05-31-2016, 10:34 AM | #67 |
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05-31-2016, 10:47 AM | #68 | |
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+12V output ---> (unregulated 12V to 5V converter) ---> Adjustment Pot ---> Sense pin You would still use the Pot to set the desired output voltage of the power supply but this added feedback circuit would allow the power supply to actively monitor its output voltage (through the sense circuit) and adjust as needed. Basically, instead of using the regulated +5V output on the power supply to feed back through the Pot a constant control voltage to the sense pin we are creating a variable +5V output using the main +12V output so we can allow for the power supply to "see" what it is outputting and adjust itself.
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05-31-2016, 10:47 AM | #69 | |
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Good question. I have a 2016 X3 35i that I could hook to my 2014 335i and vice versa.... if it would supply enough power. |
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05-31-2016, 12:24 PM | #70 |
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Actually, now that I am looking at this closer, I am seeing that the sense pin is not looking for a +5V signal, it is meant to connect at the load.
I found a thread where it says that the correct way to adjust voltage is to add resistance between pins 7 and 9 rather than injecting voltage from pin 3. http://www.ultimaterc.com/forums/sho...=174225&page=2 Could the answer be as simple as adding sense wires from the jumper cable ends up to to pins 7 and 9 with a variable Pot wired in series with the +Sense wire?
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05-31-2016, 12:35 PM | #71 | |
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I think with 3 & 9 pin setup, we are using the 5v from pin 3 and a variable resistor to show pin 9 voltage lower than 12.5v, so it starts boosting the output voltage because it thinks the sense voltage is low. "To raise the output voltage you pull -S up or pull +S down (or both) using an appropriate resistor. A simple way to accomplish this is to connect a resistor between +S & -S." So basically, if you did pin 9 and 7, it would result in the same thing, except you have to use a different resistor/variable pot (~2100 ohm vs ~400 ohm). It also says you could pull one up or one down instead of connecting both. We are pulling S+ down with our 3 & 9 pin setup. So this is correct as well. Yes, you could add sense wires to the jumper cable ends. The problem with this is if the PSU is outputting 13.6v already, and you use the sense to get 13.6v at the load, the PSU would be over the overvoltage protection voltage most likely. No matter what we are fooling the sense into seeing, this PSU cannot go above the overvoltage protection voltage. Because of this, I think it's more reasonable to just set it as high as is reliable (13.6v) and minimize the loads in the car. Headlights and fans aren't really needed when you are sitting in your garage Last edited by terahertz; 05-31-2016 at 01:15 PM.. |
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05-31-2016, 01:00 PM | #72 | |
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Googling: "The pumps from Meziere and Moroso all draw from eight to 12 amps under load." random search result. not specific to our cars. more googling: "I can confirm that my amp draw from my perma-cool fan is 9.5amps" on a honda civic That's an extra 20-25 amps. Or 30-35 amps if two fans are running. With the car drawing 20-25 amps already, that may be more power than a single PSU can output and you're right the battery might be the path of least resistance with the 10 gauge wire and such. Also, you didn't show what connectors you were using to connect to the car. Jumper cables I'm assuming? |
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05-31-2016, 01:43 PM | #73 | |
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As far as my leads, I need to get some heavier duty ones. They are probably not helping the current flow. I'm almost thinking you need three of these PSUs in parallel to provide enough current for a full flash. When I flash the VDC and GHAS I'm going to put the car on the PSU for a while to make sure the battery voltage is at 13.5 before starting. Hopefully there are no current hogs during that process. Mark |
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05-31-2016, 01:45 PM | #74 | |
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Pins 7 and 9 are the actual + and - Sense lines. These are tied into the 12V rails for their reference. The concern I have is that the power supply has no way to "See" the voltage it is putting out. By connecting pins 3 and 9 you are feeding a regulated 5V signal (plus Pot resistance) into the voltage regulator of the power supply. In this case the power supply will allow the voltage to fall as current draw increases since the 5V rail will not fall off. If, instead, we connected pins 9 and 7 together (through a different Pot) they would be referenced to the 12V rail which would allow for proper feedback and regulation of the 12V system. It would still not go above out setpoint of 13.6V and, therefore, not trigger protection but it would allow the supply to maintain a more constant voltage I think. Thoughts?
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05-31-2016, 01:47 PM | #75 | |
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05-31-2016, 02:02 PM | #76 |
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I think this and coupled with short thick cables is about as good it would get with this PSU. BTW, my water pump also triggered and my battery was topped and neither did I go for a drive before. As I questioned before, it seems that not knowing the max current draw during flashing, and coupled with a low starting battery voltage and this unregulated PSU may put someone in an undesired situation !
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05-31-2016, 02:05 PM | #77 |
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yes, the water pump ran during the DME flash, as I mentioned in my thread! and you need a proper lithium battery charger ... This PSU will not charge the LifePO4!
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05-31-2016, 03:37 PM | #78 |
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All good info. If there's a better way to do this, I'm all for it.
I did not realize the water pump ran during the DME flash. I don't think 3 PSUs is needed for this... The DME flash only takes a minute or two as thisisdave had mentioned in the past. 1 PSU should really be enough if ferrarif1's schumacher charger is reading correctly (20-25 amps) with no extra loads. Last edited by terahertz; 05-31-2016 at 03:38 PM.. Reason: accidentally a word |
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05-31-2016, 04:12 PM | #79 |
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My Phase 1 flash (DME, DSC, ICM) took 10mns, then phase 2 (EGS, GHAS, VDC) 6mns, then ASD 3 mns. So in total 7 ECUs for 19mns in three separate sessions, based on that info I'd say for my car we are looking at an hour or more for a total update, unless the remaining ECUs are faster!
