LEAF's 12V battery behaviors - and why they go bad

Awesome. But there are not a lot of devices on a Leaf that draw 750W on 12V system.
Ok, now we know that there might be a voltage drop due to inverter not being instantaneous (at least on 2011/12 model).
In terms of energy quantity this has more or less no effect on battery state of charge.


I would add more new information around the main topic: LEAF's 12V battery behaviors - and why they go bad

I have one BMW OEM AGM battery that was fully charged 4 months ago. It was just sitting for all that time.
Measured voltage before doing anything: 12.5V at room temperature.
We have some guys here who think that this is something something...
So.. lets do a really easy experiment.
I connected a trickle charger, that is limited to 13.99V and 1A charge rate.
As soon as I made connection it started charging the battery. At around 0,7A.
Only 15 minutes later battery was at 13.43V and charge rate dropped to 0,55A.
An hour later voltage jumped to 13.7-13.8V and charge rate dropped below 0.4A.
I've been keeping the power supply connected for few days now. And it still pushes
0.3-0.5A. Battery voltage more or less stable.

So what can we learn from that? Battery did not discharge noticeable. Actually not even 5%.
And it is absolutely pointless to try to charge it any further because it will not accept it.
But it will accept eloctricity. Around 5W is being pushed in by a charger/power-supply that doesn't
stop like smart trickle chargers do. Aka what normal DC-DC converter would do.

And this is ONE of the reasons why Leaf switches to 13.0V mode.
I will just, in the name of the science, keep the power supply active for a day or two just to be absolutely sure
that no more charge can be absorbed. And will disconnect supply. Will measure voltage again. A day and a week later. As a proof.
All this matches scientific data that I collected in this topic earlier.

The voltage of the original 12-volt battery in my 2015 was 12.543 (as measured with my Fluke 289 at the battery terminals) this morning about 6 hours after unplugging the L2 EVSE. The car is just over 2 years old with a little over 35,000 miles and I have never connected an external charger and never even removed the vent caps to check the electrolyte level. Therefore, the charging algorithm is ideal for my usage pattern.

Gerry

GerryAZ said:

The voltage of the original 12-volt battery in my 2015 was 12.543 (as measured with my Fluke 289 at the battery terminals) this morning about 6 hours after unplugging the L2 EVSE. The car is just over 2 years old with a little over 35,000 miles and I have never connected an external charger and never even removed the vent caps to check the electrolyte level. Therefore, the charging algorithm is ideal for my usage pattern.

Gerry

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it is ideal for most users. I think we need to realize that although it works for some, it is not the best option by a long shot hence some people will have issues. So why not fix it? who knows? but its likely that the fix is more involved than we want it to be. So now its a cost/benefit analysis still searching for an answer the bean counters can accept. If it was up to the engineers, my guess is that we would be hashing out something else right now.

although the 12 volt battery is not in play from the car when the DC inverter is on, it is still connected and still has voltage. so momentary drops in voltage means nothing. The battery is still out of play. with a normal running voltage of 13.2 volts, this insures the battery is out of play. So using LEAF Spy to make these kinds of conclusions is not a good idea. You should look at the cell voltage screen. Watch how half the pack's cell voltage will drop 300 to 500% farther than the other half. Again, shocking but not something I would concern myself with.

arnis said:

Ok, now we know that there might be a voltage drop due to inverter not being instantaneous (at least on 2011/12 model).

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My model is 2013 and I proved there was a drop. My point was that with a weak 12v battery, pressing on the brake pedal causes a drop in voltage and then the DC-DC converter increasing voltage causes the brakes to grab harder than they originally did...leading to poor braking at low speeds. I've experienced this on like 5 Leafs before I bought one. It's a common issue on these cars. My car does not do it with my lithium battery but did with a weak lead acid. That's all.

What does your test with a good-condition AGM prove? Does your Leaf have an AGM? No? Ok thanks I guess :roll:



GerryAZ, your battery should be at 12.6v or higher. But oh well. You live in the frigid, icey snow covered lands of northern Phoenix. I'm sure if it works for you it will work for anyone!

DaveinOlyWA, "momentary drops in voltage mean nothing" this is complete wrong! It makes the brakes feel poor, it makes lights dim, and it makes windows roll up slowly. All of these issues are documented on this forum. It seems like I'm the only guy reading this forum sometimes!

VitaminJ said:

DaveinOlyWA, "momentary drops in voltage mean nothing" this is complete wrong! It makes the brakes feel poor, it makes lights dim, and it makes windows roll up slowly. All of these issues are documented on this forum. It seems like I'm the only guy reading this forum sometimes!

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my comment was only made in reference to the role of the 12 volt battery after the car is running.

but your comments are interesting. so if I precondition my inverter with A/C my windows will roll up quicker?

