Switchable (not ACC) 12V Power to Bed

Hi folks,

Looking for some advice on wiring up 12V outlets to the truck bed

My plan is to run 12 AWG fuse it at 15Amp, and have a switch (separate from the ignition) in the dash. The idea is that I don't need to leave it always-on, but I also don't need to worry about locking my keys in the cab...

Given the modest current, I could run it though a 20Amp rated rocker switch on the dash, or use one of the OEM style switches that drive a relay.

My questions is about using a relay. From bench top testing that I have done i see that relays run about 90 Ohm, or about 130 mA. Is this a lot to have on for a whole day without the engine running? It seems like a lot of added parasitic draw just to keep some sockets hot in the bed.

Would I be better of with a simple rocker switch? Is there such a thing as a low-draw relay? What do other folks do?

Thanks in advance for the help!

 

The relay wouldn't be drawing any power if the switch was off. And if it's on, I'd assume it's because you are using 12v power, and anything you plug in is going to use more than that .13 amps. Or am I missing something from your explanation?

 

130ma is a very small amount of current, some car alarms can pull 500ma and a stereo with keep alive voltage is probably pulling 60ma when it's off. I wouldn't worry about that level of a draw when it comes to the vehicle battery. Compared to what the circuit itself uses, the 150ma will likely will be a very small compared to that.

 

Thank you both, yes, that's a fair point it's a small draw. I think I'll go with the relay so.

I was a little paranoid as I have had a few occasions where I left a dome light on in the back of an SUV while on vacation and arrived back to the airport to a dead battery.

Appreciate the super-fast responses. I'll post back here with the WIP/result.

 

Some dome lights can be almost an amp.

 

Just put a TDDO relay if you’re worried about leaving it on for extended period. Flick switch on and off, timer activated for 12 or so hours and times out, coil is de-energized.

something like this is cheap nowadays

$17 DROK 12V Timer Relay, LED Display 4-Mode On-Off Automotive Time Delay Relay, Electric Delay Timer Switch 0.1s to 999min

https://www.amazon.com/DROK-Automotive-Digital-Electric-Display/dp/B071XNY72Q

 

Wow, fantastic idea! I never heard of those.
Just working on this now, had a SPST relay in the parts bin so starting with that - but also just ordered one of those time delay ones.

 

Sounds like you have a good solution but just to give you some more info, 130mA seems high for a relay, I always thought they were down closer to 50mA. But even at 130, that's about 3.1 Ah per day that its on.

Your battery should be around 80 Ah capacity, higher if you went AGM or a group 27. Ideally you want to keep thr battery above 70% for starting and to prevent long term damage so you'd have 7-8 days with the relay on before there would be any real concern.

 

55-60 Ah is more like it if running a standard lead acid group 27, and it's possible the OP's Taco is running a smaller 24 depending on his truck's trim.

My 27F Optima AGM was only 66, and current 27F X2 Power AGM is 92AH. A deep cycle will let you get down to 50%, but as you said, only dropping to 70% is about as low as you'd want on a standard lead acid.

Personally, I highly recommend a deep cycle AGM (plus voltage booster), but it's probably a waste for most people.