EEVblog #35 - Inside The Varta 15 Minute NiMH Battery Charger




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Lauren Weinstein: Sometime back I mentioned that I had a AA NiMH battery charger that could fully charge empty batteries in 15 minutes. I call it my *nuclear* charger -- even has a cooling fan. Ever wonder how you can pump so much current (4C rate, in fact) into a AA without having it *explode in your face*? Well, Dave here explains, and he deserves some sort of award for what must be one of the most entertaining electronics *lectures* I've ever seen. Go Dave!

ZdenekJindra: I thought bullcrap to myself at first. Then I saw the beefy wall wart... Maybe? And I was in fact surprised when I instantly recognized those SMD MOSFETs (5A each, 2 per line) and knew there was something to it after all. But as everyone says, it can't be all truth because of the cell's over-estimated life. Dave, it's 5 years now. Would you give us a follow-up on how long did those cells last?

Frederick Roels: Haha, he has seen to manny star trek and stargate series/movies, Got to love it!

Daniel Sauvageau: I had one of those Energizer 15-min charging kits with batteries... I don't think I got more than about 100 cycles out of those before the batteries started dying. 4C is much too harsh. On that charger, battery detection was done by detecting current across contacts and I'm guessing the charge cycle control was done entirely based on I-V curves. When a battery ends up too far off the expected I-V curve, the charger flashes the failed battery code. The PCB contacts behind the "spring thingies" on my charger were actually a switch to select AA vs AAA charge current. What I ended up doing with my fast-charger is cover the battery size detect pads to make the charger operate in permanent AAA (lower current) mode so my AA batteries would not warm up anywhere near as much.

Sc0rPsX: I bet you those batteries were made in China, if not then Japan. A very good product. 10 years ago it was the Japanese laughing to the bank, in another 10 I guess it will be India?

edcjunkie: LOL @ the stargate references! Classic Geekspeak!

cepaGMOD: Whoa whoa whoa whoa. Epic Stargate references.

Chris Skoufis: LOL i really loved this comment :P

Eddy Polonia: zpm haha

g6qwerty: I love all those shows his references came from :D

EEVblog: Well, it works. Just don't expect the number of cycles claimed I recon.

fallen over: i have 2 arlec aa rechargable battery's (left) i have had for close to 25 years, they must have passed 1000 cycles by now easily and amazingly they still work as if i had just bought them other then those, varta batterys are the best if have had since them (all others life is limited to a few months, to a year if lucky) but varta work good and hold charge, the chargers are cheap and nasty though, mine blew up, and now i cant find a replacement, not a 15 minute charger anyway

Ja Ro: Nice star trek/stargate references, impressive design as well.

NosferatuD: Haha, love the di-lithium crystal comment.

theripper7675: great video Chopper reid

ilusjon: THUMBS UP, IF YOU GOT THE STARGATE SG1 REFRENCE !!!

Terrence Kuchel: love the stargate ref

God Emperor Lionel Lauer: Learn how to read. He's right, you're wrong.

Mniilla: EAT THE BATTERY!!!

Ashot Gevorgian: A bit late ;-) However would like to share. In 2008 I bought 15 minute rechargeable 2000mAh Ni-MH batteries from RadioShack labeled I-C3. Back then, did some googling and, if not mistaken, those were custom produced by Ray-O-Vac . However, everything is simpler here. Those batteries have an internal pressure operated cut off mechanism, for the end of charge! No smart electronics. If not mistaken, the gases produced at the high rate charge, create the necessary pressure. I love EEVblog!

Jacob: is he on crack?

christo930: That isn't how these work. NIMH and NICAD batteries can accept very high charge rates up until they are about 80% charged, after that a great deal goes to heat. Since it's a charger designed to handle different battery capacities, it usually doesn't even know what the C rate is. It just dumps a lot of energy into the batteries until they get warm, then the charger backs down the current for the rest of the time. You will rarely get 4 2.1AH batteries fully charged in 15 minutes. More like 80-85%

victornpb: the rated capacity is for 25mAh discharge.

Forssa1: Sup, things! I liked the video too, I have those batteries by the way.

FoamPackingPeanuts: The MCU is most likely a HT46R54A OTP EPROM microcontroller. I've got one in an Energizer 15 minute charger, but I had a Duracell one that used an Atmel ATmega8/L chip (which I accidentally erased with a programmer... oops.)

