My Leaf roll back and almost kill a kid!

[TimLee]

Be sure your 12V battery has a capacity test done at least annually.
It is warranted for complete no cost replacement to 3 years / 36,000 miles.
Dealer replaced mine at two year mark. They always check 12V battery capacity on all vehicles. Not all dealers do this.
My 12V died from lots of use in ON instead of READY. LEAF will periodically charge the 12V in ON, but it waits too long and the cycling kills the standard lead acid battery.
And never use the single button push AUXILIARY mode. No reason to use that.

 

[tombobcat]

Sorry about that. Can you please measure your battery voltage and report back here?

When the car is on, the voltage measured at 14.54V. When it's off, the voltage measured at 10.43V

 

[dhanson865]

Sorry about that. Can you please measure your battery voltage and report back here?

When the car is on, the voltage measured at 14.54V. When it's off, the voltage measured at 10.43V

Definitely need to put that battery on a smart charger or just replace the battery.

I sure wish the Leaf and Prius would show battery voltage on the dash before entering ready mode (cache the value from before the main battery comes on line and display it on the MFD or dash display during that entire drive cycle). Don't make us dig through a hidden diagnostic menu or grab a multimeter.

Someone mentioned crawling through the hatch on the Prius and someone else said no reason to do that because you can use jump points under the hood. I counter with this: it is possible for the low 12v condition to confuse the system enough that you can't get the hatch to open until you disconnect the 12v battery to let the system reset. In that case you'll end up going that way without any other option.

It'd be nice if the charging protocol on the leaf would pump higher voltage to the 12v while it is charging the HV battery so that the act of L2 charging would also be smart charging the 12v battery. Didn't I read about the Tesla model S doing that now in the 5.6 or 5.8 update?

 

[RegGuheert]

Sorry about that. Can you please measure your battery voltage and report back here?

When the car is on, the voltage measured at 14.54V. When it's off, the voltage measured at 10.43V

That low voltage matches the experience of the thread OP. Apparently when battery has a low voltage the brakes can malfunction.

Frankly, if it were me, I would file a report with the NHTSA. Nissan has been notified on multiple occasions by several of us and has done nothing to resolve this issue.

BTW, IIRC, the battery controller is powered from the ultracapacitor. Or does that only provide power to the brakes under certain conditions? In any case, if there is a bad cell (shorted or fully discharged) in the 12V battery, then that ultracapacitor will drift down to ~10.5V after the car has been off for a while. I wonder how long it takes for it to charge back up to 14.4V (or 13.1V where the vehicle sometimes operates)? It may take several minutes. I do recall that when the mechanic reprogrammed our braking unit, he did not know how to recharge the ultracapacitor. The result was no brakes with the pedal moving all the way to the floor. Perhaps this issue is related somehow...

 

[oscar]

I have the same nerve breaking problem with my LEAF, called Nissan LEAF customer support to report issue, case number 13187200.

It's your 12 volts battery!!!

All my problems disappear after the 12 volts battery replaced.

Once your 12 volts battery drop below 11 volts. Many things can go wrong.

 

[tombobcat]

I have the same nerve breaking problem with my LEAF, called Nissan LEAF customer support to report issue, case number 13187200.

It's your 12 volts battery!!!

All my problems disappear after the 12 volts battery replaced.

Once your 12 volts battery drop below 11 volts. Many things can go wrong.

You're right. I brought my LEAF to the dealer and was diagnosed with the 12 volts battery, they charged me $127.99 total (my car is over 36000 mile) to replace the battery.

 

[TimLee]

I have the same nerve breaking problem with my LEAF, called Nissan LEAF customer support to report issue, case number 13187200.

I'm thrilled that you resolved your problem!!!
And that MNL helped you do this!
But, it is sad that people are failing to pick up on the whole truth.

The right fix was the right AGM battery (e.g. Optima).

You might have bought the correct battery for the LEAF for $150 to $190 with a three year warranty!
You have to read a LOT to understand the right thing to do with a LEAF!!

 

[RegGuheert]

The right fix was the right AGM battery (e.g. Optima).

