hybridfree/eevblog-posts huggingface dataset:
Battery Current Charging MCP73831 - LiPo - Page 1
Forum section: electronics / beginners

author: made2hack
author_rank: Frequent Contributor
timestamp: June 29, 2016, 09:31:24 am
content: Hello all,Here's the circuit I have built. Vin is 4.96V from a regulated supply (computer PSU). Rprog is 2K (1%).The charging current Output is only 140mA approximately. According to datasheet, it should be at around 500mA? Am I doing something incorrectly?I have the MCP soldered to a SOT23-5 to DIP board and that DIP board soldered to a circuit on a phenolic board I etched. According to the datasheet, they recommend placing battery leads as close to the circuit as possible to avoid major voltage drops. My battery has AWG24 (solid) soldered to the leads that then solder to the circuit. Approx 15cm length each, so total 30 cm length. Could this be generating such high voltage drop? I mean, I'm getting essentially 1/3 of the charging current?Thanks,

author: Kilrah
author_rank: Unknown
timestamp: June 29, 2016, 09:43:45 am
content: What's the voltage on the battery at that point? LiPo charge is CC-CV, so once the battery reaches the terminal voltage (4.2V for most types) current will gradually reduce. Your battery might simply be near full...

author: made2hack
author_rank: Frequent Contributor
timestamp: June 29, 2016, 09:48:32 am
content: Started with a battery that had 3.4V around. When it goes into what I think is CV charging, I think it drops to around 20mA - 30mA.

author: mariush
author_rank: Super Contributor
timestamp: June 29, 2016, 12:59:56 pm
content: You have an error in your design.You must connect Vss directly to ground.Connect Prog to Ground through a resistor, to limit the current: Ireg = 1000V / Rprog (kOhm) so basically with 2k ohm you'd get 1000/2 = 500mAThe way it is shown in your picture, you're basically limiting the input current to the chip.Here's the datasheet example:

author: made2hack
author_rank: Frequent Contributor
timestamp: June 29, 2016, 02:57:12 pm
content: Hi Mariush,I connected the PROG pin to VSS through the 2K and connected VSS to GND. It seems to be ok now. My Fluke 21 maxes out at 300mA and it is OverLoaded, so, I think that was it.
Battery current draw. - Page 1
Forum section: electronics / beginners

author: ikrel
author_rank: Contributor
timestamp: August 28, 2012, 12:17:17 am
content: I have recently acquired 2 12v 7AH Lead-acid Batteries, I after much googling I still have not discovered how much current I can draw safely from a battery. So my question is: How much current can I draw safely from a 7AH Lead acid battery, or other batteries for that matter.The battery is very similar if not identical to this one:http://www.zbattery.com/b-b-12v-7ah-sealed-lead-acid-battery#the datasheet says Max discharge current 105A for 5s,and I don't understand the Discharge charts at the bottom.you can find the datasheet in the specs.

author: Jeff1946
author_rank: Regular Contributor
timestamp: August 28, 2012, 01:33:15 am
content: Current produces heat which could cause damage if too high for too long. As I read the chart it shows how long the battery can produce a constant current until the single cell voltage drops to a given voltage. In this case it shows how long to reach 1.6 to 1.8 V.

author: ikrel
author_rank: Contributor
timestamp: August 28, 2012, 01:54:21 am
content: So Basically this chart (Constant Current) is telling me I can Draw 30.8A for 5Min safely before a fully charge battery(1.75v per cell) will drop to 1.60v per cell.ORDoes it Mean I can draw 26.9A for 5Min when the battery is reading 1.75v per cell (nominal charge)?When would i need to charge the battery, nominal charge is 1.75v per cell. What kind of voltage drop do i need to look for before i know the battery needs charging?

author: G7PSK
author_rank: Super Contributor
timestamp: August 28, 2012, 08:43:17 pm
content: The terminals on those batteries are 17 amp Lucar type so that may be the practical limit to the current draw otherwise most lead acid batteries will give currents running in the hundreds of amps for a brief time including the little 7 amp hour units I have seen them in car booster units and used as a battery to start motorcycles how long they last like that is another matter.
Battery Deep Discharge – IC Workarounds? - Page 1
Forum section: electronics / beginners

author: Freshman
author_rank: Regular Contributor
timestamp: July 07, 2025, 07:59:45 am
content: I understand that PCM (Protection circuit module) disconnect due to deep discharge is a fairly common issue across many battery charger ICs.My question is: Are there any charger ICs—preferably from any vendor—that can autonomously initiate charging even after the PCM has disconnected the battery, without the need for external components? I’m specifically looking for a solution that doesn’t rely on additional circuitry.If no such IC exists, could you share insights into why charger IC manufacturers typically don't integrate a built-in mechanism to address this common PCM disconnect scenario?

author: mikerj
author_rank: Super Contributor
timestamp: July 07, 2025, 10:44:37 am
content: Quote from: Freshman on July 07, 2025, 07:59:45 amThis isn't a feature of charger ICs, it's a feature of battery management circuits for batteries using lithium ion cells. The reason for this is that at sustained low voltage these cells can form metallic lithium on the anode that makes them potentially dangerous when charged. The battery management circuits that have this feature (often the older removable laptop batteries) can use a special kind of thermal fuse that the management IC will blow when the voltage gets too low. This disconnects the battery from the output terminals, so you can no longer charge or discharge the cell. If this has happened then it cannot be worked around externally, the fuse must be replaced and usually the EEPROM memory in the management IC must also be reprogrammed.Quote from: Freshman on July 07, 2025, 07:59:45 amSafety. Although it's possible to carefully revive low voltage cells that have not been low for long, it's not something a manufacturer is willing to risk.

