Charging car battery without a wall outlet

craftsman wrote: ↑ Simple - read my statements again as you are taking both of my comments out of context. The first statement I made was in response to your statement about driving a car for 20 minutes to fully charge a battery which isn't going to happen as people have driven their cars for a hour or more trying to charge their battery fully and find that the battery still isn't full so what can 20 minutes do? Not much. As for 20 minutes vs a few minutes, that's all relative to what someone considers a long time. I consider a 20-minute drive a relatively short time when it comes to needing to charge a battery. Plus, the output of a standard alternator needs to be consistently over 2,000 to 2,500 RPM before it will generate enough power to even start charging the battery. Considering that most cars these days try to keep the RPM fairly low in order to save on gas, you need to drive that car fairly hard over those 20 minutes to even start charging the battery. Besides, where did you get the magic number of 20 minutes from anyways? I never mentioned anything about cars draining power from the battery when I responded to your comment so I don't know how you can you can connect my initial comment to you with that idea.

The second statement was in response to someone commenting that they disconnect the battery for 6 months of the year and why the battery was in decent shape afterwards. The statement I made was to add a bit of context to their statement.

You said in my "grandfather's day" yet your facts are out of date. The alternator charges at full speed at just over idling speed, so if you have 1000 rpm (which you will unless you sit still), the alternator is fully open.

I find it hilarious that you genuinely think that not even an hour is enough to fully charge your battery. Both my car batteries must be of alien origin then, because I measured them with a voltmeter, and they are fully charged after my once every 2 week 20 or so minute drive. And somehow they don't die when I drive them daily for 8 minutes, since my work place is only 6km away. Same with my groceries since RCSS is the same distance. Costco is even less, only 3km, so I get there in under 5 minutes. And this is daily. Purely by curiosity I took a multimeter to measure my 20 minute drive see how much charge it provided since it seems I never ran out of battery in my 4 years since I'm living where I live.

If you live in Vancouver, you might have the false feeling that you need to be on your commute for an hour to keep your battery from not dying. Obviously from real life stats it's not required. That or both my batteries made by different brands are of alien origin since they don't die with my daily 5-8 minute drives before I need to start my car again, and the rare 20 minute drive every few weeks.

I agree with the opinion provided by @craftsman.
Newer car wants to provide the more fuel efficiency by not engage the alternator all the time to charge the battery.

My sister has a 2015 Honda Civic with the "Honda's Dual-Mode Charging System". It surprised me when I did the A12 service on her Civic a few months ago. The battery terminal voltage was 12.4v. I connected my charger to charge the battery while doing the A12 service. After I finished my work on this Civic, the terminal voltage did not move too much. I keep charging it overnight. I got 13.1v after disconnecting my charger next morning. I drove it to my sister's garage which is half a block from my house. The terminal voltage is 12.4v again. She enabled the green mode on her Civic. Some how, the Dual-Mode Charging System is clamping the voltage to 12.4v. I suggested to disengage the green mode to let the alternator to charge the battery more often.
https://opensiuc.lib.siu.edu/cgi/viewco ... =auto_pres

I have a 1991 Honda Civic parking outside which I use it about once per week. I can start it when outside temperature is below -30°C. The engine may turn over a few more times. But that battery can still start a 30 years old car. The charging system between old car and newer car are different.

mxthor3 wrote: ↑ WTF am I reading in this thread? lol

no sh1t.

The op is either a millennial or can't get to the car in that year its parked.

So if you can't pull the battery out. Make sure its charged top up. Disconnect it and hope in a year it may still work and keep a decent maintainer on it afterwards to maybe.... help recover it.

Otherwise anything you spend money on today!! Just to keep it from sulfating? Could just go towards buying a new battery a year from now.Or buy new now!!!... In one year come back and warranty will give you a new one if its sulfated and doesn't start! Or check your current warranty on your existing battery and maybe in a year your still covered and pay nothing!

mawzi wrote: ↑ Hi guys, I have my car parked in a garage with no access to electricity. I don't want to take the battery out of the car.

I'm looking for ideas to charge it periodically. Battery is 90AH. Ease of use and cost are a factor.

