Battery Charger Testing Results

[04GTO]

I'm going to be that guy. There are significant method issues you are not taking into account.

1. temperature-there is ZERO need to take temperature into account when all of my above tests were taken at nearly the exact same time of day at nearly exact same ambient temps, with the battery resting for the same exact 12 hours. When necessary to take other factors such as ambient and actual battery temps into account, I have a BT608 tester that reads temp directly at the clamp.
2. tester technology- I am fully aware of the limitations of the tester technology. These types of testers are just meant for a quick health check, not a scientific deconstruction, elemental analysis and reconstruction of the battery.
3. parasitic load from vehicle-here again I am 100% aware of this, which is why I took all the measurements while the battery was connected to the vehicle each time, to limit variables. There is nothing abnormal or wrong with the charging system on my car. If there was a problem with the system, then I would disconnect the battery and check it that way. Just to be sure.

Considering these one at a time.-

Lead acid batteries are temperature dependent devices, and so are their measured electrical properties. For two tests of the same battery to be comparable they must be made at the same temperature, ideally in a temperature controlled chamber, but more practically, at "close" to some target temperature. Like 25C +- 1C. Minimally, note and report the temperatures during the test.

The small electronic testers don't actually measure the R and CCA, they do some tests and use a formula to derive them. They are OK for detecting a really bad battery with terrible R, but not so good for comparing the same battery in slightly different states of charge. A more accurate, but vastly more time consuming approach, is to use a device like a DTL150 to discharge the battery at C/20 and plot I and V over time (as in many of the posts in this thread). Ideally this would be down to a full discharge, but that is bad for the battery. An alternative is to do all comparisons by discharging for a known time (2 hours) or to a target voltage (like 12.4V, maybe 12.0V, not lower). Do all your tests the same way and you can compare them. Except... this is problematic because these tests take hours and the temperature will change during the test. Without having a temperature controlled place to do this the battery is changing its properties during the test.

Trying to measure a battery that is attached to a car is a mistake. It is fine to see if it is "Good" or "Bad", but it isn't OK for making precise measurements of battery properties. Merely walking near the vehicle with a key fob in your pocket can cause the car to change the amount of current it is drawing from the battery. On our Prius "testing the battery" from the front jump point gives different values than testing on the posts with the battery detached from the car. That is an AGM battery, and it would fail the former and pass the latter. (And it was a nearly worthless test because the little testers are not at all precise when used on AGM batteries.)- There is no "mistake" here, as noted above, this was intentional. Unless there is something wrong with a quick test result on the little Ancel, there is zero need to disconnect the battery for my test. When doing a quick health test on a cars battery/charging system, there is no need to disconnect a battery, unless faults are strongly suspected. Any good professional tech/ mechanic would indeed start battery/charging system diagnostics with the battery still connected. Like with my Autel BT608 battery tester, with amp clamp attached, a tech would check the battery health, followed by the starting, charging health, terminal connections and/or corrosion et al. If no problems were found from diagnostics, it would be a complete waste of time to disconnect the battery.

We live in a hot environment, and water loss is the primary killer of batteries here. Many batteries these days cannot be serviced. Is a battery drying out? Electrical tests will hint at that, weighing the battery will answer the question. So I also suggest weighing a battery periodically. Each time use the same accurate digital scale and put the scale in the same place (on a spot of the floor, position on a table,) because tilt could be an issue if the scale is in a different place. Weigh it when it is brand new, and then once a year or so, pull it out, clean it off thoroughly, dry the outside, and weigh it again. The difference will be the amount of water lost from the battery (mostly, maybe a little acid will also have escaped). - Did I say somewhere that I don't know anything about cars or batteries? You do not know my experience or knowledge anymore than I know yours.

Well, you indeed, you are "that guy". That guy who seems to assume he knows things that others do not. I have added my replies above in red. No offense, I am sure you did not intend it, but it makes you sound like a bit of a 'know-it-all', and nobody knows it all.

 

[ripcord]

Lets keep it chill... @04GTO, being a know-it-all is kind of the point of this site so try not to take things personally. If we reamed everyone who spouts off with what they know, we'd have to nuke this site from orbit, just to be sure.

 

[JackWildfeuer]

One major problem is that to get a deep charge you often need to get up to 15.5 volts for 3 to 6 hours. This is usually enough to desulfate a battery. Done once a month. Almost none of the modern chargers will do that. A lot of 12V electronics have electrolytic caps with values as low as 16V which is darn close to 15.5V and most products do not want to get that close to the edge so they stop at 14.5V and if they do pulse as high as 15.5 it is not for the 3-6 hours recomended by most lead acid flooded battery manufactures data sheets.

It was common in the 1980's to see a lot of brands that did go this high but it become an issue by the 1990's and early 2000's and it seems like over night it was a race to 13.8V

As internal resistance builds up the voltage reguired shoots up and it get's hard to recharge the battery at lower voltages. You can easily run into a situation where if you fix current at let say 2 amps and dial up a power supply to 30V you will see the batery is barely accepting .0002 amps but as the internal resistance drops and the current comes up the voltage drops and you will see the voltage has dropped to around 13-17 volts by the time the current has come up to the preet limit of 2 amps. Ohms law at work.

