Recharge car battery without charger

Top 5 Ways to Recharge Batteries Without Power | eBay
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.

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.

Fast Car Charger, Micro USB Android Charger Auto Charging Power Adapter with 3.3ft Micro USB Cable for Samsung Galaxy HTC LG Motorola, Nokia and More Android Devices(Black)
Wireless (WiseTiger)
  • Fast quick high speed Android Devices Charger.Broad Compatibilitybuit in universal standard usb ports compatible with most usb cables for Samsung Galaxy S6,S6 Edge,S5,S4,S3,HTC...
  • Charging at the same time does not interfere with car FM audio; Anti interference to mobile phone charging without affecting the performance of the car radio;3.3...
  • Intelligent Charging Control: Intelligent charging circuit design for over-heat, over-current, over-charging protection short-currency protection etc.
  • What you can count on:Safe and reliable with high quality TPE material. It is certified by most recognized testing agencies in the world and proudly meets all standards...
  • Warranty and Service: Comes with Life Time Hassle Free Warranty and full support from WISETIGER, so you can purchase with confidence. For technical support related...
Car Charger & Phone Holder, aLLreLi 3.4A / 17W Dual USB Car Charger with Battery Voltage Display + Universal Magnetic Car Phone Mount Holder for Apple iPhone, Samsung Galaxy and More
Wireless (Shenzhen RCF Electronics Co., Ltd.)
  • With this money-saving set, you ll receive a car charger for repowering the battery plus a magnetic mount holder to keep your phone screen visible while you drive
  • Our USB car charger features an Intelligent Voltage Alarm that constantly monitors your car s battery voltage and current. If the voltage of your battery ever drops...
  • With our magnetic mount holder, you can adjust the position of your phone by tilting and rotating across 360 degrees, so you re guaranteed to be able to see your...
  • Our car charger has two USB ports to re-power two devices simultaneously; Universally compatible with all USB devices
  • Magnetic mount holder can attach to any flat surface without leaving a mark or sticky residue behind, and the USB car charger will fit any cigarette lighter. You...
Car Charger: Lumsing 48W/9.6A 4-Port USB Car Charger for iPhone 7 /6s / 6 / 6 plus, iPad Air 2, Samsung Galaxy S7/ S6, Nexus, HTC, Motorola, Smartphones, Tablets and More (Black)
Wireless (Lumsing)
  • VERSATILE: This 48W / 9.6A USB Car Charger will charge your favorite mobile devices including iPads, iPhones, iPods, HTCs, Galaxys, Blackberrys, MP3 Players, Digital...
  • POWERFUL: 48 watts of power lets you charge up to four tablets, smartphones or other devices at full speed simultaneously! Forget the hassle of charging everything...
  • COMPACT: This car charger was designed for added portability and convenience. The ports are evenly spaced so as to avoid clutter and the charger itself has a narrow...
  • SAFE: Our intelligent circuit design protects against short circuiting, over-heating, over-currents, and over-charging. Our charger stops the current once your device...
  • WARRANTY: All Lumsing branded products have a 12-month warranty starting on the date of purchase. If there are any product quality problems, please feel free to...
Tekonsha Tekonsha 50-85-325 Shur-Set III Breakaway System with LED Test Meter, Battery, Switch and Charger
Automotive Parts and Accessories (Tekonsha)
  • For use on 1, 2 or 3 axle trailers equipped with electric brakes
  • Push to Test LED s indicate fully charged, charging or recharge
  • Multi-Stage Integrated Charger provides a fast recharge up to 12.8 volts
  • Weather/corrosion resistant, heavy-duty polymer case to protect battery and charger, with 3 versatile mounting options
  • 5 Amp/hr Battery and Breakaway Switch with 7.5 lead wires
The Battery Tender Battery Tender Power plus 3 Amp Charger
Automotive Parts and Accessories (The Battery Tender)
  • nput: 120VAC @ 60 Hz Output: 12 Volts DC @ 3 Amps
  • 4-Step Fully Automatic Charging (Initialization, Bulk, Absorption, Float) Automatically switches to float / maintenance voltage after fully charging the battery.
  • Quick Disconnect accessories included: Alligator clips and Ring Terminals Spark Proof
  • Water Resistant Short Circuit Protected Reverse Polarity Protected
  • Safety timer: 72 hours 5-Year Warranty 50 State Compliant Agency Approvals: UL, BC, FCC, RoHS Dimensions: 6.8 L X 3.68 W X 1.96 H Weight: 1.1 lbs (charger only)

Related posts: