Lead acid car battery related questions

Thread Starter

yourminky

Joined May 31, 2019
25
One of my car has a 7 year old lead acid battery that is still running OK. I am afraid in coming winter it will probably die. I have a few questions.
1. How to prolong the life of the old battery? I charge it using a Harbor Freight trickle charge whenever possible.
2. Is it wise to put a extremely large 1 farad capacitor in parallel with the battery? Will it help or cause more battery drainage?
3. Walmart sells their own generic brand car battery now. Have you used it? Any good?
 

Infinion

Joined Apr 2, 2016
9
I'll take a crack at your questions and answer in order:

1.
  • No idea what the characteristics of a Harbor Freight trickle charger are like, if it's just a CV CC charger, take a look at what the maximum output voltage is. If it is more than 13.7V, the flooded battery will start to quietly bubble, producing hydrogen and oxygen as it undergoes electrolysis. It's normal for lead-acid batteries over short periods. However, if it is left on the charger for days or months, eventually the electrolyte levels will drop until the cells are no longer immersed. A float voltage above 12.7 and below 13.7 should be fine.
  • To prolong the life of your battery, never deeply discharge it into and below 11.8V. After a few deep discharges your plates are going to sulfate and the effective surface area exposed to the electrolyte will drop along with your capacity very quickly. Hard or nearly impossible to reverse. You can tell your plates are sulfated if you see a lot of white buildup on a fully charged battery. Fully charged batteries in good condition should be 100% lead and black-looking.
  • If you have a serviceable flooded battery (with removable caps), open them up from time to time and check the levels with a flashlight. If the liquid level is low or at/below the plates add some distilled/deionized water and fully charge before capping (and never use tap water, it can cause accelerated self-discharge). Don't fill them up to the brim, always leave room for the liquid level to rise, at most, fill up to the bottom of the port. Electrolyte levels vary with state of charge. A fully discharged cell will have a lower liquid level than a fully charged cell.
  • Look for a battery hydrometer to check the condition of each cell's electrolyte. If you go to https://batteryuniversity.com/learn/article/how_to_measure_state_of_charge you'll see the specific gravity table a cell should read at a certain state of charge. At 100% you should have 1.265 or higher specific gravity in each cell (too high causes corrosion). If it is lower, your plates are probably sulfated (the sulfer atoms crystalized on the plates instead of the lead sulfate dissolving back into the electrolyte to raise the specific gravity of the water). It's hard to fix sulfation, but some approaches that have some success are Epsom Salts (magnesium sulfate) or Battery Chem that are used to help dissolve sulfate crystals on your plates. Dissolve in the distilled water before adding, easier to mix in. Keep in mind those additives will now be in your electrolyte forever. You'll have to confirm with someone else but I would imagine it having a negative impact on self-discharge. Some battery reconditioners that use high voltage pulses or high frequencies to agitate or even reverse sulfation exist on the market, but I can't really say much about them, I've never seriously looked at them.
2.
  • Is it a supercap? Watch the rated voltage. It needs to at least be rated for the highest alternator voltage (13.8-14.2V).
  • If you are using a hybrid supercap-battery setup does that mean your battery is undersized?
  • Yeah supercaps tend to have a higher self-discharge with the organic electrolytes they put in them. Do you have some in mind? Take a look at the datasheet for leakage current and run some back of the envelope calculations. For example, if a 15V rated supercap module has a 25mA leakage current, it will dissipate 25mAh in one hour, and 600mAh in 24h. After 2 weeks that's getting to around 9Ah. Figure out how often you'll be driving and charging your battery back up and see if the battery drains faster than your driving routine. One way to counteract the self discharge could be with a small 12V solar panel in your car.
3. Never used Walmart's car batteries. I've got a 12 year old ACDelco car battery and it is doing great. I check fluid levels once or twice a year and it keeps working. It's probably lost quite a bit of capacity over the years, but it was an oversized battery to begin with, so even with age, the capacity rating is more than enough for starting applications. If you're thinking about getting a new car battery, get one that has a higher capacity than you need, and it will continue to perform well as it ages.
When I don't plan on using my car for a few days, I throw my 12V solar panel on the sunroof of my car and it negates the self-discharge of the electronics and the battery. I don't use a solar charge controller because they tend to draw a lot of current even when there is no sunlight, in the range of 50-100mA. I'm sure there are more efficient ones on the market, but mine is not one of them.
 

jpanhalt

Joined Jan 18, 2008
8,347
@Walmart Batteries
Walmart does not make the batteries it sells. There is some dispute on the Internet whether they are made by Johnson Controls or others (https://www.quora.com/Who-makes-WalMart-car-batteries ). Apparently, Johnson Controlsmade a third of the batteries used worldwide https://batterymanguide.com/who-makes-car-batteries-for-walmart/ ) and that division was sold late last year to another company.

