Using EVSE timer for charging / 12VDC battery drain

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BillAinCT

Well-known member
Joined
Dec 2, 2021
Messages
151
Location
West Hartford, CT
Is there any issue with using the scheduling in my EVSE to start and stop charging? Does the Leaf "mind" having the charging current abruptly stop? I notice EVConnect doesn't know - it still says charging. I started charging manually and set a stop time to get me to 90% (I see about 10% per hour while charging). It stopped at 89%.

If charging has been stopped by the EVSE or you just want to stop charging, can you use the car remote to open the port. Doing this makes it click and blink like it has stopped charging. If the EVSE is left connected in this not charging state (assuming it is in that state after opening the charge port) is there still the risk of 12VDC battery drain?

Thanks!
Bill
 
BillAinCT said:
Is there any issue with using the scheduling in my EVSE to start and stop charging? Does the Leaf "mind" having the charging current abruptly stop? I notice EVConnect doesn't know - it still says charging. I started charging manually and set a stop time to get me to 90% (I see about 10% per hour while charging). It stopped at 89%.

If charging has been stopped by the EVSE or you just want to stop charging, can you use the car remote to open the port. Doing this makes it click and blink like it has stopped charging. If the EVSE is left connected in this not charging state (assuming it is in that state after opening the charge port) is there still the risk of 12VDC battery drain?

Thanks!
Bill

As far as does the LEAF mind? Well, it depends on how the EVSE terminates the charge. I know when I unplug mine (which is actively charging all but 15 times in the past 28+ months) the EVSE will "freak" out flashing like a Christmas tree half the time. I don't know if this affects the car but guessing it does in one way or another but have to think its a small thing.

On the 12 volt battery drain; the 12 volt is boosted essentially on a timer of sorts. It happens regularly (probably daily) and can happen at any time, charging, not charging, sitting unplugged or when running.

So the only real risk is the power taken from the 12 volt between these boosts when the car is not on. Having the car plugged in likely puts it in a higher state of readiness but I am thinking it eventually times out so basically forgets its plugged in. I tried to monitor this but couldn't get LEAF Spy to stay focused enough to find out. When that failed, I tried measuring the 12 volt connected to the car several times a day to see if there was ever any noticeable load. Didn't work either.

For the TLDR version

https://daveinolywa.blogspot.com/2021/04/charge-your-leaf-every-day.html
 
These concerns are a reason why we have the fancy connector and EVSE as part of the J1772 charging standards.

The J1772 specification provides safety mechanisms to prevent arcing or exposure to live mains voltage if the plug is removed while charging. One of the pins is a low-voltage "control pilot" signal. If this signal is lost, the EVSE stops providing power and charging is halted.

When you squeeze the trigger to release the handle, it disconnects the pilot signal. If this were to fail the pilot pin in the socket is shorter than the other pins, so pilot signal is lost first, still giving time for EVSE to stop delivering power before the main AC lines disconnect.
 
On the 12 volt battery drain; the 12 volt is boosted essentially on a timer of sorts. It happens regularly (probably daily) and can happen at any time, charging, not charging, sitting unplugged or when running.

The one time the car doesn't seem to be able to add charge to the 12 volt battery is when it's plugged in but not charging. This becomes an issue eventually, but a few hours isn't likely to be a problem unless the 12 volt battery was almost drained to begin with.
 
LeftieBiker said:
On the 12 volt battery drain; the 12 volt is boosted essentially on a timer of sorts. It happens regularly (probably daily) and can happen at any time, charging, not charging, sitting unplugged or when running.

The one time the car doesn't seem to be able to add charge to the 12 volt battery is when it's plugged in but not charging. This becomes an issue eventually, but a few hours isn't likely to be a problem unless the 12 volt battery was almost drained to begin with.

"seems" that way but unproven. The anecdotal evidence points to that since many have had dead 12 volts when plugged in but what if the car was simply at a higher state of readiness because of being plugged in and the extra load is what killed the battery?

This has brought to mind some ideas on how to maybe detect this? Something I haven't tried would be setting a charge timer then plugging in and seeing how much if any voltage drop we get from that? So easy to test and so obvious so why didn't I think of that when I was doing all this monitoring?
 
The anecdotal evidence points to that since many have had dead 12 volts when plugged in but what if the car was simply at a higher state of readiness because of being plugged in and the extra load is what killed the battery?

No one, to my knowledge, has observed (via the flashing blue charging light) a Leaf charging the 12 volt battery while plugged in. Also, I'd be quite surprised if the DC-DC converter wasn't providing enough amps to the 12 volt battery to compensate for a couple of modules staying awake...
 
LeftieBiker said:
The anecdotal evidence points to that since many have had dead 12 volts when plugged in but what if the car was simply at a higher state of readiness because of being plugged in and the extra load is what killed the battery?

