Quick question- 12v plug per fuse (2 Viewers)

[71cruiser71]

Hey all, maybe someone can answer this question for me, how many 12v accessory plugs should I be using per fuse position. I see a lot of diagrams and info showing you can piggy back 12v plugs off of each other but also saying you shouldn't do that.

I am installing 3- 12v plugs on my dash. 2 where the old radio was and 1 on the passenger side.
The 2 in the middle dash will have a 2in1 USB charger and a normal 12v plug. The passenger side will also be a normal plug type.

How many individual separate fuse links should I be using here?
I am installing an aux fuse block in the glove compartment with multiple ignition hot and multiple key hot terminals.

I tried to give as much info as would help answer my question. But how many should I be using here? Thanks!

 

[iwashmycar]

Depends on the amperage. If you have for instance a couple USB charges...they are usually like 2.4A...so even if we round to 3.... 4 of those would be 12A. You would probably want a 15A circuit in that case.

Rest all depends on wire size. The whole thing just needs to be sufficient.

 

[71cruiser71]

Yea, for sure. Still not 100% knowing in what that means.. I will just split the passenger side to its own dedicated fuse to be safe

 

[B y r o n]

You need to know the load on the circuit/fuse. If you overload the circuit the fuse will blow. Load is measured in amps. Add up the amps for each device on the circuit and subtract from the fuse amps. That is what is left on the circuit and you can add device(s) up to the fuse amps. Go over the fuse amps and the fuses blow.

If you have trouble figuring that out then you probably want to leave the stock fuse block alone and simply add a secondary fuse box to add your ports safely.

 

[Shark56]

What I did was run the non OEM accessories off a separate fuse block.
Sounds kind of like what you are doing. I used a Blue Sea type box with 6 circuits. Box is fed from a 20 amp inline fused wire to an on/off switch that is hooked directly to the battery.
Each accessory has a 15 amp fuse. I have a digital voltmeter wire in also. That helps me remember to switch it on or off. I run a stereo, couple usb plugs, 12 volt cigarette lighter type power plug and the voltmeter off of this. No problems in over 10 years. These old vehicles seem to be sensitive to wiring issue especially grounds. I just want to keep anything extra off the main OEM fuse block.

 

[73FJ40]

Is there a fusible link the feed to your separate fuse block? It would prevent a fire if someone who doesn't know electrical systems overloads your block.

 

[71cruiser71]

Yep, this is a secondary fuse block. Yes the secondary fuse block has a little shortstop fuse from the battery

I was just curious how many 12v sources you can potentially run on 1 fuse. I am adding 12v accessory plugs for charging cellphones or USB devices. Im not sure how much power I would need for that.

I decided to run 2 ports off 1 fuse to just charge cellphones or random stuff on it. Then have a third plug issolated to another fuse that I can run whatever else on.

 

[73FJ40]

You really need to learn more about DC circuits. The gauge of wire, amperage of each fuse and power consumption of each device needs to be fully understood to avoid problems.

Maybe Wikipedia could help you out.

 

[Wildcat Walker]

The answer to your question is that you can run as many 12v plugs as you want until you burn something down. Don't confuse the word source with receptacle. A source is defined as an active element in the circuit (Your battery or alternator). What your utilizing at the receptacle is source voltage. Fuses are designed for feed and branch circuit protection. In general, your fuse value should be 20-25% lower than the minimum current rating of the wire or minimum continuous operating current of a passive element in the circuit. The short of it is size your hardware to the current required. FYI current varies with voltage, so make sure you understand the relationship between the two, the current rating of a wire is defined at a specific voltage, you could use interpolation to get a general idea of unlisted voltages and currents, but for automotive, just assume the voltage which gives you the higher current and the circuit will have a better safety factor.

 

[Living in the Past]

I am installing an aux fuse block in the glove compartment with multiple ignition hot and multiple key hot terminals.

Are you adding a relay to separate the ignition hot circuits? Anything that runs thru the ignition switch will be fused on that circuit. Adding a relay can limit that to just the coil load of the relay.

 

[Wildcat Walker]

Are you adding a relay to separate the ignition hot circuits? Anything that runs thru the ignition switch will be fused on that circuit. Adding a relay can limit that to just the coil load of the relay.

And will add additional load to the circuit that has already been sized to the OE fuse. He could create a switched hot by using an ignition signal as the coil side of the relay, but this is still adding additional current and changes to the original circuit. The simplest method would be to bring a source and a ground directly from battery, bypassing the original circuitry all together (preveting the PO hacks we have all seen), size with an appropriate fuse just after battery connection, and then install his 12v receptacles for phones etc. Any branches would need additional fused protection sized appropriately. This would allow the safe use of those receptacles without introducing any stray voltage into factory wiring, and preserve the truck for the future.

 

[71cruiser71]

And will add additional load to the circuit that has already been sized to the OE fuse. He could create a switched hot by using an ignition signal as the coil side of the relay, but this is still adding additional current and changes to the original circuit. The simplest method would be to bring a source and a ground directly from battery, bypassing the original circuitry all together (preveting the PO hacks we have all seen), size with an appropriate fuse just after battery connection, and then install his 12v receptacles for phones etc. Any branches would need additional fused protection sized appropriately. This would allow the safe use of those receptacles without introducing any stray voltage into factory wiring, and preserve the truck for the future.

I would love to bypass taping into the old harness for ignition hot to the new fuse block. The new fuse block does have a dedicated fuse for the ignition hot wire and I connected straight from the key tumbler. Is there a better way to get a fuse block to get ignition hot?