Thanks a lot.

Some more details to answer questions:
-I need a solution for longer than one year storage
-I can't remove the battery, but I'm already disconnecting the negative
-No power outlets nearby.
-I want to charge it every three months to top up the battery, and prevent sulfation.

How empty is your battery currently?
Is the car insured, can you drive it for a couple hours to charge it so its easier to just keep topped up?

Why don't you want to remove the battery. If the vehicle is not going to be used for a year can you remove it, bring it in keep it on a charge maintainer then toss it back in the car when you want to use it someday?

A 50W solar panel might run off the ambient lighting on a 1-2 amp charge maintainer.
Or 5-25W often come with 12V battery maintainer mode. If there is some artificial overhead lighting that might be enough, you can test that with a multimeter. Or you can run a wire from outside depending on the distances and accesses involved.

You can ask a friend with an EV to visit and use a connected charger to top up your battery, they should have a 12V accessory at minimum which you can plug a cheap CT inverter into then your battery charger. Might take a long day visit from morning to night depending on the charger and battery SOC.
Socially distance or make sure everyone has their vaccines.

You can use the 100ft extension cord idea i mentioned (or two strung together for low power) or if there are standard Edison light sockets use one of these to plug in your charger in the day or at night (depending on your situation).

https://www.homedepot.ca/product/levito ... 1000105491
https://www.homedepot.ca/product/levito ... 1000106859

You can buy a power bank with 120V out. This is one of many examples
amazon-ca-jackery-explorer-240wh-200w-p ... n-2446650/

You can buy a gasoline or propane generator and use that to run your battery charger. They are loud and will attract attention.

Ask the building management if they have any ideas to help you if they are friendly.

In the end you can let the battery die and just buy a new one, a year of not driving will pay for a new battery.


Finally the irony of needing electricity to keep your ICE vehicle running is hilarious, people whine how EVs are useless and unchargeable...

Covrig wrote: ↑ You said in my "grandfather's day" yet your facts are out of date. The alternator charges at full speed at just over idling speed, so if you have 1000 rpm (which you will unless you sit still), the alternator is fully open.

Hmmm.... interesting that when testing an alternator, the commonly accepted test is to hold the RPM at or above 1500 RPM in order to see if the output is at least 13.5V. I like over 2000 to 2500 RPM so that I can check if the voltage gets to the standard charging voltage of 14.4V. Any voltage lower than the standard 14.4V (and it's not just me saying that but any and all charger manufacturers as well as battery manufacturers say that the charging voltage needs to be 14.4V for a standard flooded battery) just won't charge the battery correctly. You can believe what you want to believe and do what you want to do but it's not change the required charging voltage.

Covrig wrote: ↑ I find it hilarious that you genuinely think that not even an hour is enough to fully charge your battery. Both my car batteries must be of alien origin then, because I measured them with a voltmeter, and they are fully charged after my once every 2 week 20 or so minute drive. And somehow they don't die when I drive them daily for 8 minutes, since my work place is only 6km away. Same with my groceries since RCSS is the same distance. Costco is even less, only 3km, so I get there in under 5 minutes. And this is daily. Purely by curiosity I took a multimeter to measure my 20 minute drive see how much charge it provided since it seems I never ran out of battery in my 4 years since I'm living where I live.

Unless you let your battery sit for several hours after charging, what you are measuring is the surface charge on the battery. That surface charge is charge that is waiting be be absorbed into the battery which will take a couple of hours to do. Once that charge is absorbed, the voltage reading on the battery will give you the true charge on your battery. You don't have to believe me as all you need to do is to do a bit of research on surface charge.

Besides, the max. charging current for a standard flooded battery is between C/4 and C/5 where C is the capacity of the battery according to the battery manufacturers - once again google it if you don't believe me. So to charge a 100 Ahr battery, the max. charging current that should be applied is between 20 and 25A for between 4 and 5 HOURS for an empty battery. Even if the alternator does deliver the full charging current at the recommended charging voltage, you would need to drive for 4 to 5 hours to FULLY charge an empty battery. A 20 minute drive will only charge a battery about 1/12 to 1/15 of its capacity.... hardly anywhere near full.

