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Turtle at Half Charge Under Load?!?!?!

Posted: Tue Mar 12, 2019 11:06 pm
by Graveaxis
The turtle light is coming on, on my way home going up hill. I took the car into the dealer and they seem to think its a DC/DC convertor. I was under the impression the light was related to the traction pack. The car has had no problems charging to all 16 bars. We have seen a range drop, but I don't have any hard numbers. The dealer wants ALOT for the DC/DC convertor. You Guys have any Ideas! This is the video of the problem https://youtu.be/EQWfFRi5zgA

Re: Turtle at Half Charge?!?!?!

Posted: Wed Mar 13, 2019 1:07 am
by dracekvo
Dealer not check cells voltage?

Re: Turtle at Half Charge?!?!?!

Posted: Wed Mar 13, 2019 2:44 am
by kiev
Please add "under load" to your subject line.

Usually if turtle mode is triggered, it doesn't turn off until the pack is re-chargged. But in your case the light comes on under high load with a full throttle and with the Heater ON, then turns off when you release the throttle.

Try again with the heater OFF just to see if that affects the response.

But it is likely that one cell is lower than the rest and hitting the low voltage limit during the high load periods, then recovering up above the limit when the throttle is released.

You would need to use one of the cell voltage reading apps for android or iphone to watch the cell voltages and determine if you have a weak or worn out cell, or the entire pack is out of calibration.
Maybe try a calibration charge session to see if that affects it also.

[EDIT]
p.s. ask the dealer what diagnostic trouble codes were showing up when they connected the MUT tool--we can look up the meaning and the troubleshooting sequence.

Re: Turtle at Half Charge Under Load?!?!?!

Posted: Wed Mar 13, 2019 8:51 am
by JoeS
Graveaxis, sorry to hear and thank you for posting your video.

Yes, "under load" is important information and I modified the title to reflect that.

What year and how many miles does your car have?

I note that the outside temperature was 32°F at the time you took the video.

Totally agree with kiev's assessment and simple first step to address the issue.

An app which shows cell voltage is the primary tool you need to diagnose this problem.

As a side note, it is disturbing that the dealer's first (kneejerk) reaction was to want to change the OBC/dc-dc ... this perhaps becoming the most common i-MiEV failure? :roll:

Re: Turtle at Half Charge Under Load?!?!?!

Posted: Wed Mar 13, 2019 11:04 am
by Graveaxis
The light will come on with less load and no heat at a lower state of charge. I don't understand how the dc-to-dc converter has anything to do with battery voltage drops under load. I'm going to the dealer today to get the powertrain codes. The car is mostly charged on level one overnight. About two days a week it is drawn down to two bars. Temperature obviously assertives the situation.

Re: Turtle at Half Charge Under Load?!?!?!

Posted: Wed Mar 13, 2019 11:21 am
by JoeS
Graveaxis wrote: I don't understand how the dc-to-dc converter has anything to do with battery voltage drops under load.
The OBC/dc-dc doesn't. Edit: this could be wrong - see kiev's comments two posts down.
Graveaxis wrote:The car is mostly charged on level one overnight. About two days a week it is drawn down to two bars.
I'd be inclined not to take her down that much if you can help it. Do get an app and bluetooth OBDII adapter asap and measure those cells so you can better assess the situation yourself and see if repeated full-charge balancing is helping any. How many miles on the car?

Re: Turtle at Half Charge Under Load?!?!?!

Posted: Wed Mar 13, 2019 2:58 pm
by Graveaxis
The code is obd dtc 39 PFC output voltage fail
Or obc dtc 39 PFC output votltage fail. Kind of hard to understand him over the phone. I'm going to order a scan tool are you guys mentioned before. My current OBD 2 reader doesn't seem to work on the car. The technician was under the impression the turtle light could come on because of low voltage on the 12 volt battery. I asked them if they could draw the battery down and then do some real time capture on the battery cells. They recharged the car to full...

Re: Turtle at Half Charge Under Load?!?!?!

Posted: Wed Mar 13, 2019 6:20 pm
by kiev
What is the age and condition of the 12V aux battery--is it the original OEM or has it been changed, etc.? We have a separate thread devoted to troubleshooting the OBC/DCDC Converter with lots of detailed information in post #2 about testing the 12V aux battery.

i would have expected to hear that they found a P-code DTC, such as P0A09 or P0A10, which are codes for something wrong in the DCDC converter.

The OBC code 39 is a very specific sub-code related to the Power Factor Control circuit located in the upper plenum of the On Board Chargger which creates the high voltage necessary to recharge the pack. It has nothing to do with the operation of the DCDC.

The DCDC converter is located in the bottom plenum of the OBC box and it uses HV from the pack to create the 12V needed to recharge the aux battery and supply the 12V loads while in READY.

But here is one idea, if the DCDC is pulling a high current from the pack in order to try to charge a weak, worn or failed aux battery, then it may be that the pack is getting pulled down to "turtle" voltage level whenever the throttle is pressed, which sends HV current thru the Motor Control Unit. The combined current load may be pulling the pack voltage down. The voltage rises when the load is released so the turtle doesn't stay set.

Re: Turtle at Half Charge Under Load?!?!?!

Posted: Wed Mar 13, 2019 10:59 pm
by Graveaxis
The car has about 54,000 miles. It still got the original battery. I'll see what the replacement cost is maybe throwing a battery at the problem wouldn't be a bad idea. I ordered the Bluetooth scan tool recommended on here. We've had the car for about 40,000 miles and it has been a rockstar! Only thing I wish I could change is the color. The used car factory seems to only produce purple 2012 I-miev's.

Re: Turtle at Half Charge Under Load?!?!?!

Posted: Thu Mar 14, 2019 4:47 am
by kiev
Graveaxis wrote:The car has about 54,000 miles. It still got the original battery.


i would bet that your problems will go away when you replace the OEM aux battery. Put the money for the obdii tool toward a new battery. i hardly ever use my scantool, but i use that battery every day...