How to get moving if your 12v battery is dead (ZE1)

[mrlithium]

Here is a good battery monitor i use via bluetooth - $29

 

[RYoungberg]

The Weak Link​

The weak link in EVs is the same as in conventional vehicles: the “starter battery.” Without it, EVs are just as dead as a gasoline-powered car that won’t start in the cold. The starter battery, or more correctly the “accessory battery” powers all the car’s accessories, including the all important computer.

If the voltage of the accessory battery falls too low, it can’t turn on the computer. And without the computer, the car can’t close the contactor, enabling the big traction battery to power the little accessory battery. If your accessory battery is dead, then your EV is “bricked” and won’t go anywhere—or do anything.

So keep an eye on your accessory battery. If you live in a cold climate, replace it after three years. And as a precaution, carry a small 12-volt lithium-ion jump start battery. This emergency battery isn’t used to “turn over” or “crank” a conventional drive train—though it can do that—but instead is used to provide enough juice to turn on the computer. Once the computer is on it will close the contactor and the computer will tell the traction battery to charge the accessory battery. Then you should be good to go.

• Carry a 12-volt lithium-ion jump start battery.
• Carry a pair of jumper cables.

 

[Astral]

Didn't I read somewhere here that the Leaf will charge the 12v battery on it's own every once in a while even when turned off?

 

[cornbinder89]

I know it will when it is plugged in, You'll get only the 3rd light on the dash flashing. I don't think it does when not plugged in.

 

[mrlithium]

that amazon page lists jump starters from $30 to $200... which one ?

 

[henrydehoja]

Didn't I read somewhere here that the Leaf will charge the 12v battery on it's own every once in a while even when turned off?

Yes, the Leaf auto-charges the 12V battery via the main battery for a short period of time when the 12V battery level becomes low. This happens regularly when the EV is OFF and unplugged for an extended period of time. Also, the algorithm for this auto-charge process changed in the 2018 and newer models for improved results.

I've seen this happen a few times on mine while walking around my garage at night. It freaked me out the first time I witnessed it years ago. But after re-reading my manual, I realized it was the EV doing its thing.

 

[flydiver]

that amazon page lists jump starters from $30 to $200... which one ?

Yes, there are hoards. A LOT of it is also marketing BS. This guy does a creditable job of ACTUALLY testing a bunch in both 22 and 23. Great site, recommended.

It doesn't HAVE to be 'amazing'. You aren't starting a diesel V8, just 'booting' the car. IMO reliability is more important than massive current capability.
Long term storage is what it will do 99.99% of the time. Your climate environment will have an impact on that also.

 

[Snakebitten]

So accessory mode doesn't turn on the DC/DC converter? (digital alternator)

On my Hybrid, it does. So if the 12V battery SOC is borderline, you could hit accessory mode first, then have up to 200amp of 13V current available to assist that battery.

 

[FinnishCoffee]

So accessory mode doesn't turn on the DC/DC converter? (digital alternator)

On my Hybrid, it does. So if the 12V battery SOC is borderline, you could hit accessory mode first, then have up to 200amp of 13V current available to assist that battery.

As long as the battery is unable to energize the contactors inside the main battery, the DC-DC converter can't be used.

 

[Snakebitten]

As long as the battery is unable to energize the contactors inside the main battery, the DC-DC converter can't be used.

Thanks.

But still I'm curious if the DC/DC converter is engaged in Accessory Mode. Because if it is, you can give that 12V battery a little "boost" if it's got a borderline SOC

 

[fester]

If you don't mind parting with about 100 bucks, you can get a self-powered Voltage Data Logger, which I use to check the 12v condition either parked or driving. They just attach using alligator clips. A Data Logger can be set to "sample"over a large range of time, so you can see just what the battery and charge system are doing. Most are USB and have an app for use with a PC.
I'm using this one, but others are out there too...
https://www.amazon.com/Lascar-Electronics-EL-USB-3-Voltage-readings/dp/B003DS0BS2

 

[mrlithium]

This one does the same thing for $29

 

[Snakebitten]

I have this installed on 3 vehicles.
It logs 24/7/365 and you don't have to disturb the vehicle to get a reading or to download the log.

 

[knightmb]

Thanks.

But still I'm curious if the DC/DC converter is engaged in Accessory Mode. Because if it is, you can give that 12V battery a little "boost" if it's got a borderline SOC

Without having your foot on the brake pedal, one press is the ACC mode which only runs the radio, power ports, etc. This mode is right off the 12V battery, no DC-DC is active. When you press it again (again, no foot on pedal), you get what I call "standby" mode. This allows you see the dash, turn on seat heaters, run cabin fans, lights, etc. This also draws directly from the 12V battery, no DC-DC active. The difference between the two is the second "standby" mode will engage the traction battery when the 12V battery falls below 10.5V to charge it back up. If the 12V load is too high before it gets below 10.5V, it may not have enough power to turn on the traction battery (like if you had the cabin fan on high, seat heaters, steering wheel heater, rear defroster all going for insane high power draws), then the Leaf simply kills everything and shuts off everything to preserve the 12V battery capacity. Hopefully enough power remains in the 12V battery to simply "start" the Leaf and resuming charging the 12V battery.

 

[Snakebitten]

Thanks!
That definitively what I was wanting to know. Although disappointing.
But no worries, I'll just be more vigilant about the 12V battery than I would have been.

 

[DButch51]

Yes, there are hoards. A LOT of it is also marketing BS. This guy does a creditable job of ACTUALLY testing a bunch in both 22 and 23. Great site, recommended.

It doesn't HAVE to be 'amazing'. You aren't starting a diesel V8, just 'booting' the car. IMO reliability is more important than massive current capability.
Long term storage is what it will do 99.99% of the time. Your climate environment will have an impact on that also.

The Toyota Prius does a similar 2 stage startup. A 12 volt battery closes the contacts on the main battery. If the 12 volt battery dies or runs out of juice, you need to recharge or replace the 12 volt battery. I got a very compact BASF lithium-ion jumper kit that does the trick and holds charge for an impressive amount of time. As long as I remember to check the charge state (push a button and see that at least 2 of the 4 charge indicator lights hold, I've got enough to start. Now that I know that the Leaf also uses a 2 stage startup, I'll plonk for another BASF type pack.