author: amyk
author_rank: Super Contributor
timestamp: July 11, 2025, 02:42:11 am
content: Quote from: mikerj on July 07, 2025, 10:44:37 amThen you should ask yourself why many lion charger ICs have a "pre-charge" or "undervoltage trickle charge" mode.
Battery detection with connected charger - Page 1
Forum section: electronics / beginners

author: Lt_Flash
author_rank: Regular Contributor
timestamp: April 25, 2018, 07:14:47 am
content: Hi guys,I've got a circuit that has a battery connect socket on, let's call it, 'left side' and battery charger IC output connected on 'right side'. The question is how to detect when battery is actually connected taking into account that IC charger is active and periodically ramps up voltage on 'plus' rail to 4.2V trying to detect battery itself? The only solution I was able to come to is to have not a two terminal battery connection, but three contact one and one of the contacts is simply shorted to ground, so when battery is plugged in - we definitely have BGND and I can use resistor divider to indicate that condition. But is there anything else that can be done? Thanks!

author: David Hess
author_rank: Super Contributor
timestamp: April 25, 2018, 07:59:54 pm
content: I would probably start by leaving the battery charger output disconnected and applying a microamp current to the output while measuring the voltage. If the voltage falls from the compliance of the microamp current, then the battery has been connected.

author: Lt_Flash
author_rank: Regular Contributor
timestamp: April 25, 2018, 08:02:18 pm
content: Thanks, nice idea! Can you help me with schematic? I assume I will have to use BJT and not MOSFET in order to achieve this? Charger is quite easily disconnected with a MOSFET, no worries here. Probably that's what charger is actually doing - trying to apply some voltage and see if there's a drop to detect battery?

author: David Hess
author_rank: Super Contributor
timestamp: April 25, 2018, 10:28:23 pm
content: It is not that difficult to do. A high value resistor to a reference voltage which is slightly higher than the maximum expected battery voltage will work as a current source.Usually if the output from the charge circuit is disabled, then it will be high impedance and not have any affect on the battery presence test. Adding out output MOSFET to disconnect the charger may work but should not be necessary.

author: Lt_Flash
author_rank: Regular Contributor
timestamp: April 26, 2018, 06:26:30 am
content: Thanks a lot, I'll give it a go!
Battery Discharging Circuit - Page 1
Forum section: electronics / beginners

author: vincentleest
author_rank: Newbie
timestamp: October 30, 2010, 07:36:08 pm
content: I'm working on a project that requires me to discharge a battery from 12V to 10V with a constant current of 14A.I read about this thread and took batee's design and modified it for a bit.https://www.eevblog.com/forum/index.php?topic=1219.msg15720Q6,7,8 are IRF3910Q5 is ZXT450I am not very confident about my changes, please point out my mistakes and give me some comments.Thank you!

author: qno
author_rank: Frequent Contributor
timestamp: October 30, 2010, 08:26:14 pm
content: you need to replace the resistors of 1 k by a resistor of 0.15 ohms.You need to cool the IRF3910 on a very large heatsink that can dissipate 170 Watt.

author: vincentleest
author_rank: Newbie
timestamp: October 30, 2010, 09:38:46 pm
content: Quote from: qno on October 30, 2010, 08:26:14 pmdid you mean the 3 parallel resistors connected to the transistors? or some other resistors?and thank you for you help =)

author: qno
author_rank: Frequent Contributor
timestamp: November 01, 2010, 12:48:23 pm
content: The 3 1k in the sources of the Fets.With a source resistor of 1k no more than 12 mA can flow in the FETs.

author: Feanor
author_rank: Regular Contributor
timestamp: November 02, 2010, 07:49:49 am
content: I would just like to double check how you got a resistor value of .15ohm. I got 0.333ohm. Where dd I go wrong?14 amps / 3 = 4.667A in each source resistor.The output of the 1k/820 ohm voltage divider will settle to 0.7V greater than Vout.So the input needs to be 0.7*1820/820 = 1.553V. This voltage is the IR drop across one source resistor.4.667A flowing through the source resistor gives us 4.667*R = 1.553VR = 1.553/4.667 = 0.3327ohm ~=0.333ohm = 3X1 ohm resistors in parallel.If I made a mistake please point it out.

author: qno
author_rank: Frequent Contributor
timestamp: November 02, 2010, 08:34:42 am
content: The capacitor is series with the 820 ohm cannot pass DC.It is not a voltage divider.This is a damper or filter.The rest of our analysis is OK.

author: Feanor
author_rank: Regular Contributor
timestamp: November 02, 2010, 08:46:10 am
content: Ahh ha I see! I was miss reading the schematic! Thought there was a connection where there was not one. Thank you.
battery drain using a float charger after power failure - Page 1
Forum section: electronics / beginners

author: Brucehaslam
author_rank: Newbie
timestamp: January 23, 2024, 03:22:49 am
content: I have a Harbor Freight cheapo float charger which I have used to maintain my motorcycle battery. The red light is on when the polarity is correct and the power is supplying the charger. However, when the power is disconnected (ie my grandkid pulled the extension cord out of the wall) the red light remains on and, over time, drained the battery. My thought is to use a diode on the positive cable to prevent the battery from back charging the float charger. First of all, will this work? Secondly, is it a good idea and thirdly, if the previous two questions are a yes, what type of diode should I use? Note: I probably don't need to tell you that I am dumber than a sack of hammer handles when it comes to electronics!

