Okay, i have a very very simple question about parallel wiring. I just want to wire two 7ah 12 volt batteries together in a bank. The load is gonna be 12v at 135ma, and I'm gonna hook my 5W solar panel & charge controller to recharge. No big deal. My question is on the type of wire to use for the bank. I have 18awg solid wire, has "300v 80 deg C" printed on it, can I use this safely? Do I need a fuse or diode in there somewhere?

 

The numbers you cited sound like the wire's insulation ratings.

Wire gauge is generally specified based on the current draw, etc. of the application.

Type (solid/stranded/etc.) is more for the physical requirements such a flexibility rather than the elecrical requirements.

18 ga. is plenty for 135 ma.

Fuse(s) will protect wiring from from damage due to excessive current draw such as a short. Place them on the + terminal of the batteries (drain side) to protect ALL the wiring. 0.5 amp would be fine for a 135 ma. draw.

Diodes (in a DC circuit) will prevent current flow if reverse biased and are likely contained in the solar charge controller BTW.

 

How long will these 18 AWG wires be? We musn't forget voltage drop.

 

Be carefull , 5watt at 12 volts is is close to ,5 amp. rather go one size up on the wire.

 

hey, thanks for your super-quick replies!
so, this is going to be used to power a wireless cam in my chicken coop.
i guess it will also be able to see out into a small portion of my back yard, just to keep it from being too silly of a project. maybe ill be able to catch some of the neighborhood skunks on film.

anyway the wires arent going to be very long at all, maybe eight inches or so. solar panel kicks about 285ma or less into my battery when wired direct.. panel voltage is variable maxing at around 21 volts.
camera's draw is about half the capacity of one battery in a day, so im hoping i can rig up two and not have to manually recharge. panel regulator just monitors the battery charge, i dont think it modifies the voltage or anything.

thanks for the insight..

 

Energy used, or 135mA times hours running, must be less than or equal to energy generated, or 285mA times hours generating. All the extra battery will do is store energy, not provide it.