Lost Your Charger? How to Charge any Battery Survival-Style

Picture of 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!
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Step 1: Hands on Charging

Picture of 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...
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Doesn't work, of course.

DaniyalA12 months ago

I didn't have a phone so I connected the charger to the battery directly. Using a formula I found out the time to charge the battery completely. It took three hours. Mine was a BL-5C battery (1020 mAh). Thanks for the help!

AlexB84 months ago

You can use a unregulated power brick pretty successfully too. Find a DC wall adaptor with a close voltage and amperage setting to the battery. Because it's unregulated, the voltage will drop to match that of the battery, but the current will increase. You can check to see if it's unregulated by measuring the voltage from the adapter, if it's higher than what it's rated for with no load, it's probably unregulated. As long as you don't go too far from what the adapter is rated current wise, should you be safe. Li-ion batteries have a unique charging profile, where the voltage and current needed to charge depends on how far along the charge is. As your battery charges, the voltage will climb, and the current will drop. This is the basic charging profile for Li-ion. You don't want to overcharge Li-ion batteries. Once the voltage reaches around 4/4.1 for a single cell, I'd call it quits. Remember you're trickle charging. You're only trying to put on a small percentage of current compared to the battery capacity. When I've done this in the past, I use a multimeter to measure the voltage, and one to measure current. I wouldn't do this without one to at least measure voltage. If you don't have one to measure current, make sure the wall adapter isn't getting too hot. Don't stray too far from your operation either.(don't leave home) Disclaimer: Intended for informational purposes only

LadyAtTheL4 months ago

Thanks! I have a great cordless drill and the charger died. They don't make the battery anymore so there aren't any replacement chargers that fit it. I will explore options using my trickle charger.

What to do if we had no charger for battery of samsung galaxy fir
technogumbo6 years ago
I think Tim does a decent job of explaining the risks involved. I think I would give it a shot if I were in a jam. I would only use a very low amp source to do this though. Doing it with a car battery is too shaky for me.

Indeed the risks involved are well explained. It is true that a car battery is capable of supplying many, many amps, should something be wrong so using a low amp source would indeed make this much safer.

In fact, if you're stuck with a battery that is a single-cell lithium, voltage from a USB port should be sufficient (5V, single cell is 3.7V) without further current regulation (a 'normal' computer port is already regulated at 500mA at most; modern dedicated charging port can go over this specification and often reach 1A). If however your battery is multicell (often, 2 cells in series, 7.4V) then I guess you could fall back to a 12V battery or low current adapter.

davegriff7 years ago
Thats a pretty dangerous way to charge a lithium battery. Ever seen one burst (explode!!) into flames. Any way, if it doesn't self destruct it certainly won't have a very long life using this method of charging. DONT ATTEMPT THIS

I believe the danger of explosion from lithium batteries comes from their very low internal resistance, which may permit a ridiculous current to flow if the proper conditions are met (e.g not regulating the current and applying a higher voltage to the cell, or short-circuiting the cell).

In this case, lightbulbs are used as a crude way to limit current. OP stated he used at most 0.6A for a limited time, while checking on the temperature, which is all reasonable. Modern smartphones batteries will today charge commonly at 1A and sometimes 2A (larger phones or tablets).

Of course this method will not permit you to fully charge a lithium battery because, as stated, lithium batteries need a specific charging profile to be fully charged (which is clearly not applied here). However this method works for charging a cell to a reasonable level which will allow a good level of use, perhaps even 80% if one checks the time and monitors the temperature.

Unless you really have to.
Toga_Dan2 years ago
Some electronics do not have removable batts. I wonder if there is a way to safeguard the electronics if you need to do this with an e-phone, kindle, etc.

Ideas on this?
if its a kindle fire, it can be popped apart quite easily. as for an iphone, dont buy crapple, get an android :D
Toga_Dan2 years ago
Toga_Dan2 years ago
Nice idea. Did you check the current flow on your setup with a meter to confirm your math?
MasterErik2 years ago
IKR. Shorted my distributor in my old Honda once hooking up an old style flash timer. My right arm was thrown up and hit the hood REALLY hard. Knocked the hood off the support rod and then that hit my other hand. As my right hand continued to circle back around behind me then it pulled me back from the car. Glad it was the cheap 8000volt option...
fma_battery2 years ago
It is better to learn the fully charged voltage of the battery:
1. 1.2V Ni-MH/Ni-Cd, fully charged voltage should be 1.54-1.60V per cell;
2. 3.2V LiFePO4 (LiFe) battery, should be 3.65V per cell;
3. 3.7V Li-ion or Li-Polymer battery, should be 4.2V per cell;
And certain charging time is necessary, it is about:
(1.2~1.5X Battery Capacity)/Charging current.
Otherwise, battery maybe leakage, hot heat, damaged or explode!
harlyquin4 years ago
no one's killed themselves from a car battery because it's DC and won't stop your heart. The only part of a car that can kill you with electricity is the alternator (the current has to pass through a bridge rectifier to switch to DC, so it can be used by the accessories and engine)
Don't get me wrong, you really REALLY don't want to ground out a coil pack or a distributor. It'll feel like having your arm yanked on while being covered in a shower of angle grinder sparks.
harlyquin, you might want to youtube search for bush welding with car batteries... 90+ A/hours to some truck batteries with is well and truly enough to stop a heart (considering it takes 0.1Amp across the heart to do so)
I have been unlucky enough to take a brief spark straight out of a coil. Uncomfortable but not deadly.
@harlyquin: DC current can most certainly stop your heart, just like AC. But not usually at the 12 volts that cars use. The resistance of your skin is fairly high (around 500K ohms if memory serves), so 12 volts isn't enough to cause much current to flow. But if your skin is wet or has other substances on it, the resistance can drop severely, to 1000 Ohms or less. And that can cause much more current to flow.

