How to deliver stable voltage to the battery powered device? - Page 1
Forum section: electronics / beginners

author: Electrump
author_rank: Contributor
timestamp: September 20, 2025, 04:53:39 pm
content: Dear community, I bought a digital torque wrench for my hobby. Goyojo GN340. It is powered by two AAA batteries.Problem:The device works only 5-7 minutes before shut down. I have to use two sets of batteries for a simple half an hour job. Even when I insert the brand new 1000mAh batteries the battery status on device LCD screen is "Low" right away.Findings:Current consumption when device is Off: 6mACurrent consumption when device is ON: 9mAWith voltage I am a bit confusedMinimal battery voltage required: 2.7V. When batteries supply 2.65V the device would not turn ON.However, when powered from the DC Power supply, even 2.2V is sufficient for the device to turn on. Moreover, in this case the device shows battery status on LCD screen as "Full"!Question:What are the options to provide a stable voltage (I presume about 2.8V) so thata) the solution would fit inside the device caseb) the device operation time increasesI have considered the followingoptionsbut I am not sure how to implement themUse some sort of DC-DC voltage booster. There is 15mm*30mm*10mm empty space inside the device, but I couldn't find a proper booster to work with 2.6V and provide stable 2.8V output.Replace two AAA batteries with another power source. E.g., small Li-Ion battery but then I am limited with space inside the device. Also, it raises additional questions like how will I charge it and will it need a voltage regulator as well?Please try to make your suggestions as simple and practical as possible. Thank you

author: Grandchuck
author_rank: Super Contributor
timestamp: September 20, 2025, 05:10:44 pm
content: Have you tried a different brand of AAAs?Have your tried AAA lithiums ... non rechargeable?

author: PGPG
author_rank: Frequent Contributor
timestamp: September 20, 2025, 06:31:58 pm
content: Quote from: Electrump on September 20, 2025, 04:53:39 pmI see 1.2V written at your battery.2x1.2=2.4<2.7

author: Electrump
author_rank: Contributor
timestamp: September 20, 2025, 08:21:20 pm
content: Quote from: Grandchuck on September 20, 2025, 05:10:44 pmYes, I have tried different brand and specs of AAAs, same issue.Non-rechargeable is not a solution.

author: Electrump
author_rank: Contributor
timestamp: September 20, 2025, 08:26:09 pm
content: Quote from: PGPG on September 20, 2025, 06:31:58 pmWhen actual voltage of the charged batteries is around 2.7, the device works. When 2.65V or below the device doesn't turn on. When the device is powered by external power supply, then 2.2V is sufficient. I am struggling to see your point. What exactly do you see?

author: nali
author_rank: Frequent Contributor
timestamp: September 20, 2025, 08:43:58 pm
content: How are you getting the 2.2V value - measuring with the same meter as you measured the batteries or are you going by your supply readout?It does sound like the wrench is intended to be used with 1.5V alkalines not 1.2V NiMH. But the only thing that doesn't add up is running from a 2.2V supply.

author: zepto
author_rank: Regular Contributor
timestamp: September 20, 2025, 08:55:44 pm
content: How are you measuring the battery voltage to be 2.65/2.7? Without load? That would explain why a power supply works.

author: mariush
author_rank: Super Contributor
timestamp: September 20, 2025, 09:15:46 pm
content: You could get AAA Lithium (not rechargeable) cells. They should hold the voltage up at around 1.5v for longer time, but will cost you more.Example :https://www.digikey.com/short/f2d9703hAAA batteries are 10.5mm x 44.5mm , so you have at least 20mm by 44 mm area to put a battery in.You can get a lithium pouch battery to fit in that area ... add a small 3v or 3.3v LDO and an on/off switch and you're good to go. Or just use a plain diode (a plain 1n5819 will drop around 0.55v-0.65v)Example lithium battery :0.45" L x 1.22" W x 0.15" H (11.5mm x 31.0mm x 3.8mm)https://www.digikey.com/en/products/detail/adafruit-industries-llc/1570/50545460.98" L x 0.59" W x 0.16" H (25.0mm x 15.0mm x 4.0mm)https://www.digikey.com/en/products/detail/sparkfun-electronics/13853/66051971.42" L x 0.79" W x 0.22" H (36.0mm x 20.0mm x 5.6mm)https://www.digikey.com/en/products/detail/adafruit-industries-llc/2750/6612470You could get 2, and when one is discharged, plug the other one in and put your discharged cell into a battery charger.What else ... search for 10440 LiFePO4 or Lithium ... a LiFePO4 cell will be 3.2v nominal , 3.6v peak charge voltage. Lithium will be 3.7v, 4.2v when charged10440 is 10mm x 44mm so it would fit into a single cell slot, and you could put the voltage regulator / diode on that other battery compartment.

