How to keep car battery charged when car isn't being driven

[Hogwild]

Hi everyone:

My knowledge of electronics is next to nothing other than a few basics of how to use a DMM.

I have a chronic illness which keeps me at home most of the time. I generally have someone around to help, and they drive my car, so it gets charged. However, when I'm in between helpers, my car battery dies because there's no one drive it.

I bought a Doco charger, and it helped restore my old battery, but then the car wasn't driven again and the battery is dying again. I have to buy a new battery (but hey, the old one is 7 years old, so no complaints).

The other problem is that my landlord won't allow anyone to plug in a charger in the underground parking. So, I need something that can charge in my apartment and then maintain the charge on my car battery or some other solution.

I see the Doco units that can boost and charge, so I guess they use large capacitors, but there are some pretty nasty negative reviews, and I wondered if there were any better solutions.

What options do you suggest?

[IanB]

The best way to do this, if the car were parked outside, would be with a solar battery charger plugged into a 12 V accessory (cigarette lighter) socket. If the car is underground, this will not be an option.

The only option I can think of is to have a piggyback battery that you charge in your apartment and then plug this into the accessory socket to keep the car battery topped up. Since charging lead acid batteries indoors is not a good idea, it would be best if the piggy back battery is a lithium ion battery. I have not looked (yet), but there might be emergency lithium ion jump start packs that come in a convenient package with a handle and charger for this purpose. Someone would just have to regularly take it to your car every week or two and plug it into the accessory socket to top up the car battery.

For the accessory socket to work, it would have to be one that is always energized even with the ignition switch off.

[IanB]

So I see a jump charger called "NOCO" -- is that what you bought?

It seems like something like that, used regularly, might do the trick. The idea would be to use it before the battery is flat, not after. Also, it seems to come with crocodile clips, so someone would have to lift the hood and connect to the battery terminals. The accessory socket approach is much cleaner.

[BrianHG]

The best way to do this, if the car were parked outside, would be with a solar battery charger plugged into a 12 V accessory (cigarette lighter) socket. If the car is underground, this will not be an option.

1) If he is lucky that the 12v accessory is connected to the battery if the key isn't in the ignition.
2) And if he doesn't have to deal with snow in the winter.

If so, then yes, this might be a magic bullet.
For issue #1, he might be able to find a mechanic to wire or make an outlet which doesn't switch with they starter key.

As for indoor/underground parking, maybe there is a fluke circumstance where he may be directly under a constant on spot-light where a large enough solar charger, or maybe 2 of them in parallel, might deliver enough milliamps of positive current to offset the car's leakage OFF load (usually powering a clock and wireless key remote) and stop the battery from draining.

[nctnico]

How long is the car parked outside? 7 years can be end-of-life if the battery is of poor quality and relatively small.

My own car sits unused outside for weeks as well and doesn't have any issues. But I have put the biggest battery that will physically fit in it and I choose a good brand (=not the cheapest crap battery). Things like jump starters and float chargers shouldn't be necessary.

[BrianHG]

Reviews of which booster / charger to get:

Older brands.


Newer Brands.


NOCO GB40 = bad garbage, NOCO GB70 good.
Watch the videos for the better packs.

[IanB]

I can appreciate the problem, because during the pandemic my car sat in the garage unused for long enough for the battery to drain and have trouble turning the engine. I had to give the battery a manual boost charge every couple of weeks to keep it topped up.

[BrianHG]

Even with a new battery, when I don't drive my car for 10 days and one or 2 of the nights drops below -20deg C, I must charge my battery.  Though, I only need 10 minutes on my 12v supply which can feed up to 10 amps in the cold.

(Basically a 12v 6 amp transformer with a Full Wave Bridge Rectifier, any more than 15 minutes can overcharge my battery.)

I'm sure my neighbors laugh as I have a yellow extension chord from my third floor front porch dropping down to where my car is parked.  But, it works.  I leave it hanging there all winter even though I only use it around 4-5 times a year for only 10 minutes.

[Hogwild]

The car is not in use much, and when it's parked, it's parked in the underground garage, not outside. That garage is heated, so no cold down there unless the building's heat goes off.

There is nowhere nearby I could park it to get sunlight. And being in Canada, there ain't much of that for many months of the year anyways.

I think solar is a longshot considering how weak the lighting is in the garage.

I bought a Noco charger, not booster/(charger). I assumed we were allowed to use the one AC outlet in the garage, but I was wrong. Also, if I understand what I've read on the web so far, just boosting it may not be useful if that doesn't fully charge it, as that would still require someone to drive it to finish charging it. That's why I wondered whether the models that have a boost feature are also able to charge using those same batteries/capacitors.

I'll look at that video, thanks. I'm surprised more people don't have this problem. There are plenty of people with health issues, disabilities or the elderly. I guess many of them give up their cars, but I'm too stubborn.

[themadhippy]

surprised no ones though of putting some sort of connector on the front of the engine to allow you to crank the engine by hand if the batterys flat

[IanB]

(Basically a 12v 6 amp transformer with a Full Wave Bridge Rectifier, any more than 15 minutes can overcharge my battery.)

My approach was a bit more subtle, a regulated power supply set to 13.8 V and the current limit at the max of 5 A.

[nctnico]

surprised no ones though of putting some sort of connector on the front of the engine to allow you to crank the engine by hand if the batterys flat

One of my parents' old Ladas actually had that possibility. Must have been somewhere in the 90's I think.