 

[71cruiser71]

Amazon product ASIN B00062Z5VG
This is the new aux fuse block im using, it has a long pink wire that connects to ignition hot and a 3amp fuse. Then has a large red wire that powers from battery plus an inside 50amp fuse break from the battery.

My starter has a free power line coming from it, I can check and see if that is ignition hot? Or idk if there is any other way to get ignition hot

 

[Living in the Past]

And will add additional load to the circuit that has already been sized to the OE fuse. He could create a switched hot by using an ignition signal as the coil side of the relay, but this is still adding additional current and changes to the original circuit. The simplest method would be to bring a source and a ground directly from battery, bypassing the original circuitry all together (preveting the PO hacks we have all seen), size with an appropriate fuse just after battery connection, and then install his 12v receptacles for phones etc. Any branches would need additional fused protection sized appropriately. This would allow the safe use of those receptacles without introducing any stray voltage into factory wiring, and preserve the truck for the future.

The SPST (single pole single throw) relay is what I was talking about. Only the relay coil load is added to original wiring, very minimal. May be some kind of higher tech solutions but the relay is a simple way to keep the OEM and AUX circuits from mixing

 

[sggoat]

good advise from living in the past--plus remember the fuses don't work well if you use too resistive wiring--18/20 gauge wire will prob light up the truck before the 15 amp fuse blows--use at least 14 gauge wire through-out--any rewire should adhere to the oem circuit colors-(you will thank yourself 5 yrs from now when you have a ground prob)

 

[Grayscale]

Correct placement in the original harness will reflect the discharge on the ammeter, if hooked up to the battery it won't read right. Maybe you can just tap the fuse block and run all new wire for your new circuit. I'd do the relay switch to completely isolate the circuit if it was a big electrical load like headlamps; I do question the H4 wiring upgrade.

Do you want to run/charge accessories while the engine is running?

Many of those 12V USB charger/cigarette male plug have fuses in them. However, if you know your wattage/amperage that you might be using, it could help designing the system. Wire gauge calculators can help so that you don't look amateur and overbuild it, or under build it.

I wonder if you would just be better off with a pure sine wave inverter and run accessories on 110V AC?

 

[71cruiser71]

The SPST (single pole single throw) relay is what I was talking about. Only the relay coil load is added to original wiring, very minimal. May be some kind of higher tech solutions but the relay is a simple way to keep the OEM and AUX circuits from mixing

Yea I'm not really worried because the relay is getting power from the old cigarette lighter wire. If it can power a cigarette lighter it can power a relay.

 

[73FJ40]

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[Living in the Past]

Yea I'm not really worried because the relay is getting power from the old cigarette lighter wire. If it can power a cigarette lighter it can power a relay.

If you are talking about the long pink wire on the new fuse block the lighter is not a switched circuit. Know my FJ62 the lighter only works with the key on but my older 40 series the lighter is like the headlights and brake lights where the circuits are hot all the time. Also if your tapping in a heavier circuit would put a low amp fuse at the end of pink wire. That light gauge shorts to ground for any reason possible it could burn up if only protected by a larger fuse further on.

 

[Grayscale]

The factory put an inline fuse on the radio circuit. It makes sense to isolate the short circuit away from the main loom, or risk the short to get more complex than you want it because the loom is all tied together. I added an inline fuse to the lamps on the license plate holder just because I imagine them getting smashed being on a hinge and protruding out so much. It is intended to isolate a short so I still have brake lights because those leads, brake, stop, turn, backup are all in the same loom. I wish we had loom lay-out drawings, so much easier to visualize. I've found the blade type fuse holders to be awesome design, but I always have trouble finding them finer wires like 16g. The spring/connectivity for glass-type-inline-fuse-holders isn't the same as the spring on a Toyota fuse block, so yes, I'm suggesting to carry more diverse fuses with you.

I've been tempted to change the plug in the glove box so that it is polarized. Just an ideal, but, it might be more convenient? You could have everything operating smooth and predictable in a familiar kind of way. 12V DC but run on 110V AC wire (which is everywhere, use the kind that are twin cords joined like factory incandescent trouble lamp, not a cord packed in a common insulation). Also, if you look with a magnifying glass, 110V cord is identified with a stripe or some kind of text or whatever, so it could be a great source for 16g or 18g runs to things outside the vehicle, easily added to or shortened with additional links, more compact than using multiple cigarette lighter plug sockets, also better quality, and less expense. I could see a laptop charging in the tent outside the vehicle, or solar controller recharge applications.

The cigarette plug portion on the dash is better for routing wires away from gear shifting, heater functions. The old factory socket isn't smooth on the inside, but, it does make the connection to a USB adapter.

I have a double USB socket simply hardwired into the radio circuit, it rests in the center console or passenger seat rail kinda loose. I might charge a phone(s) if the engine is or isn't on, "acc" position on switch on the column, or I can plug into the factory cigarette lighter if I don't want to have the key in. I kinda like having wire looms run parallel to the rear heater lines; the transmission hump is a mechanical chase of sorts. I even have my reverse lamps switch sub-harness routed here with the rear heater sub-harness, fuel sender lead, and USB power sub-harness to 5V adapter plugs.

I killed an off-grid 12V AGM because the phone's operating system uses tons of power if you have wi-fi on, and I wasn't keeping close attention to the draw. The trickle charger won't deal with a battery that has been run that low. Nice thing about the 40 is it was never in that 12V to complex and electronic 5V USB-band-aid-world.