[Aaron Cake]

I am currently thinking about a new MP3 player for the Insight. Since I want to drive both the RX-7 and the Insight, I don't want to be swapping the player between cars everytime I switch.

My current player used a 12V DC-DC converter to power the AT motherboard, which is a rather expensive solution (the DC-DC goes for around $80 US). Since the Insight has wonderful 144V available at the traction pack, I am hoping to just use a standard ATX power supply in the new player. I would yank out the rectifier, and then connect directly to the traction pack. Should work just fine.

Now, I'm wondering if this will mess with the IMA system at all? The supply will draw roughly 2-3A. Will this extra (unmeasured) draw completely confuse and anger the BCM?

 

[Will M]

I very honestly doubt that there is a safe way to tie into the 144 volt system. DC voltage of that magnitude is nothing to take casually.

The 12 volt system is built to support accessories. Use it. The money you are trying to save here is much too little to justify risking your safety and the safety of the $20,000 car by messing with 144v DC.

And yes, tapping into a system that is trying to determine State of Charge, putting an unmetered load on the system likely will confuse the electronic controls.

 

[Atheos]

Since expense appears to be your primary concern, I don't think
you will find a satisfactory solution.
If you want to bypass the 12V->120V converter, your solution is here:
http://home.attbi.com/~zootjeff/
I found this on goggle, and have never done business with this person
so proceed with caution!
I'm sure there are other available if you google it and
this would be a far more efficent approach than what you are doing now.

 

[Armin]

Don't try this at home!

Aaron,

I think you will find that making a solution like this work - and at least somewhat safe - is going to be more expensive than simply using the $80 DC-DC.

That is aside from the potential damage to vital components in the Insight. While it's entirely possible to draw the current at a point after the battery current sensor (and so allowing the car to "see" it and account for it in SoC computation - as long as the ignition is on), you still have to ensure that you don't deep-discharge the battery. I don't see how you can do that without access to the battery management computer. Also check if your supply will work in the voltage range that the Insight battery swings in while driving (120V to 180V).

And most importantly, try to find a way to avoid being killed in the process. Although the voltage is not higher, 144V DC is much more lethal than AC.

 

[jameskb]

I am currently thinking about a new MP3 player for the Insight ..... Since the Insight has wonderful 144V available ... hoping to just use a standard ATX power supply in the new player. I would yank out the rectifier, and then connect directly to the traction pack..... this will mess with the IMA system at all? The supply will draw roughly 2-3A. Will this extra (unmeasured) draw completely confuse and anger the BCM?

Aaron;
I don't see why your idea couldn't work in principle: your MP3/PC player system is just another draw like the existing DC-DC converter. And I see the wisdom of what you're trying to do: why add another DC-DC converter just to waste power in an extra conversion step?

However, your motherboard wants +12V, +5V and +3v. Why go with the added complexity of another 144V downconversion using the ATX power supply at all?

Why not just feed your ATX motherboard from the existing 12V DC-DC converter and down-convert for the +5 and +3 voltages using a little bit of circuitry? You could just plug into the convenient 12V "power tap" under the radio on the dashboard, and you don't really need the "-" voltages unless you need serial ports for some unknown reason. No mods to the car and you've got the convenience of using the "power point" for easy removal of the system if need be.

Look on this web page and you'll find your brethren in this pursuit:
http://www.epanorama.net/links/psu_computer.html
There are schematics and details for building a supply that'll drive a PC motherboard off 12VDC.

Best of luck to you, you're on a noble quest:

JKB

 

[Aaron Cake]

I very honestly doubt that there is a safe way to tie into the 144 volt system. DC voltage of that magnitude is nothing to take casually.
The 12 volt system is built to support accessories. Use it. The money you are trying to save here is much too little to justify risking your safety and the safety of the $20,000 car by messing with 144v DC.

Actually, I am quite used to working around high voltages (though 144V is hardly close to "high"). Take a look at my website: http://www.aaroncake.net

As far as saving money, $80 US is a significant amount. I don't consider making connections to the 144V pack any more dangerous then plugging in a light, so to me a $20 (or maybe even free) power supply versus an $80 US (plus shipping and border charges) is a worthwhile savings. It's also kind of dumb to go from 144V -> 12V -> 12,5,-12,-5 . Too many conversions.

And yes, tapping into a system that is trying to determine State of Charge, putting an unmetered load on the system likely will confuse the electronic controls.