author: ledtester
author_rank: Super Contributor
timestamp: September 20, 2025, 09:18:30 pm
content: Quote from: Electrump on September 20, 2025, 04:53:39 pmAre you sure about this? Here is the US Amazon listing for the product:https://www.amazon.com/GOYOJO-Heavy-Duty-Automotive-Industrial-Maintenance/dp/B0CRDTB1G8/But I don't see any comments about excessive battery drain when off. However, one person pointed out that the soft power switch can be accidentally pressed if it left loose in a bag of tools so perhaps taking the batteries out when not using it is a good idea. Or -- add a physical power switch to disconnect the batteries.Another person pointed out that rechargeable lithium 1.5 cells work in the device.I've attached screenshots of comments that mentioned something about the batteries.

author: PGPG
author_rank: Frequent Contributor
timestamp: September 21, 2025, 03:54:29 pm
content: Quote from: Electrump on September 20, 2025, 08:26:09 pmAt your photo in your first post at battery on the left I see text starting from 1.2VTypical battery (not accu) is assumed to have around 1.5V.Do you measure battery voltage and external supply voltage at the same point?May be in series with batteries there is a diode to protect device against inserting them reversed, but power supply has a connection that can't be reversed so there is no diode in serie with it.

author: Electrump
author_rank: Contributor
timestamp: September 21, 2025, 08:02:41 pm
content: Quote from: nali on September 20, 2025, 08:43:58 pm@Nali the power supply has its own meter. However, as a separate experiment I have confirmed that my linear power supply readings match my multimeter to the hundredth of Volt.It seems like most obvious answer is using 1.5v batteries like you and @Mariush suggested. I will have to try it. Thank you.

author: Electrump
author_rank: Contributor
timestamp: September 21, 2025, 08:05:43 pm
content: Quote from: zepto on September 20, 2025, 08:55:44 pmThe Voltage is almost the same with or without load. For exmple, for certain set of batteries 2.74 with no load and 2.739 with load.

author: Electrump
author_rank: Contributor
timestamp: September 21, 2025, 08:14:00 pm
content: "Do you measure battery voltage and external supply voltage at the same point?" - yes, I clamp power supply to the same connectors where batteries are.

author: Electrump
author_rank: Contributor
timestamp: September 21, 2025, 08:19:14 pm
content: Quote from: mariush on September 20, 2025, 09:15:46 pmThere is a lot to choose from here. Thank you for comperehsive answer.I think I missed the very obvious here - to use 2x1.5V instead of 2x1.2V batteries. Ironically not a single 1.5V AAA battery is around so I shall get some.Thanks everyone for pointing this out!

author: PGPG
author_rank: Frequent Contributor
timestamp: September 21, 2025, 11:26:08 pm
content: Quote from: Electrump on September 21, 2025, 08:19:14 pmAfter you have written:Quote from: Electrump on September 20, 2025, 08:21:20 pmI was sure that you have already tried 1.5V batteries and they don't solve the problem (is not a solution).

author: Psi
author_rank: Super Contributor
timestamp: September 21, 2025, 11:48:26 pm
content: Quote from: Electrump on September 20, 2025, 04:53:39 pmSounds faulty to me.I cant see any reason why it should be drawing 6mA when off.Probably supposed to be drawing 3mA when on and near 0mA when off and has a constant 6mA short somewhere.It wouldn't surprise me if it has a soldering issue (short between pins/parts or something) and that's making it draw too much current. And if batt voltage sensing circuit is part of that short then that might explain why its sensing voltage wrong and turning off when the voltage is so high.Problems like this often get past QC testing when it's being done by an operator who's simply checking that the device works, rather than an automated test jig that looks at current draw.I would have a close look at the PCB under a microscope paying close attention to IC pins and resistors.Or take it back to store and explain why you think it's faulty.If it's from aliexpress or similar then i would be even more sure it's got a soldering issue somewhere as the QC on aliexpress goods tends to be lacking and done by simple human testing.

author: Electrump
author_rank: Contributor
timestamp: September 22, 2025, 06:53:58 pm
content: Quote from: PGPG on September 21, 2025, 11:26:08 pmWhen I said that 1.5V is not a solution, I meant I don't want to use 1.5V non-rechargeable batteries. Because it is not a sustainable solution. Therefore I had no non-rechargeable AAA batteries in the house. However, it seems like I may consider making an exception for this piece of technological miracle I bought. Thanks

author: Electrump
author_rank: Contributor
timestamp: September 24, 2025, 07:10:10 pm
content: 1.5V batteries solved the problem!There is a dedicated compartment for batteries in the case. I would store batteries in there to prevent drawing current when device is off.Thanks to everyone who replied. It is a pleasure being part of such a responsive community!