different battery problem

[miandy]

I flat tow my lariat hybrid. It was fine for the first 6K. Now every time I tow the battery goes dead within a couple of hours. I have tried different places to power the patriat 3 brake control but to no avail. I even towed with out anything hooked up and it still went dead. Only in tow mode. Nothing left on.

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[GPSMan]

Hmm... assume you mean the 12 volt battery under the seat but you didn't say.

Here is the thing, make sure you are correctly in the correct tow mode (I've never done it.)

Funny as it sounds, you kind of need to leave the truck on. It needs to be on at a basic level so the high voltage battery can recharge the low voltage battery that runs the lamps.

And once every 6 hours, maybe every 3 hours in your case, you need to run the gas engine for 5 minutes to recharge the high voltage battery, then again reset it to tow mode.

Sounds like a great system when set up properly but I won't be doing it. As you are finding, too many chances for "glitches".

 

[MakinDoForNow]

Hmm... assume you mean the 12 volt battery under the seat but you didn't say.

Here is the thing, make sure you are correctly in the correct tow mode (I've never done it.)

Funny as it sounds, you kind of need to leave the truck on. It needs to be on at a basic level so the high voltage battery can recharge the low voltage battery that runs the lamps.

And once every 6 hours, maybe every 3 hours in your case, you need to run the gas engine for 5 minutes to recharge the high voltage battery, then again reset it to tow mode.

Sounds like a great system when set up properly but I won't be doing it. As you are finding, too many chances for "glitches".

I do not do flat tow BUT if my 12v is at 11.8v it takes approx 45 minutes to charge the 12v to 12.6v during which time the ice will cycle on 3-4 times to charge the HVB from 30% to 40%. So unless the flat tow procedure charges the HVB to 60-70% and leaves the dcdc converter active the draw on the 12v would have to be severely reduced. Does the tow mode leave the vehicle in ready state so the ice can be cycled while towing?

 

[GPSMan]

If you are asking me, I have not tried.
99.9% sure the ICE will not cycle in Tow(ed) mode. That could be a fire or CO hazard.

What I'm wondering is: will the DC/DC converter (only) stay alive to keep the 12 volt system, well, above 12 volts while being towed?

Seems reasonable the 12v battery alone would only be good for about an hour. Seems equally reasonable the 12v plus HV battery working together could power the lamps, etc. for 6 hours.

5 minutes of engine on can replenish the HV battery. The DC/DC converter could trickle charge all, or part of those 6 hour drive cycles.

 

[jsus]

Does the tow mode leave the vehicle in ready state so the ice can be cycled while towing?

According to the manual, the procedure for flat-towing involves enabling neutral tow mode and turning the ignition off, so neither the ICE nor inverter should be active.

 

[MakinDoForNow]

According to the manual, the procedure for flat-towing involves enabling neutral tow mode and turning the ignition off, so neither the ICE nor inverter should be active.

That's what I thought. What is draw on 12v while in neutral tow mode. What wifi, Bluetooth, or text message is sent if 12v needs to be charged. If 12v drops below a certain sos will neutral toe mode become inactive and what damage could be expected. I would assume that 12v could be supplied to the jump point under the hood.

 

[miandy]

That's what I thought. What is draw on 12v while in neutral tow mode. What wifi, Bluetooth, or text message is sent if 12v needs to be charged. If 12v drops below a certain sos will neutral toe mode become inactive and what damage could be expected. I would assume that 12v could be supplied to the jump point under the hood.

The lights are supplied by the rv, I even tried running without anything hooked up to the truck, same result. Less than 3 hours and deader than a door nail.

 

[MakinDoForNow]

The lights are supplied by the rv, I even tried running without anything hooked up to the truck, same result. Less than 3 hours and deader than a door nail.

I would suspect at least something is drawing current. Possibly computer checking temp of trans fluid and run circulating pump a minute or so if needed. We need to know exactly what flat tow mode actually requires.

 

[GPSMan]

I did a test on flat ground. I put mine in Neutral Tow and looked at my ScanGauge.

ScanGauge / OBDII bus stays powered up. But goes to sleep after a few minutes, but it is easy to wake up an unlimited number of times.

The infotainment screen and radio stays powered on but goes to sleep after a few, maybe 10 minutes, but is easy to wake up an unlimited number of times. Pressing a radio button wakes it back up. Opening the driver door wakes it up as well as the scan gauge. I swear unbuckling the driver seat belt wakes it up, but may have been a coincidence. It did once, but I couldn't repeat.

5 amps was coming out of the 12v battery during my 36 minute test, which I think is quite a lot. I could turn on all the exterior lamps, and 20 amps was coming out of the 12v battery. Lights on and brake pedal pressed, 29 amps coming out of the 12 volt battery.

During my 36 minute test, nothing came out of the HV battery.

Entered Neutral Tow Mode 5:35 pm
HV battery 219v @ 43.27% charged
12v battery 12.4v @ 77% charged

Ended Experiment 6:11 pm
HV battery 219v @ 43.21% charged
12v battery 11.6v @ 68% charged

Data from OBDII CAN bus, as self reported by the vehicle, not independently tested.

You cannot remove the key, and I did not want to go to dinner and leave the truck in Neutral with keys in it.

I wonder, if at some lower threshold of 12v voltage or percent charge would the DC/DC kick on?

That was a big 12v drop for 36 minutes. But I did play with the radio, ScanGauge, headlamps, and brake pedal during this time. Once I heard some kind of pump running, but it was only for about 10 seconds.

Start 5:35 pm

Shows 10 amps coming out of the 12v battery but parking lamps and radio was on. With parking lamps off, 12v Batt Amp was -5 which is still a lot. That's 60 watts.
To end this mode you have to turn the key to run, but not actually start the truck. At this moment the DC/DC converter clicked on, and started putting 30 amps INTO the 12v battery at 14.3 volts.

36 minutes later just after turning the key to "on" (not started).

Don't be confused: for whatever reason amps out of the HV battery are positive and amps out of the 12v battery are negative.

 

[JimParker256]

According to the manual, the procedure for flat-towing involves enabling neutral tow mode and turning the ignition off, so neither the ICE nor inverter should be active.

Does anyone know what "Neutral Tow Mode" actually entails? By that I do NOT mean how to get into it - the manual covers that quite well, but rather what is actually does? (For instance, is it supposed enable the DC-DC converter to keep the 12V battery recharged? What does it actually do, other than allowing the vehicle to be safely towed?)

 

[GPSMan]

For one it prevents the truck from going into Park. Since that little dial is just an input like a joystick, Neutral time is limited to like 30 minutes if you do the car wash trick. If you don't do the car wash trick, it goes into Park as soon as you open the driver's door without the seatbelt connected.

I have not been to one of those "unmanned" car washes, but if I remember correctly you need to press L (low) after it is in N (neutral) before opening the driver's door if you want to get out of a truck and have it remain in neutral for 30 minutes. Aka "car wash trick".

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