author: Peabody
author_rank: Super Contributor
timestamp: January 23, 2024, 03:57:12 am
content: If your charger needs to read the current battery voltage, then the diode would mess that up. And even if it doesn't, there would be a voltage drop across the diode of about 0.6 - 1.0V, so the battery might not be fully charged. Maybe it's time to move up from Harbor Freight to Autozone, and see what a more capable charger would cost. But first, check Google and Youtube under the model number of your charger to see if anyone has already solved this problem.

author: floobydust
author_rank: Super Contributor
timestamp: January 23, 2024, 08:18:42 pm
content: Welcome to the forumsWhat model is the Harbor Freight charger?This guy did mods (add diode and voltage trim)Battery Charging Part 2Harbor Freight item42292.Part 3went to LM317 and missing an output diode, it looks unfinished.

author: Brucehaslam
author_rank: Newbie
timestamp: February 01, 2024, 07:37:31 pm
content: Thanks for the reply. I think you are right. I need to upgrade to a better float charger.

author: David Hess
author_rank: Super Contributor
timestamp: February 02, 2024, 05:44:08 pm
content: It is possible to make an ideal diode circuit using a power MOSFET and comparator which will not drain the battery and allow the charger to work properly, however I think it would be better to buy a better charger. I have used and can recommend both of these linked below, or similar chargers from these companies:https://www.amazon.com/gp/product/B07W3QT226/https://www.amazon.com/gp/product/B01FG7NW60/I cannot test the MOTOPOWER charger because I gave it to my father, however I tested the NOCO GENIUS10 which I keep in my pickup and with the power removed, it draws 14 microamps from the 12 volt battery which is insignificant. I would assume that the cheaper NOCO GENIUS1 will work just as well.
Battery duration - Page 1
Forum section: electronics / beginners

author: raff5184
author_rank: Regular Contributor
timestamp: June 01, 2017, 05:56:56 am
content: Hi all,this batteryhttp://www.powerstream.com/p/GMB300910.pdfhas a capacity of 12mAh at an average voltage of 3.7Vwhich corresponds to: 3.7 * 0.012 * 3600 = 160 Theoretically, if my load absorbs 6mA (at 3.7V) the battery should last 2h.If instead, the load works intermittently for only 1 millisec every minute, the battery lasts about ... 1230 years (without considering non-ideal behaviors of the battery)Is this correct?

author: IanB
author_rank: Super Contributor
timestamp: June 01, 2017, 06:03:46 am
content: Quote from: raff5184 on June 01, 2017, 05:56:56 amWhy do you think this is surprising? The calculation seems correct to me.QuoteIt would be easier to answer this question if you showed the working, rather than just quoting numbers. How can we tell if your calculation is correct if you do not show how you arrived at the answer?

author: ataradov
author_rank: Super Contributor
timestamp: June 01, 2017, 06:19:49 am
content: With intermittent mode your duty cycle will be 1 / 60000, so ideally you will get 2 * 60000 hours with the same load, which is 60000 * 2 / 24 / 365 = 13.7 years.

author: raff5184
author_rank: Regular Contributor
timestamp: June 01, 2017, 06:32:20 am
content: I was surprised because it seems quite a lot of energy.Sure here are the calculations:instantaneous power: Pi = 3.7*0.006 = 0.022 W ( = 22mW)Load energy: E = Pi * 0.001 = 22e-5 JDuration: battery_capacity / E * 60 ==160 / 22e-5 * 60 == 4.4e7 minutes // "* 60" because the load works every minute= 837 yearsThere was an error in the approximation therefore I had 1200.. but still it seems to be too long

author: ataradov
author_rank: Super Contributor
timestamp: June 01, 2017, 06:40:00 am
content: Your calculations are way too complicated. If you have 12mAh of capacity, then with 6 mA load, it will last 2 hours, ideally regardless of power consumption profile. With duty cycle lower than 1, you spread those 2 hours over time. A minute is 60000 ms, and you work for 1 ms out of that time, which means that battery will last proportionally longer, or 60000 * 2 hours.I don't really follow your math, but where do you factor in 1 ms there?No need to involve energy here for this basic scenario.

author: raff5184
author_rank: Regular Contributor
timestamp: June 01, 2017, 06:46:35 am
content: thank you for your clarification, much appreciated.the 1ms is here:Load energy: E = Pi * 0.001 = 22e-5 J (: absorbed energy = instantaneous power * 1ms).I was using energy exactly because my calculations with energy didn't seem right. So I was trying to understand what I was doing wrongBig thank you to everybody!Mistake was here: Duration: battery_capacity / E*60=
Battery equaliser  - Page 1
Forum section: electronics / beginners

author: cibimathew
author_rank: Newbie
timestamp: October 26, 2019, 02:01:21 am
content: I want to add four 12v lead acid batteries to my solax inverter. Do i have to connect a battery equaliser to the circuit and how does it work?

author: tautech
author_rank: Super Contributor
timestamp: October 26, 2019, 03:13:45 am
content: Welcome to the forum.You need a charge controller and depending on how you wish to configure the battery bank set the controller to manage battery equalisation.Do some study here and download some manuals:https://www.morningstarcorp.com/

author: digsys
author_rank: Unknown
timestamp: October 26, 2019, 03:46:34 am
content: Look up LTC3305
battery flir e30-e60 - Page 1
Forum section: electronics / beginners

author: freem
author_rank: Newbie
timestamp: March 14, 2020, 04:12:55 am
content: Hello, help me please. I decided to change the 18650 banks in the standard battery to more capacious ones. I did everything right. But after replacing the battery at the output terminals of the battery, the multimeter shows 38mV. At that time on nickel plated plates up to 3.9V protection board. I do not have knowledge in electronics. How to unlock protection board? What do I need to do?