No one, to my knowledge, has observed (via the flashing blue charging light) a Leaf charging the 12 volt battery while plugged in. Also, I'd be quite surprised if the DC-DC converter wasn't providing enough amps to the 12 volt battery to compensate for a couple of modules staying awake...

Unless the 12 volt is being boosted, the 12 VDC system provides nothing unless the car is on. My average resting voltage ran from 12.1 to 12.4 volts
 
The DC/DC Converter which charges the 12V battery, can only operate when the main contactors within the Pack are energized, such as when in READY or the EVSE is charging.

Energizing the main contactors requires 12V power from the VCM.

The VCM has multiple 12V input feeds which are switched thru relays.

Most of these relays get their control signals from the VCM.
 
Sorry for combining 2 topics - I was thinking they are related. I contacted the EVSE manufacturer (Emporia Energy) and they said they are communicating with the car when they are going to stop charging. EVConnect still said the Leaf was charging (not plugged in like it does) so I don't know what gets the Leaf back to the plugged in state. I don't want to use the EVSE scheduling only to find out in doing do I've dropped the 12V battery down to not being able to start.

About 12V charging. If your 12V battery is dead (enough not to start the car) and you jump it and it turns on, Then if you remove the 12VDC host from the Leaf, will it be in charge state until it's fully charged? I'm asking because if you get a jump in this low 12V state, how do you prevent it from not starting the next time you stop and start again? I know with an ICE, driving for even 30 minutes is enough to restart the car.
 
BillAinCT said:
About 12V charging. If your 12V battery is dead (enough not to start the car) and you jump it and it turns on, Then if you remove the 12VDC host from the Leaf, will it be in charge state until it's fully charged? I'm asking because if you get a jump in this low 12V state, how do you prevent it from not starting the next time you stop and start again? I know with an ICE, driving for even 30 minutes is enough to restart the car.

FLA batteries can have different "failure" modes. A highly sulfated battery will have low energy levels that can cause rapid drawdown of voltage/energy when stressed above normal requirements. On my ICE vehicles, this usually showed up as a rapid slowdown of the starter - might start, might not. A FLA battery with a dead cell, or a shorted/leaking cell can show a high false voltage that essentially drops to very low voltage (like 9-10 volts) with any load. In these cases, no amount of charging will "restart" the car. In my ICE car experience this results in nothing but "clicking". In my 2012 Leaf, it was simply dead!

Highly sulfated FLA batteries usually have a low "settled voltage" - 12.4 and less in my experience.
 
The 12 volt battery gets charged while you drive, but not as quickly as with a car with an alternator - at least not usually. The most reliable solution is to install a SAE lead on the battery (ground to the PDM stack or similar) so you can plug in a battery maintainer along with the charging cable. And yes, it's fine to have the maintainer working while the car is charging.

One slip-in ahead of me.
 
BillAinCT said:
Sorry for combining 2 topics - I was thinking they are related. I contacted the EVSE manufacturer (Emporia Energy) and they said they are communicating with the car when they are going to stop charging. EVConnect still said the Leaf was charging (not plugged in like it does) so I don't know what gets the Leaf back to the plugged in state. I don't want to use the EVSE scheduling only to find out in doing do I've dropped the 12V battery down to not being able to start.

About 12V charging. If your 12V battery is dead (enough not to start the car) and you jump it and it turns on, Then if you remove the 12VDC host from the Leaf, will it be in charge state until it's fully charged? I'm asking because if you get a jump in this low 12V state, how do you prevent it from not starting the next time you stop and start again? I know with an ICE, driving for even 30 minutes is enough to restart the car.
From a functional standpoint, an EV "charges" the 12v battery just like an ICE "charges" the 12v battery, so it will charge after being "jumped".
However, their are other consequences of a dead (or even weak) 12v battery in a Leaf, which is why there are (at least) a hundred posts on this Forum about 12v batteries...and replacing them before they ever get to that point.

The following 2 facts about 12v battery behavior in the Leaf may help you with your EVSE question:
  • when plugged in and charging, the 12v battery is periodically charged/topped off
  • when plugged and not charging, the 12v battery is being drained (in some form)
These come with 2 caveats:
  • you can't necessarily discern this behavior from the 3rd blinking (or any blinking) lights
  • there may be additional (parasitic) drain on the 12v depending on what type of accessories/devices are being used (e.g. ODB-II port)
Hope that helps.
 
Yes, all of all of your comments are helpful. I read many more of the battery posts. One thing that I wish were possible is to list which Gen 1 problems, quirks or issues are also in Gen 2. There are many many gen 1 posts and how do newer owners know if they apply or not to a gen 2?

