Anyone have a source for a external power supply that will keep car from shutting down? More importantly one that does not break the bank like the one JLR uses in the shops.

 

Jag Bass, keep the car from shutting down when you do what? I am not sure what you are looking for.

If you are talking about having the car shut down because you turn up the car stereo and that is driving the entire cars voltage down, stand by to spend a pretty penny. I can help you fix it, but you are probably not going to like the answers that I give you.

 

Keeping the car alive while tuning the stereo. Whats your fix to keep it from shutting down?

 

Jag Bass, based on your amps that you are running, you are probably pulling in the neighborhood of 120 amps or so to the amps (possibly as much as 150 depending on how you have the bass amp set up). So, in theory, your stereo system would be using up 100% of the capability of the alternator, leaving nothing for the car to run on. The car needs a minimum of about 30 amps to power the engine and the associated computers. That is the minimum. You need headlights, add another 10 amps. You want A/C-heat, add another 30 amps. You like a warm seat when it is cold, add another 20 amps. You can easily reach 100 amps on a cold winter day just in what the car needs. So, you are running minus 100 amps (stereo at max plus the loads of the car on a cold day above what the alternator can possibly put out). This is where the battery comes in to make up that difference. PUlling a 100 amp load on the battery is going to cause it to drop into the 11.0 to 11.5 VDC range. Yes, that will cause the car to think you are trying to start it and causing hte computers to start up and shutdown with the beat of the music. Please keep in mind that this all assumes that you have the engine RPMs up at around 2,000 RPM. You get under that, the output of the alternator drops accordingly. At idle (700 RPM), your alternator may be only capable of say 80ish amps maximum. That is even more that the battery has to make up, dropping the car's voltage that much lower.

One thing that is going to help is running a 2 gauge if not a 0 gauge wire from your power source at the front of the car to the amps. If you think running a 6 gauge wire is enough, TRUST ME. I used to do car stereo installs back in the day and I knew how to make a system be bullet proof. I used 6 gauge wiring on a 300 W RMS total stereo. You are pulling around 1200 W RMS total. More power means larger wiring. The same size wire should be used between the amp and your ground point. You can probably get away with say a 4 gauge wire between the amp and a close by ground point due to only handling 1 amp and being a very short run. That is a quick and fairly cheap thing that is going to help solve your problem.

For the immediate issues, I would say you need to find yourself say a device called a "batcap". You will want something in the 500 amp range. You are going to mount this as close as possible to your amps and run a 0 gauge wire between the batcap and the terminal you are using to split the main power wire between the two amps. What this is going to do is when the stereo demands a large current surge, the voltage is going to drop, but the batcap is going to discharge, attempting to keep the voltage from dropping too far below 12.6 VDC. This is going to do 2 things for you. It is going to keep the overall car voltage higher and it is going to even out the pulsing the alternator is seeing. As the music demands less power (between the beats), the batcap is going to recharge, so it is going to put a draw on the alternator. The downside to this is once you start overloading the alternator, it is going to remain constantly overloaded and this will most likely result in a car that shuts down and with a discharged battery (aka, you may not be able to start the car). Puts you in a really bad position.

So, the ultimate fix that you are going to need to research can be done 1 of 2 ways. The more easy way is to find an alternator that is compatible with your car (Jag is a hard car to do this with) and step up from a 150 amp alternator to a 250 amp unit at a minimum (300+ amps is going to be better). The second option is to rework the belt system and slide a second alternator on to the car. You will then move the power wire that you have tapped off of the fuse box or other similar point and wire that directly to the new alternator. The benefit of going with the second alternator is you can use say a GM based alternator with a proper pulley to match your current belt and it will be internally powered and regulated. So, wiring up things will be very simple. The issue is finding someone willing to create a custom bracket to add to your F-Type for mounting the second alternator. Not sure what that would run, but I would plan on spending probably a $1000 between the bracket, a new second alternator, and any wiring that you would need to do. I would say to spend the $300 or so on the batcap and associated wiring too to prevent killing the second alternator with the continuous beat pounds by using the batcap as a surge suppressor. This will help with the longevity of everything. You can then let the factory alternator power the car and ensure you have the power you need to get you down the road.

So, in short, plan on spending another $1500 to give yourself a reliable source of power to power your car stereo. This is going to be a lot cheaper than having to replace various computers because you have shocked them with the varying voltage because of the stereo. What I mean by this is as your stereo makes a heavy bass beat, it is going to cause the alternator to make max output. As the bass note goes away, it is going to take a moment for the ECU to realize that the load is no longer there. This is going to cause the voltage output of the alternator to spike. It may go back up to 13.7 VDC, but more than likely, you are looking at it going above 15.0 VDC which is going to be hard on all the computers, as shortly there after, they are going to get drug back down to 11.0 VDC because the next bass beat hit. Computers and varying voltage is a bad combo.

If I have gone above your head or you need me to explain something in more detail, let me know. I have a lot of experience with DC system as I have been doing car stereos for over 30 years and worked on a DC system that was capable of power a small town (well, atleast a nuclear powered submarine in the middle of the ocean when the reactor went down). My current job is working on electronics for a nuclear power plant.

 

Wow that's alot, unfortunatly not what I was looking for at all. The stereo system is not causing any issue with the cars electrical system. The shutdown I am referring to happens to all jags if turned on and not started after a period of time. More like a timeout if you don't start the car. Why Jag uses a $1000.00 supply charger to keep the vehicle alive while preforming sdd updates. I an just looking for an alternative to shelling out a grand for their recommended charger.

 

If you are just needing something to keep the car alive while you sit still, that is a completely different thing. What you had written earlier was dealing with your stereo system. If you are just wanting to say use SDD and need the car to stay alive for hours on end, I Have a cheap solution for that. Look on e-bay for a 12 VDC power supply with an adjustment to set the voltage (something like 12V Power Supply 30A 360W, Universal Regulated Switching Transformer AC 110V/220 | eBay). The power supply that I list is very similar to the one I use. You set the voltage to 13.7 VDC and then you need to wire in a standard power cord to plug it into the wall with and then you will need a set of wires to attach to the battery. In the case of your car, you are going to attach the positive wire straight to the battery and the negative to the body of the car. THe power supply will then supply enough to keep SDD happy and if you are say washing the car, it may be enough to keep the stereo powered up as long as you do not turn the volume up too far.

The purpose of the auto shutdown is to not drain the battery to the point that you cannot start the car. The power supply I listed is like $35 and then you will need to spend another $15 for the cables.

 

Thanks, got something on the way.

 

Got a dell 575watt server power supply and Modded it up. Car still will not stay live even at 13.75volts. Not sure if the later models have software changes that are sensing if the engine is running or not or maybe sets a flag to stay alive in the ECU when doing SDD updates. Even the Midtronics unit that is used by JLR has an output of 13.6 I believe so not sure why this isn't keeping the car alive.

 

What current is the car drawing?

 

About 19amps

 

Hrm so it's drawing power and the PSU is delivering it... and 575 / 13.6 = 42ish so it sounds like you're only pulling about 50% of the PSU's capacity. There's no "set a flag" step in any of the Pathfinder connection procedures I could find... they all just say "1) Connect the battery support unit, 2) Start a SDD/Pathfinder session." I guess SDD/Pathfinder might send a signal when it first connects, but I have no idea.

I can't be much more help than that I don't think, sorry

 

Actually not using for ecu updating, trying to keep vehicle live so I can tune my Helix DSP without having to keep the vehicle running.

 

Yep, I read the thread. I figured if there was something you could do to stop the car from turning itself off, it might be mentioned in those procedures.