williamjacobs

Perhaps this is a good temporary fix for diagnostic purposes. A few days of hard riding the alternator in exchange for information.
If it works, a non-ELD measured accessory is causing drain while driving. If it doesn't help, you can look for other causes. (Grounding, bad battery/alternator, fuses, etc.)

civiced

Cool. Finally in a position to advise others. First off, fix a few misconceptions. A Fixed 14.4v won't "pull current". Current is supplied by the demand of the load. The formula here is V= CxR. If the battery is fully charged, it won't draw excess current from the alternator, and there won't be a major mechanical load. There will be a bit more current (C) drawn due to the higher voltage (V), but as you can see, (R) remains unchanged. However, the main problem is that a fully charged lead acid battery shouldn't see a 14.4v source. This can result in a reduced service life. It needs a float charge of around 13.5v. This value may be left on the battery indefinitely. So, you really shouldn't defeat this charge regulation. If you must run hearing loss sound systems, change the main fuse value, and run larger gauge wiring if required. I'd tend to think this unnecessary, as the RMS wattage is vastly lower that the peak value. Any questions, I'll be glad to help, if I can.

leok99

My voltage sometimes drops below 12V at idle/low rpm and only happens after some travelling, assuming the battery is fully charged. It will back to higher voltage with higher RPM or headlight on, so looks like ELD is at work. However, when it belows 12v, looks like the alternator is completely offline and everything is on battery? is it normal?

BrotatoChip

No, that is not normal. With the engine running the battery voltage should read around 14V all the time.

leok99

Only true if you remove the ELD.

BrotatoChip

Where did you hear that? With the engine running the alternator should be charging and then keeping the battery charged. When the battery is being charged you should see 14+V, once it has been fully charged you should be seeing ~13.8V.

leok99

We're in the ELD thread and that's how ELD works.
Voltage fluctuates in our Honda but I feel mine is about 0.4-0.5V low.

BrotatoChip

After some research here's what I found:

When the circuit C voltage is pulled low by the ECM: the charging voltage at the battery will range from 12.4-12.9V. The ECM uses the low output mode when the engine is starting or if all of the following parameters are met:
-electrical Load below 15 Amps (varies with vehicle)
-vehicle speed between 10-45 mph or at idle while in drive
-engine speed below 3,000 rpm
-coolant temperature above 167°F (75°C)
-A/C Switch Off
-intake air temperature above 68°F (20°C)
Outside of these parameters, the ECM will hold the voltage on the C circuit, which will place the charging system in the high output mode. In this mode, the charging voltage at the battery will range from 14.4-14.9V.

Seth Wiget

So basically if i keep my headlights on to keepalt at 14.5v and run my system im puttin strain on alt. If i dont run lights ill put strain on battery?

BrotatoChip

If you have a large sound system you're straining the system no matter what you do.