Do I need a resistor between my car battery and 12V devices?

[Svenn]

I was going to hook up some 12v LEDs, water pump, fans directly to my Toyota hybrid 12V battery (without going through the 120v inverter) but then read something that I might need a resistor to keep the 'power' (I have no idea what the units are called lol) constant to those appliances?  Or is it only fickly LEDs that need resistors?

 

[John61CT]

No.

Most nominal 12V devices are fine with the sort of wide ranges experienced, from say 10-16V.

A "DC Converter" sometimes stabilizer, regulator, is needed for any exceptions that require a steady say 13.8V, like a well regulated power supply for an expensive ham radio would require.

If you have a device like that, it is likely cheaper to replace it with one that doesn't have that requirement, rather than buying and hooking up a known-good converter, which get darn expensive as amps go up.

Resistors would be a jerry-rig worth trying, but their effect changes with current and voltage, so. . .

 

[Svenn]

Thanks, phew that's a relief... so LEDs from say superbrightleds would probably be ok with that range?

 

[SternWake]

The hotter LEDs get, the more likely thay are to flicker and burn out.

Whether yours are voltage regulated are not is unknown. Many that are for 12v will run super hot at 14.7v.

I like LEDs as bright as possible, and use LED dimmers to take them down and reduce their amp draw heat and light output.

The actual electronic guts of this LED dimmer are a fraction of the size of the plastic casing. I usually can install the guts within other LED housings and have full dimmer control

https://www.amazon.com/XtraLED-Dimm...coding=UTF8&psc=1&refRID=HSPX6GC5VCKBBD4Q6D0E

Some voltage regulated LEDs will not respond t a PWM dimmer. Such bulbs usually list a 10 to 35vDC range or so but there are exceptions.

I buy the unregulated with a T10 wedge base. Heat at fulloutput is a factor, More voltage means more light and more heat. A resistor on such bright LEDs could extend their life. I just dim them or view them as a bit disposable as my current batch, were 50 cents each, and I have 10 left.

Resistors on LEDs are usually for the Vehicles exterior signal lights when LEDs are substituted for INcandeascnet. This is to keep they hyper blinking or the Bulb out indicator from flashing on the dashboard.

Battery charging voltages wil cause unregulated LEDS to run hotter. Whether this extra temperature is a serious detrement to their lifespan, will vary widely on the product used and the voltage it receives and the temperature it get to.

Regulated LEDs can cause RFI, radio frequency interference. They can knock out some Over the air TV stations. Even some unregulated LEDS can do this.

 

[John61CT]

Would these also work as a fan speed controller?

 

[SternWake]

Yes they will slow fans, but, the fans will likely whine when slowed.

I recommend PWM motor speed controllers that claim 21KHZ or higher for controlling fans.

15amps is overkill

https://www.amazon.com/Controller-A...ontroller&qid=1465288414&ref_=sr_1_35&sr=8-35

Or one can control fans by voltage but lose some of the top end as if ~12v in means ~11 volts out max

https://www.amazon.com/DROK-XL4016E...98987&sr=8-51&keywords=voltage+buck+converter

These 2 products are examples, not recommendations.

The LED dimmer, well I have many of them and their circuit boards all vary somewhat but each one has worked, even the 2$ slow boat from china ones.

They do make my fans whine annoyingly so. They easily handle the 3 to 4 amp screaming banshee 120mm 252 cfm Delta fan, but I will be seeking to control its speed via its 4th PWM wire. This requires a 5 volt PWM signal. The Delta fan only slows to about 2 amps worth of air moving fury before shutting off on these PWM controllers on the power wires.

 

[Svenn]

I checked with superbrightleds and it appears as if their leds have built-in voltage equalizing ability or something, they said connecting to a car's 12v vehicle battery would be fine. I'm assuming my Shurflo RV pump is similar then.

 

[SternWake]

Voltage is electrical pressure.

if appliances were not rated to handle a range of voltage, we would all know about it with failures left and right.

When one is charging batteries  above 15 volts, then some things might start protesting .

A LED which is getting too hot will usually start blinking, but there might be other signs before that occurs, and one overheating event might cause it to start blinking at lower temps from there.

Voltage Regulated LEDS might or might not have this issue