Dead 12V battery question

[LeftieBiker]

One of the advantages of AGM batteries is that they are much more tolerant of being below 100% SOC than are flooded starting batteries. I got 10 years out of a set of AGMs in an electric scooter (Oxygen Lepton) in which they were at 100% only about half the time. At that point, when I sold the scooter, they still had about 66% capacity. So even if the requirement for a full charge is a voltage higher than what the Leaf provides, the batteries seem happy enough at 95%, or whatever they get from charging at 14.2 volts.

 

[lorenfb]

I use a couple different AGM battery manufacturers for my vehicles: I replaced the Nissan OEM battery in each LEAF with an Optima yellow top D51R. In each case, the Nissan OEM flooded cell battery failed after 2 to 2-1/2 years (which is actually longer than typical for OEM batteries in gas engine vehicles in my climate).

OK, then your issue with a flooded cell type relates to a high local ambient temp.

Optima recommends float voltage of 13.2 to 13.8 and alternator output voltage of 13.65 to 15.0 for their yellow top deep cycle batteries. My experience with Optima batteries (red top starting batteries and yellow top deep cycle/starting batteries) is that overcharging kills them prematurely in the hot dry climate where I live. They last far longer than other batteries as long as the alternator output voltage on a vehicle is not too high. The DC-DC converter output on the LEAF is ideal for long life of the Optima batteries because it is 14 to 14.5 volts until absorption current drops and then switches to float voltage of about 13 to 13.5 volts (both voltage levels are temperature compensated so higher when cold and lower when hot) to avoid overcharging. I use Odyssey batteries in motorcycles, Jet Skis and a Group 65 in my SUV (since Optima does not make Group 65 size). They have about the same charging voltage recommendations.

I switched to AGM batteries after getting tired of cleaning up corrosion around flooded cell batteries and having even top-of-the-line flooded cell batteries fail after 6 to 18 months.

So again, you're saying that even with a lower charging voltage, i.e. a Leaf @ 14.2V charging but with a high ambient temp,
that an AGM lasts longer for you than even a Optima yellow.

Then the issue remains whether an AGM battery really provides a benefit, for its additional cost, for those in a less extreme ambient.

 

[lorenfb]

One of the advantages of AGM batteries is that they are much more tolerant of being below 100% SOC than are flooded starting batteries. I got 10 years out of a set of AGMs in an electric scooter (Oxygen Lepton) in which they were at 100% only about half the time. At that point, when I sold the scooter, they still had about 66% capacity. So even if the requirement for a full charge is a voltage higher than what the Leaf provides, the batteries seem happy enough at 95%, or whatever they get from charging at 14.2 volts.

You may be correct based on your experience, but personally I haven't experienced that with my '13 Leaf or my ICEVs
over 30+ years, nor have I seen data supporting that. Actually, from my experience with typical lead acid batteries,
voltages over 14.5V causes a loss of battery electrolyte over time.

 

[LeftieBiker]

There are a lot of Chinese "AGM" batteries that appear to be, essentially, gel or flooded cell batteries with a modest amount of fiberglass added. Can you list the brands and models you've used?

 

[GerryAZ]

The Optima batteries (red top starting, yellow top deep cycle/starting, or blue top marine deep cycle/starting) and Odyssey batteries are all true high-quality AGM batteries and they work very well in my climate. The Optima yellow top D51R is ideal for use with the LEAF charging algorithm and it is a direct fit to replace the OEM Nissan battery. The Optima in the 2011 was like new when the car met its demise. The Optima in the 2015 was still like new when I traded for the 2019 SL Plus. I hope to keep the 2019 long enough to find out how long the Optima lasts (it was installed 11 months ago).

I have seen a lot of low-quality automotive and powersports batteries advertised as AGM that are not truly absorbed glass mat construction. Therefore, one must shop carefully. True AGM batteries do not vent gas so their terminals do not corrode and they do not lose electrolyte unless they are continuously overcharged. They can build up enough internal pressure to cause their pressure relief valve to vent if they are continuously overcharged for extended time. They lose a small amount of electrolyte each time they vent from overcharging so they eventually fail due to loss of electrolyte. They typically last at least as long as flooded cell batteries in vehicles that overcharge them, but last a lot longer if not overcharged.

