The 12V battery charging algorithms

[jstoos]

... lead acid batteries of all sizes in all kinds of cars go dead EVERY DAY.

I don't think the fact that 12V batteries routinely die in parked ICE vehicles excuses Nissan for this flaw -- after all, unlike ICE vehicles which can only charge their batteries when the car is moving, our vehicles have a huge store of energy (up to 24HWH!) ready to be used to top off our 12V batteries whenever needed (I am referring of course to the traction battery). Not only that, but the problem occurs when plugged in-- in which case the amount of energy available to keep the 12V charged is unlimited! If only the car's "brain" would make use of it when needed...

 

[Seeley]

I don't know... If I had a lead acid battery in my Leaf that failed, and the car decided to drain the traction battery trying to keep the LA batt topped off, I'd be pretty pissed that instead of just needing a "jump" or an alternate LA battery, I also need to figure out where to get a splash of electricity for the traction battery to get me to the next charging station.

But, a manual override, to put charging power to the LA battery if "I" believed I needed it, that would be okay.

 

[LeftieBiker]

I don't know... If I had a lead acid battery in my Leaf that failed, and the car decided to drain the traction battery trying to keep the LA batt topped off, I'd be pretty pissed that instead of just needing a "jump" or an alternate LA battery, I also need to figure out where to get a splash of electricity for the traction battery to get me to the next charging station.

But, a manual override, to put charging power to the LA battery if "I" believed I needed it, that would be okay.

It wouldn't be difficult to limit the total amount of AHs sent to the 12V battery in a given period, in order to prevent the above scenario.

 

[FairwoodRed]

(2) This one requires a specially designed public EVSE station type: build one that has many cables/plugs per EVSE and a "multiplexer" system that only provides juice to one cable at a time (first come first serve) and then switches to the next one when the first one completes its charge. Then you could have as many cables/plugs as you have parking spaces they reach. (Are you listening AeroVironment, GE, Siemens etc.?)

Chargepoint is already going down that path. They now have the CT4000 http://www.chargepoint.com/files/CT4000-Data-Sheet.pdf that has two J1772's on one charger. If only one is is use, it has 6.6kw available. If both are connected, each one is limited to 3.3kw.

It wouldn't be too much more work for them to add more cords and the logic take turns.

 

[ev8309]

I'm beginning to find the multiple 12v starter battery threads amusing. On the one hand, there was (apparently) a "bad batch" of 12v batteries installed in a bunch of (2013?) Leafs; on the other hand, lead acid batteries of all sizes in all kinds of cars go dead EVERY DAY.

If you want a permanent solution, replace the 12v lead acid battery with a (good) LiFePO4 battery and your problem will be solved for years; this battery and this car (really any EV that doesn't need "cranking amps") are a very good fit for each other. Read my blog post to see what I did...

http://stanton.myevblog.com/2012/01/16/getting-the-lead-out/

I'm curious what you did. As an example, I looked at https://www.amazon.com/Optima-Batteries-8040-218-YellowTop-Purpose/dp/B000MSDKMA/ 'yellow top' and their 'will this battery fit' checker said it would not fit in my 2015 Leaf.

What are your thoughts?

Thanks.

 

[GerryAZ]

I'm beginning to find the multiple 12v starter battery threads amusing. On the one hand, there was (apparently) a "bad batch" of 12v batteries installed in a bunch of (2013?) Leafs; on the other hand, lead acid batteries of all sizes in all kinds of cars go dead EVERY DAY.

If you want a permanent solution, replace the 12v lead acid battery with a (good) LiFePO4 battery and your problem will be solved for years; this battery and this car (really any EV that doesn't need "cranking amps") are a very good fit for each other. Read my blog post to see what I did...

http://stanton.myevblog.com/2012/01/16/getting-the-lead-out/

I'm curious what you did. As an example, I looked at https://www.amazon.com/Optima-Batteries-8040-218-YellowTop-Purpose/dp/B000MSDKMA/ 'yellow top' and their 'will this battery fit' checker said it would not fit in my 2015 Leaf.

What are your thoughts?

Thanks.

The D51R Yellow Top Optima is a direct fit replacement for at least 2011 through 2015 LEAFs. I put one in the 2011 when the original failed and it was still in use when the car was totaled. I put one in the 2015 when the original failed in October 2017.

Edited to add: The charging algorithms for the 2011 and 2015 are ideal for my usage patterns so I never connected an external 12-volt battery charger to either Leaf.

 

[ev8309]

Thanks!

 

[Irling]

Hello everyone, I want to install a battery lifepo4 (4s2p 100ah cells) on my car in 2014 aze0, tell me at what voltage the battery will start charging? I reckon that up to 13 volts, my battery will be able to provide electricity to all consumers, and this will save the charge of the high-voltage battery? thanks

 

[Nubo]

Hello everyone, I want to install a battery lifepo4 (4s2p 100ah cells) on my car in 2014 aze0, tell me at what voltage the battery will start charging? I reckon that up to 13 volts, my battery will be able to provide electricity to all consumers, and this will save the charge of the high-voltage battery? thanks

If I understand your intention, this isn't going to save much charge from the high voltage battery. The 12V system on the car is generally only consuming a couple of hundred watts. You'd only be saving perhaps 1 mile of range for every hour of operation. Are you perhaps intending to use this power for other purposes such as heating?

Iirc, the dc-dc converter typically supplies 13V though there are times when it climbs up to 14.5 for bulk charging and (for some reason) while the wipers are on; perhaps to cause the incandescent headlights to be brighter (speculation on my part).

