Analyzing 6 years old Forester battery & 16 data set, can we do load test without buying a load tester

[drdavidzhang]

My Subaru Forester battery 6 years old (14D) with a small CCA=390A lasted 6 years. I noticed the battery problem last year (when it was a 5-year battery). I monitored the engine's start up for a year. With a set of 16 cars/batteries, I now know the characteristics of an old battery. I can analyze more data if other people contribute their data. How To Load Test A Car Battery Without Buying A Load Tester. 

   can we do load test without buying a load tester?

[GeneralDisorder]

Why? 

AAA has a lot more data than you will ever accumulate. Average life on batteries is now 3-5 years. More demanding vehicles (newer) have shorter lives. 

The price of a battery pales in comparison to other operational costs like fuel and fluids. You have very limited choices with regard to battery replacements and alternator choices unless you want to spend a lot of money on an Odyssey and a DC Power Engineering alternator. You can get a 10-15 year battery life if you want to spend the money and if you are very lucky. 

At the end of the day the battery is an $85 part. Replace it every 3 to 5 years and move on. 

GD

[Mike104]

And if you think it's bad just take it to any chain auto parts store and they can test it for free

 

[1 Lucky Texan]

batteries in my area are old after 3 years. i HAVE experienced a 5 year service a coupla times, and 2.5 years on 3-4 occasions. But after 3 years, any more is gravy. If a battery has ever been completely discharged, you can subtract from its lifespan, for each time it's happened.

[Stelcom66]

The chart is kind of hard for me to see but if I am reading it correctly, interesting that it shows batteries for the most part lasting longer in colder climates, where I am. I believe the battery in my truck is N/G - it's been slow to start and had to charge it yesterday. The truck started, but wouldn't again. I hope it is the battery and not the charging system. Saw the date - May 2014 so the battery is probably shot.

I know this is a Subaru forum but it's good to find a battery reference here that can be applied elsewhere. AAA will tend to get many calls when it's cold - that's why I always assumed cold climates reduced battery life. But I guess there's other factors when it's cold

[drdavidzhang]

6 hours ago, Mike104 said:

And if you think it's bad just take it to any chain auto parts store and they can test it for free

 

I took my 4 years old battery to autozone, and I did get the free test. He said: you definitely need to replace your battery. Other than replacing the battery, he did not say any reason. So I did not replace my battery. Now my battery lasted 6 years, I still can re-charge it, but because of the pandemic, no longer driving frequently, from these 16 data point, so I decide replacing it.  Another issue of not charging frequently, the sulfation will cause problem: 

 

Edited December 20, 2020 by drdavidzhang

[drdavidzhang]

4 hours ago, Stelcom66 said:

The chart is kind of hard for me to see but if I am reading it correctly, interesting that it shows batteries for the most part lasting longer in colder climates, where I am. I believe the battery in my truck is N/G - it's been slow to start and had to charge it yesterday. The truck started, but wouldn't again. I hope it is the battery and not the charging system. Saw the date - May 2014 so the battery is probably shot.

I know this is a Subaru forum but it's good to find a battery reference here that can be applied elsewhere. AAA will tend to get many calls when it's cold - that's why I always assumed cold climates reduced battery life. But I guess there's other factors when it's cold

good observation, the chart says 56 months for cold, but 30 months for extreme heat, is that correct? 

Edited December 21, 2020 by drdavidzhang

[GeneralDisorder]

By not changing the battery when it is showing clear signs of failure, you risk damaging the alternator. It's job is NOT to charge a dead battery. It's job is to top off a good battery after the engine is running and to power the electrical requirements of the vehicle once it's running to prevent the electrical system from drawing the battery down further. 

When the battery is low, it is an endless pit for amperage - the alternator will overheat and this can damage it's voltage regulator, etc. Saving less than $100 on a battery may cost you a LOT more when it takes out your factory alternator - for which there are few good replacements other than Subaru OEM, sometimes  Denso or Hitachi remans if you can source one, and places like DC Power. In any case you are going to spend at least $200, and if you want a quality unit - more like $600 for a replacement. 

Is it worth blowing an alternator to try to get another $25 out of an old used-up battery? Seems like economic suicide to me. 

GD

 

 

Edited December 21, 2020 by GeneralDisorder

[drdavidzhang]

2 hours ago, GeneralDisorder said:

By not changing the battery when it is showing clear signs of failure, you risk damaging the alternator. It's job is NOT to charge a dead battery. It's job is to top off a good battery after the engine is running and to power the electrical requirements of the vehicle once it's running to prevent the electrical system from drawing the battery down further. 

When the battery is low, it is an endless pit for amperage - the alternator will overheat and this can damage it's voltage regulator, etc. Saving less than $100 on a battery may cost you a LOT more when it takes out your factory alternator - for which there are few good replacements other than Subaru OEM, sometimes  Denso or Hitachi remans if you can source one, and places like DC Power. In any case you are going to spend at least $200, and if you want a quality unit - more like $600 for a replacement. 

Is it worth blowing an alternator to try to get another $25 out of an old used-up battery? Seems like economic suicide to me. 