I do not understand how the Optima can help here since the real issue seems to be that the LEAF does not do a great job of keeping the battery fully charged. Optimas fail just like flooded batteries.

 

[dhanson865]

The right fix was the right AGM battery (e.g. Optima).

I do not understand how the Optima can help here since the real issue seems to be that the LEAF does not do a great job of keeping the battery fully charged. Optimas fail just like flooded batteries.

Yes your amazon link shows a couple of customers that had failed batteries but I've seen dozens of priuschatters that have yellowtop optimas that work fine.

Optima on its own isn't a solution but if your regular 12v battery is discharged too low a smart charger won't fix it (it's permanently damaged) and you have to buy a new one.

Optima Yellowtop + smart charger = just recharging the 12v battery instead of buying a new one each time you drain it too low.

It's still something you have to monitor, maintain from time to time but the cost per year going forward is less than replacing batteries over and over.

 

[GIBBER]

The right fix was the right AGM battery (e.g. Optima).

I do not understand how the Optima can help here since the real issue seems to be that the LEAF does not do a great job of keeping the battery fully charged. Optimas fail just like flooded batteries.

The advantage comes from the Absorbed Glass Mat between the plates preventing sulfation which is the main cause of failure in a lead-acid battery. (Yes AGM batteries still fail but at a lower rate than non-AGM lead-acid ones). All things considered, if I were to install a AGM in my LEAF I would most likely chose the blue top (deep cycle) as the 12v is not needed to crank a starter motor peak-output is not a factor, only the ability to supply long lasting accessory power.

 

[dhanson865]

The right fix was the right AGM battery (e.g. Optima).

I do not understand how the Optima can help here since the real issue seems to be that the LEAF does not do a great job of keeping the battery fully charged. Optimas fail just like flooded batteries.

The advantage comes from the Absorbed Glass Mat between the plates preventing sulfation which is the main cause of failure in a lead-acid battery. (Yes AGM batteries still fail but at a lower rate than non-AGM lead-acid ones). All things considered, if I were to install a AGM in my LEAF I would most likely chose the blue top (deep cycle) as the 12v is not needed to crank a starter motor peak-output is not a factor, only the ability to supply long lasting accessory power.

There are two blue top optima batteries. One would be a very bad choice for a car and the other would be OK, but I'd rather use the yellowtop.

YELLOWTOP®: Use this when electrical loads are higher than average, or when the discharge cycle is more than typical engine starting, such as vehicles without alternators. This also includes vehicles with significant electrical loads that may exceed the average alternator output (for example, aftermarket audio systems, GPS, chargers, winches, snowplows, inverters, drag cars). This can also include vehicles that have a lot of electronics from the factory, such as a minivan with power sliding doors and a DVD player, especially if the DVD player is used when the engine isn’t running.

Racing vehicles without a charging system (alternator or generator)
Dedicated drag-racing vehicles
Diesel-powered vehicles with aftermarket electronics
Car audio/video applications exceeding 250 watts over the OE system
Vehicles or heavy equipment with inverters, hydraulics, winches or other accessories
Electric vehicles


BLUETOP®: The BLUETOP® starting battery (dark gray case) is to be used when a dedicated starting battery is required; it should never be used for cycling duty. The dual-purpose BLUETOP® (light gray case) can be used for both starting and deep cycling; it is a true deep-cycle battery with extremely high cranking power.

Trolling motors, marine applications with heavy electrical accessories and RVs should use a dual-purpose BLUETOP® (which is both a starting and deep-cycle battery)
Use a BLUETOP® starting battery for marine applications and RVs when the battery’s only function is engine starting

Note: The difference between BLUETOP® and YELLOWTOP® deep-cycle batteries is that BLUETOP® batteries have both automotive (SAE) posts and threaded studs, while YELLOWTOP®S (other than D31T) only have SAE terminals.

If you ever get confused on the colored tops, just remember: if it has a dark gray case, then it’s a starting battery; if it has a light gray case, then it’s a deep-cycle (dual-purpose) battery.

 

[RegGuheert]

Optima on its own isn't a solution but if your regular 12v battery is discharged too low a smart charger won't fix it (it's permanently damaged) and you have to buy a new one.