author: freem
author_rank: Newbie
timestamp: March 14, 2020, 07:36:38 am
content: It is resolved.1. soldered the "+" terminal to the protection board; "-" not soldered to 18650;2. connected the multimeter to the battery outputs;3. touched the "-" terminal of the 18650 several times and when the readings were 3.9V immediately soldered.
Battery for TS80P - Page 1
Forum section: electronics / beginners

author: pcm81
author_rank: Regular Contributor
timestamp: December 12, 2021, 08:10:24 pm
content: Can you suggest agoodbattery for TS80P soldering iron? Amazon link if possible, with a charger if can't accept standard 5v input for charging.My intention is to have iron + Battery in a travel case to take with me to remote location for quick solder jobs without having to carry my full station...Or, perhaps there is an adapter for Makita batteries?Here's the one i am looking at now: TalentCell Rechargeable 72W 100Wh 12V/8300mAh 9V/11000mAh 5V/20000mAh DC Output Lithium ion Battery Pack for LED Strip, CCTV Camera and More, Portable Li-ion Batteries with AC/DC ChargerThanks
Battery Holders - Page 1
Forum section: electronics / beginners

author: cyberwasp
author_rank: Contributor
timestamp: July 04, 2025, 07:55:13 pm
content: Can anyone point me to a place to purchase decent battery holders for 18650 18500 26650 and AA. The ones I've bought so far have been subpar, specifically they tend to use cheap 24g wire or the actual contact falls out after several uses.They will be used in an all-terrain remote operated vehicle that I'm helping my friend's daughter to design and build. Thank you!!

author: coppercone2
author_rank: Super Contributor
timestamp: July 04, 2025, 07:57:36 pm
content: I noticed a difference testing clone from china vs the one from digikey, (look identical other then the manufacturer markings), the one from digikey survived several more back and forth bends before it cracked the contact. I think it has to do with sheet metal choice or high strain in cheap china nickel platingso the 300% price difference was warrented

author: voltsandjolts
author_rank: Unknown
timestamp: July 04, 2025, 08:12:48 pm
content: Keystone18650 stuff is generally good. Type 18650 into the Part Search box.Watch out for different cell lengths, e.g. protected (circuit board) adds a few mm.

author: Kjelt
author_rank: Super Contributor
timestamp: July 05, 2025, 07:46:41 am
content: For that purpose you really need to use welded battery packs.Not only for the mechanical stability also for the resistance between cell connections.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: July 05, 2025, 02:16:18 pm
content: I agree with Kjelt. If reliability is your top prority use welded battery packs, with a piece of wire and a decent connector on the end, just like used for ages in the RC hobby world.

author: Supernaut
author_rank: Contributor
timestamp: July 05, 2025, 02:31:37 pm
content: Im also looking for a robust enclosure for 18650's or similar, ideally something with a lid on it. Ive came across a few online but as others have stated, wire gauge is sometimes inadequate, some of them have a built in on/off switch in the case or sometimes they look flimsy and don't offer any way to mechanically mount the enclosure to a device.Im looking to convert an old Exide torch to a rechargeable 18650 setup if possible.Interested to see if OP finds a solution

author: Gregg
author_rank: Super Contributor
timestamp: July 05, 2025, 06:43:01 pm
content: Awhile ago I used a Trustfire EB02https://www.trustfire.com/products/trustfire-eb02-battery-boxfor replacing a tiny lead acid battery in a crane scale. Amazon no longer has these, but the listing still exists and shows more details than the manufacturer's site. It holds 4 of the 18650 cells; they used to make a 6 cell version also.
Battery internal resistance and metal detectors - Page 1
Forum section: electronics / beginners

author: Trailboss
author_rank: Contributor
timestamp: March 23, 2016, 09:50:46 pm
content: My question concerns the effects of a batteries IR on the ckt.My question comes from the fact that when using a Lithium battery in the metal detector performance is enhanced, ie: louder audio, deeper target depth.This does not seem to be subjective, but something that has been noticed by myself among other very seasoned Detectorists.This enhanced performance was experienced when switching from NiMH or Alkalines.The Lithium is the Energizer ultimate lithium AA cell providing 6 volts.I looked at the D/S and saw the alkaline and the NiMH have roughly the same IR, about 30 to 40 milliOhms.The lithium was 3 to 6 times that value, 120-240 milliOhmsThe metal detector is a Garrett AT Pro VLF unit.I know Lithiums have a slightly higher voltage, but I would think that the Garrett would have a regulator ckt in the supply.What could be the Mojo Magic happening here,Any body want to throw there two cents in???TIA

author: johansen
author_rank: Super Contributor
timestamp: March 24, 2016, 12:08:48 am
content: I suspect they do not have a regulator.