I did read the LS 12V reading shouldn't be (necessarily) trusted. With LS showing me 11.90V to 12.2V I was worried I was close to the problem causing lower limit. With an ICE, I'm used to seeing 12.5-12.75.V.

With so many reporting gen 1's slowly draining the 12V battery, why didn't Nissan do something about it? Does anyone know technically why the charging was done like it was? And why it wouldn't be or couldn't be improved? I imagine it's to keep a very low-current path from the traction battery step-down to 14V for the battery charge. But if the 12V is low, why wasn't there a higher current path to power the dash to be able to drive? I still can't get past the fact that a charged electric vehicle needs to be jumped. If there is at least 3.2V average cell voltage, why not allow the dash to be powered? If it's about safety, I'm sure something can be done that is safe.
 
The issue appears to have been partially fixed in the Gen II Leafs. They also tend to have a lower charge level, but apparently get dead batteries much less often. I've measured three Gen II Leafs over the last 3 years, and it's common for them to run about 12.3 volts. Sometimes, through, they have more like 12.75.

I did read the LS 12V reading shouldn't be (necessarily) trusted. With LS showing me 11.90V to 12.2V I was worried I was close to the problem causing lower limit. With an ICE, I'm used to seeing 12.5-12.75.V.

Actually, it's kind of the other way around. LeafSpy usually reports an artificially HIGH voltage because the DC-DC converter is running, and masking a lower 12 volt battery voltage. If you are getting low numbers, I suspect that you are in Accessory mode when you take the reading.
 
BillAinCT said:
Yes, all of all of your comments are helpful. I read many more of the battery posts. One thing that I wish were possible is to list which Gen 1 problems, quirks or issues are also in Gen 2. There are many many gen 1 posts and how do newer owners know if they apply or not to a gen 2?

Having owned a Gen I and II - and a failure of the OEM battery in the Gen I, I do have some anecdotal comments:
- The Gen I OEM battery consistently kept the settled voltages in the 12.3 to 12.4 range. This voltage range does promote sulfation and not surprised that it appeared to have about 50% of it's original capacity when I purchased the Leaf. I don't know exactly why it finally failed, but since the the ampere draw is typically so minor in the Leaf, it gave good service even though not kept in the 12.6 to 12.7 V settled range typically needed for a FLA battery (to prevent the sulfation).
- The battery voltage readings at a given point are basically meaningless, unless the battery is essentially disconnected and let "settle" for 24 hours or so. The instantaneous ampere draw determines the voltage - it follows a well defined curve for most batteries of a specific manufacturer. If you can accurately correlate this ampere draw and voltage, it gives a good approximation of the battery condition. However, the best method is to do an accurate load test and compare to the spec Ahr rating (typically the 20 hour value).
- As my Gen II is relatively new, I have not yet tried to measure its degradation. However, the couple of tests of settled voltage so far indicate not too much difference than the Gen I - i.e., the charging profile might still be too low for the best maintenance of a FLA type battery. Treat this as early information, and I will continue testing periodically.
 
BillAinCT said:
With so many reporting gen 1's slowly draining the 12V battery, why didn't Nissan do something about it? Does anyone know technically why the charging was done like it was?And why it wouldn't be or couldn't be improved?
Some perspective here.
Most of what you see posted on a forum like this are problems from a small percentage of owners that even bother to post; luckily we also get solutions from an equally small percentage of owners that help us (like put in a LiFePO4 12v battery and don't worry about it again). The majority of owners either have no issue with the 12v battery...or they replace them (regularly) like they do with their ICE cars. That doesn't mean there isn't room for improvement in the design or that everyone wants to implement every suggestion made...but it's about perspective.
 
I think that the algorithm for charging the 12 volt battery was improved just enough to greatly reduce the number of dead 12 volt batteries, while failing to solve the issue of the batteries being chronically undercharged.
 
The charging algorithm was improved over the years. My 2011 would drop from approximately 14 volts to approximately 13 volts (float charging voltage) while the charging current into the battery was in the range of 6 to 10 amperes. My 2015 would keep charging at about 14 volts until the charging current dropped to about half the range of the 2011. My 2019 keeps charging at about 14 volts until the current into the battery drops to about 2 or 3 amperes. All three of my LEAF's kept their 12V batteries charged with my usage and charging patterns so I never connected an external 12V charger to the 2011 and 2015 and have not yet connected an external charger to the 2019. The OEM batteries in all three cars lasted longer in my climate than typical for 12V car batteries. I replaced the OEM batteries with group size 51R Optima deep cycle (yellow top) AGM batteries. The Optima in the 2011 was fine when the car met its demise and the one in the 2015 was still OK when I traded it in on the 2019. I hope to keep the 2019 long enough to find out how long the Optima that I installed last fall lasts.
 
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