Looking for IC to manage LiPo charging & LVD all in one if such a beast exists. - Page 1
Forum section: electronics / projects

author: v81
author_rank: Regular Contributor
timestamp: March 28, 2017, 11:35:59 pm
content: I have a little project that will be LiPo powered and am looking for a simple and neat solution to manage charging and low voltage disconnect of a battery around the 600mAh size.Charging will preferably by via micro USB, circuit will draw ~ 100ma max.Found plenty of IC's to manage the charging side of things, but nothing that will also manage cutting the supply at low battery.Circuit to be powered is 3 IR LED's.Any advice/assistance appreciated.

author: v81
author_rank: Regular Contributor
timestamp: April 01, 2017, 03:17:05 am
content: Wonder if i might bump this, anyone have any ideas?

author: edpalmer42
author_rank: Super Contributor
timestamp: April 01, 2017, 05:53:01 am
content: Go to Mouser, Digikey, etc. and start looking through the section on PMICs (Power Management Integrated Circuits). Look for the section on Battery Management.I'm going through a similar process. I'm trying to design a 24V LiFePO4 battery-backup system to replace a pile of NiCd cells and their rather trivial charging circuit. Quite a learning curve, but it's an interesting journey.Ed

author: v81
author_rank: Regular Contributor
timestamp: May 01, 2017, 11:51:52 pm
content: Hi Ed, unless i'm missing something obvious I've had no luck doing what you suggested.Plenty of options, but i wast able to find one able to disconnect the load at low voltage.?If it's not too much to ask is there any chance you could have a look next time you're around one of those sites?

author: allansf
author_rank: Newbie
timestamp: May 02, 2017, 12:45:28 am
content: Hi,the MCP73871(https://cdn-shop.adafruit.com/datasheets/MCP73871.pdf) has a Low Battery Indicator, i do not know if it will help you.Or try to search the for MCP738XX IC's.

author: edpalmer42
author_rank: Super Contributor
timestamp: May 02, 2017, 02:33:38 am
content: Quote from: v81 on May 01, 2017, 11:51:52 pmWell, only you know exactly what you're looking for.I went to Digikey and looked at the first IC in the 'Battery Management' section. It includes overcharge, overdischarge, and overcurrent detection. Add two external power FETs to switch the charge and discharge current. It might be worth more than the two minutes I spent looking at it. Costs about US$1 each in single quantities. S-8241 from SII.Ed

author: mark03
author_rank: Frequent Contributor
timestamp: May 17, 2017, 03:08:34 am
content: I believe the OP was looking for a part to (A) manage charging (that is, state machine providing constant-current and constant-voltage phases with proper sequencing, plus the usual safety features), and (B) provide under- and over-voltage disconnect and discharge current limit.(A) and (B) are available separately, but I have never seen them together in one part, and no one in the thread thus far has suggested any examples. Presumably it is deemed safer to have (B) in the pack and (A) on the main circuit board?

author: v81
author_rank: Regular Contributor
timestamp: May 18, 2017, 03:27:51 am
content: Quote from: edpalmer42 on May 02, 2017, 02:33:38 amI'm still really struggling with this, the IC you refer to looks ok for pack protection, but doesn't appear to have any charging functionality.Quote from: mark03 on May 17, 2017, 03:08:34 amThat pretty much sums up my situation.The cell (single cell ~ 500mAh lipo) is going to be mounted to the PCB that the circuit is on, thus there is no 'external' pack so to speak.In a perfect world there would be an IC that integrates both the CC/CV/cutoff charging and cell protection in a single chip (within reason of course!).Being that i'm only after 100-200ma for the circuit, and am only dealing with a single cell lipo i thought something might exist, am still hopeful.At this point i'll fork off and look at a 2 part solution, a cell protection IC and a charge/regulator IC.I'm a bit inexperienced at this so would still appreciate any words of wisdom from passers by.Cheers.

author: Muxr
author_rank: Super Contributor
timestamp: May 18, 2017, 04:40:31 am
content: You may not be able to find them both in the same package. This is I believe because a lot of Lipo batteries have the protection circuit already integrated on the battery itself. They also often do overtemperature protection so it would make sense for them to be on the battery. And you don't necessarily want the actual charging IC on the battery itself due to heat it needs to dissipate.This is why charging ICs if they include low battery indication are just there so that you can signal the user battery is getting low (like an LED).The best thing to do probably is to use batteries which have a protection circuit on them already.