I do find it hilarious that you make your claims without any real idea of what's going on.

Covrig wrote: ↑ If you live in Vancouver, you might have the false feeling that you need to be on your commute for an hour to keep your battery from not dying. Obviously from real life stats it's not required. That or both my batteries made by different brands are of alien origin since they don't die with my daily 5-8 minute drives before I need to start my car again, and the rare 20 minute drive every few weeks.

Driving in Vancouver really has nothing to do with it. And if you think it does, then that shows the limits of your argument.

craftsman wrote: ↑
Unless you let your battery sit for several hours after charging, what you are measuring is the surface charge on the battery. That surface charge is charge that is waiting be be absorbed into the battery which will take a couple of hours to do. Once that charge is absorbed, the voltage reading on the battery will give you the true charge on your battery. You don't have to believe me as all you need to do is to do a bit of research on surface charge.

Besides, the max. charging current for a standard flooded battery is between C/4 and C/5 where C is the capacity of the battery according to the battery manufacturers - once again google it if you don't believe me. So to charge a 100 Ahr battery, the max. charging current that should be applied is between 20 and 25A for between 4 and 5 HOURS for an empty battery. Even if the alternator does deliver the full charging current at the recommended charging voltage, you would need to drive for 4 to 5 hours to FULLY charge an empty battery. A 20 minute drive will only charge a battery about 1/12 to 1/15 of its capacity.... hardly anywhere near full.

I do find it hilarious that you make your claims without any real idea of what's going on.

I only tested my battery with a voltmeter after the ~20 minute drive out of curiosity, and yes, I know all about the surface charge. The test was next morning. Now if there is still surface charge after 12hrs, then I guess I tested it wrong.

I didn't bother testing my short 5-8 minutes drives. But the fact is, I start the car at least 2-4 times a day between my <10 minute drive for work/grocery. How come I never have a problem starting the battery if doing this for a few weeks at a time should kill my battery since even 1hr as you said it's not enough to fully charge my battery.

And my battery just hit 6 years mark this month in May, still original battery on my 2015 model.

craftsman wrote: ↑ Driving in Vancouver really has nothing to do with it. And if you think it does, then that shows the limits of your argument.

Actually it does, because a commute in Vancouver most likely takes 1hr+ with how gridlocked the GVA is during rush hour, including hwy 1. So you might be under the impression that your battery is not dead is because you spend all that time in traffic. As per above, my drives are between 5-8 minutes (6-10kms) between each engine start.

l69norm wrote: ↑ A lot of cars have alternators that are controlled by the car's main engine computer. They will only charge the battery according to what's been programmed into the engine computer
https://www.google.com/search?q=alterna ... e&ie=UTF-8

The diode mod is a popular modification some people make to fool the computer to restore the alternator to normal battery charging, just like the old days
https://www.google.com/search?q=alterna ... CA4&uact=5

To hell with all this new fangled junk.
I press the clutch and change the gears, i crank the lever and the window opens, and i press the button and i get AM/FM radio.

craftsman wrote: ↑ The first statement I made was in response to your statement about driving a car for 20 minutes to fully charge a battery which isn't going to happen as people have driven their cars for a hour or more trying to charge their battery fully and find that the battery still isn't full so what can 20 minutes do? Not much. As for 20 minutes vs a few minutes, that's all relative to what someone considers a long time. I consider a 20-minute drive a relatively short time when it comes to needing to charge a battery. Plus, the output of a standard alternator needs to be consistently over 2,000 to 2,500 RPM before it will generate enough power to even start charging the battery. Considering that most cars these days try to keep the RPM fairly low in order to save on gas, you need to drive that car fairly hard over those 20 minutes to even start charging the battery. Besides, where did you get the magic number of 20 minutes from anyways?

Back in the old days, when we had 40 or 60 amp alternators, I would agree, you needed high rpms for a decent charge.

I've tested alternators built in the last decade that are smaller and have the ability to have an output of 14+ volts and 80+ amps just sitting at idle when load testing.

