Cigarette Lighter Socket with USB for 12v battery

[wysiwyg]

Hey there,

I got a question in regards to my Trillium camper 12v battery. Its a deep cycle that can do 65amp/hour for 20 hours.

I did some research and from what I understand, this would mean I could use 3.25amp for 20 hours, is that correct?

So here is my question. I just installed a 12v outlet:
https://www.amazon.ca/gp/product/B07...?ie=UTF8&psc=1

Specifications:

Car Power Socket:
LED Display: Blue LED Light
Car Power Socket Input Voltage: 12-24V
Car Power Socket Output Voltage: 12V 15A 24V 10A
Attention: Can not light cigarettes

2 In 1 Double USB with Voltage Display:
Input Voltage: 12-24v
Output: 5V 4.2A DC(Total)

USB Port: 2 pcs
Detecting Voltage Range: 6-28V
Voltage Display: LED Blue Light

Small Switch:
Input Voltage: 12-24V
Current: 15A
Material: PA66 environmental protection material
Shell Color: Black
Input Voltage: 12-24V

Is there an easy way to calculate how many hours I could charge my phone on the USB port before the battery runs out? I think the 2 usb port are 2.1amp each. Does that mean that if I charge 1 phone in the 2.1amp socket I could charge for 30.8hours before the battery runs out?

What is the difference between the current (15amp) and the output of the device (4.2amp)? Do I need to use a 15amp fuse in my fusebox?

Thanks alot for your answers, much appreciated.

[Larry,C]

You should not discharge your deep cycle battery below 50% to extend battery life so take your available amp hours and divide by 2 then divide that number by the number of amps your device is consuming and the result is a good approximation of how long you can run it.

[wysiwyg]

Thanks for the good advice!

[wysiwyg]

So I should recharge when its around 12.2V?

[BruceW]

The key is the wire gauge size and round trip distance from socket to the battery. In DC circuits wire size should be selected to minimize the voltage drop due to wire resistance - the drop should be less than 3%. For example if distance from socket to battery is 7.5', total wire length is 15'. At 15', 16AWG wire can safely carry 5A, 12 AWG wire can carry 10A and 10AWG wire can carry 15A. At higher currents, the resistance in the wire causes the wire to behave like a heating element. Fuses and circuit breakers are "wire protection devices" and should be sized to prevent an over current condition like a short or too big of a load from causing the wire to get so hot it melts the insulation and causes a fire. So with 15' of 16AWG wire you would want to use a 5A fuse; 12AWG wire a 10A fuse, etc.
A chart can be found at www.engineeringtoolbox.com by searching on "amps, wire size, 12 volt circuits".

[RussL]

Originally Posted by wysiwyg

Hey there,
Is there an easy way to calculate how many hours I could charge my phone on the USB port before the battery runs out? I think the 2 usb port are 2.1amp each. Does that mean that if I charge 1 phone in the 2.1amp socket I could charge for 30.8hours before the battery runs out?

Your calculation of hours here actually ends up just about right but you kind of lucked into it. As Larry said, you should only be using about 50% of your battery capacity, which would be 32.5 amp hours at 12 volts. The 12 volts here is the key.

The 2.1 amps that charges your phone over USB is at 5 volts. 2.1 amps x 5 volts works out to 10.5 watts. If you take that 10.5 watts and divide it by the 12 volts of your battery you get .875 amps at 12 volts. If you round that up to 1 amp considering losses in converting the voltage etc. you then get back to 32.5 hours of charging capacity til your battery is down to 50% charge.

Russ

[wysiwyg]

Hey Bruce, thanks alot for taking the time to answer me. This makes alot of sense.

Right now, my fusebox is about 5 feet from the tongue battery. Starting from the battery, it has 12AWG (maybe for 2 feet) that merges into 14AWG (this second part of the wire was already installed and I didnt feel comfortable enought to unwrap everything and replace it). This same 14AWG (both positive and negative) enter the trailer and goes right in my fusebox. Then, from there, a 12AWG travels to the power outlet. So, I guess its around 14 feet total when you do the loop.

That being said, I feel its fine for 5 amp but my power outlet has anothet slot (cigaterre 12v). So, I guess I need to be carefull and try not to exeed using 5 amps with my actual wiring?

I hope my explanation were clear :-) thanks again

[wysiwyg]

Thanks Russ, very good info :-) Do you think the second socket et 5v or 12v on my power outlet?

[RussL]

Originally Posted by wysiwyg

Thanks Russ, very good info :-) Do you think the second socket et 5v or 12v on my power outlet?

Only the USB outlets would be 5v. The "cigarette lighter" outlet will be 12v.