NFR Should I disconnect a car battery if it’s not going to be used?

[Mark Yoshida]

Not a car person.
My Aunt has been in an assisted living facility for a couple months and it’s looking like she may be there for a while.
She has two old cars, 2001 Toyota Camry and 2003 Toyota Matrix both with less than 65,000 miles.
Should I disconnect the batteries? I charged the Matrix and drove the Camry the other day and both started, but don’t want to have to keep going over to her house to maintain them.
I have heard of trickle chargers but don’t know diddly about them, how long can you leave them on unattended or best kind to purchase.
At 92 she thinks she can come home and drive. NOT With partial cognitive issues.

Thanks

 

[Tom Butler]

Pariasitic battery drain, clock and other electronics, will eventually drain the batteries. Trickle charges are the way to go, but must be plugged in. For my MG, I have a battery disconnect switch, and each spring the battery will start the car, however I usually charge it to make sure it's hot. Disconnecting has given me long battery life. Take the positive lead off, and isolate it so it doesn't touch.

 

[krusty]

Pariasitic battery drain, clock and other electronics, will eventually drain the batteries. Trickle charges are the way to go, but must be plugged in. For my MG, I have a battery disconnect switch, and each spring the battery will start the car, however I usually charge it to make sure it's hot. Disconnecting has given me long battery life. Take the positive lead off, and isolate it so it doesn't touch.

If you're going to put a charger on them (which is most definitely best or the battery will eventually sulfonate and destroy itself) be sure it's a 'smart' charger like a Battery Tender or a NOCO. Regular chargers...even those with a 'trickle' setting will eventally overcharge and destroy the battery.

And a battery, sitting in a car connected or disconnected...will undergo damaging chemical degradation particularly in the summer if a charge is not applied through car operation or through the use of an intelligent charging system that continuously monitors and responds to battery condition.

 

[Pescaphile]

Take the positive lead off, and isolate it so it doesn't touch.

I recommend the opposite. Disconnect the negative terminal rather than the positive one. Most anything metal in the engine compartment that the positive terminal might inadvertently touch could result in a nasty short. The negative lead only has the battery's positive terminal and, if it is long enough, a couple other places like a starter solenoid terminal as potential "hot spots." This is especially true when working on the engine where you might accidentally bump the disconnected terminal. I realize you recommended to secure the terminal but things happen, e.g., another person getting in there, rodent, etc.

 

[Tom Butler]

I recommend the opposite. Disconnect the negative terminal rather than the positive one. Most anything metal in the engine compartment that the positive terminal might inadvertently touch could result in a nasty short. The negative lead only has the battery's positive terminal and, if it is long enough, a couple other places like a starter solenoid terminal as potential "hot spots." This is especially true when working on the engine where you might accidentally bump the disconnected terminal. I realize you recommended to secure the terminal but things happen, e.g., another person getting in there, rodent, etc.

I did have to think about it. When I got the MG it was positive ground, and although I made it negative ground the disconnect is still on the negative side because that's the terminal it fit's. I'd take it out and store it some where warm, but it's just too much work to reach back that far and fiddle with stuff.

 

[Bambooflyguy]

Another thing Mark, if those cars sit for a long time you might want to add Sta Bil to the gas tanks.

 

[kmudgn]

Buy a trickle charge/maintainer (they are cheap). Most plug in and work well. If plugging into a wall socket won't work, there are some that have solar panels you put on the dash to provide power. If the cars are going to sit for a few months I would also add gas stabilizer to the tank

 

[Dustin Chromers]

Get a battery tender and call it a day.

 

[Otter]

Mark, it’s great that you’re helping your aunt.

As people have written, a car’s electronics drain an un-used battery. A family member’s battery (which was about 7 years old) totally died after the car sat un-used for a few months last winter. I’ve found that batteries get weaker in the cold, so that was part of the problem.

We used to use a trickle charger all the time when our batteries were aging, or in winter. I suppose that would be useful in your case, but I’d rather just disconnect the negative wire from the battery. The negative wire is clamped to a battery post that is usually labelled with a “-“ mark, and should also have a black plastic cover. You will also see the negative wire goes from the battery to the metal car frame, and is attached there by a large screw. This makes most major metal parts of the car part of the electrical system, which simplifies wiring.

If you remove the positive wire from its battery post ( which is marked “+” and usually has a red cover) , and accidentally touch that positive wire to most any metal part, there will be a big, noisy spark. Bad for the battery, as well as dangerous. If the negative wire had already been disconnected from the battery, there will be no spark.
Hope this is helpful, and I like your Betta avatar!