author: v81
author_rank: Regular Contributor
timestamp: May 18, 2017, 12:59:05 pm
content: Quote from: Muxr on May 18, 2017, 04:40:31 amHeat should be minimal, the circuit is a head mounted IR LED, the power involved is similar to that of a bluetooth earpiece.I guess doing a teardown on a cheap bluetooth earpiece could provide some insight on how it's handled.QuoteThis could be an option also, though i fear it will push the BOM cost up significantly.These are the cells i was intending to use...300mAh450mAhJust over 1/10th the size of a cell phone battery, so not big.Battery will be permanently mounted to the PCB shaped like the weird letter ' W ' , with will be about all there is to the project, there is no enclosure.Keeping size and BOM costs down is pretty important for this project, which only leaves the option of thinking and looking harder for just the right parts.I'll look the path of separate protection circuit and charge circuits for now.Another thing to consider is how to go about regulating, thinking of going LDO linear for simplicity and because the difference between battery and regulated voltage will be minimal.looking for ~ 3v out from a cell that will run from 4.2v down to cut off whenever the ideal is for lipo (3.2-3.5v ?).Appreciate the time you guys have taken to post some info, i'm learning a bit and wondering in the right direction.

author: Muxr
author_rank: Super Contributor
timestamp: May 18, 2017, 01:52:34 pm
content: Quote from: v81 on May 18, 2017, 12:59:05 pmHave you checked the datasheet on those? (File tab on that website).It looks like they have a protection circuit.

author: rs20
author_rank: Super Contributor
timestamp: May 19, 2017, 04:20:34 am
content: Quote from: Muxr on May 18, 2017, 01:52:34 pmOnly one way to find out!!!

author: v81
author_rank: Regular Contributor
timestamp: August 22, 2017, 03:53:45 am
content: Quote from: Muxr on May 18, 2017, 01:52:34 pmNope, no protection of any kind, that's just an advisory of when the user should cut their load.Fairly typical of batteries for the RC industry.It's considered cheaper to destroy a battery buy sucking the guts out of it than have it cut out mid flight in a flying model.R/C Hobbyists often fly using voltage/current telemetry, or at least a timer so as to know when the battery is low.Also larger models can draw over 100 amps in some cases (often at >48VDC!) so finding something to switch that whilst keeping the model weight down is a consideration.I'm still on the hunt for something, have some eBay battery protection circuits on order, but they often have the IC's unlabeled, this doesn't help.I'm wanting to engineer my solution into the PCB the project is on, and have the battery hard soldered to the same PCB.//editI think i've found what i'm after!http://datasheet.sii-ic.com/en/battery_protection/S8261_E.pdfhttps://www.digikey.com/product-detail/en/sii-semiconductor-corporation/S-8261AAJMD-G2JT2G/728-1034-1-ND/1628437

author: amyk
author_rank: Super Contributor
timestamp: August 22, 2017, 06:55:24 am
content: DW01 and its supporting components, a diode, and a resistor. You get most of that already if you buy a cell with a protection circuit built in, so all you need is a current limiting resistor and roughly enough voltage to charge (5V - 0.7V diode drop is ~4.3V.) Won't charge as quickly as dedicated ICs or a current regulator, but you did say you wanted the cheapest solution... and the "soft end" to the charging would probably prolong the life of the cell (although charging will take longer near the end.)https://www.eevblog.com/forum/microcontrollers/rechargeable-battery-solution-for-mcu-projects/msg630708/#msg630708

author: colorado.rob
author_rank: Frequent Contributor
timestamp: August 23, 2017, 11:29:28 am
content: http://www.sii-ic.com/en/semicon/datasheets/power-management-ic/lithium-ion-battery-protection-ic/s-8211c/You can buy LiPo cells with protection circuits on them for pennies more than without. They will all have one of these chips, or a work-alike clone, on the tiny protection PCB.

author: jbb
author_rank: Super Contributor
timestamp: August 23, 2017, 07:23:33 pm
content: It may be easier to get the LiPo shipped if it has a protection circuit.We're having some grief at work getting Li coin cells and LiPos shipped - we're in New Zealand andcan'tget them by air freight. The rules these days restrict include all Li chemistries from flying on aircraft - LiPo, CR, BR, LiFePO4, and I guess LiSOCl.From achemistryperspective, LiFePO4 should be allowed as it tends not to catch fire, but I guess the regulators were thinking a) keep it simple and b) people might become "confused" and label everything as LiFePO4.EDIT: changed 'can' to 'can't'. So sorry if this has stuffed anyone up!