 

[Irling]

Thanks for the answer! I want to use constantly heated all the seats and steering wheel, as well as use 12V for heating the high-voltage battery in the winter. The characteristic of my battery lifepo4 allows you to discharge about 70% (2kwth) of the capacity to a voltage of 13 volts.
If the DC / DC converter always supports 13 volts, that will be enough not to use the energy of high-voltage battery. When you connect the charger, my 12 volt battery will be charged to 14.5 volts, right?

 

[LeftieBiker]

Your best bet is to use an AGM battery rather than LifePo4. It will be happy with the Leaf's system voltage and can safely be drained much more than the original small starting battery.

 

[Nubo]

Thanks for the answer! I want to use constantly heated all the seats and steering wheel, as well as use 12V for heating the high-voltage battery in the winter. The characteristic of my battery lifepo4 allows you to discharge about 70% (2kwth) of the capacity to a voltage of 13 volts.
If the DC / DC converter always supports 13 volts, that will be enough not to use the energy of high-voltage battery. When you connect the charger, my 12 volt battery will be charged to 14.5 volts, right?

I suspect you'd have to charge your LiFePO externally to make use of its full capacity. The car tends to chronically undercharge even the 12V battery. 14.5V period is brief and then drops to 13V "float charge". When I measure my 12V battery at rest, it is typically near 12.5V.

Here's a thread with a lot of LEAF vs. 12V information: https://www.mynissanleaf.com/viewtopic.php?t=19471

 

[LeftieBiker]

The car tends to chronically undercharge even the 12V battery.

This seems to be an artifact of the OEM battery being so small. Larger AGM batteries seem to charge much better.

 

[Learjet]

Did some test on my 2019 SL Plus...

Plugged in the L2 charger....12 volt battery immediately showed bulk charging at 14.4 volts and taking ~7 amps... measured with my clamp on ammeter.

After some time...20 mins or so...don't know if it's a time or amp drop that triggered the voltage to drop to a float voltage of 13.1

just some observations on the GEN 2 charging.

 

[lorenfb]

Did some test on my 2019 SL Plus...

Plugged in the L2 charger....12 volt battery immediately showed bulk charging at 14.4 volts and taking ~7 amps... measured with my clamp on ammeter.

After some time...20 mins or so...don't know if it's a time or amp drop that triggered the voltage to drop to a float voltage of 13.1

just some observations on the GEN 2 charging.

Basically the same as my '13.

 

[GerryAZ]

Did some test on my 2019 SL Plus...

Plugged in the L2 charger....12 volt battery immediately showed bulk charging at 14.4 volts and taking ~7 amps... measured with my clamp on ammeter.

After some time...20 mins or so...don't know if it's a time or amp drop that triggered the voltage to drop to a float voltage of 13.1

just some observations on the GEN 2 charging.

It drops to float voltage when the current flowing into the battery drops below about 2 amperes. 2011 dropped to float at about 6 amperes; 2015 about 3 amperes.

 

[DaveinOlyWA]

Did some test on my 2019 SL Plus...

Plugged in the L2 charger....12 volt battery immediately showed bulk charging at 14.4 volts and taking ~7 amps... measured with my clamp on ammeter.

After some time...20 mins or so...don't know if it's a time or amp drop that triggered the voltage to drop to a float voltage of 13.1

just some observations on the GEN 2 charging.

Wow. I should retest mine. I did the 12 volt charge monitoring on my 2013 and 2016 and never saw a charge session lasting longer than about 7-8 minutes. I have to go back to look at data but in EVERY case, the battery was not charged to full, just boosted and not boosted very much.

 

[eaf]

Speaking of 12V battery charging, I have a problem...

Driver side blue light flashes all the time. According to the manual it could be either due to Climate Control Timer, HV Battery Heater or 12V Battery Charging. It appears to be the latter one because there are no timers configured, it's not too cold, and I can see that the 12V battery is indeed being charged, as it has 14V on it.

What happens after I turn off the Leaf is that voltage on the battery briefly drops to 12.6V, then jumps to 14V, water pump starts making noise and the light starts flashing. All of this was going on for 24 hours already and HV charge is definitely dropping.

Any idea of what could be wrong here?

 

[GerryAZ]

Check temperature switch and entire water pump control system. Water pump should not run when car is off. If water pump runs, 12-volt battery will discharge and DC-DC converter will turn on to charge it.

Edited to add: If water pump does not start until charging starts, then that is normal because DC-DC converter is water cooled. In that case, check condition of 12-volt battery (replace if weak) and look for abnormal residual current draw.

 

[Lothsahn]

Speaking of 12V battery charging, I have a problem...

Driver side blue light flashes all the time. According to the manual it could be either due to Climate Control Timer, HV Battery Heater or 12V Battery Charging. It appears to be the latter one because there are no timers configured, it's not too cold, and I can see that the 12V battery is indeed being charged, as it has 14V on it.

What happens after I turn off the Leaf is that voltage on the battery briefly drops to 12.6V, then jumps to 14V, water pump starts making noise and the light starts flashing. All of this was going on for 24 hours already and HV charge is definitely dropping.

Any idea of what could be wrong here?

What year is your car? Any chance your high voltage battery (not the 12V) was ever swapped? We've had a couple people who posted that a 2011 battery was swapped into a 2012, which caused the light to illuminate and the battery to drain because the car was constantly searching for the battery heater that doesn't exist in the 2011 pack.

Nobody mentioned water pump noises, though, so I think your problem is different.