Is there a definitive answer on charging to 80% or 100%?

[knightmb]

Hopefully you told your friends and family that they are participating in an experiment that involves going against the usual ways of extending battery pack life.

Myself included, in 2 years we will have data on a 5 year old battery charged to 100% SOC all the time vs. others here that never charge over 80% and have some data to compare.

It's not an experiment, it's a choice for how to use your vehicle. That is similar to claiming that people living in AZ should not buy a Leaf because of the heat degradation to the battery. All my friends and family know the risk and do their own research here and other places. State of charge degradation seems to be overblown here, in my opinion, based what I've researched. It doesn't mean I claim it doesn't exist, only that the effect is not as great in the long run as other variables such as heat, age, and usage.

It's best that the topic creator get both sides of the discussion to make a proper decision later on how they want to drive or use their vehicle.

 

[Stanton]

I was wondering about the 12v battery issue since I plan on renting another car for an extended trip of 1 month. I had planned to leave my Leaf plugged in as it is set to charge to 80% every morning but 1 weekly and that 1 is set to 100%. Should I consider also hooking up my 12v battery to a battery tender like I used to keep my motorcycle battery on during off season? Doesn't the 12v battery charge off the traction battery when it needs a charge anyway?

Correct: the traction pack with "top off" the 12v battery every 5 days or so if left unplugged/unused. However, that overlooks the problems of 12v lead-acid batteries in general (hence the LiFePO4 replacement). One other thing: I would never leave my Leaf plugged in for weeks at a time simply because any sort of grid power failure/surge (weather or otherwise) could damage the EVSE/car. YMMV.

 

[LeftieBiker]

I was wondering about the 12v battery issue since I plan on renting another car for an extended trip of 1 month. I had planned to leave my Leaf plugged in as it is set to charge to 80% every morning but 1 weekly and that 1 is set to 100%. Should I consider also hooking up my 12v battery to a battery tender like I used to keep my motorcycle battery on during off season? Doesn't the 12v battery charge off the traction battery when it needs a charge anyway?

Correct: the traction pack with "top off" the 12v battery every 5 days or so if left unplugged/unused. However, that overlooks the problems of 12v lead-acid batteries in general (hence the LiFePO4 replacement). One other thing: I would never leave my Leaf plugged in for weeks at a time simply because any sort of grid power failure/surge (weather or otherwise) could damage the EVSE/car. YMMV.

Just to make this very clear: if the car will be plugged in and not charging 95+% of the time, you MUST use a battery maintainer, or the odds are overwhelming that in that length of time the 12 volt battery will be killed. The short period it spends charging daily won't make up for the loss from the EVSE-sensing drain. Neither will the once every 5 days charge from the pack.

 

[JeffnReno]

I was wondering about the 12v battery issue since I plan on renting another car for an extended trip of 1 month. I had planned to leave my Leaf plugged in as it is set to charge to 80% every morning but 1 weekly and that 1 is set to 100%. Should I consider also hooking up my 12v battery to a battery tender like I used to keep my motorcycle battery on during off season? Doesn't the 12v battery charge off the traction battery when it needs a charge anyway?

Correct: the traction pack with "top off" the 12v battery every 5 days or so if left unplugged/unused. However, that overlooks the problems of 12v lead-acid batteries in general (hence the LiFePO4 replacement). One other thing: I would never leave my Leaf plugged in for weeks at a time simply because any sort of grid power failure/surge (weather or otherwise) could damage the EVSE/car. YMMV.

Just to make this very clear: if the car will be plugged in and not charging 95+% of the time, you MUST use a battery maintainer, or the odds are overwhelming that in that length of time the 12 volt battery will be killed. The short period it spends charging daily won't make up for the loss from the EVSE-sensing drain. Neither will the once every 5 days charge from the pack.

So now I'm confused as to the best course of action to take if I'm leaving my Leaf parked for a month. Should I just charge it to 80% the day I'm leaving and don't leave it plugged in but put the 12v on a maintainer or should I leave it plugged in and let the timer keep it at 80% while I'm gone but also put the 12v on the maintainer or should I just park it at 80% and walk away assuming all will be fine 30 days later? Or is there other recommendations I need to know about to avoid problems when I return?