DaveinOlyWA said:

my comment was only made in reference to the role of the 12 volt battery after the car is running.

but your comments are interesting. so if I precondition my inverter with A/C my windows will roll up quicker?

Click to expand...

With a weak battery the car will run and drive but all sorts of problems happen like brake issues, slow windows, warning lights, etc.

Yes if the 12v system voltage is at 14.4 because you used an accessory the windows will move faster than if they start at 13v. Faster still than if you relied on only the 12v battery itself. Anyone who's owned an ICE car knows the windows are slower with the engine off.

VitaminJ said:

DaveinOlyWA said:

my comment was only made in reference to the role of the 12 volt battery after the car is running.

but your comments are interesting. so if I precondition my inverter with A/C my windows will roll up quicker?

Click to expand...

With a weak battery the car will run and drive but all sorts of problems happen like brake issues, slow windows, warning lights, etc.

Yes if the 12v system voltage is at 14.4 because you used an accessory the windows will move faster than if they start at 13v. Faster still than if you relied on only the 12v battery itself. Anyone who's owned an ICE car knows the windows are slower with the engine off.

Click to expand...

on the brake issues there are some that feel that cycling traction control helps on at least a temporary basis. Have you tried that?

Yes I pretty much always drive with TCS turned off. I have also done the pedal calibration procedure. The biggest improvement was replacing the 12v battery.

What does your test with a good-condition AGM prove? Does your Leaf have an AGM? No? Ok thanks I guess :roll:

GerryAZ, your battery should be at 12.6v or higher.

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No it should not and that is exactly what I proved. AGM is lead acid battery. Still the same lead and acid.

Brake booster has integrated capacitor bank. I would expect it is operational even while having normal driving.



PS: removed the power supply 24h ago. Voltage is 12.7V. Charge state is somewhere between 95-105%.
Lets wait little more.

5Ah 2lbs battery still going strong after 60 days. Rain, snow, and shine, heater/AC, turtling, everything still working as normal.

VitaminJ said:

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2 lbs? nice! the terminals are almost as big as the battery itself

Had my first issue with the tiny 5Ah battery this weekend. The car was driven probably 150 miles on Friday and then parked at about 30% not plugged in. I went to drive it the next day maybe 14 hours later and got the spazzing dash lights, relay clicking, etc that accompany a low 12v battery.

Luckily the Tattu LifePO4 DOES have low-voltage protection, and simply turned itself off when the voltage was too low to protect itself, after charging for an hour or so all is back to normal.

I think the cooling fan and pump ran for a long time after parking it Friday (constant AC use, highway driving, and quick charging) and drained the 12v. For others less risk-adverse I would suggest at least a 10Ah LifePO4 battery, but I am still happy with the 5Ah model especially now that I know it will protect itself.

^^^ I think your right on what might have happened, 5ah isn't much capacity for running a large fan. As a backup should this happen when out and about, I might suggest a smallish portable 12v Li battery jumper. I always carry one in the back of my Leaf for just such occasions. It came with a 12v cigarette lighter adapter or small jumper cables, oh and it also has a 5v USB output for charging portable things that use USB.
All in all for the <$30 I paid for it on sale, I believe $39 regular price, I hope it's worth it, if I ever ran into a weak 12v battery
I bought mine at a big box hardware type of store(Menards) but I believe Amazon and other places sell similar models.

It's pretty stupid that the car had 7000wh onboard but cannot keep the 60wh 12v alive running a cooling fan for a few hours. It has been proven earlier in this thread that the OEM 12v battery really only delivers 10Ah of capacity before it can no longer support any functions. It's just plain stupid IMO, and ultimately the reason this very thread exists.

I actually have a few 4S 5000mah Lipos from an RC airplane that I keep in my cars with a modified jumper cable adapter for jump starting. I just keep it in the back at about 65% charge to maximize life and minimize fire risk and it still can deliver enough current to jump start an ICE in winter temperatures.

I was so fascinated with this thread I joined the forums just to be able to read and respond. Amazing to me that:

1) People are having this struggle with such a basic component of a much more sophisticated vehicle.
2) Folks are so pationate about their arguments and battery theory knowledge.

In my former ICE hobby days, batteries were really just a disposable, if expensive, nussiance. When one went bad or wouldn't charge any more because it was sulfated or whatever, we would just haul it out and go buy another without much thought. Charging systems in European ICE cars I fiddled with just weren't that complicated, and we all learned to fight crusty ground connections first before tossing out the alternator and the like.

I'm really glad (apparently) that I have an SL with a solar cell, apparently that's good.

