Hi,
I recently plugged in a voltmeter to help keep an eye on the battery.

Something I noticed, that I did not expect, is that the voltage seems to fluctuate while driving its either around 14.4v (i thought it should always be around this while the car is running) and then other times, dips down to 12.x Volts (like the alternator is not running)

When it does dip to 12.x Volts, I can always make it go back to 14.4v by adding some load, e.g, turn on the lights, or heated screen.

If i'm driving around 50mph, then normally its 12.x, if i take my foot off the accelerator, it jumps back to 14.4v..

Does this indicate some kind of fault with maybe the alternator or Voltage regulator.

As is normally the pattern, we always get issues with the car whenever its serviced.

Thanks for your Help,
Keith.

 

yes perfectly normal.

The ELD controls/adjusts the amperage outputted by your alternator depending on the load seen by the ELD.

 

Hi,
Yes, I would expect the ELD to manage the current, but I always thought the voltage would be constant ?

 

voltage = current (amps) x resistance

current goes up voltage goes up
current goes down voltage goes down

 

Cool. So what I see is expected ?

I was comparing to our Nissan. That seems to be constantly at 14.3v all the time the car is running.

From what I understand. This ELD thingy is a Honda thing that changes the voltage, depending on load, when the alternator is running ?

Thanks.

 

The Honda ELD operation is kind of hard to predict. It's purpose is to drop the voltage (and alternator load on the engine) when it figures the battery is charged and other electrical loads are small. GM and some other brands also use a similar systems on some of their vehicles.

 

It is indeed very hard to predict.

Its behaviour probably explains why my battery keeps dying.
From what I understand, to maintain a 12V battery, the charge voltage has to be 13+ volts.
For my journey each day, i rarely see it go above 12.6V

Most of the time i'm stuck on a motorway with 50mph restriction. The only time I see 14.4V is if i let off the gas pedal, or if I turn on the heated screen, or have something extra turned on using some power.

Otherwise, I need to get the revs above 2500rpm (~60-mph)

When I come to a stop, and the engine idles, its still 12.x volts. If i turn of the heated screen and then turn it off, I see 14.4v and it stays at 14.4V - until i started driving, then drops again.

Only thing I can think of, is that the car thinks the battery is fully charged.
Each morning its about 12.3v (~63% charged)

Very strange

 

I monitor the voltage in my CR-V.

In my car, the voltage stays at ~14.5 for a good 20 minutes (all speeds of driving) before the ELD lets it drop back to 'run on the battery' (12.6V).
If the A/C is engaged or the headlights are on, the voltage stays over 14V.



Perhaps you should invest in a new ELD... it's not too expensive at ~$30 USD.

#11 in the diagram below for our '07.

 

One of the things that confuses the ELD is improperly attached add-on electrical devices. If an electrical device is added and wired directly across the battery, it's current draw will not be sensed by the ELD. This will over time result in the battery's charge not being maintained.

 

I also assume that this is why I see the headlights 'flicker' sometimes when i drive in the dark ?

I was convinced there was a loose connection somewhere

 

On mine the voltage stays above 14 if I turn on the AC in traffic.. And yes the headlight flicker exactly matches when the ELD kicks the juice up or down.. If I turn on the fog lights with the headlights it doesn't drop the voltage either..

 

I have a ScanGuage2 and have noticed voltage changes as well. Mine typically stays in the 13.6-14.5 V range in the first 10-15 min of driving, while the battery gets recharged, and afterwards I've noticed it dropping as low as 12.6 V. Also the headlight flicker when stopped at a red light or coasting in neutral. It's part of normal operating conditions, nothing to worry about. I think these "tricks" are meant to help with fuel economy.

However what I find more troubling is your above statement.
Do you care do explain that in further detail?
Maybe you need to find a new mechanic...

 

Honda cars use batteries that are unusually small compared to most. They could be more sensitive to overcharging due to small size. 12.8v is considered fully charged at about 80F. So, a voltage as low as 12.6 would not be a bad thing, assuming it goes up to at least 14 when needed. I have noticed such fluctuations myself. Battery life has been good (6 years) with my car.