John Wayland added a 75A Todd DC-DC converter to his Insight to run his stereo. I have not heard of any negative effects from this.

If you want to bypass the 12V->120V converter, your solution is here:
http://home.attbi.com/~zootjeff/

Again, too many conversions. I have been involved in the MP3CAR world for 5 years know, and know about the above supply. But it is a 12V supply, which is something I want to avoid. And I certainly don't want to use an inverter...That's just stupid. Might want to check out the MP3Car forum: http://www.mp3car.com/vbulletin/index.php

I don't see how you can do that without access to the battery management computer. Also check if your supply will work in the voltage range that the Insight battery swings in while driving (120V to 180V).

The car would maintain the charge on the pack the same way it always does. Whether there is another draw should be irrevelant...Presumably it monitors SOC via voltage, not amps in and out of the pack.

A standard ATX supply will run from about 90V to 250V, so voltage is not a concern.

And most importantly, try to find a way to avoid being killed in the process. Although the voltage is not higher, 144V DC is much more lethal than AC.

I'm sorry, I don't mean to be rude, but this is just baltently wrong. 144V DC is many times safer then 144V AC. In fact, it's about 120 times per second safer.

Why not just feed your ATX motherboard from the existing 12V DC-DC converter and down-convert for the +5 and +3 voltages using a little bit of circuitry? You could just plug into the convenient 12V "power tap" under the radio on the dashboard, and you don't really need the "-" voltages unless you need serial ports for some unknown reason. No mods to the car and you've got the convenience of using the "power point" for easy removal of the system if need be.

Can't be done. Regulating the 14V from the DC-DC down to 12V is easy...But what happens when the car is off and the 12V is at 12V? Suddenly the 1.2 V drop from the regulator becomes a problem. This is why a "real" DC-DC is needed.

 

[Armin]

too many conversions

I agree with you here! It should be much more efficient to have only one DC-DC converter instead of two in series!

The car would maintain the charge on the pack the same way it always does. Whether there is another draw should be irrevelant...

This is true only while the engine is running. If you turn the engine off, but leave the ignition on, your extra current draw should still be accounted for (have not tried this, yet , but there is no deep-discharge protection anymore. You could potentially drain and damage the 144V battery by running your PC too long this way.

Presumably it monitors SOC via voltage, not amps in and out of the pack.

Sorry, but it's exactly the other way around. You just cannot deduct SoC from voltage on any battery system. The car measures and integrates current going in and subtracts current going out. You must be careful to make your tap so that the extra current you draw still flows through the battery current sensor. And ensure that at least the ignition is on anytime you run rour PC. Wait, you can't run it without the ignition since the main contactor would be off anyway. So no danger here.

I'm sorry, I don't mean to be rude, but this is just baltently wrong. 144V DC is many times safer then 144V AC. In fact, it's about 120 times per second safer. .

Aaron, I don't know what you deduct this from or what your background is. But you got it upside down. Making such a dangerously incorrect statement about a serious safety issue, and joking about it, is not appropriate here. You cannot take this lightly, please!

The inherent saftey in (US household 115V 60Hz) AC is that it turns off 120 times per second. If you touch a wire, you can use this moment to pull away. In fact, the alternating current going through your muscles will make them twitch and pull away all by themselves. You can survive even if you got unconsious (which is unlikely at "only" 115V).

DC doesn't do that. It tends to make your fingers stick to whatever conductor you are touching. It paralyses your muscles. It takes a conscious and dedicated effort to pull away, something that takes processing (reaction) time in the brain. You will most certainly have some degree of burns before you manage that.


This doesn't mean that you can't touch and get away with it. As long as your hands are dry it's probably fine. Once. Maybe ten times. But it's not worth the risk. Be careful.

If you follow the procedures (turn off manual breaker and allow 15 min for Y-caps to discharge before opening IPU lid, don't wear rings or chains and keep one hand in your pocket), and use proper insulation on everything you do, you should be fine. But don't be fooling around! Respect the danger! I know, I sound like your mother. But she's right!

 

[Aaron Cake]

This is true only while the engine is running. If you turn the engine off, but leave the ignition on, your extra current draw should still be accounted for (have not tried this, yet , but there is no deep-discharge protection anymore. You could potentially drain and damage the 144V battery by running your PC too long this way.

