Does a car battery degrade faster when it isn't fully charged?

[Muse]

I think I heard this, so I try to charge up my cars' batteries, maybe more often than I need to just to keep them able to start the cars (2). However, I don't drive much (<2000 miles/year), and I need to put my trickle charger on the batteries once in a while.

Is it true that keeping the batteries close to full charge (over 12.5 volts, it seems) will make the batteries last longer?

 

[Zenmervolt]

A car battery is fully charged at 12.6 volts.

When a regular (i.e. not a deep-cycle) lead-acid battery is drained too far, it suffers sulfation and this reduces its useful life. Since lead-acid batteries will slowly self-discharge even if taken out of the car, it is a good idea to keep it hooked up to a Battery Tender or other quality battery maintainer.

If you are leaving the batteries in the cars while they sit, you should absolutely use a maintainer like the Battery Tender as the parasitic drain from the car will drain the battery.

ZV

 

[Eli]

Originally posted by: Zenmervolt
A car battery is fully charged at 12.6 volts.

When a regular (i.e. not a deep-cycle) lead-acid battery is drained too far, it suffers sulfation and this reduces its useful life. Since lead-acid batteries will slowly self-discharge even if taken out of the car, it is a good idea to keep it hooked up to a Battery Tender or other quality battery maintainer.

If you are leaving the batteries in the cars while they sit, you should absolutely use a maintainer like the Battery Tender as the parasitic drain from the car will drain the battery.

ZV

The same thing happens with any lead-acid battery, even deep cycle. They're just able to handle it a little better due to the plate design.

Letting a lead acid battery sit discharged will severely reduce its life, yes.

Just depends on the level of discharge. Let a battery sit completely dead for a few weeks, and it will have certainly lost capacity.

Basically, a batteries' life is dependent on how little it is discharged through its life. OK, there are other factors, but I said basically. 😉

A regular lead-acid battery may be able to handle 50 complete discharges, while a deep-cycle battery may be able to handle 200.

 

[TheSlamma]

I leave my truck parked out back and only drive it now when I need to haul/tow or when the weather gets bad my wife parks the fit drives my beater and I use the truck. few weeks ago when it dropped into the low teens it was finally the end of my yellow top optima (8 years I'm kinda bummed)

Will these "Battery Tenders" work where I I can have it charge while out in the truck even in cold temps or does it have to be moved inside to be charged correctly?

 

[Zenmervolt]

Originally posted by: TheSlamma
I leave my truck parked out back and only drive it now when I need to haul/tow or when the weather gets bad my wife parks the fit drives my beater and I use the truck. few weeks ago when it dropped into the low teens it was finally the end of my yellow top optima (8 years I'm kinda bummed)

Will these "Battery Tenders" work where I I can have it charge while out in the truck even in cold temps or does it have to be moved inside to be charged correctly?

They do have a waterproof model. However, it's still electric (obviously), so you'll want to be careful with running extension cords outside and such.

ZV

 

[Zenmervolt]

Eli, I'd be shocked if a normal automotive battery survived 50 full discharge cycles. I'd say closer to 5-10 before the battery wouldn't be able to be trusted.

ZV

 

[SparkyJJO]

I've got the battery from my old car sitting in the basement. Been there for almost 4 months now, haven't charged it or used it for anything. Probably not worth much anymore I guess.

 

[Eli]

Originally posted by: Zenmervolt
Eli, I'd be shocked if a normal automotive battery survived 50 full discharge cycles. I'd say closer to 5-10 before the battery wouldn't be able to be trusted.

ZV

A decent one should be able to... if you charge it up right away after being discharged.

The numbers I used were fairly realistic, based on the research I've done while looking for power for some mobile projects I had in mind.

It really depends on the battery, though.

 

[Muse]

Originally posted by: SparkyJJO
I've got the battery from my old car sitting in the basement. Been there for almost 4 months now, haven't charged it or used it for anything. Probably not worth much anymore I guess.

It obviously depends a lot on what kind of charge it had at the beginning of this 4 month period. Since it's not connected to a power drain (when in a vehicle, it is being drained by things like the clock), it may not be in all that bad shape. The thing to do is charge it.

I have a trickle charger I picked up at Kragen a few years back. Occasionally (every month or two) I push a 50' extension cord out a window and run it up into the engine compartment of one, then the other of my two cars, and trickle-charge the battery until the charger indicates with an LED that the battery has achieved maximum charge. Just after removing the charger, the battery generally reads 12.82-12.95 volts.

I did this with both my cars a couple of days ago or so (I gave each battery about 20 hours before checking).

