Piggy-back fuseholders - a right way and a wrong way?

[Submariner Gold]

not at all

So is Broadsman incorrect about the power surge?

Or is it only Sat Navs, that suffer from power surge issues.

I personally had never thought about it before, until I read what he said.

Sure the battery goes from say 12.6V to 14.4V when the alternator kicks in, but thats normal. All the components in the car handle that.

 

[jokiin]

Or is it only Sat Navs, that suffer from power surge issues.
.

people leave stuff plugged in all the time, ever heard of anyone killing their satnav, or anything else for that matter by leaving it plugged into power, every camera out there would be dead by now, they're always plugged into power by design

 

[jeez123]

Have you ever wondered what happens when the power goes out and the UPS kicks in on IT-systems? Or even the backup generators on the hospital when the power goes out?

Now... take a chair, sit down and relax..

If your cars speedometer would crash by a "surge created by every start and shutoff" you'd be expecting to switch out these every now and then, right?

Don't bother being nervous. The spike in the voltage is not going from 12.6 > 14.4 within 1-2ms. And the amp is DEFINATELY not surging when you start the car... That requires the generator to deliver it's maximum at start, which does not happen at all because of engine RPMs..

 

[Submariner Gold]

Have you ever wondered what happens when the power goes out and the UPS kicks in on IT-systems? Or even the backup generators on the hospital when the power goes out?

Now... take a chair, sit down and relax..

If your cars speedometer would crash by a "surge created by every start and shutoff" you'd be expecting to switch out these every now and then, right?

Don't bother being nervous. The spike in the voltage is not going from 12.6 > 14.4 within 1-2ms. And the amp is DEFINATELY not surging when you start the car... That requires the generator to deliver it's maximum at start, which does not happen at all because of engine RPMs..

Actually having thought about older cars I have had, I feel a tad foolish.
When one starts an older car, if say you have the lights on .... they dim due to a voltage/ current drain. Sure over time the alternator winds up the volts from say 12.6V to 14.4V but its not instant.
Especially with Keyless go everything is automated by pressing the engine start button, and I always let it run for 10 seconds when it drops the rpm from say 1,000 rpm to 650 ish rpm before engaging drive ... just gentler on the gearbox.
So I am now wondering what that poster meant .

 

[Broadsman]

Hi submariner gold after seeing the comments. Please note that I will post a one size fits all solution in a step by step guide it is a proven tried and tested method for cars boats motorhomes etc. It will be a little bit more expensive but can be purchased on Amazon. What you need to do is think how many items you need to connect the unit will cover cellphone's
100% cree spotlights
dashcam and satnav. Everything will be protected individually and together i.e. dual protection I think that anyone using this method will be extremely pleased with the result plus the bonus features are certain to please. There seems to be a lot of guff produced by this site I am only trying to impart my knowledge in a simple easy to understand way. I have over 50 years experience in the field. So far the posts I have seen are either from egotistical technocrats or nitpickers. My post are for people with little or no knowledge on how to do the work safely with best results.

So is Broadsman incorrect about the power surge?

Or is it only Sat Navs, that suffer from power surge issues.

I personally had never thought about it before, until I read what he said.

Sure the battery goes from say 12.6V to 14.4V when the alternator kicks in, but thats normal. All the components in the car handle that.

 

[Broadsman]

Hi submariner gold after seeing the comments. Please note that I will post a one size fits all solution in a step by step guide it is a proven tried and tested method for cars boats motorhomes etc. It will be a little bit more expensive but can be purchased on Amazon. What you need to do is think how many items you need to connect the unit will cover cellphone's
100% cree spotlights
dashcam and satnav. Everything will be protected individually and together i.e. dual protection I think that anyone using this method will be extremely pleased with the result plus the bonus features are certain to please. There seems to be a lot of guff produced by this site I am only trying to impart my knowledge in a simple easy to understand way. I have over 50 years experience in the field. So far the posts I have seen are either from egotistical technocrats or nitpickers. My post are for people with little or no knowledge on how to do the work safely with best results.