GD

 

 

good discussion and interesting theory about the life span of alternators, I would be curious to see more data. I only had alternators problem 35 years ago. I have not had any alternators break-down in recent 35 years even though all my batteries lasted more than 6 years, this Subaru is the shortest because I repeated many experiments (re-charging, overcharging, re-conditioning, Epsom salt see many of my videos). I agree the load could be larger with a weaker battery, but I don't know how significant this increase is. There are a few things I can speculate:
1. the alternators work on fixed RPM, thus fixed RPM should produce the same constant power regardless of the load, not working harder. So once the RPM changed from 500 RPM to 1200 RPM, it has little load (I assume the battery does not supply power at 1200 RPM).
2. a weaker battery would have higher resistance, thus less load with respect to the alternator, so if the alternator is charging the battery at 1200 RPM, then alternator is working lighter. At the startup, the starter motor with lower impedance would draw more current because the voltage is fixed. So I assume it is not " It's job is NOT to charge a dead battery", but rather it will need to share more load because the weaker battery does not contribute more than it should. 
3. the initial power at 0RPM should be provided by the battery only. Between it is >0 but less than 500RPM, does an alternator provide any power? If it does, an alternator need to work the hardest is only at the very start up ignition when we have max current to raise the voltage. So the start up would require the alternator to generate larger current for 1 seconds. In another word, the alternator "abuse" may happen only 1-second "occasionally".

BTW, I let the battery die too many times to perform my experiments. My wife would not have such patience, she did not argue alternators, she made me to stop the experiment +:)

 

Edited December 21, 2020 by drdavidzhang

[GeneralDisorder]

As a shop owner that routinely replaces both alternators and batteries I can tell you there is absolutely a correlation between weak batteries and alternator failures. That is WHY every alternator comes with a BIG WARNING TAG indicating that it should only be installed along side a fully charged battery.

The alternator does not work during cranking. Cranking is about 250 to 300 RPM at most. At this speed the alternator is not capable of any significant output. 

Old batteries make the alternator work harder and more often for longer periods. This can burn up the voltage regulators. 

GD

[drdavidzhang]

24 minutes ago, GeneralDisorder said:

As a shop owner that routinely replaces both alternators and batteries I can tell you there is absolutely a correlation between weak batteries and alternator failures. That is WHY every alternator comes with a BIG WARNING TAG indicating that it should only be installed along side a fully charged battery.

The alternator does not work during cranking. Cranking is about 250 to 300 RPM at most. At this speed the alternator is not capable of any significant output. 

Old batteries make the alternator work harder and more often for longer periods. This can burn up the voltage regulators. 

GD

I agree a not fully charged battery would have lower resistance than fully charged, thus the BIG WARNING TAG would make sense. But am I correct that a weaker battery would have higher resistance? See my video, I made a point on the specific weight (Hydrometer) as defined whether fully charged or not fully charged. An old battery can be weak(smaller capacity) but fully charged.

Edited December 21, 2020 by drdavidzhang

[GeneralDisorder]

A weak battery will lose charge fast - overnight or sitting for a few days. The result will be a heavy load on the alternator immediately following startup. This puts a heavier than necessary load on the alternator. Old, weak batteries aren't just "weak but fully charged" - they discharge quickly when sitting or even when required to crank the engine for a short time. 

Again - batteries are cheap. Having a dead battery is inconvenient and less than ideal for the alternator. There's no economical reason for attempting to run one beyond it's useful life. You are going to get *maybe* another six months or a year out of it at which point you have spent way more time than money screwing around with it, creating frustration and potential wear and tear on the alternator, etc. The savings - if you can call it that - would amount to less than a lunch at McDonalds. It's just not worth the frustration and the time investment for the return.

You likely spent a LOT more in time and gas than you saved waiting a year by having it tested and NOT replacing it, than just getting a new one when the store told you it was weak. 

GD

Edited December 21, 2020 by GeneralDisorder

[drdavidzhang]

agree that most people would be frustrated at a dead battery when you really need the car. So how do we determine it is the time to replace? Is it the number of years, or based on the autozone employee's recommendation? 

[GeneralDisorder]

The unromantic truth is that they get replaced when they die. Could you test them? Sure. Is it worth the effort? Probably not. One day you go out and it either barely cranks up, or it doesn't start and you have to jump it. At which point you get a new one. 

That's how you know when to replace it. 

If you want to do it military style you replace them 2 years after installation. Regardless of condition. 

Any other approaches are a waste of energy. Because the ROI (return on investment) of regular testing just isn't there. For the additional short time you might get from maximizing it's life, you save only an incremental amount of the cost of replacement. $25 to $35 at most. 

At my shop I charge $110 per hour. The time spent testing and hand wringing over such an inexpensive disposable component is not profitable. 

GD

Edited December 21, 2020 by GeneralDisorder

[drdavidzhang]

To me, I will re-charge it and then from my experiments, based on the Fall Rate and Rise/Fall Ratio, with just a 10-second video I can objectively decide whether it should go. I understand other people would have different ways to make decision.

