Any expertise here on the Honda Dual-Mode Charging System? - Page 1
Forum section: electronics / general

author: Peabody
author_rank: Super Contributor
timestamp: February 09, 2021, 11:19:36 pm
content: Honda autos have something called the Dual-Mode charging system, which sets the alternator at 14.4V when heavy electrical loads are present, but drops it back to 12.4V otherwise. The 12.4 V level leaves the battery only partially charged - about 60-70% - and I assume the thinking is that so long as it will still start the car, there's no point wasting gasoline keeping it charged any higher than that. Unfortunately, a partially charged lead-acid battery will soon sulfate up and fail. I had to replace the battery on my 2012 Civic twice over about five years. So any benefit Honda gets from quoting high MPG numbers is paid for by the customer having to buy a new battery much more frequently than necessary, now at $150 a pop.So I've taken to driving with the headlights on, even during the day. That keeps the battery charged. But I was hoping to find a way to defeat the Honda system, and keep the alternator at 14.4V as God intended, so I won't have to waste gasoline on the headlights.Earlier models (Civic 8th gen) could be hacked with the "ELD bypass", which consisted of strategically inserting an 820-ohm resistor into the Electronic Load Detector circuit in the fuse box, but apparently this no longer works on 9th gen and later cars. I was thinking of simply hacking the alternator, but it is now controlled over CAN bus, so that doesn't seem promising.Well, I was hoping to find someone who had solved this problem, or maybe a Honda engineer who could offer a solution.

author: bdunham7
author_rank: Super Contributor
timestamp: February 09, 2021, 11:38:55 pm
content: I can't think of a hack that wouldn't have unwanted side effects. The ECU controls the alternator field directly, IIRC, and any tampering with the ELD to fool it will likely trigger fault codes and warning lights. But I think headlights are the best solution anyway--studies show that daytime headlights reduce accidents slightly and the amount of energy needed to run them is pretty small, probably less than the power that will go into the additional charging of the battery.If you still want to change it, you need something like FlashPro to go into the ECU and simply turn the option off.

author: amyk
author_rank: Super Contributor
timestamp: February 10, 2021, 01:18:47 am
content: Something likehttps://www.backyardmechanic.org/how-to-build-a-external-voltage-regulator-for-dodge-jeep-chrysler/?

author: Peabody
author_rank: Super Contributor
timestamp: February 10, 2021, 04:54:02 am
content: FlashPro is $695, which is completely out of the question.

author: nali
author_rank: Frequent Contributor
timestamp: February 10, 2021, 08:59:42 am
content: Interesting, I too drive a 9th Gen Civic and I hadn't heard about that. So I took mine for a run this morning and as you say 12.4V. Then I had a thought and checked the ECON mode which was on... turned it off and went for another short drive and guess what, the battery was at 15V!So, it appears to be one of the subtle effects of ECON mode (which AIUI also backs off the aircon and changes the throttle map at least while on cruise control, not sure about normal driving).Have you triedcivinfo.comwhich is a pretty good repository for Civic nerds?

author: tom66
author_rank: Super Contributor
timestamp: February 10, 2021, 09:23:56 am
content: My Golf cycles the battery up to 15.2V and back down to 13V or so, although it's a hybrid which doesn't use the lead acid battery to start the engine.

author: NiHaoMike
author_rank: Super Contributor
timestamp: February 10, 2021, 01:14:25 pm
content: Get a solar charger or plug in charger for it?

author: Peabody
author_rank: Super Contributor
timestamp: February 10, 2021, 03:29:08 pm
content: Quote from: nali on February 10, 2021, 08:59:42 amECON has no effect on my Civic alternator voltage. But you're in the UK, and I think this may be only a US thing. My memory is that Canadians don't have the problem, so maybe UK as well. Anyway, I never have ECON on, and still have to turn on the headlights to get the voltage up.Thanks for the link. I'll give it a try.

author: bdunham7
author_rank: Super Contributor
timestamp: February 10, 2021, 03:37:41 pm
content: Quote from: Peabody on February 10, 2021, 03:29:08 pmThose places have mandated DRL. Does your car have DRL activated?

