Electronics > Power/Renewable Energy/EV's

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

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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?

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.

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.


--- Quote from: IanB on November 21, 2022, 02:01:02 am ---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.

--- End quote ---
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.

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.


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