# Recharging car battery method



## yuri (Nov 29, 2008)

I need to recharge mine ( top up ) after it sits for more than 2 weeks and have a charger with 2A, 15A, 100 full boost and 6 volt. Is it better to slow charge it with 2 amps or 15 amps and can any harm come from using 15 amps?

With 15 amps the charging needle goes back and forth quickly from full to 2 and back and forth ( full blast and then down ) and you hear it clicking on/off. I don't want to wear out the relay inside it. 2 amps takes a long time but runs slow and steady. I have lots of time so time is not the issue.

I heard that higher amp charging can overheat a battery but it is really cold where I am but I don't want to cook it internally. Any scientific known reason 2 A is better than 15 ?


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## mark sr (Jun 13, 2017)

2amp is best if you intend to leave the charger connected for a long period of time. I usually charge mine on either the 15 amp or 40 amp setting. 100 amp is for boost only.n


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## HotRodx10 (Aug 24, 2017)

2 Amp is better, if you have the time.


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## yuri (Nov 29, 2008)

How long does 2 amp take ( not a great question ). I am running a experiment today and will let it run 12 hrs. I have never seen it get to the full charge but have never left it that long. Ran the car a week ago but the weather has been extreme cold and I don't always drive it often when that cold. Seems like the computer uses power for the alarm system and in 2 weeks drains it down. 4 yr old Costco battery which has been real good so far.


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## daveb1 (Jan 15, 2010)

Charging at low amps is best for the battery. For charging in extreme cold have you considered a battery basket blanket?







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## HotRodx10 (Aug 24, 2017)

If you're trying to start it in extreme cold, warming the battery probably has more benefit than charging it, although charging it warms it also. If it's really cold, you shouldn't have an issue with overheating it on the 15 amp setting.


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## yuri (Nov 29, 2008)

daveb1 said:


> Charging at low amps is best for the battery. For charging in extreme cold have you considered a battery basket blanket?
> 
> 
> 
> ...


It is actually a lot warmer in my attached garage than outdoors and I had a battery blanket many years ago. I heard horror stories of them catching on fire and did not really notice it helped with starting my company van. I think I will stay with the 2 amps and get a new battery next year.


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## yuri (Nov 29, 2008)

HotRodx10 said:


> If you're trying to start it in extreme cold, warming the battery probably has more benefit than charging it, although charging it warms it also. If it's really cold, you shouldn't have an issue with overheating it on the 15 amp setting.


I always plug it in for 4 hours when below -18C and that makes the biggest difference ( warm oil ) . It just turned 4 yrs old and I left it for 2 weeks and it did not want to start. Boosted it and it is OK now. Normally I go drive it but it was -25 to -30 C lately and I did not feel like going through the hassle. With Amazon Prime I get stuff delivered so less shopping trips. Just need to get a routine of starting it every Monday morning and let it self charge.

I heard it is hard on the battery to fast charge it ( cooks the cells ) so I am trying to avoid that but I would like some scientific proof of that or does anyone know where that is on the net?


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## mark sr (Jun 13, 2017)

If I'm not mistaken most alternators put out in excess of 50 amps although they don't do that continuously. I've never had any issues using the 40 amp setting on my charger but then I don't set it at that for hours.


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## yuri (Nov 29, 2008)

mark sr said:


> If I'm not mistaken most alternators put out in excess of 50 amps although they don't do that continuously. I've never had any issues using the 40 amp setting on my charger but then I don't set it at that for hours.


I have used the 15 amps and it bounces back and forth a lot ( charging current needle display ) so it seems to use a pulse charge method. Eventually as the battery gets fully charged it pulses less but the 2 amps seems to take forever. I would like to know if 15 amp is hard on the battery or has anyone ruined a battery with higher charging.


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## 660catman (Aug 25, 2019)

Slow charge is best. I have the Motomaster precision series 1.5 amp battery charger. I have the quick connect fittings on my sleds as there’s not much room for alligator clips. I now use it on my diesel truck every couple of weeks. It has 6v and 12v settings and SLA or AGM settings. There is a reconditioning mode too. 













Retired guy from Southern Manitoba, Canada.