author: SeanB
author_rank: Super Contributor
timestamp: March 27, 2016, 04:01:49 pm
content: Very likely the higher voltage, as most metal detectors do not use voltage regulators, so the peak pulse power will be higher from the increased voltage, and the audio will be slightly higher from the same reason. If using NimH cells you probably will want an extra cell in the pack, using a 5 cell pack would give the same performance as the battery voltage from a 5 cell pack would be 6V typically, as opposed to 4V8 from a 4 cell pack.
Battery Monitering Circut- Cuttoff and Charging - Page 1
Forum section: electronics / beginners

author: sweekly
author_rank: Newbie
timestamp: April 02, 2014, 04:49:36 pm
content: Hey I am trying to design a circuit that I can use on a 12v 86Ah battery that has a 12v 7A load on it. I want the circuit to be able to monitor voltage and cut power to the load circuit at 10.8V. I saw some schematics using an op amp and a zener diode to create a true reference voltage. I also want this circuit or a secondary one to monitor charging of the batter to prevent overcharging. Does anyone have any suggestions on where to find schematics and formulas to create and correctly calculate the values of components I need, or commercial versions of this that are available.

author: HalfSpace
author_rank: Regular Contributor
timestamp: April 02, 2014, 11:15:59 pm
content: Hi sweekly,Try the links below they may help.http://www.reuk.co.uk/Low-Voltage-Battery-Disconnect-Circuits.htmhttp://www3.telus.net/chemelec/Projects/Low-Bat/Low-Bat.htmhttp://www.circuitstoday.com/category/battery-relatedHalfSpace

author: sweekly
author_rank: Newbie
timestamp: April 03, 2014, 02:46:20 am
content: Thanks for the reply, I like this circuit design,http://www.circuitstoday.com/automatic-changeover-circuit, I would have to change some of the parts so I can use it with a 7A load, but is there also a way I can change it so that when the battery reaches 10.5V it will shutdown output from the battery. I also need to make sure the battery won't get overcharged, and that when an AC input is connected there is no output from the battery. I think this circuit already stops battery output and prevent overcharging though I'm not sure, can someone suggest the edit to cutoff the battery at 10.5V and confirm that this circuit does meet the two conditions I mentioned?
Battery monitoring in ultra-low-power applications - Page 1
Forum section: electronics / beginners

author: tommys
author_rank: Newbie
timestamp: April 17, 2023, 06:43:51 pm
content: Hello everyone.Has anyone tried to measure the battery level in ultra-low power devices? What should I pay attention to?I saw that there are some battery measuring devices (fuel gauges) - would they be suitable for low power devices?Maybe it would be better to design measuring system with operational amplifiers?Thanks for the answers!

author: BadeBhaiya
author_rank: Regular Contributor
timestamp: April 19, 2023, 08:55:22 am
content: I use nRF Power Profiler Kit. It can measure down to 100nA and record 100kS/s with a few different current ranges. It works well enough and it is 99$, much less expensive than other products in the markethttps://www.nordicsemi.com/Products/Development-hardware/Power-Profiler-Kit-2EDIT: Sorry I misread the question, you can use the power profiler to profile the device but not the battery. For profiling the battery, you may use Otii but I don't think there are many products which can profile batteries.

author: radiolistener
author_rank: Super Contributor
timestamp: April 19, 2023, 10:19:51 am
content: You're needs for a MOSFET key to enable battery voltage divider which is used to measure the battery voltage. So you can enable that key very rarely - just for battery measurement and disable it for the rest of time. In such way you can avoid fast battery discharge through battery measurement circuit.Quote from: tommys on April 17, 2023, 06:43:51 pmNo, that is useless and lead to additional battery discharge current for power supply operational amplifiers. Most of modern microcontrollers have 12 bit ADC, which is good enough to measure battery voltage from voltage divider with a very good precision and no needs for DC offset.What is important is to take care to disable power supply for measurement circuit between battery measurement interval. Without that key it will lead to a pretty significant battery discharge.For example ultra low power microcontroller in a deep sleep mode eats current which is much less than 1 nA, but if you keep voltage divider used for battery measurement powered all the time, it can easily eat 10-100 uA or even more which is 100000 times higher than microcontroller current consumption.

author: Peabody
author_rank: Super Contributor
timestamp: April 19, 2023, 02:27:57 pm
content: Below is the kind of circuit @radiolistener is referring to. The mosfet should be logic level, but something like a 2N7000 would probably work. The circuit assumes the vattery voltage is higher than the processor's Vcc. Anyway, the idea is that you switch on the voltage divider only for the millisecond or less that it takes to read the voltage.
battery motion light  - Page 1
Forum section: electronics / beginners

author: CharlesTT
author_rank: Newbie
timestamp: February 05, 2020, 08:22:12 pm
content: Hi, I have a little battery-powered motion-activated light that I wan to change how it operates so that when it is light it will still work.should I bypass the infrared led with a resistor?

author: TerminalJack505
author_rank: Super Contributor
timestamp: February 05, 2020, 08:59:44 pm
content: Is it motion activated or light activated? You might need to attach some pictures so people will know what you are working with.

author: CharlesTT
author_rank: Newbie
timestamp: February 05, 2020, 09:11:28 pm
content: motion, but it needs to be dark for it to trigger.https://i776.photobucket.com/albums/yy41/charlestt225/IMG_3261_zpschz5clyv.jpghttps://i776.photobucket.com/albums/yy41/charlestt225/IMG_3259_zpsejcefwca.jpg

author: Margaret1964
author_rank: Newbie
timestamp: February 06, 2020, 12:24:16 pm
content: Bumping the thread, as I would also like to know the answer. Thanks for posting this, Charles!

author: johnkenyon
author_rank: Regular Contributor
timestamp: February 06, 2020, 01:23:55 pm
content: You're over thinking this one - Simulate darkness by covering the light sensor (not the PIR sensor) with a piece of insulating tape.Unfortunately your pictures don't show either sensor, so we can't tell you which exactly component to cover up, but a PIR sensor usually sits behind a segmented lens, has a metal body with a square or rectangular glass "window". A light sensor is usually in a plastic package.Avoid getting finger prints on the PIR sensor window - it will reduce its sensitivity.

