)
~0.29W power dissipated by the mosfet with 10V Vgs
Nice
"Quick" followup. Ends up with a almost 38 min long video. Classic Dave. :D
Thanks for the fun video Dave.
The periodic switch off each mosfet is to detect if the battery is still there and what is it own voltage. Sure, you could measure the lack of current on shunt resistor, but you would not know which cell was taken out (or is broken). You need to do that even if you have single cell.
The staggered signal, is there probably to measure current per cell. If you know a total current per cell 1 and 2, and you switch off the cell 1 and 2, measure voltages of 1 and 2, then switch on cell 1 back (but not 2), and measure current, you could calculate in software individual currents.
That is my guess. Very smart.
There is only one limitation of this setup. You cannot discharge and charge different cells at the same time. Same with refresh. If you are refreshing 4 cells, the device will most likely wait for all 4 to be discharged, and only then switch to charging.
+movax20h LOL
Loved this 2 part video Dave!!
Today, on the EEVBlog. Dave reviews the Varta 15 minute Battery Boiler.
Yay! Baffled Dave breaks out the big guns. Always worth a squizz - winner, winner, chicken dinner.
Magnificent! Yet another proof that engineering (science too) is an art to be continuously fooled.
The voltage discrepancy when charging is because the charger takes the voltage readings at OCV during the pauses during charging. If you captured the voltage at the cell during the pause, you'd find it would measure a lot closer to the readout voltage display, I suspect.
Regarding the series ammeter that causes charge to stop - I always understood these "fast charge" cells had a chip inside for identification, accessed through some one-wire like protocol, maybe that's to do with some of the pulses that are seen, would be interesting to scope the actual battery terminal instead of the MOSFET gates to see if any communication is visible. If I'm right it's possible the ammeter breaks the communication. I have the "old" charger, and when any normal cell is inserted it will charge it with the usual C/5 current. Only when it detects a Varta fast charge cell will it switch to 8A charging. I could be wrong and it might be based on internal resistance measurement but I doubt it, because once my Varta cells became worn it would still charge them fast. By the way I can confirm the cells don't like the treatment - mine became nearly unuseable after maybe 20 cycles, with terrible self-discharge rates and barely half of the capacity. Hopefully they've made progress, the old ones weren't eneloop-like.
Videolength > 2 * Time (Charging Batteries)
I love stuff like this!
Dave, Very Interesting reverse engineering...very cool.
Can you do a ghetto measurement of current by using a standard oscilloscope probe with a loop of wire, essentially making a current transformer? How do those clamp meters work, and how can they measure DC?
+Power Max I think the current probe is actually using a Hall effect sensor, not a simple coil. How could it measure the earths magnetic field otherwise?
I bought one of these chargers a couple of months back, and was a bit concerned about how hot the cells get. It's interesting to have an investigation like this, and confirm my suspicion that Varta are pushing the envelope quite a lot here. (I try to put four cells in at a time, to get the charging current down to slightly less insane values. It is a pity that it isn't user-settable to a lower rate.)
+boggisthecat Yeah, they should have included a 1/2/4/8A setting at least and just disable the 8A setting when more than 2 batteries are in. The hardware is clearly capable of doing this.
+KX36 Everything over 700 mA is stupid and insane. I recommend the BC-700 charger from various reseller brands. AAA should not be charged with more than 200 mA and AA not with more than 500, in urgent cases you can use 700 mA. This will increase the lifespan of quality cells quite a bit. I am only using Eneloops now, threw away all other NiMh cells because they were a pile of garbage. Fully charged and then empty the other day. LOL
If it happens that you need full cells instantly, just go ahead and buy some alkalines. There is no use for this VARTA charger. Being said by a German. ;)
I know nothing about it but the datasheet shown in part 1 gave specs at 2A charging, so it sounds like up to 2A would be OK rather than anything up to 700mA. I just plain don't use rechargable AA batteries as they last nowhere near as long per charge as the life of even a cheap single use battery so I just get those.
These videos have got me wondering what the charging current on my cordless drill is though since that charges a pack of 5x 18650 lithium batteries from the point of no movement on the drill to what the charger calls "full" in about 20 minutes.
You should test the Panasonic Eneloop cells. They are as good as any alkaline. You can even put them into a remote, lasting very long. Use Eneloop Lite for remotes, self-discharge rate almost zero.
Never trust data sheets, every cell manufacturer wants you to wear your cells as fast as possible to buy new ones. So do not charge them with more than 1A... 500mA is better for AA and 200mA for AAA.
