screw driver charging voltage

[Kamranbites]

It is old electric screw driver, it had old batterys which are dead now so I am replacing them with new one but how do I charge them so I thought of using it with 3.7v battery I can charge with them with  lithium battery charger 

 

But is it good for motor  or should 

I  get 1.2v two cells and connect them in series but how to charge them.

 

The motor specs are 2.4v

So I assume the old cells were 1.2v,it had 2 cells in series

Don't have idea about mah 

 

I don't have charger, inside there is not much circuit just a dc jack directly connected to cells.

 

 

Attaching pics of dc motor and battery 

 

 

 

[Levent]

1.2v is usually the nominal voltage. Maximum voltage will be higher. Same thing applies to 3.7 cells, which are usually at 4.2v when charged. So yeah, that aint gonna work unless you reduce the voltage.

[Subduck]

If your electric screwdriver has a 2.4V motor, then you should use two 1.2V cells in series to match the voltage. If you use a 3.7V battery, you may damage the motor or the battery. If the 1.2V cells are Ni-Cd, you need to use a charger that can detect the end of charge by either the temperature or the voltage drop of the cells. You also need to set the charging current to 0.1 times the capacity of the cells, for example, if your cells have a capacity of 1000 mAh, you need to charge them at 100 mA.

[HanZie82]

Might just be easier to get a 2xAA case with wires, like this.

And then charge them with regular AA/AAA charger, like this.

 

Also there might be chargers that can do 2xAA at the same time, but without enough information i'm not to sure about them.
Like this.

 

(disclaimer, i have no knowledge of linked products they merely serve as an example.)

[Average Nerd]

 

53 minutes ago, Kamranbites said:

I  get 1.2v two cells and connect them in series but how to charge them.

 

Get 2 1,2V NiMH rechargeable batteries (ones with soldering tabs) and a NiMH compatible charger.

Then you just put the NiMH batteries in the same configuration as the old batteries, and you should be good.

 

The old batterys are NiCd batteries, which are highly toxic and I advise you to bring them to a recycling center for proper disposal.

[Kamranbites]

What should be the amps of 1.2v battery 1 or 2 

 

[Kamranbites]

25 minutes ago, HanZie82 said:

Might just be easier to get a 2xAA case with wires, like this.

And then charge them with regular AA/AAA charger, like this.

 

Also there might be chargers that can do 2xAA at the same time, but without enough information i'm not to sure about them.
Like this.

 

(disclaimer, i have no knowledge of linked products they merely serve as an example.)

Cannot do that as my screw machine is cylindrical shape 

[Kamranbites]

Can I use 3.7v drone battery charger 

[mariushm]

So the original batteries are Ni-Cd type, which can be charged easily just by applying 2.4v on the terminals and giving them a low current. So in this regard they're a bit easier to use compared to alkaline batteries which have memory effect and need to be charged in a  special way.

 

Those Ni-Cd batteries have a diameter of around 23 mm and a length of around 34mm, so considering they're in series, you have around 23mm by 68 mm worth of space.

So you could definitely replace them with 2 AAA batteries in a super tight battery holder - an AAA is  11mm by 45mm.

 

You could pull out battery holder, replace batteries, put the batteries in charger. or use non-rechargeable batteries... less hassle.

Here's an example of very narrow holder (see picture on the right side) : 22.2mm by 61.5mm by 12mm, it should fit : https://www.digikey.com/en/products/detail/keystone-electronics/1022/2137859

 

Just have wires long enough that you could pull out the battery holder to replace the batteries.

 

You could also make your battery holder with small contacts like these : https://www.digikey.com/en/products/detail/mpd-memory-protection-devices/BK-82/2079903

 - basically drill holes in a tiny strip of  prototyping board or piece of wood and insert these contacts spaced apart enough to hold AAA batteries.

 

 

If you decide to use lithium batteries, you need to convert the voltage from the battery down to 2.4v or thereabouts. The motor will work with slightly lower voltage, it will just not spin as fast. The motor will probably work with 2.5v or even 2.8v but I wouldn't risk higher voltages.