Well, I don't really plan to leave it running very long without the engine running. I used to do this all the time with my RX-7, and I was going through one Optima battery a year...Quite expensive. The idea is to hibernate the system, or put it to sleep to minimize draw. There would be a "hard" power switch Also, I could always build a low voltage protection circuit with an op-amp, zener and relay to guard against deep discharge in case I forget. Or simply a timer.

Sorry, but it's exactly the other way around. You just cannot deduct SoC from voltage on any battery system. The car measures and integrates current going in and subtracts current going out. You must be careful to make your tap so that the extra current you draw still flows through the battery current sensor. And ensure that at least the ignition is on anytime you run rour PC. Wait, you can't run it without the ignition since the main contactor would be off anyway. So no danger here.

This should not be a big deal. I'm guessing that I can simply take the output off of the BCM. But then, I don't have a schematic/service manual so I don't know for sure. Not too worried about running the PC with the engine off.

Aaron, I don't know what you deduct this from or what your background is. But you got it upside down. Making such a dangerously incorrect statement about a serious safety issue, and joking about it, is not appropriate here. You cannot take this lightly, please!

Actually, I'm quite right. You get to learn these things when you fool around with Tesla coils...See below.

The inherent saftey in (US household 115V 60Hz) AC is that it turns off 120 times per second. If you touch a wire, you can use this moment to pull away. In fact, the alternating current going through your muscles will make them twitch and pull away all by themselves. You can survive even if you got unconsious (which is unlikely at "only" 115V).

The danger of 60Hz is the frequency used. 60Hz is about the worse possible frequency they could have chosen. I don't really want to explain it all, so the following links should basically clear things up:

http://www.icorp.net/users/kev/tesla/dang.htm
http://www.pupman.com/listarchives/1998 ... 00604.html
http://home.gallatinriver.net/mhammer/safety.htm
http://www.pp.okstate.edu/ehs/modules/e ... rotect.htm

DC doesn't do that. It tends to make your fingers stick to whatever conductor you are touching. It paralyses your muscles. It takes a conscious and dedicated effort to pull away, something that takes processing (reaction) time in the brain. You will most certainly have some degree of burns before you manage that.

AC does exactly the same thing, but has the side effect of also disrupting every electrical system in the body. Something that DC does not do. Remember, tasers are AC. A DC taser would be very ineffective.

This doesn't mean that you can't touch and get away with it. As long as your hands are dry it's probably fine. Once. Maybe ten times. But it's not worth the risk. Be careful.

Also remember that the pack is isolated from ground, so as long as you don't get your body between + and - you're fine. As I mentioned, I am very used to working around high AC and DC voltages. See my website for confirmation.

 

[Will M]

Maybe you are right to be so casual about high voltage DC because of your experience, but it would be very good for other people who lack your experience to "not try this at home". It would be a bad thing for someone else to gain your attitude without your experience and kill themselves. This is a public forum.

I was working with a mere 24v DC system when I struck an impressive arc and felt the grip go through my right arm. I was quickly released from that grip because the fireball the arc set off from all that hydrogen from the freshly charged lead-acid batteries went into the battery itself, expanding the air there much faster than the little vent holes could accommodate, splitting and distributing the resulting pieces of the mostly rubber case to the golf-cart battery I was rewiring to remote corners of the room. It was a most memorable explosion to witness at less than arms length. Fortunately, most of the pieces didn't hit me. I can only describe the sound as a huge, bassy "Pop", unlike anything Hollywood would use in a depiction of the episode.

The blinding flash and overall tingling sensation was similar to what I would expect a Star Trek transporter to feel like. I was transported into an identical universe, except the old one had a battery in front of me, and the new one had a bunch of lead plates and connectors where the battery had been. Acid sprayed everywhere. I backed out of the room without changing my arm or head position, turned and shuffled into the bathroom like some desperate android and took a quick shower in my clothes, but the bib overalls didn't survive. Cotton is particularly vulnerable to sulfuric acid.

I'm glad I wore glasses.

I don't care if this has nothing to do with 144v DC nickle-metal hydride batteries. I will always respect electricity in large voltage or amperage, especially in DC, though I respect AC, too. Your mileage may vary.

 

[Armin]

Aaron,

as Will said, maybe you're right, maybe not. It's your health, so be my guest, do what you want. We're just trying to help.

You may want to re-read some of the links you posted. The ones that have any information other than non-scientific claims from dubious sources actually do backup what I warned about.

Good Luck to your project, and take care!

