onceover

I've been letting my car sit for about a week at a time without driving it. The battery is only a couple years old, but it seemed to have trouble turning the car over after sitting. I would take it for a 5-10 minute drive to try to charge the battery up a bit occasionally.

At first I thought it was some electrical gremlin that was causing me issues, but this happened a couple times now and I believe I've narrowed it down to the charging system.

While driving around waiting for the oil to warm up I try to keep it down below 3k RPM. While driving around the past couple times, the electrics have started shutting down. First the radio will shut down, then the lights will look dim, etc. The car started to stutter, and in a panic I have it a good rev to clear it out. Lo and behold, everything came back to life and worked perfectly. I've managed to repeat this exact behavior a few times.

It's almost as if the alternator charging circuit doesn't engage until the engine revs above a certain threshold. I haven't confirmed this with a multi-meter yet, but I'm pretty much certain it's the case. Has anyone seen similar behavior? (Side note, I do have an RS alternator/fan pulley installed, but seeing as everything comes back to life, even at idle, doesn't lead me to believe this is the issue)

mojorizing

You're right - the charging rate is a function of rpm. See spec sheet my replacement alternator from Vertex (IIRC). The voltage regulator needs to output 13.5-14.5 to charge the battery. This alternator setpoint is 14.6vdc. I believe the "turn on speed" is the minimum speed for meaningful output. Definitely check the capacity of your alternator, but I think you'll find it within spec. I think you need to drive faster and longer or get a battery mainainer on the car.

newsboy

You might try monitoring your voltage with a device that plugs into your cigarette lighter. If you see correct voltage, alternator is O.K. Electrical gremlins, can often be caused by bad or dying coils.

r-mm

The most likely culprit for low voltage - if that is in fact your issue - is the combined brush/voltage regulator. This part is a direct replacement and took my charging voltage from the low 13s to the mid 14s. Anything .5 volt over battery voltage is technically charging. If you have systems shutting down while driving it sounds that you have a gross failure of the charging system which could also be caused by an internal short in the alternator or other failure.

That said its always wise to start with the battery - clean the contacts, have it load tested, or buy an inexpensive load tester and do it yourself. I would also do a parasitic voltage check. Happy to walk you thru these, I did all of above on my car and it runs/charges perfectly now.

The alternator should not need to be revved over idle to produce the voltage and amperage the car needs.

onceover

Thanks all. The weird thing is that it seems to charge just fine, only after the engine is rev'd beyond a threshold. Almost as if it needs to be "switched" on to charge. Once switched, it will charge just fine at idle. This is purely anecdotal though, I'll confirm with a multimeter this weekend.

r-mm

Does the charging light on the dash illuminate with key on (idiot lights all on) and when running but not charging?

onceover

Correct. Light on on initial key on, then shuts off as soon as engine is running.

r-mm

Does it illuminate when you perceive the charging system to be malfunctioning / not woke up ? When the systems shut down?

onceover

It does not illuminate when initially driving (before "switching").

Many of the lights illuminated on the dash when voltage was very low and the car started stuttering. I'll be honest, I was in a panic when things started shutting down, so I don't recall if the charging light was one of them.

-nick

I think you might have two separate things going on. With the RS pulley, I sometimes have to rev mine up above ~2k rpm after startup for the alternator to “turn on”. I haven’t looked into the circuit as to why, likely the regulator has something built in. The RS pulley doesn’t make much juice at lower rpm in general. You need to be very watchful using it on a street car.

Sounds like you might have a parasitic drain and/or your battery is going out too. Spending time in a low charge state knocks battery life down by a ton. Using the the alternator to charge a battery back up is supposedly tougher on the alternator, but I don’t know the details why.

I would recommend putting a real battery charger and a multimeter on your shopping list at least

r-mm

I remain baffled by the RS conversion but I will zip it on that topic and try to help

onceover

Okay, it's good to hear that you have the "turn on" behaviour as well. I assume you know this because the battery light stays illuminated on initial startup and then revving shuts it off?

I do have both a smart charger and a digital multimeter, but have been absolutely swamped between work and kids and building a new garage that I have been omitting plugging the car in.

-nick

It’s a funny quirk. I only discovered it because the tiny reserve in my lithium battery quickly depleted and shut off the electrics shortly after starting a few times. Some poking around with a multimeter showed there was no charging until blipping the rpms. That makes it sound like the alternator is not getting its initial excitation- it needs some volts across the field coil to start making its own juice.

Thinking about it, it could be because I’m running an led bulb in the alternator warning light. Are you using leds, or made sure your bulb isn’t burnt out? The initial +12v excitation comes through the warning bulb to the alternator D+ post.

Most alternators self-excite at a certain rpm regardless of getting an initial 12v input. If it’s not getting its initial D+ volts, then a throttle blip would trigger it into producing volts. With the non-RS pulley it may self-excite at idle rpm.

Antigravity

Hi Pat, just a couple of things that can hopefully help along the way to figuring it out..as I think someone touched on earlier, it might be good to see if you can monitor the voltage while driving to see how well the charging system is working. We actually have a device called the battery tracker that can do this as well as log the data as it pairs up to an app on your phone wirelessly via Bluetooth and retains that data for 30 days and displays on a grid so it's a nice way to visually confirm and see if there is anything going on. Links to both chemical options below in case you'd like more info on those.
Lead Acid Battery Tracker
Lithium Battery Tracker

One other thing to touch on as well is that short 5-10 minutes drives generally are not a sufficient enough amount of time to put a good charge back into the battery..so I'm wondering if any of the issues also might have to do with the battery just being at a really low state of charge (discharged) to begin with and is just never being brought back up?
Best regards,
Chad (chad@antigravitybatteries.com)

AOW162435

I can almost guarantee that this is your issue. Replace the LED bulb with a factory incandescent and report back.



Andreas