Recharge non-rechargeable alkaline batteries with a broken LEDs light bulb - Page 1
Forum section: electronics / projects

author: RoGeorge
author_rank: Super Contributor
timestamp: February 02, 2023, 08:15:53 pm
content: Alkaline batteries are not made to be recharged. The fine print on each battery says to not recharge. However, most of them can be recharged many times if done slow enough and without exceeding their nominal voltage. The current has to be kept small, no more than 0.1C (the lesser the better, though it will take longer to recharge), and the voltage must be topped at the nominal voltage of 1.6V ... 1.7V most, so a CC-CV (Constant Current - Constant Voltage) source would be good enough.Recharging non-rechargeable alkaline batteries doesn't work as good as a NiMH rechargeable battery:- less recharging cycles possible (5-50 cycles, depending of many factors)- can be recharged only partially (again, mileage may vary wildly)- might leak during/after recharge (didn't happen to me yet, thought alkalines might leak even without recharging them)Works great especially for low current devices like LCD thermometers, calculators and such.How do I know? I've tried out of curiosity. It works.\[ \star \ \star \ \star \]The next shows how to reuse the LED driver from a mains AC broken LEDs light bulb, and transform it into a charger for alkaline batteries, with charging current less than 100mA and 1.5V limited, to recharge a single alkaline cell.Mains AC LED light bulbs have two major failure causes, broken LEDs, or broken driver. The one used here is from a Philips LED light bulb with damaged LEDs plate. Most of the LED drivers in nowadays AC light bulbs have a mains AC bridge rectifier followed by a switching power supply with various dedicated ICs, connected as a constant current source for the LEDs plate, like this:The funny thing is the LED driver starts working as a CC at input voltages as low as 12.5V!When powered from a DC voltage source (e.g. a car battery) the rectifier bridge is not needed. Instead, the + and - pins of the bridge were lifted from the PCB and rewired as a load for the former LEDs driver.Thus, the diode bridge is used as two series diodes parallel with yet another 2 series diodes, and in practice that will limit the voltage at about 1.5V, which is just right for an alkaline battery.The AC mains filter was removed, too, so an extra fusible, a 4.2mH coil and 0.1uF to play with in other projects.The wires are from CAT5 LAN cable leftovers, and terminated with forever shiny pieces of paperclip wire!\[ \star \ \star \ \star \]Usage:- Power up the driver from a DC voltage source of at least 12.5V (drawn current is less than 20mA)- Connect a discharged alkaline battery in the AA/AAA socket- Leave the battery to charge for a day or two non-stop, then remove it from the charger- Use a plastic container while charging, just in case a battery might leak, vent or popPT4554D LED driver SMPS IC datasheethttp://www.kingsunled.net/Data/kingsunled/upload/file/20190219/PT4554D_DS_CH1.2_201806.pdfMB10F rectifier bridge datasheethttps://www.diodes.com/assets/Datasheets/MB10F.pdf

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: February 02, 2023, 08:20:56 pm
content: Alkaline batteries eventually leak and wreck everything you put them in. I refuse to use them, much less try to recharge them!

author: RoGeorge
author_rank: Super Contributor
timestamp: February 02, 2023, 09:20:27 pm
content: They might leak, but if they don't, then they can also be reused.The problem with NiMH or NiCd is that they self discharge in a few weeks to months. Even the low discharge rate NiMH won't last a year, while alkalines last at least 2-3 years in LCD devices.The alkalines that reminded me about the recharging alkalines trick are from an LCD thermometer that stopped working today. One was measuring 0V, the other one 0.8V open circuit. Charged them at least once some years ago, don't recall exactly how long ago. One has a date on it, 08-2016.The 9V battery from the LCD MTester has embossed 01-2013 on it. Charged it a few days ago with a lab supply. The GP 9V alkaline has 10 years and still keeping up!The annoying thing about using the lab power supply to recharge alkalines is that mine has a fan and it's noisy to run it non-stop for days.When I've seen today the thermometer batteries need to be recharged I've decided to make a no fan power supply with a CC-CV, but then I've bumped into a LED driver that was sitting on the workbench for days with no particular reason, and was curious if it can run at low voltage, and it does. Free CC-CV regulator, a too nice trick not to show off with it.

