How to charge a drill battery with a different charger

Introduction: Cordless Tool Battery Laptop Charger

I will start with an appology to all the Dewalt and Ryobi fans on Instructables but I am a Metabo tools man. I use their 18V Drill, Impact Gun and 4" Grinder. My van was broken into last year and the tools but not the batteries taken. I replaced the tools and ended up with yet more (10) batteries and 6 chargers.

I do some site work, all with my laptop and rarely near a power outlet so I decided to see if all of these extra batteries in my van could come in useful.

Step 1: Get Started

You will need:

At least 1 power tool battery

1 SPARE battery charger (after this 'ible it will never charge a battery again)

1 compatible laptop charger

A multimeter

Knowledge of your laptops operating voltage.

Now time for the warnings....

This instructable may expose you directly to AC electricity, this can and will kill you so be careful

Check all of the voltages and polarities carefully as getting one of these wrong may cause damage to your laptop

Please only do this if you know what you are doing yourself!

Step 2: Strip the Laptop Power Supply

pen the casing on the laptop power supply, you don't need to be very careful as we won't be using it again.

Find where the DC (laptop) side of the power supply is and using your meter confirm the voltage is correct for your laptop and identify the polarity, in my case the wire with the white insulation is positive.

Use your meter to confirm that your battery also puts out a compatible voltage, my laptop needs 19.5Vish, all my tools are 18V but I know that a healthy battery should be above this, my meter confirmed 19.7V

Step 3: Strip the Power Tool Charger

Open the casing on the power tool battery charger carefully as we need it again.

Remove all of the charging circuit and discard it, DO NOT ATTEMPT TO USE IT WITHOUT THE CASING THIS MAY EQUAL DEATH!

Remove the rubber grommet from the power cable as we will use this as the laptop power cable exit.

Following the terminals on the battery, we are only interested in the positive and negative outputs from the battery (not the charging terminals). In this case they are the red (+) and black (-). Remove the other wires to prevent confusion or a short.

Step 4: Pass in the Power Cable

Push the power cable through the grommet, I needed to carefully run a drill bit through it first as my laptop cable is round but the old power cable was 2 core flat!

Connect the positive and negative wires, I use push in 3M terminals, it save on soldering and its stronger than crimp terminals.

Step 5: Reassemble and Test

Screw the casing back together, clip on a charged up battery and plug into the laptop.

Voila, field charger from your cordless tool batteries.

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Introduction: Lost Your Charger? How to Charge Any Battery Survival-Style

My camera shut down from low battery just when I needed to take some pictures.
The light was perfect. I suddenly remembered where I'd left the charger - 3000 miles away.
Everyone's had this experience, or the similar experience of spending one's vacation searching for a cellphone charger.

Here's how to charge any battery enough to keep doing the important stuff.

Fact 1: All past and future rechargeable batteries can be safely trickle charged if you don't overcharge them. Trickle means low current, like half an amp for an average camera or phone battery.
Fact 2: Small incandescent bulbs such as flashlight bulbs and christmast tree mini lights make great current regulators.

This is the battery to my Canon S30. It's got three terminals, labeled "+", "-", and "T".
I've clipped alligator-clips onto the two obvious ones.
You don't need clips, you can just hold wires on it for as long as it takes to charge, that's probably better anyway, so you can tell if anything is going wrong.

Warning! Wear eye protection and if anything weird happens don't breathe the fumes!

Step 1: Hands on Charging

What was that other terminal marked "T" for? TIMMY of course, just like in the nursery rhyme!
It's for Timmy to to hold his finger on the battery. If it gets hot you're doing something wrong.
Actually it's "Thermistor" or similar names. Temperature sensor. Some batteries use that to regulate charging current, some just for a safety feature.

"Digital sensor, huh?" would be a running joke back when Americans knew Greek and knew that digits are fingers. But then numbers got so much use we forgot about counting on fingers, and now people barely know how to do anything with their hands.

Anyway, here's a finger used as a digital thermometer. Which reminds me of the joke about the doctor...

Step 2: Charge From Car Battery With Lightbulb Regulators

SAFETY WARNING: scroll to the bottom if you want to read safety warnings.

Here I am charging my camera's battery from my car battery. I'm using three christmas lightbulbs at once as a current regulator to get half an amp to flow into the camera battery.
Here's how it works:
As the current through a lightbulb increases, the filament gets hot. That increases the resistance, which limits the current.

