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

[coulomb]

The Hall-Effect sensor...

Duh! I assumed that they used a current shunt and op-amp. Hall effect devices are more convenient, but they have that terrible drift problem.

Perhaps they figure that they usually only need the current measurement for the first 10 minutes or so of operation, so that drift (usually a slow and steady thing) isn't a problem as they can measure the current when they know it should be very nearly zero, and simply add an offset to the measurement to cancel out the measured offset. Especially since:

I have never seen the charging voltage increase back up to absorption level without turning the car off and back on or turning on the windshield wipers.

If it wasn't for the wipers thing, this would be fine. I wonder if the wipers causing the return to absorb stage was only ever meant as a debugging tool and they forgot to take it out in production, and now find that drivers rely on it. So it remains to this day, I assume.

 

[coulomb]

The Hall-Effect sensor...

Duh! I assumed that they used a current shunt and op-amp. Hall effect devices are more convenient, but they have that terrible drift problem. [ Edit: and that makes my proposed hack impractical. ]

Perhaps they figure that they usually only need the current measurement for the first 10 minutes or so of operation, so that drift (usually a slow and fairly steady thing) isn't a problem as they can measure the current when they know it should be very nearly zero, and simply add an offset to the measurement to cancel out the measured offset. Especially since:

I have never seen the charging voltage increase back up to absorption level without turning the car off and back on or turning on the windshield wipers.

If it wasn't for the wipers thing, this would be fine. I wonder if the wipers causing the return to absorb stage was only ever meant as a debugging tool and they forgot to take it out in production, and now find that drivers rely on it. So it remains to this day, I assume.

 

[BluetoothMonster]

Here is a little video about this.

Enjoy. :roll:

https://www.youtube.com/watch?v=GXlHyZFSYoU

 

[coulomb]

Here is a little video about this.

Wow, 151 A briefly! I bet that a standard lead acid battery would not go that high.

Thanks for sharing.

 

[Nubo]

Here is a little video about this.

Wow, 151 A briefly! I bet that a standard lead acid battery would not go that high.

Thanks for sharing.

Lol, of course not. That would be 3C or above for the OEM battery. No way to get that unless maybe for that YouTube fellow "PhotonicInduction". Meanwhile, our fellow here just can't recognize that a 100AH Lithium pack represents close to a short circuit resistance to the DC/DC converter, and will take nearly everything it has to give, whereas a 40-50AH Lead/Acid battery has much higher internal resistance and is NOT THE SAME THING.

 

[BluetoothMonster]

Here is a little video about this.

Wow, 151 A briefly! I bet that a standard lead acid battery would not go that high.

knightmb has reported over 100A in the original lead acid battery on page 23. Its insane.


Thanks for sharing.

Thanks for watching.

 

[BluetoothMonster]

Lol, of course not. That would be 3C or above for the OEM battery. No way to get that unless maybe for that YouTube fellow "PhotonicInduction". Meanwhile, our fellow here just can't recognize that a 100AH Lithium pack represents close to a short circuit resistance to the DC/DC converter, and will take nearly everything it has to give, whereas a 40-50AH Lead/Acid battery has much higher internal resistance and is NOT THE SAME THING.

I needed to check out the word Photonicinduction.
And found this: Photonicinduction is the pseudonym of a personality and YouTube channel that used to mostly upload videos of him destroying or damaging electronics such as ...

I am done with you, this is the last answer i will give you.
Clearly you dont understand nothing about this, and starting with personal attack.
I will be very gently now and ask you this: Do you think the DCDC know that there is a lead acid battery in the other end, or will it give out max until...Whatever happens?

Remember, car producers uses smaller cables from the alternator in order to take down the A in the range the lead acid battery can handle.

And as a professional, you never install bigger charger then the batteri pack can take.
All this is very simpel knowledge.

Bear in mind, there are reported over 100A charge in a 2018 Leaf, in the ORIGINAL LEAD ACID BATTERY!

I will not answer you, maybe some other will.

 

[LeftieBiker]

Days like this I wonder why I moderate, because moderation is pretty clearly an archaic concept on the Web.

 

[BluetoothMonster]

Please, be a bit more civil.

Makes me wonder if this only goes for me, seeing what others clearly can write without any warning.
I am not close to that level.

But if the answers dont fit...

 

[nlspace]

A 35Ah 12V lead-acid starter battery typically has a CCA of 500 depending upon the brand, etc.

That means it can supply 500 Amps for 30 seconds at 0 F temperature.

So it could likely handle similar charging currents for very brief periods, e.g. <5 seconds.

The limiting factor might be the big fuse on the positive battery terminal, is it a 250A fuse?

 

[Nubo]

I am done with you, this is the last answer i will give you.
Clearly you dont understand nothing about this, and starting with personal attack.
I will be very gently now and ask you this: Do you think the DCDC know that there is a lead acid battery in the other end, or will it give out max until...Whatever happens?

The converter supplies power to the load. Current is drawn by the device, it is not pushed from the source, other than by varying voltage as I have already stated. Converter doesn't "know" your battery, it "assumes" that is lead-acid. The voltage in the LEAF DC/DC is controlled by an algorithm suited to lead-acid batteries. Not as well-suited as some may like but that is another story.

