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

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andygozzo72: Bet that charge current doesnt do the cells much good!!

Kirk McLoren: Opus BT-C2000 will measure capacity for you. Love mine. Reasonable cost as well.

Eddie Rod: Someone might be eating some batteries soon!

Major REX: Informative video but you never answer your own question, did it charge properly in 15 min?
Also how hot did the parts get?
And finally did yo eat the battery as you promised assuming it did charge in 15min :-)

sghost128: So I have one of these that has been re-branded by Rayovac. My question is, how does it know when you are charging their fast charge batteries, or just regular rechargeable batteries?

Shun Takara: Sir I need your advice, i am planning to build a 48v using NIMH 1.2v 3000 mah , teh question is that can i charge this with 7-step,full automatic switch mode,(reverse) pulse charging that you can buy at ebay and if i have 48 1.2 v 3000 mah how much AH i will have for my 48v battery pack can you please correct me Thank you!

Aluminum Foil: Stargate Yessss

Jose Luis Martínez Palenzuela: Clear and instructive as the previous!!! thanks.

YH Wei: life cycle exchange for charging speed. choose what you need most.

Pro1er: I know this is an old video, but about 10 years ago I bought a Rayovac 15 minute battery charger with 4 AA batteries. That thing worked a charm! The only reason I stopped using them was because I upgraded to get, (much), higher mAh batteries. I think the Rayovacs were somewhere around 1600 mAh - but that was years ago before the higher capacity batteries were available.

Ernst Stavro Blofeld: Can I use this to charge the russian nuclear batteries that I got off ebay?

1998goodboy: the dylithium crystals :DDDD

HAL900032: hhehe I almost fall off my chair everytime you say Hi at the beginning:) got pretty strong coffee down there huh?!

Олег Макаров: Русский выучи dibel

Beaches south of L.A.: I love this guy. "Is there something dodgee going on?"

Power Max: Gees, pushing 8A charging current through a small poor AA battery! 4C!?!? modern Lipos take like 2C absolute maximum!

peter bridge (Thecrakedminecraft): Is vata a good brand? I live in the uk so I don't know. I have a Bosch drill charger that can charge a 12v 1700mah NiCd/NiMh pack in 15 mins, It apparently uses a system called 'fuzzy logic' to determine exactly how much charge the pack needs and will deliver exactly that amount of charge and no more. The pack never gets hot, and according to the Bosch literature, Battery packs charged in a Fuzzy Control charger will last way way way longer than packs that are charged in a standard 'delta voltage' charger...  Would be good if Dave (or indeed Mike) could explain more about how fuzzy logic chargers work.

zwz • zdenek: 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?

Teardown Dan: 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.
EEVblog #35 - Inside the Varta 15 minute NiMH Battery Charger 5 out of 5

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