 

[Rajagra]

Also my apologies in my step by step guide in step six I think I forgot to say that when first placing the piggyback into the fusebox it needs to have a fuse in it before it can be tester to determine the correct way either by turning the piggyback around or putting the fuse in the alternative location.

To do this test you need a fuse in the slot leading to the new accessory, but no fuse in the slot for the original equipment.
(Alternatively if your tester has sharp probes that can contact metal inside the piggyback, you can leave out all fuses.)

I no longer think of the two alternative fitments being right or wrong. They just work differently. Each one has its risk of causing a fault.
The purist in me prefers (A) each device to be fed through its own dedicated fuse. (The way it would be done if you were designing the car from scratch.) The risk here is the supply line to the fuse slot may draw more current than originally intended.
The alternative fitment (B) - new device fed via both fuses - removes the above risk, but adds the risk of blowing the fuse for the original equipment.

Which is the safest option depends on what circuit you have chosen to piggyback on to. Having your lights fail due to using method B is not only more likely than starting a fire by method A, but possibly more dangerous too.

 

[Nigel]

Which is the safest option depends on what circuit you have chosen to piggyback on to. Having your lights fail due to using method B is not only more likely than starting a fire by method A, but possibly more dangerous too.

That is why you have separate fuses for left and right headlights, if you blow one you can still see

I do not believe that individual fuses are fed by individual wires. Instead a whole bank is fed by relays that turn on whole segments of the fuse box..

I guess you have never looked at the circuit diagram for your car!
Have a look in the back of any Haynes manual for the circuit diagrams. While the engine compartment fusebox is mainly a distribution panel like you suggest, the cabin fusebox certainly isn't.

Hi if you had read my postings in full you will note that I was an electrical officer in the merchant navy. I worked my way up to chief electrician. This means I have a full working knowledge of electrical systems from 12 volt batteries emergency power generation right through to massive turbine generators my first ship that I went to sea on could produce enough power to supply a town of 75000 people not just housing factories offices the lot.
During my 50 years at sea I have worked on every kind of system that it is possible to from a single high capacity 2 volt battery cell to multi megawatt generation. This included both AC and DC systems in varying voltage levels up to and including three phase electricity. What I am trying to impart is my knowledge for people to do a job correctly without endangering themselves I have tried to do this in a simple manner as not everyone is electrically minded.

OK, I'll admit that the last ship I worked on only had three 3.5 Megawatt gas turbine generators, three 4.5 Megawatt diesel generators and one smaller emergency diesel generatorr. That doesn't come close to your 75,000 homes!

What sort of ship generates around a quarter Gigawatt of power?

 

[Ralph2]

I guess you have never looked at the circuit diagram for your car!
Have a look in the back of any Haynes manual for the circuit diagrams. While the engine compartment fusebox is mainly a distribution panel like you suggest, the cabin fusebox certainly isn't.

Here.. is the circuit diagram for my Toyota Highlander.. the relay that turns on the ACC circuit seems to supply power to 4 items ranging from 25 amps to 7.5. I am guessing that there is a wire from the relay to the buss that the fusses make contact with.. but I have never tore apart my fuse box to see what is under it. In any case I doubt you could overload it to the point of creating a fire..without trying real hard.

 

[Nigel]

Here.. is the circuit diagram for my Toyota Highlander.. the relay that turns on the ACC circuit seems to supply power to 4 items ranging from 25 amps to 7.5. I am guessing that there is a wire from the relay to the buss that the fusses make contact with.. but I have never tore apart my fuse box to see what is under it. In any case I doubt you could overload it to the point of creating a fire..without trying real hard.

That is very neat, mine looks nothing like it!

Most of those fuses are joined, some via a relay, to pin 1 of the fuse box, which has a black wire connected to it so is presumably connected to ground (0V). Not sure where you are going to find +12V for the dashcam on those fuses?