[IanB]

surprised no ones though of putting some sort of connector on the front of the engine to allow you to crank the engine by hand if the batterys flat

 

I owned a car with exactly that feature (A Citroën 2CV6). I never needed to use it with a flat battery, but I tried it out one or twice to see if it worked (it did).

[BrianHG]

(Basically a 12v 6 amp transformer with a Full Wave Bridge Rectifier, any more than 15 minutes can overcharge my battery.)

My approach was a bit more subtle, a regulated power supply set to 13.8 V and the current limit at the max of 5 A.

With that, you can either trickle charge continuously, or wait 30 to 45 minutes for a good close to full charge.
However, when it is -25c / -13f outside and you need to get going and not worry about lateron in the day that your battery will crank the engine a few more times, I've stuck with my solution.

[IanB]

With that, you can either trickle charge continuously, or wait 30 to 45 minutes for a good close to full charge.
However, when is id -25c / -13f outside and you need to get going and not worry about lateron in the day that your battery will crank the engine a few more times, I've stuck with my solution.

Understood, but my car is parked in a nice warm garage and I am in no rush. I can leave it topping up for a few hours when needed.

With a car parked outside at -25°C, don't you need a block heater to help it start? I've never lived in a climate like that.

[BrianHG]

With a car parked outside at -25°C, don't you need a block heater to help it start? I've never lived in a climate like that.

I currently driving an 8 year old Toyota Camry.  No block heater.  But I have started it no problem down at -35c / -31f.

F... if you think I going out when it's -40c/f  ...  (Happens around 1 or 2 mornings per year where I live.)

[Hogwild]

I've been pondering buying a solar generator. I wonder if that might do the trick. I wouldn't use solar to charge it, I'd generally use AC, but what do you think?

As for weather, I'm just glad I don't live in New York state this weekend. One area had 6 feet of snow in some areas in 36 hours. Six feet!

[sokoloff]

In my younger days, I had a car with a bad alternator that wouldn't quite charge the battery. I got by for a couple of months using a lead-acid jump battery constantly clipped the car battery [was located in the trunk] and periodically charging the jump pack by plugging it in.

Something like this (mine was another brand, but they're all going to be a lead-acid battery, a charger, and a couple of large clips):
https://www.allstartboost.com/product-category/lead-acid-jump-starters/

Obviously a different scenario, but something like that will be "something I can charge in my apartment and then take down to the car".

Another thing you can consider is getting a negative terminal disconnect (or just using a wrench/socket) to completely disconnect the negative terminal of the car battery when it's going to be parked for a prolonged period of time. The lead-acid battery won't hold a charge forever, but it will hold it for longer when there's no drain on it than when there's the small parasitic loads from the clock, radio, remote locks/start, etc.

[Hogwild]

So, can someone answer that question. I was told by a mechanic that if I boost it, and then don't drive it, it will fairly quickly die again anyways and/or damage the chemistry. Can someone confirm or deny this? Again, the intervention is for when the car CAN'T be driven at the moment, not when it can. That alone would be easy.

[sokoloff]

It won't be good for it, but nothing about your situation is going to be great for the car.

Why would you boost it if not for the purpose of starting and driving it? If you're going to have it driven a few miles, I wouldn't sweat a boost and short drive. I would not boost it and then shut it down without driving it (entirely because I can't see the point of doing that, not because it will immediately harm the battery).

[Dundarave]

I have a similar problem (car gets very little use, underground garage, can’t leave a charger plugged in) and what I did was buy a 20 amp charger and charge it late at night (10pm to 4am or so) once every 6 weeks. 

That seems to be enough to keep it charged sufficiently. I also calendar the 6 week interval, and just treat it like a periodic chore.  I do it late so as few people as possible see the extension cord.  A bit sneaky, but cripes, it’s only penny’s-worth of electricity, and inconveniences no one.

Regarding whether or not it’s a problem for the battery, I doubt it’s that big a deal.  Car dealerships do this all the time with showroom vehicles, and they can sit there for many months before they get swapped out.  And I doubt the battery can tell the difference between a periodic charge, and a periodic drive.

[IanB]

So, can someone answer that question. I was told by a mechanic that if I boost it, and then don't drive it, it will fairly quickly die again anyways and/or damage the chemistry. Can someone confirm or deny this? Again, the intervention is for when the car CAN'T be driven at the moment, not when it can. That alone would be easy.

No, this is not true. First of all, you cannot "boost" a battery, you can either charge it or not charge it. The only variation is when you do charge it, how aggressively, and for how long. Bear in mind that when you drive the car, the onboard charging system is pretty aggressive. It stuffs charge into the battery like there's no tomorrow. It is unlikely that anything you do to charge it will be worse than what the car does when you start the engine and drive away.

One thing is that batteries like to be used. So leaving a battery sitting idle for long periods is not ideal, but it also can be unavoidable.

A second thing, is leaving a lead acid battery to sit in a low charge state is not really good for it. So if a battery must be left unused for long periods, the most helpful thing you can do for it is to keep it topped up. So giving it a bit of a top up charge every few weeks can only be good for it. Bear in mind that lead acid batteries really don't mind being overcharged, unless you get extreme about it. So the ideal would be not to use a "start the car with a flat battery boost charger", but rather to use something more gentle like a trickle charger that you can leave connected for an hour or three, that won't supply too much voltage and generate lots of gas.

[Hogwild]

So....would a solar generator provide enough power to charge it?

[IanB]

So....would a solar generator provide enough power to charge it?

If the car was outside in the daylight, yes.

[Hogwild]

No, you didn't read what I wrote earlier. I won't generally be using it with a solar panel, nor is that feasible most of the time where I live.