In my experience with Walmart batteries they work as well as any other "name brand." I buy by price and warranty.
 

dl324

Joined Mar 30, 2015
9,340
One of my car has a 7 year old lead acid battery that is still running OK. I am afraid in coming winter it will probably die.
Go to an auto parts store and have them test the battery. If you have any concerns, just get a new one. Most of the places where I get them don't have any with warranties beyond 7 years.

FWIW, the battery in my truck is around 15 years old and it doing well. When I drove it sort of regularly, it never let me down. Sears Diehard Gold. Haven't had any other battery that performed as well. I feel lucky if it gets out of warranty.
 

Hymie

Joined Mar 30, 2018
721
In olden days, a car battery would give plenty of warning that it was on the way out with slower and slower cranking of the engine. But colleagues have for some time been reporting that one day their car battery is fine, the next dead as a dodo.

I think this is due to two factors, firstly changes in battery technology and secondly that modern injection engines start much more reliably than old carburettor/aspirated engines – making less demand on peak battery current.

In my experience, a car battery typically lasts around 7 years, but I would be reluctant to replace an otherwise perfectly functioning battery for no other reason than its age, when it might be good for a number of years.
 

bwilliams60

Joined Nov 18, 2012
1,233
The average lifespan of an automotive battery is around the five year mark. Many people are happy with the fact that their vehicle starts with a battery that has surpassed the 5 year mark but the question is, is it causing damage elsewhere? Seemingly good batteries can be sulfated to the point that alternators have to work harder to keep them charged. At idle, they will put out more amperage to do the same job they used to. At high idle, they will be putting out close to maximum amperage and quietly overheating the diodes and stator. It is okay to go beyond the 5 year mark but the battery should be tested for sulfation to make sure the alternator is not being overworked.
 

Thread Starter

yourminky

Joined May 31, 2019
25
Go to an auto parts store and have them test the battery. If you have any concerns, just get a new one. Most of the places where I get them don't have any with warranties beyond 7 years.

FWIW, the battery in my truck is around 15 years old and it doing well. When I drove it sort of regularly, it never let me down. Sears Diehard Gold. Haven't had any other battery that performed as well. I feel lucky if it gets out of warranty.
15 years? That is probably a record.
I read elsewhere that Walmart generic batteries are reliable. I am not sure those remarks are from Walmart bots or real honest opinions.
Do you guys follow recommendations from the Consumer Reports magazine? They test car batteries sometimes.
 

Reloadron

Joined Jan 15, 2015
4,737
I tend to believe the life of a battery (lead acid) depends to some extent the sort of life the battery has. Some batteries used in automotive applications have much greater demands placed on them than others so there is a use factor in there. I live in the greater Cleveland, Ohio suburbs where we have some hot summers and some real cold winters where temperatures are around zero to sub zero F.

On average if I buy a quality manufactured battery with a 60 month warranty they generally last 61 months and those which exceed their warranty will, without a doubt, fail during the first freezing nights of a winter. During the winters I keep a Battery Tender on my motorcycle and my wife's truck and doing that has helped along with occasionally starting the bike and her truck. My battery tenders are just little 800 mA versions which I think I paid about $15 USD for and they work just fine.

Anyway, I figure the longevity of a battery is going to be based on several factors including the use and climate (environment) it is expected to perform in. Finally, as mentioned, there are dozens of branded batteries but the fact is Sears never made a battery in their lives, so while the DieHard Advanced Gold AGM Battery Group 34R is one of the most highly rated batteries out there it is actually made likely by Johnson Controls either in the US or Mexico and labeled for Sears.

When I replace a battery be it in my truck, my wife's truck or my bike I look for a good 60 month at least battery and call it a day.

Ron
 

Thread Starter

yourminky

Joined May 31, 2019
25
Thanks for the posts. I still need to know if it is wise to use a large 1 Farad capacitor in parallel with the battery without hooking up a solar or float charger. Have you done anything like that?
 

jpanhalt

Joined Jan 18, 2008
8,347
Here's an old discussion on AAC about a 10,000 F capacitor: https://forum.allaboutcircuits.com/threads/10-000-farad-supercapacitor-amp-hours.110851/ A standard small car battery is about 45 amp-hours. Cranking amps will be more.

Your 1 F capacitor will add very little to your cranking power as it will discharge very quickly from its static voltage to whatever the cranking voltage is.