For example, here's my test of one of these mini christmas lightbulbs hooked up to a bench DC supply:

Volts Amperes
.5 .05
1 .07
1.5 .08
2 .09
3 .11
4 .13
5 .15
6 .16
7 .17
8 .18
9 .18
10 dead. The filament burned out.

I tested two bulbs and the data was the same.

Since my car battery is at ~13 volts and the camera battery is at ~7 volts, there will be 6 volts across the bulb. So I put three bulbs in parallel to get about 0.5 amperes to flow into the battery.
I'm guaranteed that less than 0.6 amps will flow, because that would burn out the bulbs.
That's some protection against reverse-charging, but do make sure you connect the plus terminals and minus terminals correctly.

Now just stand there for fifteen minutes or so until your battery is charged enough to take pictures again, you can make calls on your phone or whatever.

SAFETY WARNINGS:
Do not leave this unattended, and don't attempt to fully charge the battery.
If you charge too long and your camera battery gets over 8 volts, bad things could happen.
"Bad things" include possibly catching on fire.
Repeat: you can safely trickle charge any rechargeable battery part way.
But it is NOT SAFE to fully charge a battery without fully understanding the rules for that specific type of battery.
Car Batteries can produce a mixture of oxygen and hydrogen which can be ignited by a spark.
The resulting explosion sprays sulfuric acid everywhere. Don't let that happen to you. For simplicity's sake this photo shows me working right on the battery, but you could just as easily get your battery voltage from the cigarette lighter inside the car, far from the explosion hazard.
Also, don't electrocute yourself. I haven't heard of anyone being electrocuted by a car battery. I have heard of the other accidents described here actually happening.

Step 3: Charging From Any DC Source and Resistor

Hopefully you own an electrical meter.
Find a source of DC electricity. Look at the voltage of your source, the voltage of your battery, and use Ohm's law to figure out what kind of resistor you need to put between the two to get the right current to flow. Then go find that resistor. A piece of a heating element from a toaster or hair dryer can work. That clothes iron in the photo worked for a certain battery and a certain DC source.

As seen in the previous step, the best improvised current regulator is usually a small lightbulb. The bulb is great because the resistance goes way up when the filament gets hot and limits the current. And you can only put an amp or so through one without burning it out, so it acts as its own fuse. And they're free gifts from garbage Santa.

Here I'm using two bulbs in series to limit the current going into a gelcell. Use your multimeter to measure what current goes through your bulb at different voltages. Or you can just cowboy it and use one tiny bulb for a few minutes, while feeling to see if the battery gets hot or not.

Wear eye protection and don't breathe the fumes!

Step 4: Current and Voltage From a Bench Supply

This step uses a bench power supply to charge a battery. A lot of us have those sitting around even if we can't find our cell charger. Or we know where to find an electronics guy who has one. Now what?

Want to be totally mystified? Look up "lithium battery charge control".
All that stuff is important if you want to fully charge your battery, make it survive many charge cycles, or avoid lawsuits.

But we just want to take pictures or talk on the phone. So here's what we do:
Turn the current and voltage knobs all the way to the left. Turn on the powersupply and
hook it up to your battery, bearing in mind that red and black wires can possibly be plugged into the wrong sockets. Read the labels and unplug it if it seems to be arcwelding on your battery.

Turn up the voltage and current limit knobs until 500 milliamps (0.5 amps) is flowing into your battery. If you feel like being careful look up how much current the experts use.
But half an amp for a few minutes won't damage any battery that's big enough for a modern camera or phone.

My electronics guy told me to set my voltage limit to 8 volts for my 7.2v li-ion battery. Usually facts like that are luxuries. The point of this method is to trickle charge anything without being able to know much about the properties of the battery.

Step 5: Time Limit

If you really have to do something else while charging your battery, you better hook up something to disconnect it after a few minutes.

The whole point of this instructable is that we're not going to fully charge the battery because we don't know how, and we're in a hurry.
We're just going to charge it enough to go back to our regular jobs. The phone or camera will tell us roughly how charged the battery is after we start using it.

So we're only going to charge it for ten minutes or so.

My camera battery has 1200 milliamp/hours of capacity. So if it's fully discharged and we charge it at 500 milliamps, it would take more than two hours to fully charge it.

Some types of batteries can be badly damaged by overcharging. Some are just damaged a little.
This picture shows how my golf cart avoids overcharging. There's a built in appliance timer that turns off the charger automatically. It won't let you charge for more than 24 hours.

That's it! Enjoy cautiously!
To make your own external battery pack, check out AT's splefty booster pack.

1 Person Made This Project!

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