 

[knightmb]

I have seen a lot of low-quality automotive and powersports batteries advertised as AGM that are not truly absorbed glass mat construction.

To jump on that one, PowerSports batteries are no-where near what they advertise for capacity. I've had to help so many friends and relatives return them to a battery store because they always only get about 1/3 of their "advertised" capacity, no matter if it is the SLA or Lithium version. Way-over priced that will certainly not meet real-life needs of the owner. Just my experience with them. I even got a local battery store to totally remove all of them from the shelves after I showed the owner how they advertise one capacity on the battery, but hidden in the tech specs, only actually perform 1/3 of that rated capacity. So yeah, the battery can start your car, but stressing it out like that just means a very short life.

 

[GerryAZ]

If Odyssey makes the correct size, that is what I buy when I need a replacement powersport battery because I know I can trust their capacity ratings and manufacturing quality. I buy Optimas for automotive needs unless they do not make the correct size for the application. I even have a 6-volt Optima red top in my antique John Deere tractor. It spins that 67-year-old motor over better than any previous battery, but I had to fabricate a plexiglass holder/insulator for it because it is half the physical size of the specified battery group number.

 

[TimLee]

My 2011, 2015, and 2019 all act the same way. HVAC and DC-DC converter function normally while car is charging on L2 or DCQC as long as SOC is at least 25%. ...

Thanks Gerry.
I had forgotten about the main pack having to be above 25% staus of charge for HVAC to work while LEAF is ON and charging.
That is probably why DC to DC was not available to put current into the 12V.
And as you point out, the cutout does not reset once SOC is above 25 percent, till you turn the LEAF OFF and then back ON with foot on the brake.
Appreciate the help.

 

[knightmb]

I think it's more GID based than SoC based because I can run HVAC at 2% (or 6%, can't remember) SoC or higher (I think, from memory)

 

[Stanton]

Based on the above and what is known about the typical Leaf battery charging voltage (14.2V), it appears that the Leaf provides an inadequate AGM charging voltage.

But that charging voltage is perfect for a LiFePO4 12v battery (most will accept up to 14.4v max).

 

[GerryAZ]

I think it's more GID based than SoC based because I can run HVAC at 2% (or 6%, can't remember) SoC or higher (I think, from memory)

It may be different for the 62 kWh battery--I have only used climate control a few times while charging and the car was not deeply discharged before starting those charges. I know the 2011 and 2015 both required 25% SOC before climate control would function while charging (blower fan would run, but compressor or heater would not draw power from the traction battery if SOC was lower than 25%).

 

[DougSchwartze]

Could someone please double check me on this:
We have a 2011 Leaf, SL, with 105,000 miles on her and SOH = 5 bars.
When charging to 80% or to 100% the 3 Blue charge indicator lights will do their thing during charge.
When charge is up, all 3 lights stay on for 15 minutes, then all 3 shut off.
From the time when all 3 lights all come on until they go off, there is a drain on the 12 volt battery pulling it down to about 12.25 vdc by the end of 15 minutes. The 12 volt battery never gets back up to its full charge value after the lights turn off.
Currently I disconnect the charge cable as soon as the blue lights all are on, or disconnect the charge cable before all lights turn on. By doing this, the 12 volt battery stays charged at a 12.5 volt charge when the car is unplugged.

Please someone, prove this to be an incorrect function.

Otherwise it could be part of the cause of premature battery sulfation and failure ?

P.S. it is always good to operate the wipers a couple of times when I come home before shutting her down and putting her away wet.

 

[LeftieBiker]

Welcome. That's a very interesting observation! If it's true of most or all Leafs, then yet another Nissan Engineering Fail is revealed. BTW, what's happening when all 3 charge lights are on steady is the pack is being balanced a bit, with low cells being charged further and high cells having charge bled off. I see no reason why the DC-DC converter needs to be off for that to happen.

I'm sure that there are at least several people here who are going to test this one.

 

[SageBrush]

Currently I disconnect the charge cable as soon as the blue lights all are on, or disconnect the charge cable before all lights turn on. By doing this, the 12 volt battery stays charged at a 12.5 volt charge when the car is unplugged.

My guess is that you are preventing dissipation of surface charge. If so, you are chasing an artefact

 

[DaveinOlyWA]

... Therefore, it is necessary to charge the 12V battery or use a booster battery to get charging started. Once traction battery charging starts, the DC-DC converter will charge the 12V battery while the traction battery is charging.

