Long Vacation - Advisable to be plugged in all the while?

Hello All,

If one were going on a long vacation, say over a month, is it advisable to leave the leaf plugged in with a timer set to come on only one day a week, and charge to 80%?
I've read the posts and the manual that suggest to charge it up to 80%, unplug it, come back after a month or so, charge it up full again a couple of times.

But is there anything wrong with just leaving it plugged in, and use the timer just once a week? That way, when one comes back, the car will still be at 80%.

-M

I recommend getting the charge to around 60%, then park (hopefully inside) and disconnect the negative terminal of the 12v battery under the hood. You only need a wrench.

When you return, simply reconnect the terminal and your Leaf will power up and drive off with only a few % loss of charge. (You will have to reset your clock on the dash)

If you leave it plugged in, you will destroy your 12v battery, and keeping the main battery at 80% is rough on it.

-Phil

Ingineer said:

I recommend getting the charge to around 60%, then park (hopefully inside) and disconnect the negative terminal of the 12v battery under the hood. You only need a wrench.

When you return, simply reconnect the terminal and your Leaf will power up and drive off with only a few % loss of charge. (You will have to reset your clock on the dash)

If you leave it plugged in, you will destroy your 12v battery, and keeping the main battery at 80% is rough on it.

-Phil

Click to expand...

for travel vacations, at what length of parked at home in 40-80-degree temperatures would you NOT just charge to 60%, unplug and leave the car sit?
one week?
3 weeks?
a month or more?

I dont get why you bother to disconnect. wont the 12v hold a charge for a month?
my ice batteries do if i leave town.

There have been several threads on this in the past few months. Please search and read those. Bottom line: Follow Phil's advice (although I didn't unhook the 12 V battery and it worked fine after two weeks). Others have tried various options that also work. What DOESN'T work is to leave it plugged in (this will drain the 12 V battery and you won't be able to restart).

For a week or maybe up to 2, you can leave the 12v connected. But even if it will "make it", it's still stressing the 12v battery out by deep-cycling it, and it will have a shorter lifespan. In addition, it's going to use some of your traction pack to attempt to charge the 12v. If you don't care about the lifespan, and don't want to bother disconnection, then don't. We are already seeing 12V battery failures in the field, so anything that can be done, (and disconnection is not hard) helps it's life and also insures your Leaf will power up when you return.

-Phil

Ingineer said:

We are already seeing 12V battery failures in the field, so anything that can be done, (and disconnection is not hard) helps it's life and also insures your Leaf will power up when you return.

Click to expand...

The above would argue that many people in fact need to disconnect their 12V batteries when they go on vacation but don't do it. Maybe a short description of how the 12V battery is properly disconnected (see Phil's previous post) and why this is a very reasonable thing to do should be added to the wiki.

Ingineer said:

For a week or maybe up to 2, you can leave the 12v connected. But even if it will "make it", it's still stressing the 12v battery out by deep-cycling it, and it will have a shorter lifespan. In addition, it's going to use some of your traction pack to attempt to charge the 12v. If you don't care about the lifespan, and don't want to bother disconnection, then don't. We are already seeing 12V battery failures in the field, so anything that can be done, (and disconnection is not hard) helps it's life and also insures your Leaf will power up when you return.

-Phil

Click to expand...

Thanks, Phil.
I think my question is really focused on whether you degrade the 12v if you leave the car parked for an extended period of time NOT plugged in. I get that plugged in is a no no.
Is that what you are saying: that the 12v gets stressed even when the LEAF is not plugged in because the 12v cycles and pulls power from the traction battery?

In the same vein, i thought the solar panel -- if you are parked outside -- would handle charging maintenance/cycling on the 12v for an extended period. Am I wrong about that?

(i get that disconnecting the 12v at the negative cable is easy. I just prefer not doing it if it is not necessary.)
((and yes, Reddy, I have read all those posts and I never got from them that leaving the car parked and not plugged -- especially an SL with the solar panel -- is an issue.))