 

[Ralph2]

On my installation I tied into the brake light fuse for continuous power and the radio fuse for ACC. Because adding one of those piggy back fuses would not allow me to replace the cover.. I also cheated (?) by soldering my leads to the cold side leg of the existing fuse. Took some effort.. had to file the leg down to make room for the wire and trim the solder to keep the same thickness / size of the fuse leg... ruined a couple until I got my technique down. But.. after all that work am happy with the fact my fuse cover still fits.
<edit> To protect the circuit I used the included inline fuses that came with my PMP
<edit 2> changed to brake light fuse

 

[jokiin]

On my installation I tied into the brake fuse for continuous power and the radio fuse for ACC. Because adding one of those piggy back fuses would not allow me to replace the cover.. I also cheated (?) by soldering my leads to the cold side leg of the existing fuse. Took some effort.. had to file the leg down to make room for the wire and trim the solder to keep the same thickness / size of the fuse leg... ruined a couple until I got my technique down. But.. after all that work am happy with the fact my fuse cover still fits.

they actually make fuses with the wire connected directly to the back side of one side of the fuse just for this purpose

 

[Submariner Gold]

On my installation I tied into the brake fuse for continuous power and the radio fuse for ACC. Because adding one of those piggy back fuses would not allow me to replace the cover.. I also cheated (?) by soldering my leads to the cold side leg of the existing fuse. Took some effort.. had to file the leg down to make room for the wire and trim the solder to keep the same thickness / size of the fuse leg... ruined a couple until I got my technique down. But.. after all that work am happy with the fact my fuse cover still fits.
<edit> To protect the circuit I used the included inline fuses that came with my PMP

You obviously dont have SBC or fly by wire braking
Wouldnt recommend that on a Mercedes ... if your continuous power circuit blew the fuse it could give you a bit of a braking problem. Unless you meant the brake lights.

 

[Deleted member 37895]

I bought a fuse tap from Amazon and it says to install it the wrong way, bypassing the original fuse and adding a second one in parallel! https://www.amazon.com/gp/B01LFXA604
This is assuming the blade is continuous up the left side (away from the red wire)

 

[Submariner Gold]

I bought a fuse tap from Amazon and it says to install it the wrong way, bypassing the original fuse and adding a second one in parallel! https://www.amazon.com/gp/B01LFXA604
This is assuming the blade is continuous up the left side (away from the red wire)

I noticed very few sellers point this out!
In my case the pigtail hit a high rise relay, so I had to downgrade the first fuse (on an unused rear cigar lighter circuit) from 15A to 10A
And then I could use a 3A on the 2nd fuse for my cams. I.e. 13A in total.

 

[Deleted member 37895]

I just used an unused fuse slot for mine so I didn't have to worry about direction. The slot is for a towing module which I don't have and it's normally 20 or 30 amps. I just put in a 2.5 amp fuse

 

[cctrader77]

I am trying to hardwire a Cellink Neo (in honda crv 2014) with an add-a-fuse which is rated at 9 amps (using 20 amp fuse). I have to use an occupied fuse slot, as no empty slots are ignition activated. I was wondering if this is too much of a load on the fuse buss to piggy back? Someone mentioned in here that for example a device rated for 5amps might use a 7.5amp fuse and the fuse wiring might be rated for 10 amps. Is this true? If so then adding an additional 9 amps could be dangerous right? Would it be safer to piggy back off a 20 amp slot? Perhaps the higher the rating, the more safety buffer they add to the wiring. any insight is appreciated, thanks!

 

[Broadsman]

I am trying to hardwire a Cellink Neo (in honda crv 2014) with an add-a-fuse which is rated at 9 amps (using 20 amp fuse). I have to use an occupied fuse slot, as no empty slots are ignition activated. I was wondering if this is too much of a load on the fuse buss to piggy back? Someone mentioned in here that for example a device rated for 5amps might use a 7.5amp fuse and the fuse wiring might be rated for 10 amps. Is this true? If so then adding an additional 9 amps could be dangerous right? Would it be safer to piggy back off a 20 amp slot? Perhaps the higher the rating, the more safety buffer they add to the wiring. any insight is appreciated, thanks!