I agree with you Kyodai. Having used a Rayovac 15 minute fast charger manufacturers CAN (and did in one case) build robust high quality fast charging NiMH batteries. Unfortunately Rayovac discontinued this amazing system 8 years ago (I think) probably because it was too successful. It was a proprietary battery and charger system that actually charged their AA and AAA batteries in 15 minutes or less and they did get hot. But they lasted forever. I had used them daily for years (400 to 600 cycles on most of them) and they worked under very high drain conditions. In fact I still have a few batteries that are still working (easily 10 years old) albeit at lower capacity.
I'm going to get the Varta and test it on my Eneloops b/c it's the only charger that actually monitors the individual cell temperatures with active cooling. We'll see if it actually works like my Rayovacs did...
Really enjoyed this one, thanks!
Good video, thanks for digging far
+EEVBlog Dave! Draw an arrow on your current probe pointing to magnetic north... Just for laughs :)
Now I want a Keysight 3000-series MSO and a magnetic current probe! But both are very expensive :(
Too many of these videos begin with "Just a quick follow up...". Still love it though.
That was a really good video! And damn, I want this sexy current probe!
Hey Dave, what multimeter probes did you use in your video to measure the discharge current? Looked pretty nice.
One question about the solder loaded traces that should carry more current: Why is that solder interrupted periodically? Doesn't that defeat the purpose? I mean if you have just the trace on that 1 mm where the solder is interrupted, isn't the extra solder just useless?
Love it "here's a quick follow up"... 37 minutes quick
Love the video! please look at the board with thermal imaging while discharging 👍🏼
Regarding the difference between the built in voltage display and that measured by the meter, could it that it's measuring the battery voltage during the dips when the charging current is bypassed/off?
Another quick one... over a half hour, dave.
It's probably not at bad measuring the voltage as you think if it's measuring the cell voltage during those blips every second.
+ceriand he dun did batterized it.
Great job.
I did a quick Google search on the Varta and only found a eBay link to your part of the world , no US availability ?
Dave you mention the lack of accuracy on the charger , my 1st thought was its a battery charger , not a piece of test gear , is it that critical , and if so , could we find a better unit ?
Thanks again
John
Use your thermal camera to see where the power is dissipated during discharge. That would have helped to figure out the discharge path.
So, but the thing is, if you charge a battery at 8 amp, but have the batteries switching 50 50, can you really say that it's 4 amp?
I thought in the first video that they stated it as being 8 amps only when charging 2 cells.
Antonio Tejada Yeah, but it's still 8 amp with 4, just that it's flicking them on and off in a 50 50 sequence.
Need more cool reverse engineering :)
Thank you for your videos. Can we have one for dc ac inverter tear down and some repair tips.
Great video.
At 14:13, only one charge FET is on at a time, all others in bypass: it must be measuring individual cell voltages during this time, then returning to muxed charge. But why does the D0/D1 cell measurement take ~6 times as long as the others?
+FlyingShotsman maybe it is doing something else during that cycle, not only measuring cells' voltages. Maybe checking temperature sensors or something else.
Probably so, given how the PTCs appeared to be wired. Good thought...
Wauw, i-Prober 520 / FLIR E8, what stuff doesn't you have? Very nice toys indeed!
i can''t be the only person amazed by the pen Dave is using. i mean he wiped this stuff with his finger. what is that?
+h00d - I think he had a plastic overlay for that and just a regular erasable marker.
20:50 Where the meter can't measure current properly, is it because it's in auto mode? I've had issues with my meter messing with the device on current mode because its auto was switching the shunt or something, where it worked fine if I disabled auto and switched to a higher range and left it there.
AAAAnd the word of the day iiiiis : "ACTUALLY" :D :) love ya man great vids :)
I recon those drops every second is when it measures the voltage, not when it charges, that's why you're a bit off.
if you could physically place a couple batteries in series; and hipotetically the charger went to 3.3v: ¿could they be carged in series and enjoying the same voltage, 1/2 * VDC?
"Just a quick followup" -> 40 minutes. Yup, this is EEVBlog alright.
Circuit eval. Great entertainment.
Happy "BOO!" day here in "USA! USA!" land.
Now this is off topic, but as I think almost everyone use it, it should be mentioned.
How many of you are using Adblock? I do, but I have dave's channel in the whitelist.
The least I can do since he's been doing this for ages. I hope you do the same, peeps.
Go to settings and tick "Allow whitelisting of specific TH-cam channels" Go to specific channel and press the adblock button and select whitelist 'nnnn' channel
+Christian Ivarsson You know how to do the same using uBlock Origin v1.3.2??
+Christian Ivarsson Sorry, I can't see how to do that. I've just got Options. Using Chrome and Adblock Plus (and a great little tool called tabs outliner).