Anyway, pleased to be on the forum, I'm enjoying the battery discussion.

jjeff said:

^^^ I think your right on what might have happened, 5ah isn't much capacity for running a large fan. As a backup should this happen when out and about, I might suggest a smallish portable 12v Li battery jumper. I always carry one in the back of my Leaf for just such occasions. It came with a 12v cigarette lighter adapter or small jumper cables, oh and it also has a 5v USB output for charging portable things that use USB.
All in all for the <$30 I paid for it on sale, I believe $39 regular price, I hope it's worth it, if I ever ran into a weak 12v battery
I bought mine at a big box hardware type of store(Menards) but I believe Amazon and other places sell similar models.

Click to expand...

Be careful with assuming that those LiIon jump-start packs will jump-start a Leaf with a discharged 12V battery.

The ones I have used, will only output 12V for jump-starting for a second or two - because they are small, their cables are small, and the current required to crank an engine would set fire to them in a few seconds.

The Leaf will not charge a 12V battery which is very deeply discharged - for example, if the voltage is too low. I have seen this with mine when the 12V battery went bad and was down to <11V. The Leaf would "start" on the power button and drive, but the DC-DC converter stayed off, because the 12V battery "looked bad" to the Leaf's electronics.

This second or two of power from a LiIon jump-start pack is not long enough to both power-on the Leaf, and have the Leaf decide the 12V battery is good enough to charge & start charging.

It takes no more than 10 amps to power up a Leaf, so I think the above doesn't apply. The caveat about not saving a dead 12 volt battery does apply.

VitaminJ said:

It's pretty stupid that the car had 7000wh onboard but cannot keep the 60wh 12v alive running a cooling fan for a few hours. It has been proven earlier in this thread that the OEM 12v battery really only delivers 10Ah of capacity before it can no longer support any functions. It's just plain stupid IMO, and ultimately the reason this very thread exists.

Click to expand...

Well two days ago I detailed my Leaf (and carpeting measurements for aftermarket special order). I was listening for the radio
for all the time in ACC mode. And had volume cranked up so I wouldn't hear the door open beeping :lol: :lol: 12V battery was supplying juice without DC-DC running. Then I went for a drive. Before doing that I took my DC-ammeter to measure current flow after switching vehicle on. Battery was sucking 30-40A. Though I had no time to measure for long.
It didn't go to 13V mode for few hours though, that I was monitoring. And HV pack was discharging 700-900W while parked (LeafSpy), no AC/fan running, no radio. Only 12V battery charging happening. 14V*40A=500-600W.
Well, I'm absolutely sure I drained much more than 10Ah out of that battery during those hours. 5-6 hours :lol:

Though I have 2014 Leaf. Those have different 12V algorithm than 2011/12.
OEM battery. Made in the beginning of 2014.

strowger said:

jjeff said:

^^^ I think your right on what might have happened, 5ah isn't much capacity for running a large fan. As a backup should this happen when out and about, I might suggest a smallish portable 12v Li battery jumper. I always carry one in the back of my Leaf for just such occasions. It came with a 12v cigarette lighter adapter or small jumper cables, oh and it also has a 5v USB output for charging portable things that use USB.
All in all for the <$30 I paid for it on sale, I believe $39 regular price, I hope it's worth it, if I ever ran into a weak 12v battery
I bought mine at a big box hardware type of store(Menards) but I believe Amazon and other places sell similar models.

Click to expand...

Be careful with assuming that those LiIon jump-start packs will jump-start a Leaf with a discharged 12V battery.

The ones I have used, will only output 12V for jump-starting for a second or two - because they are small, their cables are small, and the current required to crank an engine would set fire to them in a few seconds.

The Leaf will not charge a 12V battery which is very deeply discharged - for example, if the voltage is too low. I have seen this with mine when the 12V battery went bad and was down to <11V. The Leaf would "start" on the power button and drive, but the DC-DC converter stayed off, because the 12V battery "looked bad" to the Leaf's electronics.

This second or two of power from a LiIon jump-start pack is not long enough to both power-on the Leaf, and have the Leaf decide the 12V battery is good enough to charge & start charging.

Click to expand...

It depends upon the quality of the Li jump starter. I have used mine to start a 4.0L inline 6-cylinder, several different V-8 engines, motorcycles, and my 2015 Leaf (completely dead battery). Both of my Leafs (2011 and 2015) started just fine and recharged their 12-volt batteries after being completely discharged.

A little OT but tesla is abandoning 12V and CAN Bus in the model Y. Some facts here

https://teslamotorsclub.com/tmc/threads/no-can-bus-no-12v-for-model-y.90184/

In today's 1Q conference call, Elon stated that Model Y will not use a CAN bus, and instead use a new high speed bus. He said that while Model S used 3 km of wiring, and the Model 3 uses 1.5 km of wiring, the Model Y will use 100m.

He also said they will finally discard the legacy 12V power, which he derided as saying wasn't the right voltage for anything.