When hooking up a new toy to a vehicle what is the maximum amount of amps something would draw before a relay would need to be added?
That is a question that is impossible to answer.
It all depends on where you are hooking it up to, what else is on that circuit, and what size the OEM fuse is.
You can hook up an amp that pulls 100A without using a relay, but then run in to issues if you hook up something that pulls 5A.
In most cases, relays are used on low current outputs (200mA output, for example). Most accessory circuits in todays cars will be able to support 'normal' add ons.
How big is the load you want to add on? Where would you source the power from if you did use a relay? Why don't you just use that source to begin with?
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Kevin Pierson
I'm looking to put seat heaters in. The specs show that they run at about 5.5 amps each seat. I want it switched with the ignition on so that they will turn off when the truck is turned off so as not to run the battery down by forgetting to turn them off. I could hook them up 1 each to the 2 power outlets which both have their own 15 amp fuses. I did install a power box under the hood where I brought power over from the battery ( using 8 ga. wire) that has a fuse block and ground bar for added accessories with a small ga. trigger wire to activate relays which runs off the ignition. So the question is could I run them for the power outlets (which would be easier and faster) or from the power box using relays? If it's better to go with the relays could I run both seats off of 1 relay or need to use 2? And if 1 relay what fuse size would I use to protect both seats if they were on at the same time? If it's 2 do they make a double relay that is in one housing with harness? Thanks
You could probably get away with tapping in to the vehicles accessory circuit directly, as long as you fuse it. I would fuse it at 15A (5.5 x 2 = 11, next 'standard' automotive fuse is 15).
To do it the 'right' way you would probably want to run a wire directly to the battery, and use a relay triggered off of the accessory circuit to turn them on and off. This will give you a dedicated power line, independent of all other truck electronics. If you go this route, make sure you install the fuse within 12-18" of the battery.
A standard Bosch automotive relay is good for 30A so you can run both seats off of one.
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Kevin Pierson
If you go this route, make sure you install the fuse within 12-18" of the battery. What is the reasoning for have to be so close to the battery?
A standard Bosch automotive relay is good for 30A so you can run both seats off of one. Just run 1 wire off the relay that will feed power to the seats and T-Tap a second wire onto that?
To do it the 'right' way you would probably want to run a wire directly to the battery. The power box I mentioned is like a sub electrical panel for a house so my thought would be that this would be like putting the fuse by the battery???????? Thanks for your help Kevin