Remember, car producers uses smaller cables from the alternator in order to take down the A in the range the lead acid battery can handle.

This is wrong on the face of it. That would potentially overheat the cable and cause a fire. Perhaps you're confusing this with a "fusible link", which is there to protect against short circuits, not throttle the battery charging.

And as a professional, you never install bigger charger then the batteri pack can take.
All this is very simpel knowledge.

Wrong again; people regularly install larger alternators when they want to supply large stereo systems, winches, etc... The "bigger charger" is there whether or not those other systems are in use. It doesn't harm the battery.

Bear in mind, there are reported over 100A charge in a 2018 Leaf, in the ORIGINAL LEAD ACID BATTERY!

That was reported for a nearly-flat battery under 11V. In such case, yes it can take a large absorption charge, which will quickly taper down as the SOC rises. This doesn't harm the battery -- you will see the same behavior in other cars as well. When the lead-acid is at normal SOC, this does not happen. At least not for any appreciable length of time.

 

[Nubo]

...

 

[Nubo]

Days like this I wonder why I moderate, because moderation is pretty clearly an archaic concept on the Web.

Sorry. I'll be more tactful going forward.

 

[BluetoothMonster]

A 35Ah 12V lead-acid starter battery typically has a CCA of 500 depending upon the brand, etc.

That means it can supply 500 Amps for 30 seconds at 0 F temperature.

So it could likely handle similar charging currents for very brief periods, e.g. <5 seconds.

The limiting factor might be the big fuse on the positive battery terminal, is it a 250A fuse?

As we know, the CCA specification dont say anything about charge, is all about discharge when cold at a given volt, time and temperature.
The manufactors say, at best 0.3C charge, on the most expensive and best batteries. I stick to that, its for a reason.

But there are some data that says you may can go up to maybe 1.5C on lead acid, but under strictly conditions.
Sadly what the Leaf DCDC does is not that for a lead acid battery. Look at link in the bottom.

I think that the battery dont even start to boil and turns dry, the amperage is so high, and pulses, that the battery is beeing internal damaged before that happens. The better battery quality/conditions, the longer it will hold.
But thats just my opinion, based on the fact that I have read and seen my self.

After my temporary LiFePO4 swap, I have no problems.
Its not like what some people here thinks, that building a 100Ah pack will just change the problem parameter, and not the problem.
I used 100Ah since that was what I had in my shop.
I could use much smaller lithium pack, and the one I will build for permanent use will be 10Ah.
Its not the size here that matters, but what it can take in charge and discharge without beeing damaged rapidly.

It will be damaged to early in the end anyway, all the information about 12V batteries and Leaf confirmes that. (Also other EVs have this problem.)
But all this is about my nordic 2017 30Kw Leaf. I have not any clear picture over the differences between even the same year model and upgrades...
But why should it be so different on other models? We know that 2018model have over 100A charge in the original 12V lead acid battery.




https://batteryuniversity.com/article/bu-403-charging-lead-acid

 

[nlspace]

i wasn't talking about the typical charging for a long duration, but for brief quick time events.

Current flow is a chemical reaction in both directions, and there is no reason that it can't happen as quickly in one direction as the other, for short durations.

 

[BluetoothMonster]

Here is an Nissan e-NV200 owner that finds out that the charge can be a little high when it comes to A.

"In my env200 campervan I started off by changing the lead acid to a lithium battery, then I decided this was a bad idea since if you let it run flat the van will charge it almost 100A (I measured it!), this is too much current for a lithium to charge at....It got a bit warm."

Bad idea to swap back to lead acid if you asks me.

 

[coulomb]

Bad idea to swap back to lead acid if you asks me.

To me, the conclusion is: Don't switch to a tiny LFP battery; choose one that can take 100 A. So at least 30 Ah. If you can't afford that, use an AGM battery instead.

 

[fotajoye]

I haven't posted for sometime so forgive me if this is a misdirected question;
At times in this thread LiFePO4 batteries have been referenced.
My first Leaf was a 2011 SV, number 669 off the line and I replaced the 12 volt battery twice...that's 3 batteries in 9 years of use. I now have a 2019 S and anticipate having to replace the 12 volt battery sometime soon.
The question:
'What Lithium battery would you recommend as a replacement?'

 

[LeftieBiker]

You want LiFePo4, aka LFP, because it's a very stable chemistry, unlike the "LiPo" batteries. You also want to be in a climate where it rarely falls much below freezing, because it's not recommended that LFP batteries be charged when they are themselves at sub-freezing temps. If your corner of NorCal meets that requirement, then I suggest you look for a well-reviewed battery with a market history, rather than one by an unknown or little known Chinese company. I'd also suggest it be at least 20AH.

 

[goldbrick]

I'd also add that the 12V charging on the newer Leaf's appears to be better than what was used in some of the older model years. The 12V battery in your 2019 may last quite a bit longer than the 2011 although at 5 years or so, I'd replace it just to be safe.