+Christian Ivarsson I have ABP but whitelist youtube because there's so many good channels I want to support. With patreon and YT red it seems like there are now alternatives, but the ads here are mostly unintrusive (except on vevo channels).
discharge is half watt right? what if you discharged one cell for an hour then got out the flir cam would that show you if mosfets or current sense resistor is passing that 400 ma?
+marty mure - Well it would be about 400mA x 1.5V = 600mW... close enough depending of the battery's state of charge. I think you might be able to see it in IR but it's only 300mW per resistor and there are likely other parts that are getting hotter. IDK maybe!
Maybe they are discharging by applying PWM to both MOSFETS at the same time, Thereby controlling the rate
EDIT>NOPE. guess not
Can't escape Dave! He'll figure it out with all the awesome tools :)
+nikotwenty But then how do you measure the current. Plus you cant control the rate because of the battery esr. I have some AA that give 5A+ when shorted, but other with more charge cycles that barely give 2A
That's one clever charger... but why would they make something that will eventually kill your batteries?
+Eviltech why would the battery company sell something that makes you buy batteries more frequently? hmm. I don't know. ;-)
I think they probably can push the specs *a bit* because of the fan cooling and presumably safety monitoring and that they will have tested in house with their own batteries, but yeah it does seem very dodgy.
+Eviltech it would be cool if it had a normal charging mode as well, or did it and I've missed it?
+Coolkeys2009 I can recommend the BC-700 charger, it's not from a single brand, in Germany it is reselled by Technoline. It can charge with 200 500 and 700 mA adjustable, can discharge, can test, also refresh and costs only ~$30.
BE CAREFUL, THE SOCKET ON THIS THING IS A 12V SOCKET BUT IT IS DRIVEN WITH ONLY 3 VOLTS! Carefully take a look which power plug you stuff into it's back before putting in the power plug / wall wart...
Wasserverschmutzung That's what i meant...
+Eviltech I deleted my original comment about my Maha charger when I realised I may have been over discharging some of my batteries damaging them. However I've just discovered that as well as refusing to recharge older higher impedance batteries, the discharge test when set to 100ma also tells you the batteries have 0mah capacity which has caused me to throw away many batteries. These batteries can supply 1 to 2amps+ of short circuit current and light a 200ma+torch bulb for hours. From the reviews I read on Amazon it looks like all the chargers(intelligent ones) suffer from similar issues, definitely causing people to throw away batteries with plenty of usable capacity.
Nice analysis Dave. Would the FLIR like Oscar and James suggested a week ago detect the higher current paths albeit thicker tracks? does it detect a 1 or 2 degree change? Keep up the Great work :)
good stuff!
While it is really convenient to rapid charge one's batteries. Doing so will drastically reduce battery life. I have a US version of this charger made by Energizer and it charges fast, but the batteries are so hot after you can hardly touch them. I wouldn't use this fast charge very often, only when needed. 90% of the time I slow charge my batteries at .200 MA.
Isn't the waiting periods so they can detect the negative ΔV required for NiMH charging?
I did got why they have the 4 bypass mosfets. Can someone tell why they could not have the 4 charge mosfets in parallell?
Why do they need to drive one the second, third and fourth mosfets through the bypass instead of driving them in parallel with the first?
الحلم سيد الأخلاق.
Can anyone explain the purpose of that resistor between the AA and AAA terminals.
Current limiting. Watch part 1...
Thanks for the hint, but i still don't get it. Current limiting makes no sense to me since t uses a constant current source.
Something I don't get is the use of a dc to dc converter. What does it do?
+RandomVideos produces 15V bias necessary to open the mosfets as wide as possible I guess.
DolganoFF i have no idea what anything you said means.
'Quick followup' is longer than the original video :D
30:30 I'm total noob but for me charger do constant current, and shows voltage of cell not charging voltage. (measured during for few ms break in charging)
So, if this is multiplexed, does that mean it'll take 30 minutes to charge four batteries? Also, don't you hate it when the fast battery charger you bought keeps charging your batteries too quickly. ^-^
I do not get it... that little MOSFET + the 6.2||6.2 resistors cannot handle the 500mW discharge, and survive for that long ...
MOSFET is a SOTx, and the Rs are maybe 0.10W each? Those three components would be burning hot if they are the discharge path.
+Ivan Kocher - IDK, are those 1206 resistors? 0.25W each.
+Ivan Kocher I was thinking the same. The PCB around the resistors looks bit burnt.
+Ivan Kocher Not a problem for the mosfet as it would be wide open and dissipating little power. All the dissipation happens on the resistors. Maybe warta did push the specs a little there too :D
+DolganoFF The mosfet is not the one I really worry about. If all 1206 resistors are dissipating .25W each, such a small volume will heat up. But as you said, varta is pushing the specs a little, if they do that to the batteries, who cares about a little resistors ;)