author: CharlesTT
author_rank: Newbie
timestamp: February 06, 2020, 08:52:13 pm
content: Of course, what a simple solution...thanks

author: pcmad
author_rank: Regular Contributor
timestamp: February 07, 2020, 06:25:39 pm
content: just remove the ldr resister
Battery pack voltage vs. No. of cells - Page 1
Forum section: electronics / beginners

author: Jiri_L
author_rank: Newbie
timestamp: September 05, 2017, 12:31:49 pm
content: Hello All,my name is Jiri, coming from Europe, my occupation is a teacher/researcher on university, I am dealing with electrochemistry, especially with li-ion batteries.I would say I have got a knowledge in batteries topic, electrode materials, electrolytes ....just basic research. Unfortunately i have zero practical experience. I decide to star building my own battery boxes for electric vehicles and that is the reason why I sing in to this board.May I ask you about battery voltage in the pack?Lets assume that I am using only 3.6 V cells (nominal working voltage) charged to 4.1 V, the difference is 0.5 V per cell.How many cells in series I need to build up the packs with these nominal voltages:24 V nominal = 6s or 7s ?36 V = 10s48 V =13s or 14s ?If the nominal voltage of the batt. pack is for example 36 V and we have 10s the charger must reach charging voltage 41 V, am I right?Thank you for not so cleaver question but I am confused about it.Thank you,Jiri

author: Zero999
author_rank: Super Contributor
timestamp: September 05, 2017, 12:51:53 pm
content: Yes, the voltages add, so if the nominal nominal voltage per cell is 3.6V and 4.1V fully charged and they're ten in series, then the nominal pack voltage will be 36V and the maximum pack voltage will be 41V.The same thing is encountered with 12V lead acid batteries. If the nominal voltage of each battery is 12V and 14.5V fully charged, then three in series will have a nominal voltage of 36V and a fully charged voltage of 43.5V.The electrical system will need to be designed to work from the minimum and maximum battery voltages.Often cell voltage balancing is required, especially for lithium ion. You will need to design/purchase a suitable charger. There should also be an under voltage warning and disconnect, to prevent the batteries from discharging past their minimum safe voltage.

author: tszaboo
author_rank: Super Contributor
timestamp: September 05, 2017, 01:03:14 pm
content: Same happens with 9V batteries. The old standard is 6x1.5V primary battery. Then there are rechargeable batteries, some are 6x1.2 some are 7x1.2V and now some are 2x3.7V, which is not even close.Though, 24V seems to be 7x3.7V, 48V is 13x3.7V and 36 is 10x3.7. Usually packs are mentioning the base cell, like 18650 (size) 2600mAh and then a numbering, like 7S3P, which means 7 in series, 3 in parallel.And good chargers should have balancing inputs, or the pack should have this built in.
Battery power small electronic project CT related - Page 1
Forum section: electronics / beginners

author: scarrier
author_rank: Contributor
timestamp: December 13, 2014, 09:55:19 pm
content: Hi,Sorry for my english, it's not my first language.I have made some micro-controller project before, mostly with Atmel. I am now starting a very small project. I am aiming at a low cost and long battery(more than 1 year).The project itself as 3 current transformer input. and when any of them go below or higher than a programmable threshold 1 LED per channel will be open.Obviously i need 3 ADC for the CT that and 3 output for the led all of that is possible with all the at tiny's almost. I would also need 3 input for the programmable threshold.I have several question and most of them are power related.How do I power the micro-controller?Can I power it directly from coin-cells?Should I use coin-cells or AA batteries? (which is most easy and offer the simplest electronic integration?)If I do not have a voltage regulator I will need a voltage reference for the ADCs. What is the best kind of cheap voltage reference for low power application?Can I power the LEDs directly from the CTs?Is it a good practice to power things from a CT ? will it change the readed Value?If I want to switch the led on from the CTs I need a switch. What is the easiest way for the witch to keep is position while the micro-controller is in sleep mode.Thank You a lot in advance. I know this is a lot of question, feel free to help me on the subject you can. If you have any other advice I will happily listen to them.
Battery Power Supply for NEMA 17 Steppers - Page 1
Forum section: electronics / beginners

author: Tater
author_rank: Newbie
timestamp: April 18, 2017, 07:23:50 am
content: Hi all,I'm looking to build a simple robot, with 2, maybe 3, NEMA 17 stepper motors, controlled by an Arduino. I have attached arough sketch of the setup that I have had working, albeit poorly which includes;Nema 17 StepperBig Easy Driverhttp://www.schmalzhaus.com/BigEasyDriver/a couple of 9V Batteries in parallelArduino UNOI have also attached the data sheet/schematic for the drivers and motors. I know 9V batteries are not optimal and do not last a significant amount of time, maybe a couple of test runs.The big easy driver based on Allegro A4988 says it accepts 8-35V but when I tried switching to an 18V drill battery or 15V SLA battery the driver chip got super hot (like 150oC) (I know I've fried that one).I did some testing when the setup was working with the 9V battery and getting at max 500mA from the battery, even when adjusting the current adjust pot on the driver board.What does it really mean by accepts 8-35V? I just would like to know how to go about powering this setup correctly.Any help and tips would be greatly appreciated.Edit; I used this guidehttps://learn.sparkfun.com/tutorials/big-easy-driver-hookup-guideas my basis.