 

[LeftieBiker]

You can leave the car charged to 80% and unplugged. As long as you have no OBDII code reader plugged in, or other 'phantom drain' on the 12 volt battery, it should be fine. It would be a good idea, though, to make sure the 12 volt battery is charged fully when you leave home. The only real drain on the pack is the battery warmer, and that only comes on in frigid temps.

 

[JeffnReno]

You can leave the car charged to 80% and unplugged. As long as you have no OBDII code reader plugged in, or other 'phantom drain' on the 12 volt battery, it should be fine. It would be a good idea, though, to make sure the 12 volt battery is charged fully when you leave home. The only real drain on the pack is the battery warmer, and that only comes on in frigid temps.

Sounds good to me. I searched some other threads on this forum for this subject and there seems to be alot of over thinking this. Thanks.

 

[Nubo]

So now I'm confused as to the best course of action to take if I'm leaving my Leaf parked for a month. Should I just charge it to 80% the day I'm leaving and don't leave it plugged in but put the 12v on a maintainer or should I leave it plugged in and let the timer keep it at 80% while I'm gone but also put the 12v on the maintainer or should I just park it at 80% and walk away assuming all will be fine 30 days later? Or is there other recommendations I need to know about to avoid problems when I return?

50% would be ideal, but 80% is probably fine. I would not let the car sit for a month with the 12V battery connected. Dark current will either run the battery flat in that time, or at least could weaken it. Most 12V are not deep-cycle batteries.

For the 12V the ideal would be a maintainer, but the simplest thing imho is to simply disconnect the 12V battery. A 10mm wrench and you're good to go. This is what I have done but I have never left the car idle for more than a month. Much longer than a month then I would start looking more seriously at the maintainer to keep the 12v topped off from self-discharge. Some of this depends on how often you plan on these episodes. There's a slight hassle when reconnecting the battery and resetting timer preference, etc... This seems to bother some folks more than others.

 

[Stanton]

You can leave the car charged to 80% and unplugged. As long as you have no OBDII code reader plugged in, or other 'phantom drain' on the 12 volt battery, it should be fine. It would be a good idea, though, to make sure the 12 volt battery is charged fully when you leave home. The only real drain on the pack is the battery warmer, and that only comes on in frigid temps.

Sounds good to me. I searched some other threads on this forum for this subject and there seems to be alot of over thinking this. Thanks.

Every time the OP gets it "figured out" someone comes along and derails him! Stick with this plan and let us know how it goes.

 

[baustin]

My car is always plugged in when I'm not driving it. It has a charge timer that kicks off every morning at 2am. It sat for several ten day stretches, during the winter, with no issues. I check the 12v battery every spring and top off the cells with distilled water. They were down at least a third when I bought the car. The only time I had 12v battery issues was when I left the blue-tooth dongle plugged in for several days without driving the car.

 

[LeftieBiker]

My car is always plugged in when I'm not driving it. It has a charge timer that kicks off every morning at 2am. It sat for several ten day stretches, during the winter, with no issues. I check the 12v battery every spring and top off the cells with distilled water. They were down at least a third when I bought the car. The only time I had 12v battery issues was when I left the blue-tooth dongle plugged in for several days without driving the car.

If you mean that it sat for several ten day stretches without being driven, while plugged in, that's amazing. Was the battery warmer running and draining pack charge?

 

[baustin]

My car is always plugged in when I'm not driving it. It has a charge timer that kicks off every morning at 2am. It sat for several ten day stretches, during the winter, with no issues. I check the 12v battery every spring and top off the cells with distilled water. They were down at least a third when I bought the car. The only time I had 12v battery issues was when I left the blue-tooth dongle plugged in for several days without driving the car.

If you mean that it sat for several ten day stretches without being driven, while plugged in, that's amazing. Was the battery warmer running and draining pack charge?

I'm not sure it gets cold enough here to turn the battery warmer on. We had maybe ten days below freezing all winter. Due to range needs, I changed the charging timer around the end of November to six days at 100% instead of two days. Since the SOH is now down to 74%, I have left it that way. I believe the 100% charge cycle, six days a week, keeps the 12v battery topped off. The charge cycle takes 25 minutes when the battery is already at 100%.