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## diyorpay (Sep 21, 2010)

Possibly consider a trickle charger.

US amazon: Amazon.com : trickle battery charger

Thanks for the great library of solid advice you've provided to the site over the years!


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## HotRodx10 (Aug 24, 2017)

mark sr said:


> If I'm not mistaken most alternators put out in excess of 50 amps although they don't do that continuously.


Most of the new ones have the capacity to put out 125 or 200 amps, but they don't output anything close to that recharging the battery. With the voltage differential at only 1 or 2 volts, the current flowing into the battery is typically in the 10 to 20 amp range.


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## Bud9051 (Nov 11, 2015)

I know you read some negative info on battery blankets, but I suspect not all options are a concern. Warming up that battery and possibly the oil would do wonders for performance. Years ago I experimented with a variable resistance heat wire. When cold it produces more heat and as it warms up the slows down. I haven't researched it in recent decades but I suspect there are retail products using that technology today. Very safe. Your extreme temperatures would need to be researched.

Modern engine oil today is often a blend of synthetic oil. From the prices I see it must have gold mixed in. But (again decades ago) my experience with synthetic was impressive in cold weather. Maine gets cold but probably like Florida compared to what you get.

Bud


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## yuri (Nov 29, 2008)

660catman said:


> Slow charge is best. I have the Motomaster precision series 1.5 amp battery charger. I have the quick connect fittings on my sleds as there’s not much room for alligator clips. I now use it on my diesel truck every couple of weeks. It has 6v and 12v settings and SLA or AGM settings. There is a reconditioning mode too.
> 
> 
> 
> ...


I have a 10+ yr old Motomaster charger and am not the most patient guy in the world even though I am retired. I am used to dealing with fire alarms in a hospital etc and like to get things done fast and ole 2 amps is like turtle speed. I put it on at 730 AM today and will see how much charging it can do in 12 hrs.


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## yuri (Nov 29, 2008)

Bud9051 said:


> I know you read some negative info on battery blankets, but I suspect not all options are a concern. Warming up that battery and possibly the oil would do wonders for performance. Years ago I experimented with a variable resistance heat wire. When cold it produces more heat and as it warms up the slows down. I haven't researched it in recent decades but I suspect there are retail products using that technology today. Very safe. Your extreme temperatures would need to be researched.
> 
> Modern engine oil today is often a blend of synthetic oil. From the prices I see it must have gold mixed in. But (again decades ago) my experience with synthetic was impressive in cold weather. Maine gets cold but probably like Florida compared to what you get.
> 
> Bud


I found it to be too cumbersome and then you have a extra plug to deal with etc etc. Had one on my company van and never noticed a difference. Can almost buy 2/3 of a new battery for what it costs.


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## yuri (Nov 29, 2008)

diyorpay said:


> Possibly consider a trickle charger.
> 
> US amazon: Amazon.com : trickle battery charger
> 
> Thanks for the great library of solid advice you've provided to the site over the years!


My ole Motomaster trickles along at 2 Amps and I would like maybe a 5 amp one. Happy medium between trickle and gallop.


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## yuri (Nov 29, 2008)

660catman said:


> Slow charge is best. I have the Motomaster precision series 1.5 amp battery charger. I have the quick connect fittings on my sleds as there’s not much room for alligator clips. I now use it on my diesel truck every couple of weeks. It has 6v and 12v settings and SLA or AGM settings. There is a reconditioning mode too.
> 
> 
> 
> ...


Light bulb moment. I will grab the ole multimeter and check dat der voltage.


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## Bud9051 (Nov 11, 2015)

Not sure how weather in Fairbanks compares to what you get but I often refer to "what they do in Alaska" to find cold weather advice for here in Maine. So I searched although probably old news for you.

Don't Get Stuck with a Vehicle That Won't Start This Winter
Winterization Fairbanks, AK | Ken's Fairbanks Alignment

I also searched for the cable I experimented with, being you have a technical background. Readily available now and called "Self-regulating heat tracing cable". Doesn't solve your aversion to having one more thing to plug in but it is technically interesting.

