Rechargeable Battery Solution for MCU Projects - Page 1
Forum section: electronics / general

author: TJ232
author_rank: Frequent Contributor
timestamp: March 16, 2015, 09:40:10 am
content: What are your favourite Rechargeable battery solution for your MCU Projects?My proposal it's based on a 3.7V Li-ion Cell and a charger/monitor circuit to ensure proper usage for the Li-ion Cell.See more details :http://www.esp8266-projects.com/2015/03/mailbag-arrival-new-battery-solution.html

author: JohnnyBerg
author_rank: Frequent Contributor
timestamp: March 16, 2015, 09:54:51 am
content: I am also using the TP4056 on my NanoLipo. I am now at REV. C and the REV B. version used the MCP73831/ But this chip was unstable, when no battery was connected.Do you also have a load separator circuit?When the battery is charging, the load is decoupled from the battery, so it will not disturb the loading process.

author: TJ232
author_rank: Frequent Contributor
timestamp: March 16, 2015, 10:10:03 am
content: Quote from: JohnnyBerg on March 16, 2015, 09:54:51 amVery nice workI was also dissapointed by the MCP Battery Management series, looks like it needs some sort of loading to remain stable.Separate MOSFET Switch is used in case we want the loading to be done off-line. I know it might not charge fully 100% when load is not decoulped but in my case it's not desirable to have it decoupled.A compromise must be done, depending also on the application. I have designed also redundant battery charging circuits for 100% 24/7 systems where you have 2 separate Li-ion Cells with charging and monitoring circuits and when one it's charging offline the other one it's powering the circuit.

author: JohnnyBerg
author_rank: Frequent Contributor
timestamp: March 16, 2015, 10:21:34 am
content: I have done it like this:When USB is connected (VBUS), then the mosfet Q1 decouples the battery from the input of the regulator. The input for the regulator is then coming though diode D2. The relative large capacitor C3 ensures that there are no power glitches when USB is connected or disconnected. Resistor R4 pulls the gate of Q1 to ground when no USB is connected.The MCU can determine the battery status through D2/D3. This lines are also interrupts, and can wake the CPU from sleep.The regulators quiescent current is 8 uA, so that is effectively the current drawn from the battery when the mcu is in sleep. If that is to much, the regulator can be left out, and resistor R19 is placed.Current in sleep is then 160 nA !!And resitors R13 and R14?These are part of the "foolproof plan"When a user programs D2 or D3 as outputs, the resistors prevent then that D2/D3 are "hard" shortened to ground.R2 is the charge current programming resistor.

author: Howardlong
author_rank: Super Contributor
timestamp: March 16, 2015, 10:43:46 am
content: How are these devices determining the USB host charging capabilities, ie SDP, CDP and DCP (and others like Apple)?For SDP host ports, is there control of charge and load current pre-enumeration?The reason I ask is that I have recently been through this pain, and it's frustrating that as yet there doesn't appear to be a reasonable integrated solution covering host port capability detection, separate charge and system load management, and the charging itself, leading to 20 or so BOM parts just for a charging circuit.

author: JohnnyBerg
author_rank: Frequent Contributor
timestamp: March 16, 2015, 10:55:28 am
content: Quote from: Howardlong on March 16, 2015, 10:43:46 amAs far as I know, the TP4056 and MCP73831 have no detection what so ever.For me, it was simpleI set the programming current resistor to 2k2, giving 500 mA charge current. That is in fact what SDP can do. I just assumed that there is a modern USB 2.0 or 2.0 capable charger connected.note: seehttp://www.maximintegrated.com/en/app-notes/index.mvp/id/4803

author: TJ232
author_rank: Frequent Contributor
timestamp: March 16, 2015, 11:08:43 am
content: Quote from: Howardlong on March 16, 2015, 10:43:46 amMore or less the same as JohnnyBerg above, in case of direct USB port charging, I was looking to not exceed 500mA charge current. The approach didn't created any trouble until now. I was doing my best to avoid the SDP, CDP and DCP madness

author: PeterFW
author_rank: Frequent Contributor
timestamp: March 16, 2015, 02:25:37 pm
content: This one is done now, but i have not updated the thread further since noone seemed to be interested:https://www.eevblog.com/forum/projects/one-lithium-battery-to-rule-them-all/msg624869/The charging and battery management is complete and works, currently im routing the board.It will be a sandwich design, two boards, one battery management and one for the voltage regulators.

author: JohnnyBerg
author_rank: Frequent Contributor
timestamp: March 16, 2015, 02:35:24 pm
content: Quote from: PeterFW on March 16, 2015, 02:25:37 pmQuite a large BOM ..No idea how big the boards gonna be?For comparison, my board is 50 x 23 mm .. MCU+Charger+Status+RegulatorHave you measured what current you draw in sleep? Regulators are nasty things, when you trying to sleep

author: PeterFW
author_rank: Frequent Contributor
timestamp: March 16, 2015, 02:45:34 pm
content: Quote from: JohnnyBerg on March 16, 2015, 02:35:24 pmIt could be quite small, but since i am 0805 components and big IC packages im at about 55x30mm.But i am more concerned with battery life, i am ok with that.I dont want to build something small and shiny like a phone, what will only hold a charge for 10 hours.Quote<100µA, my meter wont measure currents <100µ reliably.

author: JohnnyBerg
author_rank: Frequent Contributor
timestamp: March 16, 2015, 02:55:13 pm
content: Quote from: PeterFW on March 16, 2015, 02:45:34 pm100 uA is still a lotDo some math with a 230 mAh battery .. woohI am down to 8 uA with 3V3 regulator and 160 nA without. That gives a reasonable time on battery

author: PeterFW
author_rank: Frequent Contributor
timestamp: March 16, 2015, 03:01:31 pm
content: Quote from: JohnnyBerg on March 16, 2015, 02:55:13 pmThis is designed to run with at least 2Ah batteries, for days at a time without power saving. Months with power saving.As i said, i do not want to make something like my smartphone that runs flat faster then i can push the buttons.

author: amyk
author_rank: Super Contributor
timestamp: March 16, 2015, 03:52:15 pm
content: How about... single-cell battery right across the Vbus with a blocking diode.Before anyone asks, this circuit was used successfully in tens of millions of products...

author: JohnnyBerg
author_rank: Frequent Contributor
timestamp: March 16, 2015, 03:58:32 pm
content: Quote from: amyk on March 16, 2015, 03:52:15 pmOk, I'l take the bate: where is the charger?Or is this a "free energy" project ?Serious, this is just a load share, and the same as mine. D101 = D2, Q101 = Q1, R107 = R4

author: janekm
author_rank: Unknown
timestamp: March 16, 2015, 04:00:45 pm
content: Quote from: JohnnyBerg on March 16, 2015, 03:58:32 pmI think you missed the bit where Q101 and R107 are NC! So I guess the charger is the combination of current limit through R125 and the over voltage protection on the battery... Scary...

author: JohnnyBerg
author_rank: Frequent Contributor
timestamp: March 16, 2015, 04:10:06 pm
content: Quote from: janekm on March 16, 2015, 04:00:45 pmI didQuoteQuoteTjaaa .. I rest my case .. I think