Before charging this week, the batteries showed 11.82 and 11.81 volts respectively. What I'm wondering is if I should not have let them get that low. At just what voltage should I have put the charger on? I could (but wonder if it's necessary) trickle charge continually. I'd need an additional charger, for one thing.

My mechanic told me that if he had a car he used very sparingly, he'd disconnect the battery. I did this for a while, but got tired of it and just decided to do the occasional trickle charge. For one thing, we had a disagreement. I'd just loosen the bolt holding the cable to the battery's positive terminal and pull it off or shove it on with a few twists for good measure. My mechanic said he'd wrench it back tight. This struck me as too much trouble.

 

[Eli]

11.81V is quite low, the batteries State of Charge is only at ~25% at that point, depending on the rate of discharge.

For example, a battery that has a load of Capacity/100 will read 11.8V when at 0% SoC.

A battery that has a load of C/3 will read 9.5V when it reaches 0% SoC.

Most batteries are rated at C/20. That is, how much power they can dish out in 20 hours, which is where I got the 25% figure.

To preserve optimum battery life, it should never dip below 12.7V.

 

[Muse]

Originally posted by: Eli
11.81V is quite low, the batteries State of Charge is only at ~25% at that point, depending on the rate of discharge.

For example, a battery that has a load of Capacity/100 will read 11.8V when at 0% SoC.

A battery that has a load of C/3 will read 9.5V when it reaches 0% SoC.

Most batteries are rated at C/20. That is, how much power they can dish out in 20 hours, which is where I got the 25% figure.

To preserve optimum battery life, it should never dip below 12.7V.

SoC means State of Charge?

I guess what you're essentially saying then is that for maximum life you pretty much have to keep the battery topped up. IOW, my little used cars should have a trickle charger on them all the time. I suppose, then, the trade off I have to evaluate is the cost/day of running the trickle chargers versus how much extra life I get from the batteries. Sort of a head scratcher.

 

[Eli]

Originally posted by: Muse

Originally posted by: Eli
11.81V is quite low, the batteries State of Charge is only at ~25% at that point, depending on the rate of discharge.

For example, a battery that has a load of Capacity/100 will read 11.8V when at 0% SoC.

A battery that has a load of C/3 will read 9.5V when it reaches 0% SoC.

Most batteries are rated at C/20. That is, how much power they can dish out in 20 hours, which is where I got the 25% figure.

To preserve optimum battery life, it should never dip below 12.7V.

SoC means State of Charge?

I guess what you're essentially saying then is that for maximum life you pretty much have to keep the battery topped up. IOW, my little used cars should have a trickle charger on them all the time. I suppose, then, the trade off I have to evaluate is the cost/day of running the trickle chargers versus how much extra life I get from the batteries. Sort of a head scratcher.

I don't think keeping them hooked up all the time is quite necessary, even something like once a month would greatly extend their life.

I actually misspoke. C/20 is the load they're measured at. Thats usually how they obtain amp-hour figures and such. So at load of C/20, your battery only has 25% left at 11.81V.

Yeah, optimally the battery would be kept full. This could result in a life of ~8-10 years.

Maybe you could come up with a regimen.. figure out how fast the batteries discharge, and slap the trickle charger on there every 2 weeks, or however long it takes for the batteries to get down to 12.1V or something. That should increase their life a bit.

I think we may be overstating the importance of it, as long as you aren't letting them sit completely discharged. You probably won't really notice if a battery only lasts 5 years instead of 8.

:shrug;

 

[Zenmervolt]

Originally posted by: Eli

Originally posted by: Zenmervolt
Eli, I'd be shocked if a normal automotive battery survived 50 full discharge cycles. I'd say closer to 5-10 before the battery wouldn't be able to be trusted.

ZV

A decent one should be able to... if you charge it up right away after being discharged.

The numbers I used were fairly realistic, based on the research I've done while looking for power for some mobile projects I had in mind.

It really depends on the battery, though.

Good point on charging it immediately. I was thinking more along the lines of batteries that go dead over winter and don't get noticed until spring. When they're left dead for several months, there's usually not that much one can do to save them after the 3rd or 4th time.

ZV

 

[Muse]

Originally posted by: Eli

Originally posted by: Muse

Originally posted by: Eli
11.81V is quite low, the batteries State of Charge is only at ~25% at that point, depending on the rate of discharge.

For example, a battery that has a load of Capacity/100 will read 11.8V when at 0% SoC.

A battery that has a load of C/3 will read 9.5V when it reaches 0% SoC.

Most batteries are rated at C/20. That is, how much power they can dish out in 20 hours, which is where I got the 25% figure.

To preserve optimum battery life, it should never dip below 12.7V.

SoC means State of Charge?

