Power supply plans - comments please

Install a 50AMP fuse in series before your load when building this PS

Thank you both! I didn't expect such a fast response. I really appreciate the advice.

120vac is rated in rms. The simulator requires peak values. So you take 120*1.414 to get 169 or 170 volts peak. This error will cause a difference from 10 to 15 vdc.

I would suggest looking closely into the specs of your cordless, 50A on the DC side seems quite high but not impossible with the right batteries...Im just skeptical yours would draw that much. In any event, I would definitely recommend fusing the AC side as your primary protection, itll probably save a potential fire if any wiring mistakes are made.

A simple rectifier like you have will probably get you by ok if you choose the right transformer...but honestly, why go through the trouble of making something unregulated like this...it is dangerous if youre not comfortable with electrical.

It would be far easier and cheaper (unless you already have a transformer) to buy an smps with the right voltage (many general smps have a volt adjust). Alot safer too. In general, its always easier and good 'engineering' practice to buy a rated power supply when you can. Unless youre hellbent on building it as a hobby or whatever, then thats a diff story.

50 amps? Its for a hand drill not a hand cannon.

Right. I would figure cordless drills draw something like 20A typically.

Around 6 amps no load for 12 volt motor. 30 amps is when its stalled out. However, a corded drill comes double insulated. The battery drill has little to no insulating mechanisms. The insulation issue along with your inexperience is a major concern. Agentaero has a better solution all around. The product you need is a 10 amp/12 volt battery charger for a car. Plug the battery charger into a ground fault circuit interruptor. Use the 12 volts to power the drill.

This circuit is not suitable. More important, for a first project this is not straight-forward and, as already mentioned, comes with serious safety concerns. If you can't buy a suitable smps (switched mode power supply) then ditch the drill.

I have found the Rigid tools to be fairly good and it is surprising that the lithium batteries have died. That being said, you will probably find that a power supply, including a 10 amp battery charger would cost the same as a new battery. In the past, I have bought batteries on eBay and repacked the existing case,it works out a lot cheaper all way round.

Both the drill and battery have chips that communicate with each other. If the drill doesn't get the secret nuclear launch code from the battery, then the drill will not respond to any power supply. Your only option is to get a rigid battery pack.

rich1129200, I wonder if it would be still possible to put New batteries in?

I have 18 volt cordless drill I am converting. Youtube video shows it should work. https://youtu.be/h4tbtsqbrn8

@Imccoig that isn't lithium batterys

The chip could be defective. That could have been the failure in the first place.

use an old computer power supply. they are cheap and gutsy and have their own protection built right in and you don't have to worry about killing yourself off the mains. you should have no trouble finding one with 12V 10A output.

If you do, look up the pinout as you'll need to enable the output by connecting a particular pin to earth (or positive - it's a while since I last looked).

@Robby. The lithium cells communicate through a serial data pin, that's also how they get their balanced charge also. A nimh or nicd doesn't need a balanced cell charge, all they need is a yes/no pin.

Hi @rich. OK, I was just pointing out that if a PC power supply was used there will be no output from it unless it's enabled - catches a lot of people out :-)

Great suggestion for the drill, there right if the drill run's at 10.5v it should be able to run at 12v just don't try to make a lathe or something else full time use from the drill. Drilling should not be a problem.

Thank you to everyone for all the helpful comments. You guys are awesome. rich11292000, The drill came with two battery packs and both of them died about the same time. I disassembled one of the dead packs, but I couldn't find any chip inside. The only components were three 18650 lithium cells, a couple resistors and a diode. The cells battery pack cells are lithium manganese oxide, which apparently can handle up to 20-30 amps (even 50 amps in one-second bursts), but generally have a shorter life span than other types of lithium cells. I considered just replacing the cells, but I'm not 100% sure that would work, since I've read that the charger is sometimes the culprit with these Ridgid drills. I'd rather just switch to simple, corded power. I've looked at regulated power supplies, but the only ones I could find that were capable of supplying 20-30 amps were astronomically expensive. Living in Canada doesn't help. If anyone has suggestions on where I might get an affordable, high current PSU, I'm all ears.

It's possible the individual cells in the battery are not properly balanced so it may be possible to resurrect it. You should check the output of each cell with a voltmeter. If any or all of the cells lie below 0.5 V the charger will most likely indicate a problem and will not charge. If you have a car battery charger, set it to 6 volts and carefully charge any cell with a low reading by constant contact at one end of the cell and quickly tapping the other end repeatedly in a series of quick split second charges until you get somewhere near 1 volt then try charging the battery in its proper charger. Might work.

No chip = no problems. You should be able to easily modify as you will.

For €30 you can get a 12V 30A PSU which you can also finetune +-%10 http://m.ebay.de/itm/351516493897?_mwBanner=1