 

I would suggest buying a micro dc-dc converter that you can configure to output 2.5v or less, here's an example :

 

https://www.ebay.com/itm/155931144909

The above is 15mm by 18mm, it should fit inside the handle. Connect battery on one end, motor on out, but adjust the voltage before with that small trimmer, set it to output 2.4v-2.5v

 

If you don't care about efficiency, you could get any linear regulator with a fixed output of 2.5v or less, for example : https://www.digikey.com/short/b2q7882c - it will be even smaller space, like 1cm by 1cm..

 

The above list contains regulators that output a fixed voltage,  2.5v most of them - I put the filter to show only between 2.3v and 2.5v, and 200mA or more - Ni-Cd batteries can't output a lot of current, so I don't think the motor uses more than 200mA, but you can easily test that out. Get a multimeter and a battery holder for 2AA batteries and put the multimeter in series with the battery holder, on the DC current range and it will measure how much current the motor consumes.

 

Most regulators will have  3-4 pins , input, enable , ground and output ... and won't require anything fancy, maybe just a couple ceramic or electrolytic capacitors on input and output, the datasheets will show you how to wire them

 

For example for the big fat 1117 that would be very easy to solder - https://www.digikey.com/en/products/detail/diodes-incorporated/AP1117D25G-13/1934058

 you'd just need a couple electrolytic capacitors, I'd use something like 33-100uF rated for 16v..50v anything higher than 5v would do.

 

Battery ... any lithium battery... you can get them very small, from vape things, or you can get small pouch batteries like this

https://www.digikey.com/en/products/detail/tinycircuits/ASR00003/7404516

- 20  mm by 20 mm

or

https://www.digikey.com/en/products/detail/adafruit-industries-llc/3898/9685336

- 35 mm by 15 mm

 

As for charging these batteries, any charger board from eBay would do the job, just set the charge current to a low value.

 

Example : https://www.ebay.com/itm/282424445286

 

-------------

 

edit : you can still buy those Ni-Cd batteries, even with solderable tabs : https://www.digikey.com/en/products/filter/batteries-rechargeable-secondary/91?s=N4IgjCBcoMwExVAYygMwIYBsDOBTANCAPZQDaIALAAw0CcEAuoQA4AuUIAyqwE4CWAOwDmIAL6EKYBNBApIGHAWJkQMABw0AbAFYQTEGw7d%2BwsaNFA

 

they can be shipped by air so no big deal about buying them, unlike lithium cells.

 

 

[Ralphred]

2 hours ago, Kamranbites said:

So I assume the old cells were 1.2v,it had 2 cells in series

Yep, these "1.2v NiCad" cells were ubiquitous when non-lead acid rechargeable batteries hit the market, and were considered "rechargeable replacements" for standard 1.5v alkaline/acid single use cells.

The low internal resistance lead to the revolution of higher current uses, such as your screwdriver. Because of the charge/voltage curves it was common to charge them as "a single unit" (whether in parallel or series) with low current trickle chargers.

Searching for "1.2v rechargeable tagged cell" from suppliers like Farnell.com, rswww.com or newark.com should yield a list of results that are suitable NiMH replacements, BUT I'd check with the local "mom & pop" electronic model store first; these cells were extensively used for model cars/boats etc.

 

If you have the original charger it should be fine with NiMH cells, if not you want a current limited and voltage limited trickle charger: Charging time should be around 9~10 hours, so current limit appropriately for the capacity of the cells, and if in series limit to 3v.

 

Personally I'd tap the "middle tags" and create a 2 circuit charger with high initial current burst that tails off into trickle charging after ~1.3v per circuit, as the NiMH cells can handle that. DON'T use a charger for lithium based cells, the charge/voltage curve is different and the best case scenario is shortened battery life/sub-optimally charged cells.

[Kamranbites]

23 minutes ago, mariushm said:

So the original batteries are Ni-Cd type, which can be charged easily just by applying 2.4v on the terminals and giving them a low current. So in this regard they're a bit easier to use compared to alkaline batteries which have memory effect and need to be charged in a  special way.