author: james_s
author_rank: Super Contributor
timestamp: February 02, 2023, 09:26:31 pm
content: Alkaline batteries are notorious for leaking even if you don't abuse them by recharging. If you recharge them they are virtually guaranteed to leak eventually and when they do they will damage whatever equipment they're in. I don't understand why someone would even want to risk this. Proper rechargeable batteries that don't leak are not expensive.

author: RoGeorge
author_rank: Super Contributor
timestamp: February 02, 2023, 09:47:27 pm
content: I have plenty of NiMH including low self discharge, just that they still self discharge eventually, that's why I'm still using alkalines in room thermometers. Those thermometers were $1 or so, and are all plastic anyway.Then, there are places where it's visible if it leaks, like in this MTester with the 9V battery:The box is all plastic, battery is visible, and if it were to leak then it smells immediately.I fully agree to not use alkaline batteries with expensive items.All my DMMs, point and shoot camera, etc. are using low self-discharge NiMH.

author: RoGeorge
author_rank: Super Contributor
timestamp: December 28, 2024, 06:55:51 pm
content: Forgot about this topic. After a few more tries, I've give up to the idea of trying to recharge alkaline AA/AAA, mostly because once recharged, about half of them leaked in the first 2 weeks or so while just sitting on the workbench doing nothing.I am convinced now that even a single recharge will dramatically increase the chances of leakage. It is not just bad luck or leak caused by the age of battery. The leak happened only in the lot of the recharged battery.From the entire bowl of used batteries kept as witnesses, none leaked during those couple of months of experiments. All the leaks happened in the lot of recharged AA/AAA alkalines, and usually it happens a few days later, long after unplugging from the charger.

author: IanB
author_rank: Super Contributor
timestamp: December 28, 2024, 07:23:24 pm
content: Quote from: RoGeorge on February 02, 2023, 09:20:27 pmI have a digital camera that has been sitting in a cupboard as an experiment with the same set of NiMH batteries in it for 14 years since the day I dropped it and damaged it, and it still powers on after all that time. No prizes for guessing what kind of batteries they are.

author: harerod
author_rank: Frequent Contributor
timestamp: December 28, 2024, 09:16:10 pm
content: Quote from: RoGeorge on December 28, 2024, 06:55:51 pmThank you for that post. We "experience is the sum of past mistakes" old farts had a gut feeling that you would get leaking batteries.My upvote is for your coming back and sharing the experience that your idea didn't work out.Edit: I am a bit younger than you.

author: Analog Kid
author_rank: Super Contributor
timestamp: December 29, 2024, 08:14:14 am
content: Looks like the experiment ended in failure.But I have to give the OP a lot of credit for being an intrepid explorer, daring to go where others fear to tread.That's how we learn interesting stuff like this!My hat's off to you,@RoGeorge.

author: RoGeorge
author_rank: Super Contributor
timestamp: December 29, 2024, 09:41:23 am
content: Well, thank you, but I've remembered about this topic by accident (another topic reminded me of this one), and noticed I didn't tell how it ended. In fact it didn't really ended, in the sense that I'm still curious about other ways of recharging (for example by forcing the temperature to stay at room temperature, to test if the higher temperatures during charging is causing the battery to leak later, though, not sure if I'll ever take the time to test for that).P.S. Please don't use @ in front of my nickname, because that forces a notification that can not be blocked from the forum settings.

author: Analog Kid
author_rank: Super Contributor
timestamp: December 29, 2024, 08:59:33 pm
content: Quote from: RoGeorge on December 29, 2024, 09:41:23 amOK, gotcha.