author: v81
author_rank: Regular Contributor
timestamp: September 01, 2017, 05:32:11 am
content: Appreciate the replies!I have not found a ~ 500mAh lipo with protection other than from Adafruit where they are A) expensive and B) don't ship to Australia, otherwise this would be an ideal solution.Any one able to link a source for such a cell that might ship to Australia?This is pretty much exactly what i'm after, dimentions and all...https://www.adafruit.com/product/1578I can get the cell pictured above for about half that price or less without the protection, thus what lead to my thinking of implementing the protection myself.

author: rs20
author_rank: Super Contributor
timestamp: September 01, 2017, 06:46:04 am
content: https://tronixlabs.com.au/power/battery/lipo/adafruit-lithium-ion-polymer-battery-3-7v-500mah-australia/Is exactly the same cell you like, is 11.86 USD + cheap shipping. If you're going to complain about the extra <$4 over the 8 USD direct from Adafruit, then I wish you luck at implementing your own protection for <$4. Welcome to Australia!

author: LukeW
author_rank: Frequent Contributor
timestamp: September 01, 2017, 11:58:48 am
content: The MCP6541 comparator has very low quiescent power consumption - might be a good choice for battery low-voltage cutoff, combined with a micropower voltage reference and a FET capable of handling the desired load current.For extremely high discharge currents (e.g. some RC applications) it's not really practical though.Here are a couple of other candidates from our friends at Silicon Chip.http://www.learningelectronics.net/circuits/images/solar-battery-protector-prevents-excessive-discharge-2.jpghttp://www.learningelectronics.net/circuits/images/versatile-micropower-battery-protector-circuit-diagram-2.jpgPersonally, I'd really like something that can do single-cell lithium charging combined with buck conversion (or buck-boost or SEPIC or whatever) back up to 5V in a single chip.

author: mark03
author_rank: Frequent Contributor
timestamp: September 03, 2017, 04:30:53 am
content: Quote from: LukeW on September 01, 2017, 11:58:48 amTI has some parts that do this. They are intended for USB OTG but you can use the 5V boost capability for other purposes.Seehttp://www.ti.com/product/BQ24193.

author: v81
author_rank: Regular Contributor
timestamp: September 08, 2017, 08:53:11 am
content: Quote from: rs20 on September 01, 2017, 06:46:04 amYour link offers a battery @ $19.95 shipped.I can get them for about $3 ea without the protection.Against what you've linked we're talking about a difference of $17.Multiply by between 5 and 50 units (not sure how many of these i'll end up building) and that price difference becomes significant, we're back at a situation where a discrete solution looks plausible, even though i was having trouble finding one, however given what has been posted after you i think what i'm looking for has been found!Quote from: LukeW on September 01, 2017, 11:58:48 amThis looks like exactly what i need.The total cost of these components, plus the $3 batteries (just found today on eBay, hobby king are low on stock) is possibly going to save a few $100.I'll take a closer look, thanks again.

author: v81
author_rank: Regular Contributor
timestamp: September 08, 2017, 09:14:16 am
content: I think I've kinda found what i'm after and have a plan...The protection circuithereis very close to exactly what i'm after, found them 10 for AUD$3.80 delivered.I can use them as they are, it looks like these are similar to the protection circuits on the Adafruit cells.I could even go as far as integrating the circuit into my design and blowing the components off the ebay boards with a hot air gun, given it's a total of only 5 components, then pop said components directly onto my board.Without finding an all in one solution on a chip for a dollar, and without finding the IC's that these protection boards are made form getting the boards themselves seems to be a good option.This looks like it will be good enough to allow me to progress my design... looking forward to it!

author: v81
author_rank: Regular Contributor
timestamp: September 09, 2017, 11:04:29 am
content: I think i've found an IC that does over/under voltage and over current all in a single package with 2 or 3 external discretes.Best of all it's about 12 cents in 10+ qty.This is almost exactly what i've been after from day 1Now all i need to do is add a PMIC for charging from a microUSB port and the power side of the project is done.

author: mark03
author_rank: Frequent Contributor
timestamp: September 09, 2017, 09:41:30 pm
content: Quote from: v81 on September 09, 2017, 11:04:29 amSo... don't hold us in suspense; what's its name?