author: Peabody
author_rank: Super Contributor
timestamp: February 10, 2021, 03:51:39 pm
content: Quote from: bdunham7 on February 10, 2021, 03:37:41 pmDRL is on all the time on mine. There's no way to disable it, at least not officially. In any case, it still charges at 12.4V with DRL on.Quote from: NiHaoMike on February 10, 2021, 01:14:25 pmYes, I have a 1.5A "maintainer" that I use when I forget to turn on the headlights. But I shouldn't have to mess with that every time I drive back into the garage. What's needed is for Honda to give me the option of turning off the Dual-Mode system, and have it charge at 14.4V all the time. But they aren't going to do that, and I suspect my next car won't be a Honda. Hopefully other makes don't do it this way.

author: nctnico
author_rank: Super Contributor
timestamp: February 10, 2021, 05:57:58 pm
content: Quote from: Peabody on February 09, 2021, 11:19:36 pmIn general it is recommended to turn the headlights on during the day for safety. My guess is that Honda considers having the headlights on during driving as standard; just be thankful they force you to make participating in traffic safer.

author: bdunham7
author_rank: Super Contributor
timestamp: February 10, 2021, 06:06:08 pm
content: Quote from: nctnico on February 10, 2021, 05:57:58 pmIn Europe, UK and Canada, yes. Here in the US the NHTSA concluded that DRL does not improve collision statistics appreciably and they actually banned full-power DRL at one point because of concerns that it would interfere with the discernability of the turn signals in certain lighting conditions. Having driven a lot on 2-lane rural highways before moving to the vast metropolis that I now live in, I have to disagree with the NHTSA position. Headlights are a big help, especially on grey overcast days on those two-lane roads. Anyway, here in the US headlights on is not standard and Honda considers the half-power DRL as normal operation. On cars that turn the headlights off automagically when you turn the car off, as all three of mine do, you can just leave the headlight switch on all the time. If you don't have that feature, you have to remember to turn them on and off all of the time, which is probably why the OP is annoyed.

author: coppice
author_rank: Super Contributor
timestamp: February 10, 2021, 06:13:13 pm
content: Quote from: bdunham7 on February 10, 2021, 03:37:41 pmIn the UK the DRL regulations started for new type approvals in 2011, so most 2012 cars, like the Honda Jazz we have, don't have DRL.

author: tom66
author_rank: Super Contributor
timestamp: February 10, 2021, 06:56:37 pm
content: I drive with headlights on all the time, with the exception of very clear days with excellent levels of light. Since the UK is predominantly rainy, overcast, or foggy -- sometimes all three -- the headlight switch rarely moves from its 'on' position.

author: thm_w
author_rank: Super Contributor
timestamp: February 10, 2021, 09:17:32 pm
content: Sounds like it should be a bit higher, 12.6V:https://www.civicforums.com/forums/181-8th-9th-generation-civic/369269-alternator-12-6-volts-unless-lights.html

author: nali
author_rank: Frequent Contributor
timestamp: February 10, 2021, 09:21:40 pm
content: Just doing a bit of searching this does seem to be a US thing. Apparently there is a charging mode input to the alternator and disconnecting it forces the alternator into "conventional" mode.Here's a link where you'll find wiring diagrams should you want to go poking around in the engine bayhttps://drive.google.com/drive/folders/1oB5uVTd8aZKrcxAtC7S3L3zIgehH_sh2

author: Peabody
author_rank: Super Contributor
timestamp: February 10, 2021, 11:20:33 pm
content: Yes, I'm afraid I have the LX model, not the EX, so I have to control the headlghts manually. I can't just leave the switch on. Driving in daytime with headlights on is not something seen often in the US. But almost all cars now have DRL.I would even accept the low voltage mode being something like 13.2V, or even 13V, at least high enough that it doesn't actively drain the battery down to 12.4V as the current system does.Well, there doesn't seem to be an affordable solution other than the headlight solution. I've been unable to find an explanation of how the current system actually works - what sensors are involved, etc. I'm not above mounting a man-in-the-middle attack on my alternator, but I would need to know how that all works. And I wouldn't want to be generating all kinds of error codes.

author: bdunham7
author_rank: Super Contributor
timestamp: February 11, 2021, 01:30:22 am
content: Quote from: Peabody on February 10, 2021, 11:20:33 pmUnfortunately, I don't have a model-specific wiring diagram for that car and I can't find one online offhand. Perhaps if you sign up for an Alldata or Mitchells per-car manual (I don't think the cost is very high) and obtain a wiring diagram, I could give you some ideas about how to circumvent the system.