Easiest way to integrate Lithium Ion batteries into a project with a 5V input - Page 1
Forum section: electronics / projects

author: Ehryk
author_rank: Contributor
timestamp: December 05, 2015, 06:19:31 am
content: I'm building a speaker with a clear lexan front panel, and I'd like to put 2-8 red LEDs inside for illumination.I at first thought about putting in a 9V battery, because I don't particularly want extra wiring going to my center channel, or even worse to draw power off the signal, but damnit this is 2015 and I shouldn't be replacing batteries.I do have many used, but good 3.7V lithium ion batteries out of cell phones, cameras, and other electronics through the years. What is the easiest way to reuse one of these into my project, charged from a standard USB 5V power supply? Are there single IC solutions that handle all the charging and discharge cutoff and everything? If not, what's the simplest circuit do implement this reasonably?The load is just going to be some red LEDs, very capable of operating on a fairly variable power source from 3.3V (low battery) to 4.3V (charging voltage), or even 5.0V.If this is terribly difficult, I could just wire them up to a USB connector for a constant 5V, but requiring an extra connection isn't the greatest, nor is replacing alkaline batteries.

author: Ehryk
author_rank: Contributor
timestamp: December 05, 2015, 07:48:26 am
content: Just to clarify - does any single IC component exist with +5V charging in, Bat+, GND, and load out (3.3V to 4.3V or so), that will automatically handle the charging and low voltage dropout for the LiIon batteries?

author: bingo600
author_rank: Super Contributor
timestamp: December 05, 2015, 08:47:26 am
content: Would this one be usable ?http://www.ebay.com/itm/191749958596http://www.ebay.com/itm/171756271408http://lygte-info.dk/review/Review%20Charger%20TP4056%20UK.htmlBtw: I have Q for use of this charger, to a electroncs guru.Can one use/load the lipo while it's charging from the charger, or would that be a No..No.I mean to have it permanently connected to the charger, and the load at the same time.I have a "natural fear" of FIRE/Bingo

author: JohnnyBerg
author_rank: Frequent Contributor
timestamp: December 05, 2015, 08:56:22 am
content: TP4056MCP73831Do not forget to implement a "load share" circuit, otherwise the LI-ion will never get fully charged.

author: mariush
author_rank: Super Contributor
timestamp: December 05, 2015, 09:02:18 am
content: Have a look at mcp73831 :http://www.digikey.com/product-detail/en/MCP73831T-2ACI%2FOT/MCP73831T-2ACI%2FOTCT-ND/1979802Big enough that it's still easy to solder. You only need a couple of capacitors and resistors.Ready made boards with it and microusb connector :1.http://www.ebay.com/itm/Micro-USB-Lipo-Charger-MCP73831-/201432374042?hash=item2ee64e1b1a:g:r0sAAOSwwbdWORS0or2.http://www.ebay.com/itm/Adafruit-Micro-Lipo-USB-LiIon-LiPoly-charger-v1-/191436750683?hash=item2c9284ff5b:g:EtMAAMXQuTNTLrsy

author: Ehryk
author_rank: Contributor
timestamp: December 05, 2015, 03:03:50 pm
content: Thanks, those do the charging part - but what about the separating the load from the charging and the low voltage cutout? I'm looking for something with a separate load + pin, either as an IC or a standalone board - or do I have to do that separately?

author: onlooker
author_rank: Frequent Contributor
timestamp: December 05, 2015, 10:12:51 pm
content: Since ebay is already mentioned, I would suggest search for "usb power bank case".A single 18650 case (board+case) is about $0.74 each. It should satisfy all your requirements plus having a free case, except, maybe, charging and discharging at the same time (for that, an extra circuitry (=2 diodes) to power your LEDs directly from the charging source would be needed).In one of my uses (different case), I adjusted the output voltage from 5V to 8.5V.

author: Fungus
author_rank: Super Contributor
timestamp: December 07, 2015, 08:17:33 am
content: I'd use these, they have chargerandprotection IC:http://www.ebay.com/itm/221533778016

author: Ehryk
author_rank: Contributor
timestamp: December 11, 2015, 05:39:12 am
content: Quote from: Fungus on December 07, 2015, 08:17:33 amFungus, I ordered them to try them out. Do you know if they output +4.2V or +5V while charging? Have you used them before?

author: v8dave
author_rank: Regular Contributor
timestamp: December 11, 2015, 06:10:18 am
content: The MCP73871 will do power path and seems to be what you are looking for.You'll need a buck/boost on the output to generate your 5V from the battery or USB/DC input but the MCP73871 takes care of the charging and applying power to your device seemlessly.I've not found any boards based on this IC as most seem to use the MCP73831 which is not ideally setup for permanent connection of the power source as you might want with projects that need standby power. It's really designed for handheld type devices where you plug in, charge and then unplug again. The MCP73871 under micro control can halt charging at any time. A much better solution for standby power systems.You'll also need a DS2745 or equivalent to measure the battery current and voltage especially if you have a microcontroller that this is going to be used with. It allows you to control the charging by monitoring the battery etc.

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: December 11, 2015, 06:24:15 am
content: Quote from: Ehryk on December 11, 2015, 05:39:12 amThey will output the voltage of the battery, that is between 3.7 V and 4.2V. If you need higher voltage,you add a small boost converter of similar size after this charging/discharging board. Its work well,but do not overload them.