TheSuperGZ: Varta is owned by Johnson Control

ProblemsChild4eva: MEANS?? is this varta 15mins batt rechargeble good or bad ?? wanted to get 1 for my rc toys.

Lachlant1984: I have one of these battery chargers at work and generally I like it, the batteries do charge up in 15 minutes, but I like to leave mine on for a day at least to trickle charge the batteries properly. The batteries certainly do not hold their charge over a 12 month period, that's for sure.

enliteneer: So to a charge a 2100mAh battery in 15 minutes (4C), why isn't the AC-DC plug pack adapter rated at 8.4A? (Or more since it can do 4 batteries at once) What's the model of this? I'd like to see how it price compares with the PowerEx C9000 or even the Battery Wizard that can recharge standard Alkaline batteries! Oh, also, did you have to eat the battery? Were you thinking that the # of cycles would decrease the faster you charge it?

george456789: Would be nice to know the actual results like energy density after the 15 minute charge and the charge cycles. One issue with these chargers if you use standard NiMH batteries on this charger they gas electrolyte which destroys them quickly. The other thing is I'm not sure the formulas work out NiMH batteries have a typical charge efficiency of 65% so you need to ad 35% onto the numbers to allow for loss. Gotta go along with you tho with the 1000 cycles BS

usaamerica1: thank, its about time that we show what bull crap products the chinese actually produce and why we are so stupid to buy it. the chinese are laughing all the way to the bank, or shouyld i say to world power!

nigeleyeit: checkout the Powerex brand, i use the imedion ones 2400mah retains 85% charge upto 1 year, insane! I also use the MH-C9000 battery charger and found it very good, Does temperate sensing, delta v and timer cutoff and charges each battery independently. Might be another review idea?

Americanstu: Do you have to use the " labeled" 15 minute batteries with this charger or can you use the charger with any NiMH batteries? I have been using Eveready 2450 mAh with my Varta charger, which may be an earlier version of the one that you demo'd as it only has 1 LED per 2 batteries inserted however the LED will go on when only one battery is inserted...thank you for your post!

theripper7675: gotta go duracell baby

rocketman221projects: I don't know why they always say they can be recharged 1000 times. I have gone through a lot of AA & AAA nickel metal-hydrate batteries and I am lucky to get 80-100 cycles from them. That is using a microprocessor controlled charger that charges each cell individually at 500mA. The timer based chargers get even less cycles because they almost always overcharge the batteries and usually charge in series to cause even more problems.

NeMewSys4: So how can those batteries take so much current at charge?

Charles McCune: and I thought I was the only Star gate SG1 fan lol

Liu YueKun: Can I charge other branded NiMH batteries with it? Like the Sanyo Eneloop?

kildas: dilithium crystals, ZPM .... something tells me you are Sci-Fi fan :D

LPFthings: It's kind of strange how they can shove so much into a battery and not have it explode, and even have that many cycles! Nice review though.

NotSoLiberal: Where is the rest of the video?

renxula: I lolled at the goa'uld reference :D

EEVblog: @enliteneer It's about wattage. The plugpack does not need to do 8.4A because of the internal DC-DC converter that generates a lower voltage at a higher current.

Sc0rPsX: The NiMH types are, this is the first I seen the better 'low discharge' NiMH being able to recharge so quickly. Takes me an hour for triple & double A types but since they only lose less then 2% charge a month I always have a few ready.

GerbilEssences: Madness? THIS IS VAAAAAARTA!!!

David Adams: You might want to watch again with your glasses on. His math is spot on. He didn't write 10C, he wrote C/10. That's 1/10th the charge rate, and 10 times as much time. A battery that has a C rate of 1 hour has a 4C rate of 15 minutes. gramar tip: It's "albeit" not "all be it".

victornpb: I'm gonna make a 5 minutes charger, to see if that bitch can handle 25amps. bang

TheCentralServices: And where is the Dilithium crystal?

TutoElectro: Really good vid Dave, I've looked the price for that charger with 2500mAh batterties and car adapter and is cheaper than what I thought only 40 pounds. Please let us know if the number of charging cycles is anywhere close to what they claim. Thanks!

Allan O'Brien: @enliteneer It would definitely decrease the cycle life of these batteries, batteries are fairly fragile with the amount of current pumping into them. I would be surprised if you got anywhere near 500 cycles out of them.
Rating:
EEVblog #35 - Inside the Varta 15 minute NiMH Battery Charger 4.9 out of 5

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EEVblog #35 - Inside the Varta 15 minute NiMH Battery Charger