As for increasing the drain on your battery, yes, there will be a certain leakage current in the capacitor and the battery will have to compensate for that. That current may be approximately 5 to 20 uA for a 1 F capacitor (https://www.electronics-tutorials.ws/capacitor/cap_3.html ).
 

bwilliams60

Joined Nov 18, 2012
1,233
A couple of quick questions regarding your capacitor. Is it classified as a super-capacitor and if so, what is the voltage rating on it. To my knowledge, most of the super capacitors being used in motive power are rated in the range of around 2.4-2.7 volts and are usually connected in series to form a pack equivalent to the battery. As mentioned above, it will discharge quickly on cranking and is generally used as an addition to the battery. The trucking industry is moving quickly towards using super-capacitor packs in their battery arrangements for starting purposes so it is doable but you may want to do a little research on it before you pull the trigger. It is a very effective addition to the starting system but it will take up space and if you have a battery that is failing, you are still doing harm to the alternator.
As for the battery subject, there are only about four or five major battery manufacturers and here is a true story about how it works. When I had my rebuilding shop, I went on a plant tour in a battery warehouse. There were rows upon rows of every size and configuration of batteries that you can think of but no identification. At the front of the warehouse was a room and there were bars loaded with several labels for their customers. Sears, Walmart, you name it. There they were. Pick a battery, pick a label, here you go.
I have always dealt with Interstate because I think they have the best battery and the best program in the market, bar none. You get what you pay for. If you are over 5-6 years on your battery, you are on borrowed time and if your alternator dies, look to your battery as a cause. Sulfation overworks the battery every time.
 

jpanhalt

Joined Jan 18, 2008
8,347
@bwilliams60

Interstate does not make batteries in the USA. It brands them.

Source:https://www.b4usa.com/interstate-battery/
Interstate Battery
Updated, March 24, 2019 by contributing editors. "Search America 1st"
Always verify USA Origin
Automobile Battery, Commercial Truck Battery, Automotive Batteries, Small Engine / Lawn Mower Battery
The actual origin of the manufacturing process for Interstate Batteries is vague. The automotive, truck, and marine batteries are made by Johnson Controls which makes 65% of the automotive, truck, and marine batteries sold in the USA. Johnson Controls also makes the batteries for Wal-Mart and AutoZone. From Louisiana to Southern California the Interstate brand batteries are made by a Johnson Controls manufacturing plant in Monterrey, Mexico. In the other states, the batteries are made by Johnson Controls in the United States.
What you pay for is the warranty*. A 5-year battery will likely work 4+ years and die at 61 months.

*Be sure to understand "pro-rata" warranties: https://www.interstatebatteries.com/support/class-action-settlement
When I had a Walmart implement battery die, I got a full "free" replacement.
 

bwilliams60

Joined Nov 18, 2012
1,233
@jpanhalt

Not sure where I said that Interstate makes batteries anywhere but if we want to follow Wikipedia or whatever listing you have there, then you are correct. Interstate batteries are made by Johnson Controls in New Mexico as well as Exide.
Having been an Interstate dealer, I can only tell you that their warranty is great, their batteries outlast most I have seen on the market and their best asset is that their batteries are moved around constantly and not left to sulfate at the bottom of a skid in the back of a parts department.
As far as warranty, I fully understand pro-rata so I don't need to look it up but thanks for the link. They are pricey but like I said earlier, you get what you pay for.
My information comes from having sold thousand of batteries, not Internet links or Google adventures but again, thank you for the links.
 

Infinion

Joined Apr 2, 2016
9
Your 1 F capacitor will add very little to your cranking power as it will discharge very quickly from its static voltage to whatever the cranking voltage is.

As for increasing the drain on your battery, yes, there will be a certain leakage current in the capacitor and the battery will have to compensate for that. That current may be approximately 5 to 20 uA for a 1 F capacitor (https://www.electronics-tutorials.ws/capacitor/cap_3.html ).
Agree that 1F wouldn't account for much. It may provide 1% of the energy required to start, and take a bit of an edge off of the inrush current, but not more than that.

That 5-20uA is for a typical electrolytic capacitor. Supercapacitors have a significantly greater leakage due to their construction and will typically be indicated in the datasheet of the supercapacitor module. If there is no info, it's fairly straightforward to calculate.

Thanks for the posts. I still need to know if it is wise to use a large 1 Farad capacitor in parallel with the battery without hooking up a solar or float charger. Have you done anything like that?
You need to ask yourself a few key questions first, and then do back-of-the-envelope calculations to create some ballpark numbers for your requirements.