author: lapm
author_rank: Frequent Contributor
timestamp: April 18, 2017, 08:13:59 am
content: Those 9 volts batteries are going to be depleted fast. Nema 17 size stepper motors eat current... If i were building robot that needs independent power, i would lok for Li-Ion batteries. They are cheap considering current capasity and rechargable with proper charger...
Battery Power UpGrade Questions - Page 1
Forum section: electronics / beginners

author: Oscar Mersaid
author_rank: Newbie
timestamp: June 26, 2020, 08:07:42 pm
content: Hello all,I have a small devise that takes the small 3.7 / 870mAH LiPo Battery in the attached photo.I would like to up grade this devise to a larger Li-Ion 3000 MaH Bat.I've been told that the PCB connected to the LiPo Bat is a BMS.If that is true, would it be possible to use the same BMS on the larger Mah Li Ion Bat, or would I need to figure out amore proper BMS for the larger bat ?Much appreciated, Oscar
Battery power with mixed voltages - How do you decide your approach to power? - Page 1
Forum section: electronics / beginners

author: Aston01
author_rank: Newbie
timestamp: July 16, 2024, 07:47:10 pm
content: I have a project I would like to do that will require 3.3v & 12v to be supplied with battery power and I am having a hard time getting my head wrapped around the mixed voltages on a single battery aspect.Using this project as a reference, the power allocation would be the following:ESP32 (3.3v) 160~260mA w/ WIFIGPS RTK (3.3v) 68mA - 130mA -futureSoil Sensor (12v) 1 mA Idle, 25 mA for 2s ActiveIn a scenario like this how do you generally decide on the battery voltage to use?When converting to different voltages what aspects drive your decision-making on when you start opting for different or more $$$ methods of conversion?FWIW - I am aware this is a bit of a general question, but despite having done a fair amount of looking into this area, if someone put me on the spot and asked me why you'd opt for one method or another I still couldn't give an informed answer.

author: Phil1977
author_rank: Frequent Contributor
timestamp: July 16, 2024, 08:00:08 pm
content: Can you somehow specify how large the battery should be?If the battery is more on the small side I´d take a medium voltage between 6 and 9V. So the conversion ratio for the DC/DCs is not too high which is good for the efficiency.If the battery should be larger I´d go for something more usual like a 12V-LiFePo - then you could power the soil sensor directly from V_bat.Deciding about the type of converter is an endless topic. Just take something that´s good enough, because there´s always something better

author: Aston01
author_rank: Newbie
timestamp: July 16, 2024, 09:53:27 pm
content: Quote from: Phil1977 on July 16, 2024, 08:00:08 pmBack-of-the-envelope math with GPS etc ...a weeks worth of usage would probably be ~2700mAh @3.7vQuote from: Phil1977 on July 16, 2024, 08:00:08 pmThat is an interesting point I hadn't thought of. Would you go as far as to prioritize the conversion efficiency based on the relative load at each voltage?

author: BeBuLamar
author_rank: Super Contributor
timestamp: July 16, 2024, 10:09:15 pm
content: Quote from: Aston01 on July 16, 2024, 09:53:27 pm

author: Phil1977
author_rank: Frequent Contributor
timestamp: July 17, 2024, 06:27:27 am
content: Yes of course, conversion efficiency from 3.7V to 3.3V can even be higher if you use a high-quality synchronous converter that can work with 0.2V of dropout.Dropout voltage is the buzzword here. A single Li-Ion can go down to 3.4V, then you always have some cable and plug resistance. That means, if your GPS and ESP work as well with 2.8V as with 3.3V then it may be a good idea, but if you want a lot of margin for the converter and a stable 3.3V - then I´d go for a higher voltage battery.Look into the conversion efficiency curves of a common step-down IC. Efficiency vs. input voltage is usually quite the same up to a ratio of 1:2.5 (by my gut feeling, please confirm with the part of your choice).
Battery Powered Application (LiPo) - Page 1
Forum section: electronics / beginners

author: stoic
author_rank: Newbie
timestamp: June 08, 2014, 10:23:18 pm
content: Hi there,I'd like to look into the design of battery supply circuitry for a small battery-powered application and had a few conceptual questions, would be grateful for thoughts:I'd like to use a 5000 mAh LiPo single cell as the charge circuitry seems straightforward and the batteries are easy to integrate. I've been looking at cells fromhttp://www.powerstream.com/(as mentioned in Dave's battery charging video) as they seem to include on-board protection circuitry.I'm wondering, is on-board low voltage cutoff and charge / discharge protection sufficient? Should I factor in redundant cutoff circuitry in my design to prevent usage below cell discharge voltage? Do "proper" designs typically rely on additional cutoffs? I'd just like to make sure this is safe and "proper" for the sake of learning and understanding.Ideally I'd power this circuit with two series cells as I need 5 V (@ 200 mAh) for some of the digitals. Because charging is complicated due to balancing for multi-cell packs, so I'm settling for a simple boost converter design to boost supply to 5 V.I have some analogs operating at 13.56 MHz (RFID decoding) and I realize supply noise may be introduced into the amplifier stages and cause issues. I had an idea to boost supply to 6.5 V and use 5 V LDO with good PSRR to ensure noise is not coupled into the analogs. Is this sufficient? Worst case would be to add LC LPF and keep switching frequency far higher. Does that seem right?To prevent the overall device from being powered on during the charging, is it sufficient to place some sort of load-disconnect line which is toggled when device is brought into charge mode (by connecting a charging cable)? I'm mostly worried about the device powering on as the battery voltage rises during charge cycle and reducing overall battery life. I think most charging ICs take care of this but again, wondering if redundancy is useful in proper design.Thank you very much,-Sam
Battery powered Arduino's What do yo do? - Page 1
Forum section: electronics / beginners