So short trips a few times a day won't cause a problem on late model charging systems, if your starting off with a decent, charged battery.

billford wrote: ↑ Back in the old days, when we had 40 or 60 amp alternators, I would agree, you needed high rpms for a decent charge.

I've tested alternators built in the last decade that are smaller and have the ability to have an output of 14+ volts and 80+ amps just sitting at idle when load testing.

So short trips a few times a day won't cause a problem on late model charging systems, if your starting off with a decent, charged battery.

The problem is that newer cars typically have a higher current draw - ie we aren't just powering the AM radio anymore - so the higher current output is needed. Plus, a lot of new cars these days don't engage their alternator all of the time anymore in an effort to reduce the drag on the engine to reduce fuel consumption.

l69norm wrote: ↑ But these days, don't you need all the extra amps at idle just to run a modern engine - fuel injection system (computer, fuel pumps, etc) ? i thought it was like 20-30A ?
In the old days, you just needed amps at idle enough to run the ignition 2-3A ?

Don't forget those LCD screens and other electronics in the car. They will need power as well.

craftsman wrote: ↑ The problem is that newer cars typically have a higher current draw - ie we aren't just powering the AM radio anymore - so the higher current output is needed. Plus, a lot of new cars these days don't engage their alternator all of the time anymore in an effort to reduce the drag on the engine to reduce fuel consumption.

True, there are higher demands. But I see more than enough charge capacity to cover these demands and still keep the battery fully charged. Smart charging systems will engage as needed.

I know a lot of people, mostly retired who just drive short trips, 5 or 10 minutes to the mall at city speeds without any issues.

Just saying, you don't need to drive for hours just to keep the battery charged anymore.

billford wrote: ↑ True, there are higher demands. But I see more than enough charge capacity to cover these demands and still keep the battery fully charged. Smart charging systems will engage as needed.

I know a lot of people, mostly retired who just drive short trips, 5 or 10 minutes to the mall at city speeds without any issues.

Just saying, you don't need to drive for hours just to keep the battery charged anymore.

One other thing... that extra charge capacity won't really matter once the battery approaches approx 80% charge as the charge current required by the battery drops from C/4 or C/5 to just a few amps at about 80% as the bulk charging is no longer that effective to charge a battery - ie it won't matter if you have 5A of extra capacity or 50 A, the battery will only accept so much as it approaches 80%. Of course, that's provided the car is smart enough to have a multi-stage charging system install. If it is, then once the battery gets past 80%, the required charging current may drop to below 1A as the battery enters an absorption charge but it needs to be applied for hours - ie a 100 Ah battery which is 80% will require another 20 Ah of power to get fully charged so at 1A another 20 hours is required.

Just saying that you DO need to drive for hours to fully charge a battery.

Has anyone said, use a generator?

Alligatorclip wrote: ↑ Has anyone said, use a generator?

There's a convenient generator located under the hood.

Alligatorclip wrote: ↑ Has anyone said, use a generator?

I mentioned it.

craftsman wrote: ↑ One other thing... that extra charge capacity won't really matter once the battery approaches approx 80% charge as the charge current required by the battery drops from C/4 or C/5 to just a few amps at about 80% as the bulk charging is no longer that effective to charge a battery - ie it won't matter if you have 5A of extra capacity or 50 A, the battery will only accept so much as it approaches 80%. Of course, that's provided the car is smart enough to have a multi-stage charging system install. If it is, then once the battery gets past 80%, the required charging current may drop to below 1A as the battery enters an absorption charge but it needs to be applied for hours - ie a 100 Ah battery which is 80% will require another 20 Ah of power to get fully charged so at 1A another 20 hours is required.

Just saying that you DO need to drive for hours to fully charge a battery.

Sorry, I don't think anybodys going to drive 20 hours for a battery charge.

The short trip retirees I mentioned sure don't, and they don't have any battery problems.

Alligatorclip wrote: ↑Has anyone said, use a generator?

Thats blasphemy. Despite the half dozen mentions so far
My favourite was the generator attached to a bicycle to charge the battery of a gasoline powered car

billford wrote: ↑ Sorry, I don't think anybodys going to drive 20 hours for a battery charge.

You mean you don't drive from Toronto to Winnipeg once a week, every week?