Charging Question?

[EH Jeff]

I have a 2022 All-Weather model that supposedly has the upgraded alternator and battery to accommodate such. But every now and then when I start the vehicle, (Especially after sitting a day or two.) I see that the battery light on the I/C lights up for about 45-90 seconds, but the goes out. I've verified that there is no parasitic draw with the key off. Is this normal? I also noticed that the dealer added a single wire from the alternator to the I/P fuse panel. I've also read comments on a diode being installed backwards. Does this come into play here? I see that it is in the I/P fuse panel, but how do I know if it is installed correctly or backwards? Once the light goes out, I am showing 13.2-14.1vdc at the battery terminals while running. So I know that the charging system is working. But is it all working correctly? That added wire from the alternator to the I/P fuse panel has me wondering.

 

[Colderweather86]

What is the voltage before you start it?

 

[1BB]

How did you verify you have no draw on the battery?

Did you remove the neg side cable and put a voltmeter between the cable and battery post? That should read zero or dang near it, but it should not have a full battery voltage draw on it.

Since your vehicle can sit a couple days and still start, you don't have a diode problem, because if you did, you'd have a dead DEAD battery by morning. I'm pretty sure the diode trio is one piece and impossible to install wrong. Diodes are not installed individually....anymore at least.

An alternator makes three phase AC electricity, and the diodes rectify that into DC. Each phase has a pos and a neg wave, and a diode is needed for each side of that wave, and with three phases, you need six diodes. If one diode goes bad, you lose one third of the power of your alternator, but more importantly you have a dead short that kills your battery as fast as leaving the lights on all night. Since you don't seem to have a dead battery, that tells me your alternator "SHOULD" be fine.

While I don't know EXACTLY how this system is setup, the principle is generally the same. The alternator will NOT start charging until the rotor is excited. It only takes a very small amount of power, amperage, to excite the rotor, and when it's excited, that creates the magnetic field that passes through your stator's magnets, and it starts producing your working power.

The light on the dash comes on when it's not charging, and that generally means the rotor is not being excited since it sounds like the alternator is working, just not right away. What causes that delay, I don't know for certain without looking at it, but if I was to venture a guess, and taking into account you're in the cold state of Wisconsin and it is winter, I used to live there so I know, and you say this happens after sitting a while, I'm thinking that "MAYBE" it's your battery.

The cold takes A LOT out of your battery, while at the same time your engine is requiring MUCH more to get it started. Then you have the electrical preheater going, and then you're cranking the engine, and all this takes its toll on your battery. Your battery voltage "MAY" be too low for that 45 seconds, to provide enough voltage to cause your regulator to excite the rotor, and start the charging process.

It may be that after your battery catches its breath, so to speak, for that 45 seconds, that only then does the battery voltage return to the level needed to excite the rotor, and allowing your alternator to start producing power. Until that happens, your dash light will be on.

What that wire is that the dealership added....that I would be asking them. If you do ask them, please come back and share what their reason is for doing this. I'm really curious as to what they say.

 

[EH Jeff]

Thanks for the detailed reply. As a H/D diesel technician of 40+ years, I fully understand the points that you make. I have done all the parasitic draw tests, charging system tests, ground tests, battery/charging system load tests, voltage drop tests, etc. All checked out ok. That's what prompted me to make my original post. It's just puzzling that this is intermittent on a new unit with the upgraded alternator and new heavy duty battery to match. In all my years, any one of the tests that I performed usually gave me a venue of a fault of some sort. The only thing I have left to investigate is the possibility of the ignition switch not completely opening all circuits with the key off. That's one thing that was always hard to put your finger on especially when the issue is intermittent. I won't rule it out even though it only has 100 miles on it. I just have to keep testing daily before every first morning startup. As the MUTT sits with everything turned off, my parasitic draw is only .9mv, which is quite amazingly low compared to the standard .7v accepted max value. I'll keep you all posted as I track this ghost down.

 

[motormd]

Mine just started doing the alt light. It only started doing this once it got cold enough to trip the intake heater.
And it does it for 30 to 45 seconds, or less if I rev the engine. I think the battery drops below a preset voltage and it takes the alternator a little while to charge beyond that. I will put a meter on it and see what that heater draws, and watch the voltage after starting.

 

[WY_ROX]

Mine has also started doing the same thing, as stated above. It’s only recently started as the intake/grid heater has been turning on due to the cold.

 

[motormd]

Reference voltage before starting was 12.85, which is very good, anything over 12.6 indicates a fully charged battery. Temp around 45.
Battery was also tested with a PBT-100 conductance tester and came out good at the 750 cold crank level.
This is on a 2022 model Roxor. Turn key on and see the grid heater light activate, lights are in the off position, and I can hear the fuel pump.
I don't crank engine at this time. I then recheck the voltage.
Battery voltage has dropped to 12.3 volts, so a pretty substantial draw. Start engine, alt light stays on. Meter reads 14.05 volts,alt light still on.
When the voltage reaches approx 14.15 to 14.20 alt light goes out. I was in and out of the vehicle to read alt light and meter, so might be off by a tenth of a volt.

 

[lost1wing]

Mine did this today. 65f outside yet it still took 30 seconds for the GP light to go off. After starting it, the battery light remained on for 20 seconds or so. That brought me here to see if others have seen this as well. I think that convinced me to install a volt meter. I saw the cluster they make for this. I may give it a try.

 

[lost1wing]

The owners manual states the battery light could remain on for up to 120 seconds during colder temps. I'm done wondering why the light stays on for a while.