Bud


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## yuri (Nov 29, 2008)

Bud9051 said:


> Not sure how weather in Fairbanks compares to what you get but I often refer to "what they do in Alaska" to find cold weather advice for here in Maine. So I searched although probably old news for you.
> 
> Don't Get Stuck with a Vehicle That Won't Start This Winter
> Winterization Fairbanks, AK | Ken's Fairbanks Alignment
> ...


I just looked at their weather and it is about the same as ours depending on the winter. A severe one here can be 6 weeks or more of -25 to-40C weather. Just checked the battery and it is 12.5 volts which is 95%. I have CAA and won't be stranded and I don't do anymore 4 hour road trips to the small town I lived in from Wpg anymore. Used to carry insulated coveralls and extra boots and clothes for that but if you stay on the main highways someone will find you within 4 hrs due to the traffic flow.


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## SeniorSitizen (Sep 10, 2012)

Don't all battery chargers cut back as the battey is charged . I have a old Schaurer with a range of 20 or 30 ? down to 0 that does . The next time it's convenient you might have the battery load tested .

Regulated heat cable could be a good idea on some roofs also . It's been around 50 years .









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## Matt1963 (5 mo ago)

You could reach out to viper over in the electrical thread...
He seemed to be a expert on batteries, charging and looking for periodic draining.


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## yuri (Nov 29, 2008)

SeniorSitizen said:


> Don't all battery chargers cut back as the battey is charged . I have a old Schaurer with a range of 20 or 30 ? down to 0 that does . The next time it's convenient you might have the battery load tested .
> 
> Regulated heat cable could be a good idea on some roofs also . It's been around 50 years .
> 
> ...


It is at 12.5 volts now and I am waiting to see if the green full charge light will go on. Used to. It seems like these battery makers have ALL designed them to last no more than 5 years just like roof shingles don't go more than 20. I got it at Costco but every other brand I got lasted 5 years , planned obsolesce it seems. My Gal has a Costco card and maybe I will get a new one there if this one gets worse.

Those heat cables I believe are illegal to sell in Manitoba same with those non vent space heaters. We had too many cottages burn down with those cables and I think they are not available here.


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## Matt1963 (5 mo ago)

yuri said:


> It is at 12.5 volts now and I am waiting to see if the green full charge light will go on. Used to. It seems like these battery makers have ALL designed them to last no more than 5 years just like roof shingles don't go more than 20. I got it at Costco but every other brand I got lasted 5 years , planned obsolesce it seems. My Gal has a Costco card and maybe I will get a new one there if this one gets worse.
> 
> Those heat cables I believe are illegal to sell in Manitoba same with those non vent space heaters. We had too many cottages burn down with those cables and I think they are not available here.


From what I was told it's the recycled Chinese lead in them....they don't last.


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## yuri (Nov 29, 2008)

Matt1963 said:


> From what I was told it's the recycled Chinese lead in them....they don't last.


Probably although lead is lead like gold is gold.


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## SeniorSitizen (Sep 10, 2012)

I suppose miles of stainless sheath heat cables installed in natural gas plants , that never failed that i know of , are history .


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## yuri (Nov 29, 2008)

SeniorSitizen said:


> I suppose miles of stainless sheath heat cables installed in natural gas plants , that never failed that i know of , are history .


The ones I am talking about are your cheap H Depot NOMA type and probably people pounded staples thru them and shorted them. They used to get hard like those cheap orange extension cords you can buy harden up in the Winter. That and rodents chewing them.


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## Matt1963 (5 mo ago)

yuri said:


> Probably although lead is lead like gold is gold.


Well I read up on it some because I was getting very short term battery life from the good old days. They really were down on the recycling process used.

For $300 plus you can get a American made battery with new lead, not recycled and it's performance and longevity is much better.

All's I know is the batteries I'm buying these days are junk.


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## 660catman (Aug 25, 2019)

Matt1963 said:


> Well I read up on it some because I was getting very short term battery life from the good old days. They really were down on the recycling process used.
> 
> For $300 plus you can get a American made battery with new lead, not recycled and it's performance and longevity is much better.
> 
> All's I know is the batteries I'm buying these days are junk.