But it is NOT the fact that it's DC that makes it less dangerous - plenty of people have been electrocuted by high voltage DC. It's the fact that the battery voltage is so low. Coil packs can generate 50,000 volts or more - that's why they are more dangerous than the battery.

Just want to make sure that no one thinks that DC current is "safe", that's the way people get careless, and killed.
Tru dat

Unfortunately it's not that simple either.
The characteristic of a power supply that makes it dangerous is actually the.. um ... power rating. And that's best determined from the current (Amps) rating. High voltage IS what will let the power supply (battery / whatever) overcome the high resistance (low conductivity) to get to your vital organs, but current gives it the power to do something when it gets there.
So any high current situation is dangerous, PARTICULARLY at high voltage.
And your car battery has plenty power to do serious damage under the right circumstances.
I disagree. The power rating on a car battery would be around 7200 watts for one with 600 cranking amps. Much bigger than, say, the PS on an old CRT or a PC or a refrigerator. Yet compared to any of those things, the car battery is much less of an electrocution risk, because the voltage is only 12 volts.

The amount of current that can kill you is so small (anything over about 100 milliamps - that's tiny!) , that almost any power supply can kill you if it has enough voltage to push the current through your skin.

A 1000V power supply that can only deliver .2 amps is just as deadly - at least from electrocution - as a 1000V power supply that can deliver 100 Amps. The converse: A 12V battery that deliver 600 amps is not any safer than the same battery that can only deliver 5 amps.
Which part do you disagree with? The bit where i agree with you, or the bit where i back up your comment that DC isn't necessarily safe (see that i said "under the right circumstances")?

The rest is semantic argument and probably not best suited for this thread. But i'd be glad to learn more if you want to message me.
ReCreate6 years ago
i have two lithium ion(i think) 3.5-3.7v cellphone battery cells and i want to slowly -safely charge it(like in 24 hours or so)becouse i dont want it to catch on fire
so how do i do it? Are there any ibles that show me how?
You'll need to find the charging voltage for the battery (try the manufacturer's website) and then apply a tiny amount of current. To work out just how much, divide the capacity of the battery (in mAh or Ah) by the time you want to spend charging. You then have the charge current in mAh or Ah and the amount of time required. Usually it's safest to take over 10 hours, but some Li-ion batteries can handle more. Better to be safe seeing as they can have quite nasty reactions to being charged too fast.
scienceguy4 years ago
I need to charge a 7.2 volt 1000mAh cell phone battery. I am at home and have a little over 100 different chargers but none match those numbers. If i take a charger that is below both those numbers, would the battery charge and still be safe to leave alone or be safe at all? Would it be best to get the closest match on voltage or mAh? And finally, what should i do to reduce the voltage or the mAh if need be? thanx
As long as the voltage matches, the current doesn't really matter AS LONG AS IT'S SMALLER THAN THE ORIGINAL VALUE. Because then it just takes longer. But a higher current means the battery could explode.
dpark764 years ago
I think these instructions were pretty well thought out, and would be rather useful for mechanically or electrically inclined people, and NOT for the average Joe.  These instructions help the "initiated" to think outside the box. Just like everything else in's a calculated risk.

Heaven forbid if I'm driving through the mountains and get stranded without my phone charger, and my phone dies, at least now I know i can hack together a few wires, and light bulbs to charge my phone to send out that brief but urgent SOS. That's empowering to know.
jay886 dpark764 years ago
Start keeping christmas lights in your car haha :]
lukeyj15 jay8863 years ago
Or your headlights. I hope you keep them in your car.
I guess I cant do this...
Now, I know what to do when I lost my charger again. This thing is very Big help to me. The charge current depends upon the technology and capacity of the battery being charged. For example, the current that should be applied to recharge a 12 V car battery will be very different from the current for a mobile phone battery.
This is a very important point some Protection Circuit Modules (PCMs) have an Overvoltage Protection that is close to the typical pack voltage. So applying 12V to a cell phone battery will have no charging effect.
papalevies7 years ago
...and you get to lose a finger if it explodes! I don't get the joke either...
Another word for 'fingers' is 'digits'..

therefore, digital sensor could be interpreted as 'finger sensor'
bears0 KahlZun3 years ago
and "digital" thermometer, reminds him of a joke about a doctor. lol
love74213 years ago
Allow me to qualify myself, Associate, Bachelor and Master Degrees in Radiologic Sciences and now earning a PhD. I understand electricity far better than an electrician. This does not mean I can perform a complete house wiring but I understand what one can and more importantly, cannot do.

With all of that behind us, I have a lovely drill and I accidently threw out the charger for the batteries. No problem, I whipped out the 'ole car charger with both 6volts and 12 volts settings and a trickle setting for each voltage at 2 amps or a charge of 6 amps for bigger batteries, like a car battery as the manufacturer intended. I placed the charger on 6volt, 2amp trickle, tested temp, set a timer, and all is at peace now. Very easy fix just be sure to use the right setting, do it in the right place (not in your house), and right time (when no one else is around to get their fingers in the way like my son wanted to do).

The real fun was that neither the battery nor the drill listed which terminal was positive or negative. That is easy enough to fix because the charger has a built in indicator of charge and if you get it is obvious.

Do not be so scared, it is for individuals that understand electricity and know when to stop, however it can save you from a major problem if a device is dead and you MUST have it.
shama naz3 years ago
you r mad???
jay8864 years ago
Or possibly cutting a USB extension cable and using the black and red wires in the same fashion on the contacts of the battery, but keep your eye on it.
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