Turtle and EMU lights

I'm putting this in General Tech Discussions because I don't have a clue what the nature of the problem is, or if there is in fact a problem. Did a search from within and from outside the forum and got no joy.

Two days ago I took a local trip that would be just within my comfortable range in nice weather. But it was in the low 30s (°F). At one point on the way out I caught a glimpse of the yellow turtle light while I still had probably 12 bars. It was brief, happening on the highway at around 50+ mph, maybe slightly uphill, and caused no effect on throttle response. I thought it was strange and that I should look into it later, but promptly forgot about it.

When I returned home (after bringing the charge down to under 2 bars) I plugged in and walked away. Came back later and found the EMU light (car outline with exclamation point symbol) was on, but the car was charging normally. Checked a few more times and the EMU light was still on, but the car was still charging normally.

Checked yesterday morning, all warning lights off, seems perfectly normal. Checked coolant level, it's above the "Low" limit. Left it sit, checked again this morning, still looking normal. I took a look at battery status in Cani0n, and all cells are between 3.99 and 4.00 V.

Like nothing ever happened.

Should I be worried?

You didn't say what model year and mileage (odometer) on your car? Have you been driving every day or has the car sat for long stretches?

What is the age and condition of the 12V starter battery? Is it the OEM or been changed? Do you keep it fully charged if not being driven frequently? An old, weak or worn out battery can cause a multitude of issues and throw fault codes and EMLs.

Did the car fully charge to 16 bars?

Getting a turtle when accelerating hard such as up a hill can happen if one of the cells is weak and out of balance with all the rest, and drops voltage below the cutoff limit. It usually happens more at lower charge levels such as between 2 and 8 bars. You might be able to trigger it to occur again by making some wide open throttle acceleration runs.

A weak cell has less capacity than all the rest, and it's voltage will fall quickly under load, and rise back up quickly when charging. At full charge a weak cell will not show up in the cell voltage graph; take a look at them again with the pack down to 8 and 2 bars.

kiev said:

You didn't say what model year and mileage (odometer) on your car? Have you been driving every day or has the car sat for long stretches?

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Sorry, 2012 (12/11 build), 39.4k miles. The car gets mild but frequent use, almost never sitting for more than a day between shortish trips.

What is the age and condition of the 12V starter battery? Is it the OEM or been changed? Do you keep it fully charged if not being driven frequently? An old, weak or worn out battery can cause a multitude of issues and throw fault codes and EMLs.

Click to expand...

Hadn't thought about that, since it's never had an issue booting up since I replaced the battery years ago. My thinking was that if it boots up the DC/DC kicks in and everything's fine. And now that I think of it, it might be five, even six years old now.

Did the car fully charge to 16 bars?

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Yes. If I hadn't happened to be in the garage and see the EMU light on, I would have no indication there was any issue. (Except for the brief turtle light, which I quickly forgot.)

Getting a turtle when accelerating hard such as up a hill can happen if one of the cells is weak and out of balance with all the rest, and drops voltage below the cutoff limit. It usually happens more at lower charge levels such as between 2 and 8 bars. You might be able to trigger it to occur again by making some wide open throttle acceleration runs.

A weak cell has less capacity than all the rest, and it's voltage will fall quickly under load, and rise back up quickly when charging. At full charge a weak cell will not show up in the cell voltage graph; take a look at them again with the pack down to 8 and 2 bars.

Click to expand...

Well, I rarely have the power needle (energy use indicator) much past vertical, so there was no heavy throttle involved. Maybe a moderate load combined with the cold weather would stress a cell. Since the car seems to be eerily normal otherwise, I'm inclined to take it out, do as you suggest and see if I can get a cell to sag. Doing that at a lower SoC might be a challenge, since I'd rather not be too far from home. (And getting my phone to stay paired to my LX OBDII dongle has been problematic too.)

I also think I need to resolve this quickly. Assuming my car was first sold in 2012 (and the warranty period begins at date of first sale), my 10 year pack warranty is ending soon. Though as I recall, that only pertains to not being able to charge it up completely? If true, a weak cell wouldn't fail a pack and I'm out of luck.

ctromley said:

kiev said:

What is the age and condition of the 12V starter battery? Is it the OEM or been changed? Do you keep it fully charged if not being driven frequently? An old, weak or worn out battery can cause a multitude of issues and throw fault codes and EMLs.

