State of the battery while on vacation

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Alex0913

Alex0913

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Hi all,
This might be a silly question but I’m gonna ask it anyways in case any of you has any experience with this..
We are going on vacation for over a month and I had a question about the battery.
Should I leave it full charged or not? Or it doesn’t matter?
The car will be sitting in my garage so the battery won’t be exposed to the summer heat. Thanks!!
 
Others with better knowledge of your question will likely chime in (though you'll also probably get answers all over the map). I think the bigger issue will be the 12V battery. Put a battery maintainer on that, make sure rodents can't get in your garage, and don't set the parking brake. It will all be fine with only a 30-40 day "rest".
 
I left my car in the garage (full charge) over a month since I didn't need to use it at the time. When I turned it on, all the warning lights were on. I turned it off, plugged it in for like 10 minutes and then all the lights went off except the engine light. I brought it to the dealer who said there was no problem and they reset the light.

A few days after use & charging, I had problems charging - this is probably unrelated since Honda did end up fixing it and said it was a one-off. Note that my Clarity then sat in a Honda garage for another month while they tried to fix the issue. So in short, I think that you'll be fine leaving it in the garage for a month. Just don't be surprised if you see all the warning lights on when you turn it on. In terms of leaving the battery full or not, I don't have the technical expertise to answer that.
 
Last edited:
Thank you both for your replies!
I’ll leave it fully charged and hopefully everything will befine at our return.
Furtunately, I don’t have to leave it at a parking garage and worrying about that.
 
This got me thinking. Does anybody know if you charge and leave the charger plugged in long term, will the Clarity request a charge much later when the HV battery gets low? And when in the off state, will it keep the 12v battery charged from the HV battery if 12v battery gets low?
Thanks.
 
Alex0913 said:
I meant to ask, why not set the parking brake? Thanks again!
Click to expand...
Many years ago I set the parking brake on a car stored over the winter. In the spring, one wheel's parking brake was impossible to disengage without a hammer. Parking brakes have certainly improved in the ensuing decades, but putting your Clarity in Park should be sufficient to prevent it from rolling out of its storage location.

There was an earlier thread that warned about dealers who ignored the Honda bulletin explaining that damage could result from leaving the batteries discharged.
 
Page 466 of the owner's manual

High Voltage Battery
The High Voltage battery gradually discharges even if the vehicle is not in use. As a
result, if your vehicle is parked for an extended period of time, the battery level may
get low. Keeping your vehicle’s battery level low can shorten the battery life. To
maintain the battery while the vehicle is not in use, recharge the battery at least
once every three months.
The High Voltage battery life can also be affected by ambient temperature. In
particular, when it is cold outside, the vehicle’s driving range on electric power can
be reduced, and a longer battery charging time is required. In addition, parking in
extremely hot or cold environments can accelerate battery drain.
To help extend the lifespan of the battery, it is recommended that you fully charge
the battery each time prior to driving.
 
insightman said:
Many years ago I set the parking brake on a car stored over the winter. In the spring, one wheel's parking brake was impossible to disengage without a hammer. Parking brakes have certainly improved in the ensuing decades, but putting your Clarity in Park should be sufficient to prevent it from rolling out of its storage location.
Click to expand...
 
This got me thinking, would this apply to a car parked on the street for a long period of time? Or just in the garage?
I have been using the parking break for all my life for the other cars we park on the street, thanks for the great info!
 
If you're not going to start your car for 2 weeks or more, you should always put the 12V battery on a good and proper battery charger.
Unfortunately, it's hard for the typical person to know if a (12V) battery charger is good, or just a bunch of marketing BS.

So, I suggest that people buy the Battery Tender brand-name products. That's what I use on my two cars and lawn tractor that sit during the winter. Yes, I have separate Battery Tender chargers for each.

All you need is a trickle charge.
I use the cigarette lighter adapter.
I leave the charger unit on the concrete ground, and run the wire into the car, then shut the door on the wire. That's fine. And, it makes sure that the charger unit gets plenty of air flow.

I don't like "wall wart" chargers.
So, I don't like the cheaper .75amp $25 charger.
https://www.amazon.com/Battery-Tender-021-0123-Junior-Charger/dp/B000CITK8S/
Battery Tender
Battery Tender 021-0123 Junior 12V, 0.75A Battery Charger
#1 Best Seller in Battery Chargers
Price: $25.88

But, that charger does work fine!
I have one, as a backup, in case one of my other units breaks or gets broken. More likely to get broken with me. :)

I use the cigarette lighter adapter, instead of the battery clips. It just plugs right into the charging cable.
https://www.amazon.com/Battery-Tender-Cigarette-Lighter-Adaptor/dp/B003E02MMC/
Battery Tender
Battery Tender Cigarette Lighter Adaptor
Price: $7.64

I use the .8amp charger, since I don't like "wall wart" chargers.
https://www.amazon.com/Battery-Tender-021-0123-Junior-Charger/dp/B000CITKCE/
Battery Tender
Battery Tender 800 is a Super Smart Battery Charger that will Constantly Monitor, Charge, and Maintain your Battery. It's Encapsulated and Protected from Moisture by an Electrical Insulation
Price: $36.75



Fwiw, many of the junk battery chargers just have "on/off" cycles. That's not good, nor what you want. The Black and Decker charger that Home Depot sells is like that. There are a number of electrical reasons why that is bad.

Good Luck!
 
Don't know if this applies to car Li batteries but the general advice for Lithium ion batteries for consumer electronics is to charge it only to 50% for storage, never a full charge (their advice is also never to fully charge or fully discharge the battery during everyday use, even with the device's battery management system, for best longevity).
 