On my 2011 LEAF, I recently observed that while L2 charging the main pack, that if the LEAF is ON, the DC-DC converter is inactive and NOT available to charge the 12V battery while the traction battery is charging.

I only discovered this because I left the LEAF ON to keep the 12V auxiliary outlet powered for charging my cell phone that had LEAF Spy Pro running creating a graph of the pack charging that I planned to Save.

I only discovered the situation when I turned the windshield wipers on to have the LEAF DC-DC raise the 12V buss voltage to check the 12V battery completeness of charge and saw that the buss voltage did not change.

Turning the wipers on is a simple way to fully charge the 12V. With my AGM you know it is pretty fully charged once the current with 14.2 V on the buss drops very low to 0.86 or 0.67 amps.

I had done a similar thing a lot while using DCQC. And with DCQC charging the pack and the LEAF ON the DC-DC is active. But on my 2011 it is NOT while doing L2 with the LEAF ON.

There are also differences on HVAC availability with LEAF ON between DCQC and L2. HVAC works with DCQC, but usually NOT with L2.

One last note on killing the 12V. I killed it once with the headlights turned ON. With the headlight relay closed and 12V buss voltage very low, took a stout 12V source to be able to get the headlight relay to open.

The 12 volt gets boosted on essentially what is a algorithm based timer. The ONLY method to manually charge the 12 volt is running the windshield wipers (quite intuitive, right? )

So it WILL charge the 12 volt when the traction pack is charging when its time to charge based on the algorithm and not before.

On the forced charging, I tend to see as little as .2 amps but guessing that is more to do with other things running in the background.

But I have done SEVERAL observations of LEAFs over the years and despite what is widespread knowledge thru out the EV World, Nissan has failed to address the issue in any significant way other than likely minor tweaks. I repeated many observations on the Plus to look for changes and was unable to determine that there were any?

https://daveinolywa.blogspot.com/2021/04/charge-your-leaf-every-day.html

 

[DougSchwartze]

Currently I disconnect the charge cable as soon as the blue lights all are on, or disconnect the charge cable before all lights turn on. By doing this, the 12 volt battery stays charged at a 12.5 volt charge when the car is unplugged.

My guess is that you are preventing dissipation of surface charge. If so, you are chasing an artefact

All I have to test is our mature 2011 Leaf s/n 000570. When using our 240 volt 20 amp EVSE as a charging source and monitoring the 12 volt battery with a dvm, immediately the voltage at the battery rises to 14.5 vdc. It stays there for about 45 seconds, then slowly tapers down to 13.10 vdc and stays there until the traction battery is finished with its charge and all 3 blue lights are now on.

At that time the charge to the 12 volt battery stops, the battery reads 13.10 vdc and a mysterious discharge (load) begins slowly pulling the battery down for the 15 minutes time that the 3 blue lights stay on.

It is much more of a current draw than just the normalization of a battery. My experience is that if I disconnect a lead acid battery after a full charge it will slowly normalize down to 12.5 vdc at the lowest in 15 minutes time.

What I am seeing is the battery output is sucked all the way down to 12.25 vdc at the lowest I have seen. Then after the 15 minutes the load is magically removed and the battery output slowly normalizes drifting back up towards 12.4 vdc or so...

If someone could monitor the battery output load on their Leaf and let me know.
Are they all doing the same thing?
Was there a software fix we missed ?

 

[GerryAZ]

What you are seeing is probably normal. There are numerous control modules (computers) that are active when the car is on or charging. Also, the DC-DC converter charges the 12V battery whenever the car is on or actively charging. The DC-DC converter stops charging the 12V battery as soon as the traction battery stops charging or the car is turned off. The computers stay active for a little while after charging stops or the car is turned off. They then go into low power sleep mode after a few minutes. What you are seeing is the 12V battery current drops when the control modules go to sleep. Your 12V battery may be getting a little weak so that the voltage drops a little lower during that time when the control modules are active.

FWIW, I have never connected an external charger to the 12V battery in any of my LEAFs. The only time I had trouble was once when I forgot to unplug the Bluetooth OBDII adapter and left LEAF Spy running on an Android device left on the passenger seat while the 2011 was parked at my office for extended time. I returned to a dead 12V battery and had to jump start the car--the 12V battery was fully charged by the time I arrived home. I also had to jump start the 2019 LEAF when I inadvertently left the car on after shutdown during a traction battery discharge test (lights, HVAC blower, and radio were running from 12V battery after the main DC contactor opened) and a few months later when the OEM 12V battery failed suddenly.

