What resistor to run a 5V 4 Channel Relay Module?

Hi there, this is my first question here. I’m not a guru, so haven’t been able to work this one out on my own.
I recently bought a 5V 4 Channel Relay Module 10A (SKU CE05279) to run off a 12volt AGM battery. I’ve built a trailer unit for my wife’s van using a similar one from Jaycar before that was very successful (+ trigger using resistors on each trigger), but thought I’d try one from Core as I’m intending to use it with Arduino shortly to count laps and flash lights for RC pylon racing.
My problem is that I couldn’t get it to work using one resistor that in theory would reduce the voltage from 13 volts down to 5. I used a 2.4K resistor of 0.5watts. If I used any resistor between the battery and VCC, the LED’s would barely glow and the relays would not operate. Running straight off the battery worked perfectly. No heat, smoke or smell, SO I DIDN’T KILL IT but it no longer operates the relays, but the LEDs still work. Something elso must have caused the module to fail. Not me…
My question is, when I buy a new one (I’m too scared to ask for a replacement under warranty!), can I use a resistor in this fashion (more watts?) or is the load of one relay and all 4 creating too much variance in the Ohms law thingie for a reliable voltage to drive the unit. I’m not smart enough to measure how much load the relay module draws to work it out on on-line calculators.
After this failure of the device (…not my failure you’re beginning to understand…) I’m thinking of using a BEC unit which we use in RC aircraft to reduce the voltage of 2 and 3 cell Lipos to 5 volts.

Yes, you probably didn’t kill it, but this size resistor doesn’t allow much current to operate the solenoids of the relays.

The battery elimination circuit (BEC) of the electronic speed controller (ESC) is a step in the right direction, but they only need to drive a small load, so probably won’t drive the relays either.

The BEC is just a voltage conversion circuit, converting the battery voltage to a lower voltage. What you need is something like this

Also if you don’t have a multimeter, now would be a good time to get one.

If you want to drop a voltage from 13 down to 5V you will need at least 2 resistors in the circuit. I have draw up the circuit diagram of what you might want below. As long as you keep the ratio between the resistors the same you will get 5V on the output lower resistance will mean higher current.