Standalone LIR2450 3V Lithium Battery Charger - Page 1
Forum section: electronics / general

author: DonKu
author_rank: Regular Contributor
timestamp: February 21, 2025, 04:40:02 am
content: My quick search for a suitable charger came up empty. The DIY charger circuit shown below looks fit for purpose. Can anyone offer any words of wisdom about the circuit?

author: TERRA Operative
author_rank: Super Contributor
timestamp: February 21, 2025, 05:07:41 am
content: CR2032 are not rechargeable.Are you thinking of LR2032?

author: DonKu
author_rank: Regular Contributor
timestamp: February 21, 2025, 05:26:35 pm
content: Quote from: TERRA Operative on February 21, 2025, 05:07:41 amMy post pertains to a2450 3V Lithium battery. In retrospect, Inet searches for "CR2450" quietly return "2450" product. Thread title changed to reflect new reality.

author: Kjelt
author_rank: Super Contributor
timestamp: February 21, 2025, 06:24:16 pm
content: Oh man please check if you're battery has "rechargeable LiIon" on it.CR2450 are Lithium but NOT LiIon and are NOT rechargeable, you'll blow it and have gunk all over the place or even a fire. It is 3V nominal.Here are the two versions, the rechargeable one has this marked and has a different prefix like LR or LIR for Lithium Ion Rechargeable. It is 3.6V nominal.

author: Gyro
author_rank: Super Contributor
timestamp: February 21, 2025, 09:23:56 pm
content: Quote from: DonKu on February 21, 2025, 05:26:35 pmScreenshot from your link...

author: DonKu
author_rank: Regular Contributor
timestamp: February 22, 2025, 05:39:57 am
content: Thank you everybody for clearing things up. Apparently a LIR2450 is needed. Unfortunately it's 0.6V above a CR2450 3V. So the original battery powered circuit now needs a silicon diode modification to drop the voltage down to the original 3V.Note: Title again changed to reflect newest reality.

author: Peabody
author_rank: Super Contributor
timestamp: February 22, 2025, 03:56:27 pm
content: I think the LIR2450 would be charged with the same algorithm as any lithium ion or polymer cell, which would begin with a constant current phase, followed by constant voltage at 4.2V, followed by termination of charging. Could you describe how your circuit works?

author: DonKu
author_rank: Regular Contributor
timestamp: February 22, 2025, 04:24:14 pm
content: Quote from: Peabody on February 22, 2025, 03:56:27 pmIn reality it's G4USP's circuit:Quick & Easy Lithium Ion Battery Charger

author: Peabody
author_rank: Super Contributor
timestamp: February 22, 2025, 04:53:46 pm
content: Will you be charging at 4.2V or 3.6V? At 3.6V I think the cell will be less than half charged.Something like a TP4056 circuit would typically be used, but it would end up at 4.2V. So if you really need a 3V rail, you would need a regulator after the battery if you go that way.

author: DonKu
author_rank: Regular Contributor
timestamp: February 22, 2025, 05:19:05 pm
content: Quote from: Peabody on February 22, 2025, 04:53:46 pmMy intention is to periodically remove and re-charge the battery from an AVR Butterfly. It originally used a CR2450 3V cell. The diode mod to the Butterfly is intended to lower the nominal LI2450 voltage from 3.6V to 3V.If instead, an apropos LDO, for example, is used to mod the Butterfly, it seems there's a good chance the LI2450 voltage will eventually droop below 3V. Then again, the CR2450 itself probably droops during its lifetime.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: February 22, 2025, 06:59:36 pm
content: There are plenty of simple & chealp lithium charger chips like the TP4054 for a few cents - why not just use one of those ?

author: DonKu
author_rank: Regular Contributor
timestamp: February 22, 2025, 07:10:43 pm
content: Quote from: mikeselectricstuff on February 22, 2025, 06:59:36 pmMy intuition hinted the solution was probably more complex than a simple LM317 circuit. (Ergo, this thread.)But it's hard to use something you don't even know exists. In retrospect the TP4054 looks simple and cheap. Thank you guys for bringing it up.Now my sole remaining problem is to mod the AVR Butterfly to accommodate the higher LIR2450 voltage.