  1. How much energy does it take to crank the engine?
  • Measure Power (voltage x current) at the inrush time and the final cranking time of your engine start. This is easiest to do with a clamp meter through battery ground, and an oscilloscope to capture the voltage curve, but you can just use a clamp meter and approximate . My car starts after about 1 second of cranking.
  • IMG_20190610_143631.jpg
  • You've now got two data points and a downward slope of power. To find energy in joules, we find the area under the curve. I've attached an information-dense chart for my own car with all the calculations.
  • Car Start Energy.png
2. How much capacitance do we need in order to store enough energy to crank the motor once?
  • Energy stored in a capacitor is defined as E = ½CV². We will use our calculated energy in part 1 as E
  • We will use a voltage range of 11V to 12.6V. Voltage range is very important because this is the range of useful energy that is available for cranking only. All the energy under 11V might not be useful for starting, so we are only concerned with the 100% fully charged lead acid battery voltage (12.6V) and the lower voltage limit to crank the vehicle engine successfully (11V). This range is an ideal one. After a week of sitting, the battery voltage might drop down to 12.4V (~65% charge) or lower, and have a wider range and longer start time. So make some design decisions here. Whatever you expect to encounter, design for the worst case.
  • With our voltage range, E = ½C(Vstart²-Vend²), we must now rearrange the formula to solve for capacitance C. Our new equation is C = 2E/(Vstart²-Vend²). So in order to start my car completely off of a supercapacitor module, I would need a capacitance of 2*(2146.6)/(12.6²-11²) = 113.7 Farads. If you want to crank more than once, multiply it by #attempts.
3. How much of the required energy will come from the capacitor bank vs the battery?
  • The calculated capacitance is for 100% of the energy provided by the capacitor. If the capacitor and battery are simply wired in parallel, then we have much more energy available and shared between the two, and you could get away with a smaller bank. The ratio of the load shared between the two energy storage devices is based on their dynamic resistance, which is a combination of internal resistances and other factors. Basically if the capacitor bank has a lower internal resistance than the battery, then more current flows through the capacitor until voltage drops low enough that they are equally balanced.
  • To crank a car off just a supercapacitor bank, decouple the battery from the load by placing a larger impedance in series with it. V=IR implies that the path of least resistance is the path energy will prefer to take. You can do this with a power resistor or a choke/inductor. The resistor adds...resistance, the choke adds impedance to a certain frequency/transient, like the starter's duration of inrush current. After a certain time, an inductor will act like a wire, with its impedance approaching zero, leaving only the wire resistance. Compared to power resistors that dissipate energy as waste heat (P=I²R) Inductors are nicer to deal with because they store energy in their magnetic field, and release that energy back into the circuit when current decreases; they always try to maintain a constant current, whether that is zero or nonzero, like a flywheel with inertia. This will generate almost no heat in the process of starting, because storing energy in an inductor is almost lossless. If you want to look into this technique, I recommend looking into the LR time constant. Find how long the inrush time period is, set that as your time constant, approximate the total series resistance of your battery + cables + starter windings, and solve for the required inductance. Or say "to hell with it" and use a 1-5 ohm power resistor.
Projects like these are both exciting and educational. It's a shame traditional ICE cars have such basic energy management systems, but from a reliability vs cost point of view, the industry decided that the least number of parts with oversized batteries would be the industry standard, because it works, is reliable enough, and creates a strong demand for batteries.​
 

Thread Starter

yourminky

Joined May 31, 2019
25
The capacitor I have is a Monster Cable High Performance Stiffening Capacitor with 1 million micro Farad 20 volt capacitance (which is 1000 Farad). I found this photo of a similar capacitor on the internet, mine don't have the 3 digit display segment on top. It weighs several pounds.
Capture.JPG
 

Thread Starter

yourminky

Joined May 31, 2019
25
I am thinking about connecting the large capacitor in parallel to the car battery. Have anyone done this before? I know there will be a leakage current through the capacitor. Is that leakage current high enough that the car battery will be dead after sitting for a few days?
 

oz93666

Joined Sep 7, 2010
702
Thanks for the posts. I still need to know if it is wise to use a large 1 Farad capacitor in parallel with the battery without hooking up a solar or float charger. Have you done anything like that?
It's definitely a good idea to put a capacitor across the battery ... it will take all the strain when starting the engine ... but 1F is not enough

Last month I bought one of these to put across my car battery 12 pounds UK inc delivery ... Six 100F caps in series that makes 17F @16V ..even that is rather small ... with a good cap your battery should last another few years , then you can use it on your new battery , caps last forever , or should do .
https://www.ebay.co.uk/itm/1PC-16V-20F-Ultracapacitor-Engine-Battery-Starter-Booster-Car-Super-Capacitor/352673092713?hash=item521cf45469:m:msDHRGwpzP5DiED-F8i4oNw


EDIT ... just seen your post above ...I can't believe that is a 1000F 20V , it's too small , some advertisers exaggerate ..anyway it looks bigger than mine ...
 
Last edited:
Top