 

[Sam Roffe]

Ideally the batteries should be exercised. Sitting connected for months at a time will discharge them. But just sitting disconnected the batteries will self discharge. I think the reco

I did have to think about it. When I got the MG it was positive ground, and although I made it negative ground the disconnect is still on the negative side because that's the terminal it fit's. I'd take it out and store it some where warm, but it's just too much work to reach back that far and fiddle with stuff.

i kind of agree with disconnecting the negative instead of the positive. My truck has two batteries, that is a definite must. I don’t see how that is an issue when you have a single battery. Either lead that gets disconnected prevents the flow of electricity. I suppose there could be some residual charge somewhere…

 

[FinLuver]

I recommend the opposite. Disconnect the negative terminal rather than the positive one. Most anything metal in the engine compartment that the positive terminal might inadvertently touch could result in a nasty short. The negative lead only has the battery's positive terminal and, if it is long enough, a couple other places like a starter solenoid terminal as potential "hot spots." This is especially true when working on the engine where you might accidentally bump the disconnected terminal. I realize you recommended to secure the terminal but things happen, e.g., another person getting in there, rodent, etc.

Take both off and isolate…
Have tried both one or the other and the only way was to take both off.

 

[FinLuver]

Ideally the batteries should be exercised. Sitting connected for months at a time will discharge them. But just sitting disconnected the batteries will self discharge. I think the reco

i kind of agree with disconnecting the negative instead of the positive. My truck has two batteries, that is a definite must. I don’t see how that is an issue when you have a single battery. Either lead that gets disconnected prevents the flow of electricity. I suppose there could be some residual charge somewhere…

Not necessarily…
I found that it was still powering up something on the background.
I was resetting the computer/electronics.

 

[nwbobber]

I'd just put the trickle charger on. If you disconnect the battery, you are going to have to reset the clock, perhaps lose all the radio presets as well.
Disconnecting at the negative terminal prevents accidentally arcing from the (positive) battery post to ANYTHING metal around it, and is standard practice when wrenching. The positive wire will not do anything on a single battery system if touched after disconnecting from the battery. On my pickup, yes. Most cars no.

 

[krusty]

All of my stuff goes on a smart charger when sitting idle. You don't need to disconnect terminals. Our motorcycles get plugged into a smart charger after every single ride.

Summer temps and lack of maintenance charge is what kills batteries....and you find out how badly they've deteriorated in the winter when you attempt to start a cold engine full of thick cold oil....which consumes a lot of amps just to turn over.

Had an OEM battery maintained 17 years that way...and it never failed...I just got nervous trusting such an ancient battery.

 

[Sam Roffe]

Not necessarily…
I found that it was still powering up something on the background.
I was resetting the computer/electronics.

So you had something else energize, and got a spark when you touched the positive lead to ground??? Do you have a small Staying alive battery tucked some where else in your vehicle? I see where disconnecting the negative first is important now.

 

[FinLuver]

So you had something else energize, and got a spark when you touched the positive lead to ground??? Do you have a small Staying alive battery tucked some where else in your vehicle? I see where disconnecting the negative first is important now.

not what i said...

 

[Bambooflyguy]

Actually sounds like you and your family should sell them Mark.

 

[jaredoconnor]

All of my stuff goes on a smart charger when sitting idle. You don't need to disconnect terminals.

How did you determine that it was safe to do so? I was wondering about this myself, but I could never find a definitive answer. I use a NOCO, a few times a year, because we barely use one of our cars. It would be a lot easier if I didn't have to disconnect the battery.

 

[Lue Taylor]

I have a battery tender that shut off when battery fully charge an only come on when low I retired in 2016 had my batteries on it ever that year I still use them to this day but my batteries are Deep Cycle.

 

[cdnred]

Not a car person.
My Aunt has been in an assisted living facility for a couple months and it’s looking like she may be there for a while.
She has two old cars, 2001 Toyota Camry and 2003 Toyota Matrix both with less than 65,000 miles.
Should I disconnect the batteries? I charged the Matrix and drove the Camry the other day and both started, but don’t want to have to keep going over to her house to maintain them.
I have heard of trickle chargers but don’t know diddly about them, how long can you leave them on unattended or best kind to purchase.
At 92 she thinks she can come home and drive. NOT With partial cognitive issues.

Thanks

It doesn't really answer your question but I think that with your aunt being in assisted living and being 92 with partial cognitive issues that perhaps her driving days have passed. We all enjoy the freedom that cars allow us but I think it would be better to discuss with her and the family about finding a new home for the cars or at least for one of the cars. It's not merely the battery but the cars will need to be driven, maintained regularly along with the yearly registration and insurance. You'll save yourself a lot of frustration and money as well. I know that wasn't the answer you were looking for but it will save everyone a lot of stress..