Click to expand...

Hadn't thought about that, since it's never had an issue booting up since I replaced the battery years ago. My thinking was that if it boots up the DC/DC kicks in and everything's fine. And now that I think of it, it might be five, even six years old now.

Click to expand...

Click to expand...

Possibly 90% or more of the unusual and hard to eliminate problems experienced with these cars can be traced to an older, weak 12 volt battery - Yes, it still boots up the car just fine, but often times when you replace the battery, your oddball problem magically disappears

Just as an update, I haven't had much time to mess with this, but the car seems OK. Not sure yet because I can't get Cani0n to stay paired to my phone to save my life (Samsung Galaxy S7, OBD Link LX, works fine with the OBD app in my RAV4 and with the OBDZero app). OBDZero isn't great graphically or for watching battery activity in real time, but it records. Now I have to transfer some files and play with Excel. More time.

In the meantime, the worst the car has done is flash a brief turtle on a partial charge with heavy throttle in low 30s weather. I haven't seen the EMU light again. The car feels perfectly normal.

Don said:

ctromley said:

kiev said:

Hadn't thought about that, since it's never had an issue booting up since I replaced the battery years ago. My thinking was that if it boots up the DC/DC kicks in and everything's fine. And now that I think of it, it might be five, even six years old now.

Click to expand...

Click to expand...

Possibly 90% or more of the unusual and hard to eliminate problems experienced with these cars can be traced to an older, weak 12 volt battery - Yes, it still boots up the car just fine, but often times when you replace the battery, your oddball problem magically disappears

Click to expand...

So this has me curious. Is it low battery voltage before the DC/DC kicks in? Which means I can tell if it's an issue with a simple voltage check? Or does a tired battery sag too much from inrush current to the DC/DC when the connection is made?

Or should I just stop thinking about it and pay the $80 for a new battery? (I'm guessing that's the answer.)

ctromley said:

...So this has me curious. Is it low battery voltage before the DC/DC kicks in? Which means I can tell if it's an issue with a simple voltage check? Or does a tired battery sag too much from inrush current to the DC/DC when the connection is made?
Or should I just stop thinking about it and pay the $80 for a new battery? (I'm guessing that's the answer.)

Click to expand...

Before you do anything else with the 12v battery, after the car has been sitting overnight and before turning anything on I would lift the hood and make a simple voltage check directly at the 12v battery terminals. Then, go into the car and turn the key to the first notch and take a reading, then turn the key further to the second notch just before it goes into READY and see what the voltage reading is to see how much sag exists. After that, turn the key to go into READY which activates the dc-dc. Make sure you have a calibrated DVM.

For reference, I just went into the garage and measured the old (5 years?) 12v FLA battery in my wife's i-MiEV that was been sitting for about 30 hours since it was last driven with the garage around 50°F:
Initial measurement: 12.57v
(I had to open the door to open the hood but the dome light had extinguished a couple of minutes before the reading with door closed)
Opening door and dome light lit: 12.27v
First key position: 12.06v (radio turns on)
Second key position: 11.76v (seat heater switch is on and fan runs as well as radio as well as other car systems)
READY: 14.56v
My take: I was surprised to see it sag this much and will probably install the AGM that I recently pulled out of my i-MiEV (when I put in the NOCO LiFePO4)

The condition of the 12v battery should have no effect on the turtle you've been seeing.

Follow-up/resolution:

I did check the 12V battery as JoeS suggested, and all seemed pretty normal. On another forum a kind member clued me in that CarScanner includes a profile for the i-MiEV. I downloaded it and it's stable with my phone.

It doesn't have a real-time graph of battery voltages, but it does have values for lowest battery voltage and highest battery voltage. And the free version lets you graph 2 variables in real time. So I let the SOC drop to around 50%, setup CarScanner and did some full throttle runs. I never got a difference more than .2 volts.

So while I have no idea why I got an EMU light while charging (and it still charged), everything seems to be working fine now. So I'm going to drive it as if everything is fine. If that changes I'll do another update.

Thanks for all the help!