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2013 Honda Accord - Battery Voltage Fluctuates

20K views 11 replies 7 participants last post by  keep_hope_alive 
#1 ·
I've been monitoring the battery voltage through my OBD2 sensor. While I'm driving, the battery voltage moves from 14.1 V to 12.5 V. It's not constant or follows a pattern. Sometimes it'll stay at 14.1 V. Other times it'll bounce between these voltages or stay at 12.5 V. Is this normal or is there something wrong with the alternator?
 
#3 ·
The ELD (Electrical Load Detector) has been around since the early 90's. Basically if there is low current draw from the electrical system, the alternator is commanded to charge in low mode. If the current draw from the Electrical system is higher (AC on, headlights on, defroster on...Etc) the alternator is charging in high mode.

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#4 ·
I've been monitoring the battery voltage through my OBD2 sensor. While I'm driving, the battery voltage moves from 14.1 V to 12.5 V. It's not constant or follows a pattern. Sometimes it'll stay at 14.1 V. Other times it'll bounce between these voltages or stay at 12.5 V. Is this normal or is there something wrong with the alternator?
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IMO this ELD is exactly why these batteries die so soon, especially the 51's. Low capacity and the one step forward, two back way of charging the battery. I NEED to drive my daily route with the headlights on always since my 15 mile trip would NEVER go to 14.4 Volts, during the trip if I didn't.

Idle in Park, No lights, 14.4 volts. Drive with no lights 12.6 V. Drive and Turn lights on, 14.4 V. Route is 5 miles stop/go (suburban) 10 miles 65 MPH expressway, no traffic slow downs ever.

It (ELD) saves on gas and HP, but blows it in extra charging, new batteries every few years (earlier than necessary), aggravation.

That's the way it is though.

My suggestion to you is to run with the lights on at all times especially if there is not enough miles in your trips to charge the battery properly at 12.6 V.
 
#6 ·
What's funny to me is, I just bought one of those little battery voltage indicators that just plugs into the charging port. Just as OP described, I've noticed that it fluctuates between 12.5v and 14.5v randomly, with no rhyme or reason.

Reading this thread explained why, so thanks peepz! :nerd
 
#7 ·
This thread caught my eye several days ago and I finally found my Elmscan OBD-II device. I made a 10 mile round trip today and monitored the control module voltage as well as the adapter voltage. The voltage at the adapter (and would imagine this is the same as you'd see at the 12V accessory outlet / cigarette lighter) was a constant 14.3V. The control module adapter bounced around a little between 13.8 and 14.3V. I checked with different current draws - headlights, A/C fan, audio system all in different variations of on and off from all off to all on at once and while driving as well as idle.

Never dropped below 13.8V. I understand that voltage and current output are regulated intelligently by a control module but if charge voltage drops to 12.5V, then that is essentially no charging at all. That wouldn't be enough to overcome the electromotive force needed to push electrons into the battery.

I'll continue watching mine for a few days to see what it does and post back. It's kind of wild that Honda would allow the battery to ever be in a discharging state for any length of time.
 
#12 ·
it is not uncommon to measure a voltage drop at the power port in the dash relative to the battery. the factory wiring is small and will have measurable voltage drop.

yes, our alt is controlled by the ECM and regulates output at 12.5VDC to match the battery float voltage and reduce the load on the engine by the alternator.

with headlights on it jumps to 14.4VDC to resolve the dimming issues people use to report on older generations.

when braking or coasting, it jumps to 14.4VDC for "regenerative" effects.

i have a few youtube videos demonstrating this.
 
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