best and simple way to lower 3v CR2032 button battery to 2v - Page 1
Forum section: electronics / projects

author: sub2001zero
author_rank: Contributor
timestamp: May 21, 2018, 04:20:47 am
content: Hi everyone I just want to know the best and simple way to lower 3v CR2032 button battery to 2v.I want to make a simple board layout to take a 3v battery and have an out put of 2v.The board is for a vintage electric lighter that ran on 2v acid battery and you cant buy anymore.Thanks!

author: tautech
author_rank: Super Contributor
timestamp: May 21, 2018, 04:37:32 am
content: Considering a LA battery is a nominal 2.2V just a silicon series diode will reduce the lithium cell ~0.6V. If you need more then add a Schottky diode too for an additional ~0.3V drop.

author: rdl
author_rank: Super Contributor
timestamp: May 21, 2018, 04:40:07 am
content: For that type application a diode in series is probably enough to lower the voltage, but yeah, you probably won't get enough current out of a coin cell. They're only good for a few mA at best. I'd just try the full 3 volts and see what happens. Probably nothing.

author: sub2001zero
author_rank: Contributor
timestamp: May 21, 2018, 06:40:22 am
content: Hi everyone the lighter has small light bulb that is 1.8v bulb it a push button and has a coil i guess Nickel Chromium wire for the lighter to light a small wick with lighter fuel.

author: Richard Crowley
author_rank: Super Contributor
timestamp: May 21, 2018, 06:46:00 am
content: Since we (and you?) don't know how much current is required, and since you did not describe the original "2v acid battery" your question really cannot be answered.If it uses an incandescent lamp and a resistive heating element it is almost guaranteed that no "coin cell" will provide anywhere near enough current.Furthermore, if the load is only an intermittent incandescent lamp and a resistive heating element, it is not apparent that you even really need to drop the 3V down to 2V. The actual voltage required to do that job is not that critical.

author: NiHaoMike
author_rank: Super Contributor
timestamp: May 21, 2018, 06:54:18 am
content: How much space do you have to work with? A pair of NiMH could be close to a drop in replacement.

author: Zero999
author_rank: Super Contributor
timestamp: May 21, 2018, 08:32:10 am
content: Quote from: Richard Crowley on May 21, 2018, 06:46:00 amYes, I suspect that a lithium battery won't be able to provide enough current to power the lighter.

author: sub2001zero
author_rank: Contributor
timestamp: May 21, 2018, 09:15:08 pm
content: space size i have to work with 10mm Wx 34mm height x 30mm length. I know it can be done with some kind of battery, I read back on a website someone made one to fit it. Thanks for all the help

author: NiHaoMike
author_rank: Super Contributor
timestamp: May 21, 2018, 09:34:12 pm
content: Best bet would probably be a small R/C lipo, although the voltage is a bit high.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: May 21, 2018, 09:41:13 pm
content: Not much space, but if you can find a higher voltage battery, maybe you can do an efficient buck converter to get the voltage you need.

author: sub2001zero
author_rank: Contributor
timestamp: May 21, 2018, 09:47:56 pm
content: some like thishttps://www.ebay.com/itm/2A-DC-DC-Boost-Buck-Converter-Step-up-Voltage-Module-Adjustable-3V-5V-9V-12V-24V/323013308636?hash=item4b3517f0dc:g:8aYAAOSwGPxaKgbn

author: sub2001zero
author_rank: Contributor
timestamp: May 21, 2018, 10:04:00 pm
content: hi can some one tell me the a mah i would need thanks

author: SiliconWizard
author_rank: Super Contributor
timestamp: May 21, 2018, 10:05:50 pm
content: Quote from: NiHaoMike on May 21, 2018, 09:34:12 pmThen use an LTO (Lithium Titanate) battery. Way, way safer, high current and 2.4V nominal. Take a look at this:http://www.batteryspace.com/Lithium-Titanate-Battery.aspxOf course, it won't quite be as small...

author: sub2001zero
author_rank: Contributor
timestamp: May 21, 2018, 10:30:42 pm
content: LTO (Lithium Titanate) battery how do i go about charging them!

author: ucanel
author_rank: Regular Contributor
timestamp: May 21, 2018, 11:19:18 pm
content: If it fits just use two AAA Cell battery as series.You may use (1,2V) rechargable ones, it fits better in your situation.

author: BrianHG
author_rank: Super Contributor
timestamp: May 21, 2018, 11:56:46 pm
content: These should do and they are rechargeable, they are already 2.4v:https://www.amazon.com/VARTA-55608602059-BATTERY-80mAH-BUTTON/dp/B00DJY1HUQhttps://www.amazon.com/Varta-V150H-150mAh-Battery-55615302059/dp/B00960JZX8Use a Schottky diode in series if you want 2v on the dot.Size AAA also exists, but, you need 2 of them.

author: NiHaoMike
author_rank: Super Contributor
timestamp: May 22, 2018, 03:17:59 am
content: Since the load is resistive, it should be possible to make a PWM circuit that connects in series and allows the existing switch to turn it on without modifying the device.

author: james_s
author_rank: Super Contributor
timestamp: May 22, 2018, 06:20:54 am
content: There are AAAA batteries too if you need even smaller. You can extract them from some types of 9V batteries, both alkaline and NiMH.

author: Zero999
author_rank: Super Contributor
timestamp: May 22, 2018, 01:17:00 pm
content: Quote from: james_s on May 22, 2018, 06:20:54 amThat's a good idea, but some rechargeable 9V batteries have rectangular, flat, button cells, not AAAA, although they will also probably work.

author: SiliconWizard
author_rank: Super Contributor
timestamp: May 22, 2018, 02:56:48 pm
content: Quote from: sub2001zero on May 21, 2018, 10:30:42 pmI was mentioning it out of interest for (sort of) cutting-edge tech, but frankly I wouldn't really recommend that for your simple project.LTO batteries are not difficult to handle though. They are charged the same way as Li-ion batteries, only at different voltages and usually can take a much higher charging current for a given capacity.So you basically need a constant current/constant voltage charger, and the constant voltage should be at 2.75 V instead of 4.2 V (for LiPo). Some chargers are available on the market that can handle multi-chemistry batteries. Or you could build your own charger, there are some ICs for that. Of course there are not many ready-made chargers for LTO batteries, so again, I would not recommend that for a small project. But those batteries are really great.