Not your normal battery question


Old 06-23-13, 11:46 AM
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Join Date: Jun 2013
Posts: 1
Not your normal battery question

Hello everyone. This is my first time here and I do have a specific question, but seeing the wealth of knowledge available I can tell I will be back!

I'm working on an oddball project and am having some electrical issues, and was hoping somebody might be able to give me some troubleshooting tips. I am building a battery case to use with a hobby of mine that requires power in remote locations. To do so I am using a deep-cycle marine battery (12V DC) that needs to power a cigarette lighter style adapter. I have the following components in line, and am using a combination of 14 gauge wire (directly from the battery) and 16 gauge one it reaches the components. I will eventually be duplicating this chain in a parallel connection so that I have two outlets available, but am working on getting the first one right before I complete the second.

Positive terminal on battery
ATM style blade fuse (5 amp fuse being used)
On/Off switch (rated to 20 amp)
Cigarette lighter receptor (rated to 20 amp)
Chain of resistors to 560 ohms (to step down before LED)
Red LED indicator
Negative terminal on battery

The circuit is completing, and I am getting 12 volts across the system. The LED is lit up, the switch works, fuse has not blown. I am using the cellphone charger for my car to complete the circuit in the cigarette lighter, and for some reason the indicator light on the charger is irregularly blinking. I've used a multimeter to check all the connections and they seem to be solid. Furthermore, the LED down the line is lit consistently. Any tips on how I can troubleshoot this?

Thanks for your help!
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Old 06-23-13, 11:58 AM
PJmax's Avatar
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Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 46,255
Welcome to the forums.

Many devices that use 12v car power and can be left plugged in all the time are conscious of battery voltage. They measure the available power and if it's over 12.5v it will charge. If the voltage is under that it won't charge.

Every device has a different cut-off voltage. I just picked 12.5v as a realistic figure. So some chargers know if the vehicle is running/charging. This is done so that the charger/device won't kill the battery.

A different charger may respond differently.
Old 06-24-13, 04:55 AM
Join Date: Apr 2007
Location: Near Buffalo, NY
Posts: 4,239
Your 560-ohm resistors and the LED in series are limiting current. As a test, remove or bypass them and try the charger again.

If all the LED does is indicate if the switch is on, the circuit should be parallel to the working (load) circuit after the switch.

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