 

Those Ni-Cd batteries have a diameter of around 23 mm and a length of around 34mm, so considering they're in series, you have around 23mm by 68 mm worth of space.

So you could definitely replace them with 2 AAA batteries in a super tight battery holder - an AAA is  11mm by 45mm.

 

You could pull out battery holder, replace batteries, put the batteries in charger. or use non-rechargeable batteries... less hassle.

Here's an example of very narrow holder (see picture on the right side) : 22.2mm by 61.5mm by 12mm, it should fit : https://www.digikey.com/en/products/detail/keystone-electronics/1022/2137859

 

Just have wires long enough that you could pull out the battery holder to replace the batteries.

 

You could also make your battery holder with small contacts like these : https://www.digikey.com/en/products/detail/mpd-memory-protection-devices/BK-82/2079903

 - basically drill holes in a tiny strip of  prototyping board or piece of wood and insert these contacts spaced apart enough to hold AAA batteries.

 

 

If you decide to use lithium batteries, you need to convert the voltage from the battery down to 2.4v or thereabouts. The motor will work with slightly lower voltage, it will just not spin as fast. The motor will probably work with 2.5v or even 2.8v but I wouldn't risk higher voltages.

 

I would suggest buying a micro dc-dc converter that you can configure to output 2.5v or less, here's an example :

 

https://www.ebay.com/itm/155931144909

The above is 15mm by 18mm, it should fit inside the handle. Connect battery on one end, motor on out, but adjust the voltage before with that small trimmer, set it to output 2.4v-2.5v

 

If you don't care about efficiency, you could get any linear regulator with a fixed output of 2.5v or less, for example : https://www.digikey.com/short/b2q7882c - it will be even smaller space, like 1cm by 1cm..

 

The above list contains regulators that output a fixed voltage,  2.5v most of them - I put the filter to show only between 2.3v and 2.5v, and 200mA or more - Ni-Cd batteries can't output a lot of current, so I don't think the motor uses more than 200mA, but you can easily test that out. Get a multimeter and a battery holder for 2AA batteries and put the multimeter in series with the battery holder, on the DC current range and it will measure how much current the motor consumes.

 

Most regulators will have  3-4 pins , input, enable , ground and output ... and won't require anything fancy, maybe just a couple ceramic or electrolytic capacitors on input and output, the datasheets will show you how to wire them

 

For example for the big fat 1117 that would be very easy to solder - https://www.digikey.com/en/products/detail/diodes-incorporated/AP1117D25G-13/1934058

 you'd just need a couple electrolytic capacitors, I'd use something like 33-100uF rated for 16v..50v anything higher than 5v would do.

 

Battery ... any lithium battery... you can get them very small, from vape things, or you can get small pouch batteries like this

https://www.digikey.com/en/products/detail/tinycircuits/ASR00003/7404516

- 20  mm by 20 mm

or

https://www.digikey.com/en/products/detail/adafruit-industries-llc/3898/9685336

- 35 mm by 15 mm

 

As for charging these batteries, any charger board from eBay would do the job, just set the charge current to a low value.

 

Example : https://www.ebay.com/itm/282424445286

 

-------------

 

edit : you can still buy those Ni-Cd batteries, even with solderable tabs : https://www.digikey.com/en/products/filter/batteries-rechargeable-secondary/91?s=N4IgjCBcoMwExVAYygMwIYBsDOBTANCAPZQDaIALAAw0CcEAuoQA4AuUIAyqwE4CWAOwDmIAL6EKYBNBApIGHAWJkQMABw0AbAFYQTEGw7d%2BwsaNFA

 

they can be shipped by air so no big deal about buying them, unlike lithium cells.

 

 

 

 

Thanks for your response 

 

 

Option 1)Using lithium battery I need to step down the voltage to 2.3v I can use LM2596 DC-DC Buck Converter Adjustable Step Down Power Supply Module then for charging them I need to use lithium battery charger tp4056

 

option 2) get nimh 1.2v battery keep them in series directly connect to motor for charging use nimh dedicated charged and charge it 

attaching pic of nimh charging module 

 

 

so which one is best option and most effective

 

 

[mariushm]

LM2596 is a horribly inefficient dc-dc converter that needs a high input voltage to output anything, and it will output it at low efficiency.  It will basically consume the battery just idling, waiting for you to press the button.