Tell that to the guys on the GM truck forum I follow. Guys in the heat belt are getting maybe 4 years out of US made ones. I got 8 years out of mine in my 2013 Silverado. 


Retired guy from Southern Manitoba, Canada.


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## yuri (Nov 29, 2008)

I think it is not as simple as just ordinary lead. There must be other metals that the cells are made from along with the electrolyte and I am sure these manufacturers are making it so that the cells and connectors corrode at a certain rate and fail. Just like AC companies take a unit and test the paint for fading and corrosion in a lab I am sure they have the time and expertise to measure corrosion.

I worked with very expensive chillers in a Convention center and we had sacrificial anodes/copper test plugs in a loop in the chillers which got removed and weighed and measured and tested once a year by Betz the chemical company to see how much copper was being eaten and how effective our and their water treatment was. Too much corrosion and the copper tubes in the condensor failed and that is a HUGE expensive problem.


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## Matt1963 (5 mo ago)

660catman said:


> Tell that to the guys on the GM truck forum I follow. Guys in the heat belt are getting maybe 4 years out of US made ones. I got 8 years out of mine in my 2013 Silverado.
> 
> 
> Retired guy from Southern Manitoba, Canada.


Which battery's were you using?

I have a 4 year old battery in my truck that's junk and 11 year old Sears diehard in a tow behind compressor that still works perfect. 

Explain that.


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## HotRodx10 (Aug 24, 2017)

Matt1963 said:


> I have a 4 year old battery in my truck that's junk and 11 year old Sears diehard in a tow behind compressor that still works perfect.
> 
> Explain that.


Output demand, usage frequency, and environment.


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## 660catman (Aug 25, 2019)

Matt1963 said:


> Which battery's were you using?
> 
> I have a 4 year old battery in my truck that's junk and 11 year old Sears diehard in a tow behind compressor that still works perfect.
> 
> Explain that.


Mine was still the original GM. I got 11 seasons out of a genuine Arctic Cat AGM battery. I got 5 out of my SLA battery in my 2016 Bearcat sled. I had a replacement fail in 18 months in my ATV. 


Retired guy from Southern Manitoba, Canada.


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## mark sr (Jun 13, 2017)

I agree today's batteries are poor compared to their predecessor. 15 yrs ago I bought a $75 battery for my pickup that lasted 11 yrs. That battery had a 6 yr warranty. When it died I bought another one [same brand/number] for $150 It only has a 2 yr warranty and is already showing signs of dying. At 11mpg I never have drove my truck a lot and I'm already having to charge this battery if I don't drive it every week - didn't have to do that with the previous battery until yr 10. 

I hate that you can't buy anything with the quality the same item had yrs ago.


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## yuri (Nov 29, 2008)

Final result: Left it on for 12 hrs and it hit 12.6 volts which is + 95% full charge but the full charge green light did not come on and it was still charging. I think it is impossible at this age to get to 98-100% so now I will just test the voltage and when it gets to 12.6 shut it off manually. I will determine how many hrs it takes to get there and set a timer.


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## diyorpay (Sep 21, 2010)

Recollections from the 70's:
The VW bug was newish for me so to the battery I added some kind of catalyst/additive in small bottles and,
the battery was under the back seat, out of the weather extremes (an outdoors car).
(I think Mercedes may still have some in the trunk/boot.)

Battery lasted a really long time.

Conspiracy theory tie-in: 
Battery makers want planned obsolescence but want us also hands off. So sealed battery introduced. 

Also note that when a battery was near end of life, it sounded that way. Like in the horror movies.
Now, turn key, either click click or nothing at all.


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## SeniorSitizen (Sep 10, 2012)

diyorpay said:


> Recollections from the 70's:
> The VW bug was newish for me so to the battery I added some kind of catalyst/additive in small bottles and,
> the battery was under the back seat, out of the weather extremes (an outdoors car).
> (I think Mercedes may still have some in the trunk/boot.)
> ...


Man , you got the* NOTHING AT ALL *part right . 4 y o battery that came in a new pickup truck , no warning at all , wouldn't even unlock the door using the fob but had 12.3 V .