I guess what you're essentially saying then is that for maximum life you pretty much have to keep the battery topped up. IOW, my little used cars should have a trickle charger on them all the time. I suppose, then, the trade off I have to evaluate is the cost/day of running the trickle chargers versus how much extra life I get from the batteries. Sort of a head scratcher.

I don't think keeping them hooked up all the time is quite necessary, even something like once a month would greatly extend their life.

I actually misspoke. C/20 is the load they're measured at. Thats usually how they obtain amp-hour figures and such. So at load of C/20, your battery only has 25% left at 11.81V.

Yeah, optimally the battery would be kept full. This could result in a life of ~8-10 years.

Maybe you could come up with a regimen.. figure out how fast the batteries discharge, and slap the trickle charger on there every 2 weeks, or however long it takes for the batteries to get down to 12.1V or something. That should increase their life a bit.

I think we may be overstating the importance of it, as long as you aren't letting them sit completely discharged. You probably won't really notice if a battery only lasts 5 years instead of 8.

:shrug;

Yea, there's a point of diminishing returns, a happy balance. Maybe I should do the disconnect the battery routine and just ignore what my mechanic said about wrenching the connector onto the terminal. I think just pressing it on and twisting if it's reasonably tight will get a reasonable snugness. But then my clock would be wrong and I wonder if my radio would remember its presets... 😕 With one of the cars, I don't care. I only use it when hauling stuff from Home Depot and such (other than the occasional trip to keep things working, every 5-6 weeks!).

 

[cardiac]

Also, for those of us in the colder climates, don't forget that a discharged battery, even partially, will freeze quite a bit easier than a fully charged battery. Then it is toast.....

Bob

 

[Throckmorton]

You should look into getting an Optima battery. They are almost twice as expensive as regular batteries, but they're sealed and have a much much longer shelf life. I got one for my Jeep when my old one died, because I don't drive often.

 

[Muse]

Originally posted by: Throckmorton
You should look into getting an Optima battery. They are almost twice as expensive as regular batteries, but they're sealed and have a much much longer shelf life. I got one for my Jeep when my old one died, because I don't drive often.

They don't degrade as fast when "neglected"? i.e. not topped up frequently?

 

[Eli]

Originally posted by: Muse

Originally posted by: Throckmorton
You should look into getting an Optima battery. They are almost twice as expensive as regular batteries, but they're sealed and have a much much longer shelf life. I got one for my Jeep when my old one died, because I don't drive often.

They don't degrade as fast when "neglected"? i.e. not topped up frequently?

I don't know about that, all batteries are susceptible to damage if left discharged. The amount of damage depends on the level of discharge and the time that has passed.

They may have a lower internal resistance, though. That means that the battery wouldn't self-discharge as fast, ontop of whatever load the car is presenting.

 

[Killrose]

Whoa! this thread just reminded me that I forgot to remove my boat battery for the winter!

 

[Muse]

I made it to Harbor Freight today and bought this charger. They call it a "float charger." On the box it says "Not A Trickle Charger." I wonder what they mean by that. It was 5 bucks.

The instruction leaflet inside says it won't overcharge a battery, that you can just set it and forget it, and it's for "flooded or gel-cell batteries." It's supposed to supply 13.2 volts.

The instructions also say to disconnect the battery before charging. I don't intend to do that and wonder if that will be a problem. Of course, I don't want to remove the battery from the car or even remove one of the cables from a battery terminal.

Would I be better off getting a "trickle charger?" What's the difference between a float charger and a trickle charger?

What I figure I'll do is run a power cord out to my cars and hook up my trickle charger that I got from Kragen to one of the batteries. I'm not sure it's a trickle charger... it charges and when it senses that the battery is full, a red LED lights up, and presumably it stops supplying current. When it stops sensing that the battery is full (usually 30 seconds or so), the LED goes off and it starts charging the battery again. I always remove it when it gets to that point (when I notice it). I figure I'll run a second cord from one car to the other and put this "float charger" on the other battery and just plug and unplug the main cord from time to time rather than leave both batteries charging all the time. Maybe have them going a couple days a week, and monitor the voltage on the batteries until I have a feel for what percentage of the time these chargers have to be plugged in to keep the batteries fairly topped up. Of course, this assumes that both chargers do a similar job, which may or may not be the case. I could supply power to them separately in that case.

 

[Eli]

Originally posted by: Muse
I made it to Harbor Freight today and bought this charger. They call it a "float charger." On the box it says "Not A Trickle Charger." I wonder what they mean by that. It was 5 bucks.

The instruction leaflet inside says it won't overcharge a battery, that you can just set it and forget it, and it's for "flooded or gel-cell batteries." It's supposed to supply 13.2 volts.

The instructions also say to disconnect the battery before charging. I don't intend to do that and wonder if that will be a problem. Of course, I don't want to remove the battery from the car or even remove one of the cables from a battery terminal.