 

[DougSchwartze]

What you are seeing is probably normal. There are numerous control modules (computers) that are active when the car is on or charging. Also, the DC-DC converter charges the 12V battery whenever the car is on or actively charging. The DC-DC converter stops charging the 12V battery as soon as the traction battery stops charging or the car is turned off. The computers stay active for a little while after charging stops or the car is turned off. They then go into low power sleep mode after a few minutes. What you are seeing is the 12V battery current drops when the control modules go to sleep. Your 12V battery may be getting a little weak so that the voltage drops a little lower during that time when the control modules are active.

FWIW, I have never connected an external charger to the 12V battery in any of my LEAFs. The only time I had trouble was once when I forgot to unplug the Bluetooth OBDII adapter and left LEAF Spy running on an Android device left on the passenger seat while the 2011 was parked at my office for extended time. I returned to a dead 12V battery and had to jump start the car--the 12V battery was fully charged by the time I arrived home. I also had to jump start the 2019 LEAF when I inadvertently left the car on after shutdown during a traction battery discharge test (lights, HVAC blower, and radio were running from 12V battery after the main DC contactor opened) and a few months later when the OEM 12V battery failed suddenly.

Thank you for the good information Gerry. My Leafs battery is an 8 month old Interstate battery and seems to be holding its own.

No charging system I have run into allows a battery to be pulled to 12.25 vdc
without triggering charging assistance. But what do I know ?

Would you be willing to test your 2019 SL during the period where the 3 blue lights are on solid for the 15 minute equalizing period to make sure this load is not happening on newer Leafs ?

Maybe it is only happening on our old 2011 (I hope).
Maybe all Gen 1's do this.
Maybe all Leaf's suffer with this.

I appreciate any help you can offer.

 

[LeftieBiker]

No charging system I have run into allows a battery to be pulled to 12.25 vdc
without triggering charging assistance. But what do I know ?

Welcome to the wonderful world of driving a Leaf. I see 12.25 fairly often, which is why both our Leafs are hardwired for a battery maintainer.

 

[DaveinOlyWA]

Currently I disconnect the charge cable as soon as the blue lights all are on, or disconnect the charge cable before all lights turn on. By doing this, the 12 volt battery stays charged at a 12.5 volt charge when the car is unplugged.

My guess is that you are preventing dissipation of surface charge. If so, you are chasing an artefact

All I have to test is our mature 2011 Leaf s/n 000570. When using our 240 volt 20 amp EVSE as a charging source and monitoring the 12 volt battery with a dvm, immediately the voltage at the battery rises to 14.5 vdc. It stays there for about 45 seconds, then slowly tapers down to 13.10 vdc and stays there until the traction battery is finished with its charge and all 3 blue lights are now on.

At that time the charge to the 12 volt battery stops, the battery reads 13.10 vdc and a mysterious discharge (load) begins slowly pulling the battery down for the 15 minutes time that the 3 blue lights stay on.

It is much more of a current draw than just the normalization of a battery. My experience is that if I disconnect a lead acid battery after a full charge it will slowly normalize down to 12.5 vdc at the lowest in 15 minutes time.

What I am seeing is the battery output is sucked all the way down to 12.25 vdc at the lowest I have seen. Then after the 15 minutes the load is magically removed and the battery output slowly normalizes drifting back up towards 12.4 vdc or so...

If someone could monitor the battery output load on their Leaf and let me know.
Are they all doing the same thing?
Was there a software fix we missed ?

Completely normal and if the lowest you are seeing is 12.25 volts, your battery is in pretty good shape relatively speaking. I see much lower and have never had a starting issue. The weather is "finally" expected to turn (at least for a few days) at the end of this week which means 12 volt monitoring will be stepped up.

One likely load is the monitoring of the inverter. It heats up and once I heard the water pump run for about 2 mins after the car was unplugged (this only happens on AC charging) so naturally, had to load up LEAF Spy. It did appear the fan was running of system power and not the battery though.

https://daveinolywa.blogspot.com/2021/04/charge-your-leaf-every-day.html