Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Power supply build query

Status
Not open for further replies.

Enzy

Advanced Member level 1
Joined
Mar 20, 2016
Messages
488
Helped
2
Reputation
4
Reaction score
2
Trophy points
18
Activity points
4,607
I have a battery drill and the batteries aren't good and I realize I have several of these drills I wanted to build a power supply to power the drill.

I don't see a current rating on the drill I see 18v on the drill and on the battery.
I planned to just guts the battery and put a circuit in it but because of the size of the case I couldn't use a transformer and also I don't have any that small and I doubt it would give me the power I need even if i had any...

I was wondering if it would be ok to use a voltage divider circuit to step down the mains voltage to about 18v and convert it to DC and power the drill.
 

A transformer provides isolation so that you do not electrocute yourself.
The drill requires a high current.
A voltage divider supplies a low current.
Why don't you replace the battery?
 

Your drill probably needs a couple hundred Watts. Several Amperes. A resistive divider is impractical since the resistors will need to dissipate kW of power. Nor is capacitive drop practical, nor capacitive transformer.

An SMPS can do the job as described in the web article below. It attracted numerous comments from readers.

https://www.instructables.com/id/Cordless-Power-Tool-Conversion-18VDC-to-120240VAC/
 

I agreed with Audioguru. The drill requires a high current and the simplest way is to replace the battery. Frankly it is easy to buy one battery pack for the laptop computer. maybe the second-hand one is enough.
 

Replacing the battery is out of the question.... Batteries and the drills are the same price hence me having several batteries drills with bad batteries so I'm just trying to make use of them by building a power supply circuit to power them also even though I can't see the amp I use them often even more powerful ones and normally I would see like 3amp hours on the batteries, I would be ok with a circuit that can manage atleast that or a little more

- - - Updated - - -

And u said batteries and drills are the same price that's because duty tax is so high out here importing anything is like 3 times the price of purchasing it so that's pointless.
 

You did not say if the batteries are lead-acid, Ni-Cad, Ni-MH or Lithium.
Ah is not the maximum Amps a battery can produce, it is how long the battery can produce a certain low current.
A 50Ah car battery can provide 600A (!) to the starter motor on a cold day when the oil is thick. The Lithium batteries for my radio controlled model airplanes can provide 70 times their Ah rating.

The drill uses a high current when it is working hard. If you use a weak power supply then it will not be able to work hard.
 

OK i see.... The batteries are black&decker hpb18

Nicd batteries
 

If you have more than one drill with bad battery's then an external power supply makes sense.

eBay
120W 18V 6.7A Single Output Switching power supply for LED Strip light AC TO DC
$19
This is the lowest current supply i would use.

You should gut the battery pack, add a connector, and add a capacitor in the battery housing, the more uF the better but to big might cause the power supply to trip out on current limit. Use the physical size limit as you guide.

Use an electrolytic capacitor rated for 25 to 35vdc.

My guess on capacitor size.

https://www.digikey.com/product-sea...=1&stock=1&quantity=0&ptm=0&fid=0&pageSize=25
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top