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## yuri (Nov 29, 2008)

Scary stuff. Mine just usually not hold a decent charge for very long but I have never had one flatline. I don't miss those old batteries you had to add water to or check. Apparently a lot exploded in people's faces from overcharging/quick boosting as they gave off fumes so they went with sealed batteries.


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## GrayHair (Apr 9, 2015)

Lead acid batteries have sulphated since they were invented. It's a natural process that can be accelerated, leading to drastically reduced battery life.

A couple of things we can control are storage temperature. Storing without a full charge speeds up susfation. Battery maintainers keep the voltage above the critical point (I've forgotten what that voltage is).

Increased temperature speeds up most if not all chemical reactions, so storing batteries tn too warm an environment increases the sulfation rate.

There are most likely other reasons, but over the ensuing years, that info has "sulfated over" in my head.


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## Langer1 (Aug 24, 2021)

Why not just get a battery Tender and leave it connected all the time? Oh also in cold weather a battery will never show as a full charge.A good battery @ 95% will read 100% if you bring it inside and just allow it to warm up, nothing else.


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## HotRodx10 (Aug 24, 2017)

Car batteries produce electricity by a chemical process, which slows down dramatically at low temperatures. Even a fully charged battery can only output less than half the amperage when it's below 0F than it's capable of at 75F.


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## dschae1 (Jan 19, 2020)

I use one of these to test my batteries, however, I do not recall paying this much for it. I also have a cheap tender from Harbor Freight to provide the trickle charge. I have left that connected for a week or more before.








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Automatic Battery Float Charger


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## FM3 (Aug 12, 2019)

SeniorSitizen said:


> Don't all battery chargers cut back as the battey is charged .


A dumb charger will keep outputting whatever amps it's set to. Because it's dumb. Sometimes dumb is good.


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## HotRodx10 (Aug 24, 2017)

FM3 said:


> A dumb charger will keep outputting whatever amps it's set to. Because it's dumb. Sometimes dumb is good.


A typical dumb charger will output a steady *voltage*. The amperage output will depend on the voltage differential, but the effect is the same - a cooked battery if left on too long.


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## Head_Unit (Jan 26, 2010)

yuri said:


> I am sure these manufacturers are making it so that the cells and connectors corrode at a certain rate and fail.


😄 Well I worked a long time in automotive engineering and highly doubt that-it's unnecessary because batteries get so punished anyway 
- I agree with @Langer1 and I've used several each of these trickle chargers with no problems https://smile.amazon.com/gp/product/B000CITK8S and https://smile.amazon.com/gp/product/B07H97P93H Yeah as @HotRodx10 and @FM3 note some chargers are dumb, no microprocessor to monitor the charge state, avoid that stuff.


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## yuri (Nov 29, 2008)

I have a method now were if I don't drive it for a week I just pop the hood and take my volt meter and test it. Today it was under 12.5 so I put the charger on and it is climbing quick. Nice when you have an attached garage and can do that real easy.


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## jayhanig (Feb 1, 2019)

I have a battery maintainer on the battery of every vehicle I own: car, truck, boat, and motorcycle. Before I moved to the beach, I had a riding lawn mower that was on one. I mount the ring terminals on the batteries so there is just a short pigtail that comes out from under the hood. Consequently, the maintainers stay inside my garage out of the weather and I don't have to raise a hood to connect one of them to a vehicle, which includes the boat that sits outside 24/7/365. They offer 12 volt extension cords that make things very handy.

A maintainer is more than just a trickle charger. It also deals with the sulfination of batteries and greatly extends the life of one. No danger of an overcharge. I typically get around 7 years out of a battery as a result.

I pull into my garage and immediately connect a maintainer right after I get out (or off) of the vehicle. At the point where the battery is starting to get wonky, I pull out my big charger for one last charge to get the vehicle started and I head off to the auto parts store to get the alternator and voltage regulator checked before I pay for a new battery. One way or the other, I'll leave the auto parts store with the solution to my problem.


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## yuri (Nov 29, 2008)

Just checked it after sitting for a week and it was 12.3 volts. Put the 2 amp charger on and in 4 hrs it was 12.6 so now I know how much time it takes to top it up.


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