Using Li-Ion in place of 1.5V batteries: sharing my few successes - Page 1
Forum section: electronics / projects

author: Cricri
author_rank: Contributor
timestamp: December 18, 2024, 03:18:55 pm
content: Just wanted to share few applications where I powered devices normally using 1.5V batteries with a salvaged Li-Ion:Nintendo Game & Watch dual screen: normally uses 2xLR44 batteries (3V). I used Li+Ion + 2x 1N4007 diodes to drop the voltage somewhat, USB charging board taped to the battery; worked fine for many months as a desk clock, eventually reversed the mod to sell the G&W.Nintendo Game Boy (original): normally uses 4xAA (6V). I saw many mods that include a 6V step up converter, but also found info that to power some parts of the device (e.g. LCD), the device includes it's own step up converter, which let the Game Boy still work when it gets just over 3V from the batteries (can't remember the source or the exact voltage). So installed a LiIon battery + USB charging board in the battery door compartment soldered straight to batteries terminals, works fines.Hewlett Packard HP 48SX: normally 3xAAA (4.5V). bought this calculator cheap only to find the common top row buttons fault. Disassembled it (which is a PITA, so don't do it unless you HAVE too), fixed the buttons but shattered the battery tray in the process. Connected a Li-Ion to the batteries terminals and stored the battery in an expansion card slot (so no more card functionality, but let's be honest, good luck finding one of those anyway, although if I shuffle stuff and put a slightly thinner battery I should be able to use 1 of the 2 slots), USB charging board in the battery compartment, and it's been working great for years so far.

author: globoy
author_rank: Frequent Contributor
timestamp: December 18, 2024, 04:20:25 pm
content: Good job. I have thought about trying to add a rechargeable battery to my wireless Apple keyboard replacing the 2 AA batteries.

author: RoGeorge
author_rank: Super Contributor
timestamp: December 19, 2024, 06:07:13 am
content: Body-weight scale, replaced its CR2032 (3V nominal) with a rechargeable Li-ion leftover from a former USB modem (battery made in Japan, 3.7V nominal, 4.2V max). Did this because the CR2032 were dying inside the scale after a few months. Took the risk and soldered the Li-ion directly, no voltage regulator.Fully charged the Li-ion to 4.2V two years ago, and never recharged since. Logging its voltage once a year, out of curiosity. After 2 years, still has more than 3.8V. Happens that no longer than yesterday measured it again:https://www.eevblog.com/forum/beginners/li-ion-cell-instead-of-a-cr2032-for-a-domestic-wight-scale/msg5751629/#msg5751629If it weren't for the self discharge rate, one recharge should last for about 18 years.

author: Irilia
author_rank: Regular Contributor
timestamp: December 19, 2024, 08:29:13 am
content: I think a LFP battery will be more appropriate in this case, 3.6 maximum 6000 cycle will last 300 time longer than the product itself 😉

author: rteodor
author_rank: Frequent Contributor
timestamp: December 19, 2024, 08:48:42 am
content: Quote from: RoGeorge on December 19, 2024, 06:07:13 amDon't they degrade chemically after 13 years or so ?

author: psydaddy
author_rank: Contributor
timestamp: December 19, 2024, 09:36:01 am
content: Well done.But take into account that step-up converters waste a lot of energy comparing to step-down converters. If you want to increase the voltage, it is better if you add 2 batteries in series and use a step-down. Bare in mind that charging 2S batteries might be a challenge.For small applications, you can also use a LDO. Using diodes waste a lot of energy.

author: RoGeorge
author_rank: Super Contributor
timestamp: December 19, 2024, 09:44:49 am
content: Quote from: rteodor on December 19, 2024, 08:48:42 amThey do, but most are still usable. That Li-ion battery I've put in the weight-scale is from around 2005, 20 years ago and still doing OK. I have many other from old 2G mobile phones, the kind of phones with physical buttons for the numerical keypad, 10-20 years old. Many of their batteries are still usable.Some may look bulged, but not all of them, and they usually have only 50-70% left from their nominal mAh, but still usable.Same for very old NiMH or NiCd that were used in the very first mobile phones, before Li-ion became the norm. Still usable batteries, but with lower capacity. In fact the failure rate of Li-ion is much lower, followed by NiMH (with much higher failure than Li-ion). From the NiCd, only a few of them survived, but I still have some 300mAh AAA NiCd in use inside of a hallway light activated by an IR motion sensor. Once charged they last about 2 month, and I suspect most of the charge loss is caused by self-discharge.Another reused batteries tale (though not Li-ion, this time NiMH), my DMM accepts 3 x AA, either alkaline or recheargeables. Since it has an internal recharger that is almost always plugged into mains, inside the DMM I've put 3 Ni-MH cells cut out from a pack of 5 that used to power an ancient Motorola 8700 MicroTac, from the 90s!https://en.wikipedia.org/wiki/Motorola_MicroTACThe funny thing is that I've found the Motorola battery while cleaning the lab, forgoten in one of the scrap boxes from decades ago. Measured the pack out of curiosity, and it was not zero, which came intriguing. These were NiMH, and supposed to have a pretty big self-discharge rate (when compared to Li-ion).Opened the battery pack, and 3 out of 5 NiMH cells were still usable, charged them at the beginning of the year, and more than 6 months later they were still keeping their charge (left unused). So i've put them inside the DMM, more like an homage (they have about half of their nominal 700mAh, which means only about 10 hours on for the mtx3283 DMM, though the DMM is plugged into mains most of the time, which makes the battery capacity irrelevant).Attached is the discharging chart of the 3 still usable cells out of that pack of 5. They were measured at 140mA constant discharging current (0.2 of nominal C=700mAh). Note the mAh in the upper right corner, that is the true value calculated from the measured I/V plots of each cell, and it's about half their nominal C.The short circuit current (after letting them charged for about half a year) was still noticeable, about 1-2A. For the internal resistance of my DMM, the normal I short for NiMH is about 2A for 10-20 years old ones, and about 10A for brand new NiMH cells.What was absolutely puzzling (about those 5 NiMH from the Motorola phone) was that one of the cells, the one in the middle, was measuring only 0.2V instead of 1.2V, yet it was able to deliver energy and some short-circuit current at that 0.2V nominal.

author: Cricri
author_rank: Contributor
timestamp: December 28, 2024, 03:05:39 pm
content: Found the source of where I found that the GB worked fine down to 3V, so I#m adding the link for completeness in case someone is interested:https://blog.gg8.se/wordpress/2009/07/22/testing-gameboy-input-voltage-ranges/

author: Konkedout
author_rank: Frequent Contributor
timestamp: December 28, 2024, 07:54:31 pm
content: Quote from: globoy on December 18, 2024, 04:20:25 pmBut what to do if I want a keyboardless apple wire?