What about if the car is parked outside & the spoiler is exposed to some sunlight during the day?

Isn't that what the spoiler solar cells do? Trickle charge the 12 volt?

Philip

Alternately to disconnecting the 12 volt battery, you can put the 12 volt on a battery tender (plugged in to 120v). Of course, leave the J1772 unplugged with the traction battery at mid range energy level.

That way you won't lose any settings like the clock and won't need a wrench. Battery tenders are $10-$50.

thankyouOB said:

Is that what you are saying: that the 12v gets stressed even when the LEAF is not plugged in because the 12v cycles and pulls power from the traction battery?

In the same vein, i thought the solar panel -- if you are parked outside -- would handle charging maintenance/cycling on the 12v for an extended period. Am I wrong about that?

Click to expand...

Unlike Lithium batteries, Lead-acid batteries are happiest when they are kept or near 100% SOC. A normal ICE car battery uses a few percent of its capacity to start the car and is then "put back on the charger", so to speak, as the car is driven. This is a very shallow discharge cycle.

When unused, the LEAF tops off the battery every 5 days. Based on peoples reports of coming back to dead batteries, the battery might use 20-30% of its SOC in that time. That's a significant strain on a conventional car battery. If you're gone for a month, then the battery is subjected to 4 of those deep cycles. Or, if it's plugged in you come back to a 0% SOC.

As time goes on and the battery gets weaker, the depth of the cycles gets deeper, all else being equal.

As far as the spoiler panel, it's basically just for show from what I've read. At best case (high noon in June), around 5 watts. You could charge a couple of AA batteries with it. Over the course of a day probably not even enough to maintain the service battery with no load, and of course the service battery does have a load. The power contribution from the panel is negligible compared to the the cost of paint and fabric degradation that will occur from being parked in the sun for days at a time.

The issue of dead "vacation" batteries exists for ICE vehicles as well. All recently manufactured vehicles experience "dark current" -- load on the battery to support things like computer memory, car alarms, keyless entry, etc. These are small loads but on a 7x24 basis they add up. LEAF adds Carwings telematics to the load.

I'm amazed at the amount of discussion these 12V battery threads (and policies) get!
I always leave my car "unplugged" with a moderate (~50%) charge when gone for a week or two--and have NEVER had a dead 12V battery.
However, I understand the issue of deep cycling lead acid batteries which begs the question: shouldn't we be replacing the stock 12V battery with something like a LiFePO4 battery at the first opportunity (or sign of trouble)? Cost notwithstanding, it seems like a standard 12V lead acid battery is "out of place" in the context of this car's design.

Stanton said:

I'm amazed at the amount of discussion these 12V battery threads (and policies) get!
I always leave my car "unplugged" with a moderate (~50%) charge when gone for a week or two--and have NEVER had a dead 12V battery.
However, I understand the issue of deep cycling lead acid batteries which begs the question: shouldn't we be replacing the stock 12V battery with something like a LiFePO4 battery at the first opportunity (or sign of trouble)? Cost notwithstanding, it seems like a standard 12V lead acid battery is "out of place" in the context of this car's design.

Click to expand...

It sounds promising but I don't know enough to say whether or not LiFePO is truly compatible with the LEAF charging algorithms. And I'm not sure that Lithium 12V replacements are "ready for prime time" as a proven application. Are there any well-known car battery suppliers in the field? I see Braille has some at exorbitant prices. The lower priced ones seem to be generic Chinese stuff.

Yes, I have not tested this, but apparently even in bright sun the Leaf's daily parasitic loads are more than the solar panel can offset. So I'm sure it delays the dead battery a little, but still it will die.

The parasitic loads in the Leaf are quite high, and that battery is much smaller than in a normal ICE car, since it's not used for running a starter motor. The Smart-key, Telematics (CarWings), and all the computer standby modes all add up for a relatively high draw.