The implication of this statement is that these LEAF batteries have died because they were very deeply discharged. Perhaps that is the case, but I don't think we have any evidence that is the case. What we do know is that the LEAF 12V charging system often keeps the battery at around 50% SOC, which typically results in loss of capacity through sulfation?

But we don't know anything for sure. You may be correct. Or perhaps some of the OEM batteries in the LEAF simply are low quality and they develop a short in one of the cells after a rather short life.

The advantage comes from the Absorbed Glass Mat between the plates preventing sulfation which is the main cause of failure in a lead-acid battery. (Yes AGM batteries still fail but at a lower rate than non-AGM lead-acid ones).

I'm not sure why you think AGM batteries do not suffer from sulfation, but it is not true. They will sulfate just like any other lead-acid battery. Here is a quote from Concorde Batteries regarding their SunXtender AGM batteries:

The following procedure is effective if the batteries are not too badly sulfated.

The procedure which they are discussing is used to try to break up sulfation in those batteries.

 

[dhanson865]

Optima on its own isn't a solution but if your regular 12v battery is discharged too low a smart charger won't fix it (it's permanently damaged) and you have to buy a new one.

The implication of this statement is that these LEAF batteries have died because they were very deeply discharged. Perhaps that is the case, but I don't think we have any evidence that is the case. What we do know is that the LEAF 12V charging system often keeps the battery at around 50% SOC, which typically results in loss of capacity through sulfation?

But we don't know anything for sure. You may be correct. Or perhaps some of the OEM batteries in the LEAF simply are low quality and they develop a short in one of the cells after a rather short life.

If you believe the marketinging/faq on the optima website a lead acid battery is only discharged about 5% in normal use on an ICE vehicle. If a Leaf drains the 12v much lower because they are charging slower or draining more in different usage patterns it could be that normal use of a Leaf is hard on the 12v battery. I'd consider 50% much more drain than 5%.

I don't know about the average Leaf owner but I've drained my Prius 12v well below normal in various user errors at least 3 times within the last few years. I'm guessing that others make mistakes less often than I do but more than zero times in a 3 year period. Once I did it the first time I paid attention to voltage and realized my car wasn't charging the battery as fast as a standalone battery charger and wasn't keeping ahead of my usage patterns at all times. If it isn't keeping the 12v battery fully charged then any mistake by the user is likely to pull it down low enough to damage the battery.

A lot of the threads about the 12v battery on the Leaf have sounded just like the ones I read about the Prius. So in my mind I've made the association that even if the cause is somewhat different the effect is that the Leaf needs a reliable 12v battery just like the Prius needs a reliable 12v battery. Highly computerized cars just don't behave well with a weak battery.

I'd love to have a Leaf to test, or I'd love to see more data on what's happening from a technical Leaf user but for now I'm just sharing what I've seen from what I consider to be a similar vehicle.

 

[RegGuheert]

If you believe the marketinging/faq on the optima website a lead acid battery is only discharged about 5% in normal use on an ICE vehicle. If a Leaf drains the 12v much lower because they are charging slower or draining more in different usage patterns it could be that normal use of a Leaf is hard on the 12v battery. I'd consider 50% much more drain than 5%.

50% is not how much the LEAF battery is discharged in a typical trip. As mentioned previously, the LEAF does not drain the 12V battery much at all during use. The issue is that it does not recharge it.

I don't know about the average Leaf owner but I've drained my Prius 12v well below normal in various user errors at least 3 times within the last few years. I'm guessing that others make mistakes less often than I do but more than zero times in a 3 year period. Once I did it the first time I paid attention to voltage and realized my car wasn't charging the battery as fast as a standalone battery charger and wasn't keeping ahead of my usage patterns at all times. If it isn't keeping the 12v battery fully charged then any mistake by the user is likely to pull it down low enough to damage the battery.

That's true. And that could be an issue. But simply holding the battery around 50% SOC will cause the other 50% of the battery's capacity to be lost to sulfation.

A lot of the threads about the 12v battery on the Leaf have sounded just like the ones I read about the Prius. So in my mind I've made the association that even if the cause is somewhat different the effect is that the Leaf needs a reliable 12v battery just like the Prius needs a reliable 12v battery. Highly computerized cars just don't behave well with a weak battery.

