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Found this thread very interesting, but it's crazy to realize that hardly anyone understands the elementary ohms law and the elementary basics of Voltage, Current, Resistance. To me, it should be obvious that if you have smaller guage wires like that found in the ELD wiring, that you are not pulling much current through them, so putting a 40A or 30A rated relay is just simply overkill and only for convenience as they are readily available to purchase and easy to connect.
What I've learned from this thread is that the PCM ultimately decides when to "tell" the alternator to output voltage and NOT how much voltage to put out as that is a factor of the internal regulators. We are simply tricking the PCM into thinking the current demand has gone up in the vehicle and that it should react to assist with that increased demand by triggering the alternator to charge the battery as well as supplement the power. The PCM contains code that looks at various inputs and has the logic to determine when to trigger the alternator to output. We are just manipulating one of those inputs in an attempt to force that output.
It's been a while, and I wanted to return to this subject. I would like to be able to drive in the daytime without having to turn my headlights on, but my understanding is that the ELD bypass doesn't work for 9th gen cars like my 2012 Civic LX, and later models. They have an ELD, but apparently other inputs to the computer also affect the alternator voltage, so the 820-ohm resistor doesn't work. At least I haven't found any report that anyone was able to make it work. I haven't tried it on my car because getting access to the bottom of the fuse box appears to be a major undertaking which I would rather not undertake unless I can be pretty sure the mod will work. If I'm wrong about the bypass not working for later models, I hope someone will correct me, and direct me to a link.
There are two mysterous sensors on the negative battery terminal. I think one senses current into and out of the battery. I don't know what the other does. Is it possible that either or both of these sensors affect the alternator voltage?
Then there is the alternator. I was hoping for a three-wire ot four-wire connection, but instead I see a single control line, which I assume means it's CanBus. So I was thinking perhaps it would be possible to perform a man-in-the-middle attack on the alternator, inserting an Arduino-based controller into the CanBus line. It would receive the control messages from the computer, and pass those along to the alternator, but never pass on instructions to go into low-voltage mode.
Actually, I also wondered whether there might be a way to just change the voltage level of low voltage mode - so it would be, say, 13.2V instead of 12.4V as mine is. Then I think the battery would stay charged and not die quickly as it does under the Honda dual mode system - unless you keep the headlights on.
Well, I just wondered if I had missed the solution to this problem. I also wondered if this problem persists with the new Hondas. If so, I might need to see if Toyota or Hyundai models are free from it. Shame on Honda for getting their MPG ratings at the cost of frequent battery replacement. I guess the economics work for Honda, but they certainly don't for the customer.
Originally Posted by keep_hope_alive
I still haven't bothered to dig further into the 9th gen ELD bypass, but i'm starting to get annoyed at the low output voltage and may be enticed into developing the bypass this winter (at 195k mi.).
I have been looking into a way to keep my voltage up around 14V for my 4th gen Honda CRV (2012). It also has a one-wire LIN controlled alternator like the 9th gen accords. I tried disconnecting the ELD under the fuse box, but it did not have any noticeable effect. Voltage was still dropping to around 12.3 while the car is running, and only going up to 14 with the headlights on. I think the PCM has a lot more inputs for alternator control other than the ELD. Surprisingly, I didn't get any codes with the ELD disconnected. It looks like there has been some success online with tapping into the battery voltage and shunt connector on the negative terminal of the battery harness. I haven't tried anything yet, but it may be possible to trick the PCM into thinking the battery isn't fully charged by doing something inline there. Would probably be a lot easier than taking that damn fusebox apart.
ELD 2007 accord lx 2.4