 

[Aaron Cake]

Yeah, those were the best links I could find. They weren't very good, but that was all that is available....HAMs should know about the 60Hz hazard, as well as most EEs. Unfortunately, I am neither...

I'm not saying the danger isn't there, and I'm certainly not recommending that everyone start playing around with their 144V pack. But if you know the precautions, it is a fairly safe thing to work around.

Anyway, it looks like I'm just going to have to hunt down a wiring diagram and figure this out for myself.

 

[Will M]

...Also remember that the pack is isolated from ground, so as long as you don't get your body between + and - you're fine. As I mentioned, I am very used to working around high AC and DC voltages. See my website for confirmation.

I'd just like to point out that there is a reason they call it "ground". Grab a hot wire while your body provides a sufficiently conductive connection to the Earth and you might not need to touch the rest of the electrical system to discover the electrical capacitance of the Earth. I am not an electrical engineer and have no special training beyond my avocational work with cars and solar electric home systems, but I do know one thing:

Lightning is DC.

 

[Aaron Cake]

That is true in the mains system, but not in the Insight system. There is no connection between the - on the pack and ground/earth.

Lightening is actually static, which doesn't really count as either AC or DC.

 

[Guest]

My current player used a 12V DC-DC converter to power the AT motherboard, which is a rather expensive solution (the DC-DC goes for around $80 US). Since the Insight has wonderful 144V available at the traction pack, I am hoping to just use a standard ATX power supply in the new player. I would yank out the rectifier, and then connect directly to the traction pack. Should work just fine.

What you need is a computer specifically designed for mobile/embedded applications. Have a look at the Open Brick http://www.openbrick.org/ . It only needs +5.5 volts DC and ground. I forget the current draw, but it is teeny.

Those DC inverters that people use to get a 110 AC socket in their car are not good to use for computers and audio equipment, as they are really noisy. You haved to spend a lot of money to get one that produces relatively clean power.

 

[Guest]

Lightening is actually static, which doesn't really count as either AC or DC.

Lightning is DC. Think of the source of the bolt in the clouds at one pole of a battery, the positive, and the ground as the other pole, the negative. The lightning bolt travels in only one direction - from the cloud to the ground.

 

[Aaron Cake]

What you need is a computer specifically designed for mobile/embedded applications. Have a look at the Open Brick http://www.openbrick.org/ . It only needs +5.5 volts DC and ground. I forget the current draw, but it is teeny.
Those DC inverters that people use to get a 110 AC socket in their car are not good to use for computers and audio equipment, as they are really noisy. You haved to spend a lot of money to get one that produces relatively clean power.

Yeah, thanks...You know, because I'm not already aware of this...I assume you didn't read the topic fully.

Lightning is DC. Think of the source of the bolt in the clouds at one pole of a battery, the positive, and the ground as the other pole, the negative. The lightning bolt travels in only one direction - from the cloud to the ground.

Actually, no. Lightening is static. The "current" travels from the ground up.

See http://science.howstuffworks.com/lightning.htm

 

[james]

OK, I'm lost here. Why do you want to put a motherboard in the car anyway? If you want an onboard computer for some reason, why not just pick up a cheapo used notebook?

 

[Guest]

Yeah, thanks...You know, because I'm not already aware of this...I assume you didn't read the topic fully.

Actually, no. Lightening is static. The "current" travels from the ground up.

See http://science.howstuffworks.com/lightning.htm

Gee, please accept my humblest apologies for skimming too quickly.

And a bolt of lightning is current, and regardless of which direction it travels, when it does so it ceases to be "static". But according to howstuffworks.com, "The strike is the sudden, massive, flow of electrical current moving from the cloud to the ground." (emphasis added)

 

[james]

And if you're not confused enough, the electric current is really an arbitrarily defined concept: when a current flows from A to B, it's really a bunch of electrons moving from B to A.

All thanks to Ben Franklin, who defined positive & negative long before anyone discovered electrons

 

[fscott]

K.I.S.S.

For the uninitiated, this means Keep It Simple, Stupid.

Why go to all this trouble when there's a functional component out there that will do exactly what you need to do? This isn't just my idea. It's a well understood rule of design.

I'm aware that you want to save money, but consider this.

Take your hourly wages, and divide them into the $80.00 cost of that power supply. Work that many hours this week and you'll have paid for the power supply. If your alternate solution takes more than taht many hours to research, design and build, then you're wasting your time.

Then again, I've made bolts on my lathe rather than drive ten minutes to the store to buy one...

Fred