Hi
I have posted many replies as to the correct way to fit a fuse tap. First of all check to see if you have a spare fuse location in the fusebox this would be the best option as it is unlikely that the vehicle's fusebox is fully used. The add a fuse is used to add a second connection on the live side only. As for what size fuse to tap into it is more important that the fuse you are intending to use is not safety related for example use cigar lighter - heated rear screen. Use the recommended hard wire kit. This method it is simple and correct, use the correct fuse for the camera, find a fuse of the same or slightly higher size.
Remove the fuse.
With a simple tester find the live side.
Plug in the add a fuse with the red wire on the opposite side away from the live side.
Replace the original fuse, note this may now have to be replaced with a mini fuse as long as it is rated the same amperage as the original.
Now this is important for determining that it is correctly fitted.
The original circuit should work as before.
Now test the red wire on the add a fuse it should be dead - no current. If this is the case the add a fuse is correctly fitted.
The red wire should only be live when the second fuse is added, this is the live side starting point of whatever you wish to add. As for worrying about overloading the circuit this happens when you do not use the method I have just described. My way you are making two circuits independently fused the only thing shared with the original fuse is the live feed for the fuse.
It is important to use fuses of the same or similar ratings don't be put off by this because you are creating a new circuit. Should you fit lager rated fuses than what is recommended that will be the start of your troubles to come and dangerous.
Best ofmluck

 

[Ralph2]

I am trying to hardwire a <snip>

Please read this thread from start to finish.. the subject has been beat to death.

 

[cctrader77]

Hi
I have posted many replies as to the correct way to fit a fuse tap. First of all check to see if you have a spare fuse location in the fusebox this would be the best option as it is unlikely that the vehicle's fusebox is fully used. The add a fuse is used to add a second connection on the live side only. As for what size fuse to tap into it is more important that the fuse you are intending to use is not safety related for example use cigar lighter - heated rear screen. Use the recommended hard wire kit. This method it is simple and correct, use the correct fuse for the camera, find a fuse of the same or slightly higher size.
Remove the fuse.
With a simple tester find the live side.
Plug in the add a fuse with the red wire on the opposite side away from the live side.
Replace the original fuse, note this may now have to be replaced with a mini fuse as long as it is rated the same amperage as the original.
Now this is important for determining that it is correctly fitted.
The original circuit should work as before.
Now test the red wire on the add a fuse it should be dead - no current. If this is the case the add a fuse is correctly fitted.
The red wire should only be live when the second fuse is added, this is the live side starting point of whatever you wish to add. As for worrying about overloading the circuit this happens when you do not use the method I have just described. My way you are making two circuits independently fused the only thing shared with the original fuse is the live feed for the fuse.
It is important to use fuses of the same or similar ratings don't be put off by this because you are creating a new circuit. Should you fit lager rated fuses than what is recommended that will be the start of your troubles to come and dangerous.
Best ofmluck

Thanks for the response! I've checked every fuse slot and all the empty ones are constant, thus I have to piggyback off an existing one. The dilemma I am having isn't how to wire the add-a-fuse, it's whether the wire feeding into the fuse can handle the additional load of 9 amps. According to this video I watched (

), if the feed wire is not rated high enough to handle both the original device and the new device, it can overload the wire that feeds into the fuse box. It doesn't matter whether whether it is hard wired correctly or not.

I've read through this thread and many others and the best response I have seen is that if I don't know the feed wire's rating then I should I assume it is rated only enough for the original device. For example, if the device uses 3 amps, then the fuse might be 5 amps and the feed wire would be 7 amps. I'm trying to see if anyone knows this is true or not, or if car manufacturers set all feed wires to say 40 amps.