No argument. This thread points to a rather severe problem caused by faulty 12V batteries. The question I have is whether an Optima battery will live longer in the LEAF charging system than any other battery. Perhaps it will, but I'm not sure why that would be.

I'd love to have a Leaf to test, or I'd love to see more data on what's happening from a technical Leaf user but for now I'm just sharing what I've seen from what I consider to be a similar vehicle.

Here is a plot showing our LEAF's 12V battery going from 100% SOC to about 70% SOC in about three weeks' time:

Notice that driving the LEAF does NOT return the SOC to 100% when it is driven as is done in any other vehicle I have ever seen. It charges at the normal 14.4V for a very brief time only and then it quickly goes to float voltage of 13.1V, which does not charge the battery.

 

[Reddy]

Reg, thanks for the graph. I wish I'd seen that back in 2012. I finally took Phil's advice and bought the CTEK battery maintainer. Now I hook it up every night to the Leaf and then switch it over to the IEC in the morning. It's a pain, but it does the job and keeps both batteries above 13 V.

 

[rusang]

I have the same problem with my Nissan Leaf 2014 model.

It happens to my wife once but I didn't believe her last month. I've ask her what happen and describe in sequences. She told me had her foot on brake, press start then put it in Reverse while the foot still on the brake from the beginning. Once in Reverse she looks back and saw people coming so she kept her foot on the brake. All of sudden the brake just felt soft and sink to the floor and car roll. She panic and lift her foot half way off the brake and press again it still roll; while the parents walking in back screaming. My wife pulls the electronic brake it didn’t work. Finally she applied the parking brake and it stopped. The parent came screaming at her trying killing her kid. I first brushed it off thinking she must have done something wrong. After that I had few experiences myself with same symptoms. I had my foot on the brake press Start Button then put the car in Reverse and the car roll while my foot is still on the brake. The brake just sinks straight to the floor. I have to change the gear to Parking or stop the car. One workaround I have found so far is that after I start the car, I lift my foot from the brake wait 1-2 sec and then apply brake and change to reverse - it works.

I gave my car to Nissan service and lets see what they come back with.

 

[keydiver]

If you have read this thread, you would already know what the problem is: a bad/discharged 12 volt battery. Did you tell the dealer about the battery issue? If not, expect to get a "we couldn't duplicate the problem" answer back from them.

 

[rusang]

I told him about it and he said there is no way battery issue can be related to the brake issue. So, I will wait for the guy to come back.

 

[2k1Toaster]

I told him about it and he said there is no way battery issue can be related to the brake issue. So, I will wait for the guy to come back.

People on here know much more about the Leaf than the dealer "Leaf tech". Just like PriusChat and PTS contain people much more knowledgeable about the Prius than any Toyota dealership mechanic I have ever seen.

Force the issue/

 

[RegGuheert]

I told him about it and he said there is no way battery issue can be related to the brake issue. So, I will wait for the guy to come back.

It's a shame that Nissan has technicians and/or service writers who are so ignorant of their modern vehicles. All Nissan techs should by now know the following:

1) LEAF braking system is electrohydraulic. There is no vacuum available in the LEAF for boost. If the 12V ultracapacitor is discharged, the brakes do NOT work. My local LEAF technician learned about this the hard way when he tried to apply the new firmware and did not know how to recharge the ultracapacitor. The result was the car had no brakes (pedal to the floor) and they loaned me a car for the weekend. I do not know what the minimum safe voltage for the braking system is.
2) All modern vehicles depend on proper operation of the CANbus for proper operation of the vehicle. The CANbus only works properly above a certain voltage of the 12V bus. Once the voltage drops below a certain level, all bets are off regarding what kind of problems occur.

In addition, Nissan needs to work to improve the 12V charging system for the LEAF. Their Coulomb-counting system seems to ignore loss of charge which occurs while the car is off for extented periods.

I'm disturbed to hear that there are still safety issues with the LEAF braking system which are endangering pedestrians. I have personally told several people in Nissan's management chain about this issue, but I don't see any evidence that any action was taken.