Page 18 of the owners manual: "There are two types of batteries used in this vehicle, a standard 12-volt battery that powers the airbags, the interior and exterior lights, and other standard 12-volt systems, and a high voltage battery that is used to power the propulsion motor and recharge the 12-volt battery."

As long as the HV battery has a charge, there is no need to do anything with the 12v battery.
 
Here are the options I have seen while perusing some of the Tesla and Leaf forums:

1.) Leave battery between 40% and 60% SOC. Set your timer to come on once a week and add around 10% each charge. This should care of both batteries.
2.) Leave battery between 40% and 60% SOC and attach Battery Tender to the 12 volt.
3.) Leave battery between 40% and 60% SOC and disconnect the negative ground on the 12 volt.

Do you have a Level 1 or 2 charger? If you have a level 2 then you could exercise the battery:

4.) Leave battery between 40% and 60% SOC. Set remote conditioning to come on for a set time each week. This would be the closest to driving it. If it stays cool in your garage, preconditioning may not turn on however.

It seems the universal theme is to leave it at a mid state of charge. Lithium batteries are like humans (or like the Matrix showed, humans are batteries ;), and like to rest/sleep at a comfortable temperature and not too full, but not starving either.
 
GrayRed said:
If you're not going to start your car for 2 weeks or more, you should always put the 12V battery on a good and proper battery charger.
Unfortunately, it's hard for the typical person to know if a (12V) battery charger is good, or just a bunch of marketing BS.

So, I suggest that people buy the Battery Tender brand-name products. That's what I use on my two cars and lawn tractor that sit during the winter. Yes, I have separate Battery Tender chargers for each.

All you need is a trickle charge.
I use the cigarette lighter adapter.
I leave the charger unit on the concrete ground, and run the wire into the car, then shut the door on the wire. That's fine. And, it makes sure that the charger unit gets plenty of air flow.

I don't like "wall wart" chargers.
So, I don't like the cheaper .75amp $25 charger.
https://www.amazon.com/Battery-Tender-021-0123-Junior-Charger/dp/B000CITK8S/
Battery Tender
Battery Tender 021-0123 Junior 12V, 0.75A Battery Charger
#1 Best Seller in Battery Chargers
Price: $25.88

But, that charger does work fine!
I have one, as a backup, in case one of my other units breaks or gets broken. More likely to get broken with me. :)

I use the cigarette lighter adapter, instead of the battery clips. It just plugs right into the charging cable.
https://www.amazon.com/Battery-Tender-Cigarette-Lighter-Adaptor/dp/B003E02MMC/
Battery Tender
Battery Tender Cigarette Lighter Adaptor
Price: $7.64

I use the .8amp charger, since I don't like "wall wart" chargers.
https://www.amazon.com/Battery-Tender-021-0123-Junior-Charger/dp/B000CITKCE/
Battery Tender
Battery Tender 800 is a Super Smart Battery Charger that will Constantly Monitor, Charge, and Maintain your Battery. It's Encapsulated and Protected from Moisture by an Electrical Insulation
Price: $36.75



Fwiw, many of the junk battery chargers just have "on/off" cycles. That's not good, nor what you want. The Black and Decker charger that Home Depot sells is like that. There are a number of electrical reasons why that is bad.

Good Luck!
Click to expand...

But, if the 12V receptacle in the car is off when the car is off, how does the power get from the trickle charger to the battery?
 
DaleL said:
Page 18 of the owners manual: "There are two types of batteries used in this vehicle, a standard 12-volt battery that powers the airbags, the interior and exterior lights, and other standard 12-volt systems, and a high voltage battery that is used to power the propulsion motor and recharge the 12-volt battery."

As long as the HV battery has a charge, there is no need to do anything with the 12v battery.
Click to expand...
But do we know that the HV battery recharges the 12v battery when the car is OFF?
 
Alex0913 said:
This got me thinking, would this apply to a car parked on the street for a long period of time? Or just in the garage?
I have been using the parking break for all my life for the other cars we park on the street, thanks for the great info!
Click to expand...

The parking brake shoes/pads can rust-weld onto the drums/rotors if left engaged for a long time. The drums/rotors are steel and will rust at different rates depending on the local weather and salt use. I've had brakes get at least grabby from rust after just a few days and stick pretty tight in a week of no use. A parking brake locked on for a month would be great risk for sticking whether the car was parked on the street or in a garage. Regular use of the parking brake in normal driving patterns is not a risk for that problem.
 
jdonalds said:
Page 466 of the owner's manual

High Voltage Battery
The High Voltage battery gradually discharges even if the vehicle is not in use. As a
result, if your vehicle is parked for an extended period of time, the battery level may
get low. Keeping your vehicle’s battery level low can shorten the battery life. To
maintain the battery while the vehicle is not in use, recharge the battery at least
once every three months.
The High Voltage battery life can also be affected by ambient temperature. In
particular, when it is cold outside, the vehicle’s driving range on electric power can
be reduced, and a longer battery charging time is required. In addition, parking in
extremely hot or cold environments can accelerate battery drain.
To help extend the lifespan of the battery, it is recommended that you fully charge
the battery each time prior to driving.
Click to expand...

This is too vague for most forum readers. "extended period of time" needs more precision. Do L-I cells discharge more quickly than the common low-discharge NiMH consumer batteries? Those batteries retain 85% after 1 yr of storage. Does anyone have actual data for SOC of a stored Clarity over a few weeks? My suspicion is a 10% loss per month.

Also, via the Honda scheduling methods, we are unable to schedule a weekly charge. So a daily charge of 30 minutes on 120V or 6 minutes on 240V?
 
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