Would I be better off getting a "trickle charger?" What's the difference between a float charger and a trickle charger?

What I figure I'll do is run a power cord out to my cars and hook up my trickle charger that I got from Kragen to one of the batteries. I'm not sure it's a trickle charger... it charges and when it senses that the battery is full, a red LED lights up, and presumably it stops supplying current. When it stops sensing that the battery is full (usually 30 seconds or so), the LED goes off and it starts charging the battery again. I always remove it when it gets to that point (when I notice it). I figure I'll run a second cord from one car to the other and put this "float charger" on the other battery and just plug and unplug the main cord from time to time rather than leave both batteries charging all the time. Maybe have them going a couple days a week, and monitor the voltage on the batteries until I have a feel for what percentage of the time these chargers have to be plugged in to keep the batteries fairly topped up. Of course, this assumes that both chargers do a similar job, which may or may not be the case. I could supply power to them separately in that case.

That's float charging.

A trickle charger supplies a very small amount of current all the time.

For maintaining a battery at full charge, you want a float charger.

For charging up a battery that is below full capacity, you at least want a trickle charger. A trickle charger will charge a discharged battery, but it will take a long time, at least when compared to even the smallest "regular" charger.

 

[Muse]

Originally posted by: Eli

"That's float charging."
- - - -
[/quote]Thanks. So both chargers are float chargers. One's just fancier than the other. I figure I can leave everything hooked up and then just unplug the power part of the time so I won't be using a continuous 20 - 30 watts (energy conscious). That in itself, if left unplugged 1/2 the time should save 15 bucks/year or so.

Edit: The cheaper, Harbor Freight charger (Product ID: 42292, $5 on sale, $6 now for the next few weeks) uses less energy -- about 5 watts or less to keep the battery charged. The "fancier" charger (Schumaker, from Kragen, cost me ~$15, but would probably run you close to $30 now) draws 29 watts when charging, 12 watts when the battery's at the top... it cycles from one to the other when fully charged.

 

[Muse]

Originally posted by: Muse

Originally posted by: Eli

"That's float charging."
- - - -

Thanks. So both chargers are float chargers. One's just fancier than the other. I figure I can leave everything hooked up and then just unplug the power part of the time so I won't be using a continuous 20 - 30 watts (energy conscious). That in itself, if left unplugged 1/2 the time should save 15 bucks/year or so.

I've had the Harbor Freight 5 buck float charger on the battery in one of my cars for a few days now and I like what I'm seeing. It draws less than 5 watts off the grid and very slowly increases the voltage on the battery. It was around 12.3 volts 3-4 days ago and around 12.5 volts now. The battery's hooked up to the car. Conditions are around 40 degrees at night, close to 50 during the day.

My other Kragen-bought, Schumaker charger is much more aggressive (and costs 3-5 times as much). It draws around 29 watts while charging, 12 watts while it sees the battery as fully charged. It will bring a 12.3 volt charged battery up to full charge in 2-3 hours.

I can leave the $5 float charger on all the time, which isn't a hassle when I don't expect to be using a car for a long time, which has been usual for me at least with one of the cars. I have a mind to buy another of these for my other car. Neither car gets used a lot, on average.

 

[SVT Cobra]

marked

 

[Throckmorton]

Originally posted by: Muse

Originally posted by: Throckmorton
You should look into getting an Optima battery. They are almost twice as expensive as regular batteries, but they're sealed and have a much much longer shelf life. I got one for my Jeep when my old one died, because I don't drive often.

They don't degrade as fast when "neglected"? i.e. not topped up frequently?

Well the yellow top is deep cycle, so even if it does discharge, you charge it up and it's good as new. They're rated for 350 deep cycles, while I think just one will ruin a normal battery.
http://www.batterymart.com/p-o...ellow-top-battery.html

The red top, which is what I got, is rated for 50 cycles. Don't know if they are "deep" cycles or what. http://www.batterymart.com/p-o...8-red-top-battery.html

Then they also discharge slower while left unused.

Optima Red Top Batteries are designed to take abuse. Optima's patented SPIRALCELL® Technology offers 15 times more vibration resistance and twice the life of an ordinary battery.

Optima Red Top Batteries are specifically designed for starter applications and deliver a higher level of power in the critical first 10 seconds of the starting cycle.

Optima Red Top Batteries are ideal for applications that only require seasonal use. Fully charged, this Optima Red Top Battery can sit unused for up to 12 months at or below room temperature, and still deliver the starting power you need.

The SPIRALCELL® Technology and Sealed Case make this battery completely spill proof, preventing external gassing and and leaking which may damage engine components and limit battery performance.