I located a good local source of very good quality AWG copper, not the crap that is mixed copper/alu and I'll redo a cable of 3ft AWG8, probably will make a small difference but why not |
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05-31-2016, 05:55 PM | #80 | |
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05-31-2016, 07:14 PM | #81 |
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Let us know how that goes. I also bought 10 and was planning to test 3 pots in series as well, but I don't have power near my car in my complex's parking structure so I have to borrow a friend's garage.
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05-31-2016, 07:49 PM | #82 | |
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I think, again :P |
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05-31-2016, 11:05 PM | #83 |
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I read you guys talking about pin x and pin y and how everything should be plugged together to get the result you want.
It's very informative and entertaining to read although I understand squat about what you are writing about. Made me smile tonight and reminded me of a VERY old joke by Steve Martin about a plumbers convention and wanted to make a special joke for them (of course there were no plumbers in the audience). So here it goes: “This lawn supervisor was out on a sprinkler maintenance job and he started working on a Findlay sprinkler head with a Langstrom 7″ gangly wrench. Just then, this little apprentice leaned over and said, “You can’t work on a Findlay sprinkler head with a Langstrom 7″ wrench.” Well this infuriated the supervisor, so he went and got Volume 14 of the Kinsley manual, and he reads to him and says, “The Langstrom 7″ wrench can be used with the Findlay sprocket.” Just then, the little apprentice leaned over and said, “It says sprocket not socket!” |
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06-01-2016, 07:05 AM | #84 | |
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P=U.I, so at 100% efficiency, with zero loss in cables and zero heat dissipation, theoretical I~52Amps at the rated regulated Voltage 12.1V using sense pins. Increasing the voltage to 13.5V by adding the pot in theory would decrease the output power by ~10% from the realistic 47A, but who really knows how the voltage regulation works in this PSU especially in the parallel configuration. The post that eluded to unpredictable behaviour at higher voltage is 1720. Now If we add a real life model, we need to account for cabling loss, connection loss for every joint we make, ... U=R.I, then P=R.I^2 or I=sqrt(P/R), so as wire resistance increases, I decreases... At 30Amps draw, using ohms law, calculate Voltage drop for 6ft cable, assuming 100% ohmic conductor; For AWG10, loss is 1mOhm per 1ft, Vd=0.18 For AWG8, loss is 0.6mOhm per 1ft, Vd=0.1 So in summary, not knowing the current draw, and having an unregulated PSU, one would need to tread carefully (and let not forget current surges like if a water pump decides to go on!) so important to have a full battery as a start and have shorter thicker cables (AWG8). Note: I am not trying to shoot down this DIY, it's lots of fun, rather I want everyone to know the risks and understand as much as possible and I suck at circuits... Links: http://www.rcgroups.com/forums/showp...postcount=1717 onwards http://www.rcgroups.com/forums/showp...&postcount=603 http://www.rcgroups.com/forums/showp...&postcount=613 Last edited by aboulfad; 06-01-2016 at 07:53 AM.. |
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06-01-2016, 08:11 AM | #85 | |
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06-01-2016, 10:24 AM | #86 |
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I had a few observations and thoughts on this whole subject.
If I'm not mistaken the only way for current to flow is as a result of a voltage difference (potential). When I was flashing, the PSU was set at 13.6 volts and the voltage at the terminals on the car were as low as about 13.12 volts. At the time my amp meter was indicating 10+ amps. I'm not sure how accurate this is but it's the only thing I have to go on. This leads me to believe that with my current setup, my PSU needs about a 0.5 volt difference to put out around 10 amps. I know that this isn't necessarily a linear relationship but would the above observation mean that in order to pump out 30 amps, there would need to be around a 1.5 - 2.0 volt potential between the PSU and the terminals on the car? If that's the case and I want to maintain at least 13.3 volts at the car while it's drawing 30 amps, I would need a PSU that could supply around 15 volts? Since this PSU goes into over voltage protection at 13.8, there's no way to achieve this without two PSUs in series and adjusted properly? Seems that you would need to be able to sense the voltage at the terminals on the car and reduce the PSU voltage accordingly if it reached a set threshold like 13.6 volts. Food for thought. |
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06-01-2016, 04:01 PM | #87 |
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I'm not sure how the voltage difference works, but from what I understand, even a slight voltage difference would cause power to be drawn from the higher one.
This is why running PSU in parallel is hard unless it has the current sharing capability like these do. If one PSU was slightly higher voltage than the other without current sharing pin, the higher PSU would put out all of the amps until it started to get overloaded and the voltage started to fall and/or the PSU shut off. If the PSU voltage is falling that low, either the PSU can't handle the amount of power draw, or there's not a good connection between your PSU and the car? And the car is drawing from the battery instead? Also, you can't apply 15v to the car or the lithium battery will shut off to protect itself. |
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06-01-2016, 05:21 PM | #88 |
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@HDDMark , as terahertz said, your voltage drop is not normal... Mine drops from the configured 13.45 to 13.35 with ignition, fan, heaters low beam, rear fogs, ... So check your wiring, or post a pic I got my new awg8 and forgot the pots gotta go back tomorrow...
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