Steve Jobs leased a car every six months he traded it in for a new one. People say time is money, my problem is that if I saved time, I can't use the saved hours to make money. This is a different subject:  When I showed my friends my time saving and money saving youtube videos, they shrugged "time is money!" How do you respond if you were me? It is obvious if I have choice of either spending an hour saving $20 or spending an hour making $100, I would choose making $100-$20=$80. However since most people don't have a way to use that hour to make $100, then this "time is money!" is not valid to them. So I think my response should be: unless you can figure out a way to use your extra hours to make money, you should not abandon saving/being frugal.

Edited December 21, 2020 by drdavidzhang

[idosubaru]

Some of your assumptions are incorrect but this is a long thread I’m not going to respond to each one.

Weak batteries reduce alternator life.  Subaru alternators are quality units and I don’t see any failures before 10 years old.

So it’s basically like eating terrible and being morbidly obese - sure that’s fine for a 20 year old with good blood work and oxygen and cholesterol can test perfectly fine.  But you will pay for it later and eventually those numbers will tank fast. 

A well taken care of daily driver Subaru will have an alternator last the life of the vehicle.  Playing battery roulette it will not.

If “frugal” means keeping this car 10 more years then running a weak battery now matters as it could cost you an alternator in the future.  

If you’re not going to keep the car much longer then the battery doesn’t matter, and that might not be frugal. 

[heartless]

just skimmed through this.. but imho - far too much effort for very little gain. An old/weak/dying battery is going to get replaced in my vehicles. Period. I don't have the time, energy, or money to waste on testing something that simply just needs replacing, and/or could cost me even more down the road by killing my alternator.

I live out in the country - running to the parts store is not a couple minute thing here.. 30 mins one way to get to the nearest. I NEED my vehicle to be reliable and ready to go at a moments notice, not screwing around with chargers and wasting time/energy with testing that is only going to tell me what I already know - the battery needs replacing.

To each their own, and if doing all this makes you happy, then by all means, feel free. But for the majority of us, it is neither frugal, nor expedient to bother with it.

Batteries have a lifespan, and where you are located - geographically - will affect that lifespan. I will spend the $80-85 on a quality battery when I need to, and have the confidence that my vehicle wont leave me stranded somewhere.

[1 Lucky Texan]

16 hours ago, drdavidzhang said:

good observation, the chart says 56 months for cold, but 30 months for extreme heat, is that correct? 

yes, in cold climates, you need CCA, in hot climates, you want reserve capacity. Plus, everytime a battery goes completely dead, sulphation occurs on the plates and that further reduces lifespan.

just Google automobile battery life expectancy or lifespan, etc. I live in DFW area, if I get 3.5 or 4 years from a battery, I will dance a jig like I invaded Paris!

 

(what? too soon?)

[drdavidzhang]

I think the idea of  "the confidence that my vehicle wont leave me stranded" is very  compelling, that most people would not want to be stranded. So the question is how do you decide if it needs replacement. If you replace it every 2 years, may be you can cancel your AAA membership, may not be too bad. Or you could lease a new car every 6 months. If I just had jump-cable started and go to autozone, he may tell me to replace it because the battery was not recharged and he does not check with Hydrometer first. The purpose of my experiment is to find a way for those people who don't have a load tester. I am pretty happy with the result, it only involves to take a 10-second video to get a characteristics of the battery, combined with a cheap Hydrometer, I should be able to easily determine if I should replace it. Another advantage is the load used in my method is the real load, not the fixed 100A current, different car should affect battery differently. My 16 sets of sampling data come from different cars/batteries, so it is not just Subaru specific.

I am happy to learn that a battery may damage an alternator. Although I think alternators are running all the time (because alternators supply 100% of the electricity needed while running), so it is not alternators running longer time, but rather it could be running harder. During the 300RPM to 500RPM, the alternator can not be damaged because the current generated from alternators is too low. When you have higher RPM, suppose the circuit was designed in such a way to charge a battery quickly, then you will have larger load and potential damage specially at larger RPM. If the circuit is designed to have alternators slowly charge a battery, then it may have little damage.  

Edited December 21, 2020 by drdavidzhang

[Stelcom66]

On 12/21/2020 at 1:11 PM, 1 Lucky Texan said:

On 12/21/2020 at 1:11 PM, 1 Lucky Texan said:

Plus, everytime a battery goes completely dead, sulphation occurs on the plates and that further reduces lifespan.

just Google automobile battery life expectancy or lifespan, etc. I live in DFW area, if I get 3.5 or 4 years from a battery, I will dance a jig like I invaded Paris!

 

I do believe my truck battery had reached the stage of sulphation - now the power locks won't even work. I hear ya re: the heat in the DFW area - was in Irving a few times years ago for training. An interesting observation to me was the roads were mainly cement - not tar like here in New England. 

Another reason I miss my old Forester especially this time of year, the cloth heated seats were great. On another forum I've seen a few reports of dead batteries in newer Subarus. A lot of electronic are evidently still in use when not running. It's more prevalent now with them not being driven consistently - or as much as before March/April.