Every 120 hours (5 days) the VCM will wake up and test the 12V battery, and charge it for up to 5 minutes if it needs it. It will do this by consuming your main battery charge. However, 5 minutes is not apparently enough in some cases to keep the 12v from dying, so this feature should have been set to either a shorter timeout, or allow a longer charge period.

Tony is correct, you can alternatively install a small battery charger to keep the 12V charged. I find disconnection easy, so I never bother.

I simply replaced the fixed metric nut with a wing-nut that's easily removable without tools:


If you can find one, the top nut (black) would be a better choice for wing-nut replacement.

-Phil

If the 12v replacement has it's own "charge controller" (BMS) it should be fine to use with the Leaf. They are very expensive though!

The Leaf's algorithm is a 3-stage temperature-compensated system designed for lead-calcium. That will not directly work properly on any other chemistry.

-Phil

OK: how about this one (Tenergy 12.8V, 20A LiFePO4)? It claims to be a "drop-in replacement" for lead acid, which implies that it has some sort of BMS.

http://www.all-battery.com/Tenergy12.8V20AhLiFePO4RechargeableBattery-31943.aspx" onclick="window.open(this.href);return false;

FYI: The Original is 40ah, so 20ah would be half the capacity.

-Phil

Nubo said:

It sounds promising but I don't know enough to say whether or not LiFePO is truly compatible with the LEAF charging algorithms. And I'm not sure that Lithium 12V replacements are "ready for prime time" as a proven application. Are there any well-known car battery suppliers in the field? I see Braille has some at exorbitant prices. The lower priced ones seem to be generic Chinese stuff.

Click to expand...

There are 12v LiFePO4 batteries that come with their own BMS and charger.

Edit: ok, it looks like this was already answered. Yes, the battery I quoted is half the size of the original 40 amp.

However, when comparing the two batteries, I would think that the lead/acid has to be significantly oversized to get any life out of it. But, a lithium would be quite happy being left significantly discharged.

I have no idea if a 20 amp LiFePO4 battery would be sufficient, but there are plenty of other sizes.

Thanks to all for the answers.

Because I am a newbie here, I still have a bunch of questions. I have been looking at the different threads and am still a little puzzled.

1. Why is it bad to leave the car plugged in, when it is on a timer that is set to only one day of the week?
2. Is it just bad for the 12v battery? or is it bad in general?
3. If the timer is set, say, to come on at Sunday for an end time of 5am, for a target of 80%; and I leave town on the prev Saturday.
It then it turns-on on Sunday morning, there is nothing to do, so the charging stops. One week later, it comes on, presumably there is a little
charging to do to get back to 80%. And so on for the next three weeks or so, until I am back. In the meantime, for the other days of the week,
being plugged in is effectively like being unplugged. (Except for lightning surges etc).

Could someone explain why is this bad, and what is it bad for?

-M

TonyWilliams said:

However, when comparing the two batteries, I would think that the lead/acid has to be significantly oversized to get any life out of it. But, a lithium would be quite happy being left significantly discharged.

I have no idea if a 20 amp LiFePO4 battery would be sufficient, but there are plenty of other sizes.

Click to expand...

So that's the rub: will this 20A LiFePO4 battery be sufficient given the Leaf specs? I would like to go this route, but am hesitant to do so without some first-hand experience/recommendations or at least confirmation of this particular brand/type.

Murali said:

1. Why is it bad to leave the car plugged in, when it is on a timer that is set to only one day of the week?

Click to expand...

The car draws more heavily on the 12v battery when plugged in, and worse, fails to do the every 5-day charge up. The 12v battery can maybe make it those 7 days you're asking it to (and maybe not), but it will be hard on it to do those deep cycles. Some people have tried scheduling 5 minute daily charges to combat the problem, but I think it's just easier to unplug the car, and disconnect the 12v battery.