 

 

If you go with the lithium battery, you need a dc-dc converter / step-down regulator / buck regulator that can work with voltages lower than 4v - your battery will be between 3.5v and 4.2v, most of the time the battery will be at around 3.7v

 

Lithium works best if you want to recharge anytime you want.  Ni-Mh batteries have memory effect, it's best to have them discharge as much as possible and then charge them over night, not to charge them after using the screwdriver for a few minutes. You'll ruin the batteries this way.

 

NiMh also charges slowly if you charge them in the screwdriver you'd need to set low current, and have them charge for 6-8 hours.  You can get a charger for 5-10$ that can charge 4 AAA batteries in a few hours once they're discharged, so it would be easier to just pull out the batteries and put freshly charged batteries in the screwdriver when you need to use it for a day. Finish the job and pull out batteries to charge.

 

 

 

[Kamranbites]

6 minutes ago, mariushm said:

LM2596 is a horribly inefficient dc-dc converter that needs a high input voltage to output anything, and it will output it at low efficiency.  It will basically consume the battery just idling, waiting for you to press the button.

 

 

If you go with the lithium battery, you need a dc-dc converter / step-down regulator / buck regulator that can work with voltages lower than 4v - your battery will be between 3.5v and 4.2v, most of the time the battery will be at around 3.7v

 

Lithium works best if you want to recharge anytime you want.  Ni-Mh batteries have memory effect, it's best to have them discharge as much as possible and then charge them over night, not to charge them after using the screwdriver for a few minutes. You'll ruin the batteries this way.

 

NiMh also charges slowly if you charge them in the screwdriver you'd need to set low current, and have them charge for 6-8 hours.  You can get a charger for 5-10$ that can charge 4 AAA batteries in a few hours once they're discharged, so it would be easier to just pull out the batteries and put freshly charged batteries in the screwdriver when you need to use it for a day. Finish the job and pull out batteries to charge.

 

 

 

Pulling out is a big issue,

 

The casing is screwed and below we have dc jack also in middle we have  screw hole area 

 

Attaching some pics of casing,

Also I had placed a 9v battery inside for reference regarding internal space 

[Kamranbites]

23 minutes ago, mariushm said:

LM2596 is a horribly inefficient dc-dc converter that needs a high input voltage to output anything, and it will output it at low efficiency.  It will basically consume the battery just idling, waiting for you to press the button.

 

 

If you go with the lithium battery, you need a dc-dc converter / step-down regulator / buck regulator that can work with voltages lower than 4v - your battery will be between 3.5v and 4.2v, most of the time the battery will be at around 3.7v

 

Lithium works best if you want to recharge anytime you want.  Ni-Mh batteries have memory effect, it's best to have them discharge as much as possible and then charge them over night, not to charge them after using the screwdriver for a few minutes. You'll ruin the batteries this way.

 

NiMh also charges slowly if you charge them in the screwdriver you'd need to set low current, and have them charge for 6-8 hours.  You can get a charger for 5-10$ that can charge 4 AAA batteries in a few hours once they're discharged, so it would be easier to just pull out the batteries and put freshly charged batteries in the screwdriver when you need to use it for a day. Finish the job and pull out batteries to charge.

 

 

 

Ni-mh has memory effect?

I thought ni-cd had memory effect

 

Regarding step up consuming battery I will install the module after switch

 

(So from battery to switch then from switch to step up then to motor in this case there is no power loss the step up only runs when the button is pressed)

 

But as this is electric screw driver button will be pressed many times will it have any effect on step up like change in voltage or something else.

 

[HanZie82]

On 1/26/2024 at 5:53 PM, Kamranbites said:

Can I use 3.7v drone battery charger 

No. Not the same voltage, also meant for different type of battery.

 

On 1/26/2024 at 5:52 PM, Kamranbites said:

Cannot do that as my screw machine is cylindrical shape 

Maybe read the rest of the message too.