The topic of recharging and desulfating a flooded lead acid battery can get as complicated as you chose to make it. In a perfect world you would pull your battery once a month and charge and test it in a way that produced best life expectancy. You might find you need to charge and partial discharge a battery a few times to recover lost capacity before it is gone for good. That said nothing lasts forever.

I have considered making my life more complicated to extend the life of batteries due to ever increasing cost. Best bet for me would be to use a bench power supply that allows me to dial the voltage from 0 to 30V and 0 to 10A where I can set a current limit. There are other ways but not this controlled some people use stick welders. Keeping close tabs on temp. is also key. Sticking to manufactures data sheets for safety is also key.

 

[ripcord]

One major problem is that to get a deep charge you often need to get up to 15.5 volts for 3 to 6 hours. This is usually enough to desulfate a battery. Done once a month. Almost none of the modern chargers will do that. A lot of 12V electronics have electrolytic caps with values as low as 16V which is darn close to 15.5V and most products do not want to get that close to the edge so they stop at 14.5V and if they do pulse as high as 15.5 it is not for the 3-6 hours recomended by most lead acid flooded battery manufactures data sheets.

It was common in the 1980's to see a lot of brands that did go this high but it become an issue by the 1990's and early 2000's and it seems like over night it was a race to 13.8V

As internal resistance builds up the voltage reguired shoots up and it get's hard to recharge the battery at lower voltages. You can easily run into a situation where if you fix current at let say 2 amps and dial up a power supply to 30V you will see the batery is barely accepting .0002 amps but as the internal resistance drops and the current comes up the voltage drops and you will see the voltage has dropped to around 13-17 volts by the time the current has come up to the preet limit of 2 amps. Ohms law at work.

The topic of recharging and desulfating a flooded lead acid battery can get as complicated as you chose to make it. In a perfect world you would pull your battery once a month and charge and test it in a way that produced best life expectancy. You might find you need to charge and partial discharge a battery a few times to recover lost capacity before it is gone for good. That said nothing lasts forever.

I have considered making my life more complicated to extend the life of batteries due to ever increasing cost. Best bet for me would be to use a bench power supply that allows me to dial the voltage from 0 to 30V and 0 to 10A where I can set a current limit. There are other ways but not this controlled some people use stick welders. Keeping close tabs on temp. is also key. Sticking to manufactures data sheets for safety is also key.

I recently recovered a weak 6 year old battery with my bench power supply to the point where it will hold a good charge again. The equalization charge brought the specific gravity of two weaker cells back to near the rest of them. Hopefully it lasts until I can sell the rig.

 

[pasadena_commut]

Well, you indeed, you are "that guy". That guy who seems to assume he knows things that others do not. I have added my replies above in red. No offense, I am sure you did not intend it, but it makes you sound like a bit of a 'know-it-all', and nobody knows it all.

Temperature: The T that matters is inside the case. It cannot be measured directly and is something like "the average of outside T over the last 4 hours". Ideally battery testing is done in a temperature controlled chamber or bath. Few, if any, of us have a space like that, so the best we can do is report the case temperature(s) during the measurement. You may have measured that, or at least felt that the air temperatures were similar, but unless you include those values in your post nobody else can know what they were.

Testers: Don't take my word, read this for a thorough discussion of the limits of the little electronic testers:

https://marinehowto.com/are-battery-conductance-testers-worth-it/

Parasitic load: Yes, battery diagnostics in a shop begin with the battery attached - because they are first looking for an obviously bad battery. That isn't what you are doing. You are looking for small changes in battery parameters, and the differences you want to measure will be affected by a change in the parasitic load. You think that isn't time varying on your car, and maybe it isn't. For yucks, try testing your battery in the car, then remove the negative lead, wait at least 20 minutes, then test it again. If the parasitic load is so small that it doesn't change anything the two readings will be the same.

 

[04GTO]

Temperature: The T that matters is inside the case. It cannot be measured directly and is something like "the average of outside T over the last 4 hours". Ideally battery testing is done in a temperature controlled chamber or bath. Few, if any, of us have a space like that, so the best we can do is report the case temperature(s) during the measurement. You may have measured that, or at least felt that the air temperatures were similar, but unless you include those values in your post nobody else can know what they were.

Testers: Don't take my word, read this for a thorough discussion of the limits of the little electronic testers:

https://marinehowto.com/are-battery-conductance-testers-worth-it/

Parasitic load: Yes, battery diagnostics in a shop begin with the battery attached - because they are first looking for an obviously bad battery. That isn't what you are doing. You are looking for small changes in battery parameters, and the differences you want to measure will be affected by a change in the parasitic load. You think that isn't time varying on your car, and maybe it isn't. For yucks, try testing your battery in the car, then remove the negative lead, wait at least 20 minutes, then test it again. If the parasitic load is so small that it doesn't change anything the two readings will be the same.

Thank you Professor K.I.A.

 

[4wd]

Wooo doggies that Jethro can cipher !
Several smart chargers can do the plate repair cycles …