author: FearTec
author_rank: Regular Contributor
timestamp: May 18, 2014, 05:29:06 pm
content: HelloI have tinkered with Arduino's but want to build stand alone Arduino boxes (with sensors) that run off batteries.Should I go lipo/motorbike battery and solar or cheap disposable batteries?What have you done with Arduino's running on batteries?My Blog:http://simon.fearby.com/blog/?cat=351

author: Rerouter
author_rank: Super Contributor
timestamp: May 18, 2014, 08:52:29 pm
content: The power source comes down to what sensors / peripherals your running,One big thing to be aware of is the arduinos default voltage regulator slurps down a very large amount of power compared to the micro in sleep mode, same for the serial chip,for my own battery powered test box i built up my own board (atmega328, a 16Mhz Crystal and your good to go) used a switchmode regulator with a shutdown pin, (was driving a moderate sized LCD display with backlight) and whenever it could turned off the lcd, turn off the switchmode, and put the micro into sleep, to wakeup on brownout detect and turn the switcher back on for a second, or a button press in which case fully wake up.. this little project was happily lasting weeks on a single 9V,

author: Richard Crowley
author_rank: Super Contributor
timestamp: May 19, 2014, 03:08:42 am
content: Quote from: FearTec on May 18, 2014, 05:29:06 pmWhen making a decision like that, several important factors must be considered. None of which you have revealed in your question.How much power will your circuit use?How often does it need to operate? Continuously? Intermittently? Can you do a hibernation period to save power?How reliable must it be?What size restrictions are there (if any)?What weight restrictions?What cost restrictions?Any access issues? (For changing batteries)And likely half a dozen others I didn't think of at this moment/.

author: TheBorg
author_rank: Frequent Contributor
timestamp: May 19, 2014, 05:07:03 am
content: Search for Arduino nightingale, it's about as bare bones and power saving as you can get. Standard 328 chip.
Battery-powered Motor Without Flyback Diode? - Page 1
Forum section: electronics / beginners

author: ruthsarian
author_rank: Contributor
timestamp: August 03, 2017, 04:03:02 am
content: I did a teardown of my beard trimmer because it'd been acting up. While looking at the PCB I noticed that there's no flyback diode across the motor, which is a 3.7v DC brushed motor. There are two small capacitors wired in series across the motor (for noise suppression?), but that's it. When the trimmer is turned off it disconnects the positive terminal of the motor from the circuit, with the exception of those two capacitors.My question is why doesn't it have a flyback diode? Is it not needed in this sort of application? Do the capacitors somehow help out here? Or is this a case of it probably should have one, but it's not absolutely necessary so they didn't include it?One other thing. The trimmer is powered by a 3.7v li-ion battery. There's a 6-pin battery charger/protection chip along with two A1870 chips. I looked that chip up and each contain a pair of mosfets. I've seen typical application schematics for those protection chips showing 1 mosfet on the discharge pin, and another on the charge pin. But this thing has 2 mosfets in parallel on both the charge and discharge pins. Why would it have two mosfets in parallel like that? Is it to distribute load in case of current spikes?Thanks

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 03, 2017, 05:43:51 am
content: What's it switched by? A switch?Switches don't mind sparking, so it's not a problem. I mean, it might only last 10,000 cycles instead of 100,000...As for the doubled up battery chip, maybe for double the current capacity?Tim

author: Benta
author_rank: Super Contributor
timestamp: August 03, 2017, 06:19:47 pm
content: Not a lot of kickback from brushed DC motors. There's the back EMF, which is roughly equal to the supply voltage, so no problem there.Stray inductances can give some spikes, but they are low energy.The caps will absorb this, but they are primarily there to attenuate noise from brush arcing (which is minimal on such small motors).
Battery protection circuit for 3.7V LiPo battery - Page 1
Forum section: electronics / beginners

author: justageek
author_rank: Newbie
timestamp: March 05, 2021, 02:00:19 am
content: Am looking to build a battery protection circuit for Lipo batteries. While searching across internet I came across this circuit-https://www.instructables.com/2-Cell-NiMH-Battery-Protection-Circuits/. I was wondering whether this can be adapted for a 3.7V LiPo battery ?

author: kjr18
author_rank: Regular Contributor
timestamp: March 05, 2021, 10:12:09 am
content: Why bother with something he made specifically for two NiMH? As he stated in article:Quotethere are off the shelf solutions, that you can use for lipo cells. Simple DW01 and 8205a combo will work just fine for almost any cell. If you need more current you can replace mosfets for something stronger.There's no need to reinvent the wheel again. And I noticed that author mentioned different cutout voltages depending on load, something that could ruin your lipo when powering some low current stuff. Cut off voltage should be set at certain voltage, independent to current that load takes. Another thing, this circuit only provides discharge protection. There is no overcurrent or over charge protection. Would you rather was forced to take out your cell, charge it, put back in device? Or simply connect usb lead and charge your cell in device? You can get ready to use charge-protection modules for really cheap.

author: sairfan1
author_rank: Frequent Contributor
timestamp: March 05, 2021, 02:41:01 pm
content: There is a project done by Great Scott, much appreciated, check that one if it full fills your needs