Your battery voltage - truck off and at rest

[jebiruph]

Can't actually test the battery, only measure the voltage unless that's what you meant - and at that, it can't do that unless the PCR is open. It's measuring the equalized voltage of both batteries.
Unless you trigger the PCR to open it, you can't get the voltage of the aux battery alone.
That's why I have a lead at N1 so I can read things during an ESS stop. Otherwise they are tied together. If such a device had two voltage inputs, that would be absolutely ideal.

You would have to fully disconnect the aux battery before testing it, but with a battery tester you have that option.

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[ShadowsPapa]

You would have to fully disconnect the aux battery before testing it, but with a battery tester you have that option.

Testing a battery requires a full charge, draining the surface charge, then applying a known load and watching voltage under that load - like the dealers do.

That being the case, a volt meter won't "test" a battery, but it's a tool for recognizing patterns in voltage and behavior. You can pretty much tell when there's a battery issue vs. something else.
(and it was good to find out James has two of his "watchers" so he can more easily tell what's going on.)

I've always said that having a volt meter in a car is one of the single best tools you can have.
Ammeters in cars years ago were all but worthless. They meant little but were cool for sports car enthusiasts. Along came volt meters and I was like - thank goodness someone had a clue.
The volt meter in my SX4 will tell me more about that car's electric systems than the AMX cluster in my Javelin with ammeter could ever tell.

Anyway, my point is that a volt meter won't test a battery, but will give an indication of SoC and how well it handles a load. Is it handling it well enough for the rating/size of that battery or not?
It's a tool once one knows what to watch for.

This is how you test a battery and charging system ->

 

[jebiruph]

Testing a battery requires a full charge, draining the surface charge, then applying a known load and watching voltage under that load - like the dealers do.

That being the case, a volt meter won't "test" a battery, but it's a tool for recognizing patterns in voltage and behavior. You can pretty much tell when there's a battery issue vs. something else.
(and it was good to find out James has two of his "watchers" so he can more easily tell what's going on.)

I've always said that having a volt meter in a car is one of the single best tools you can have.
Ammeters in cars years ago were all but worthless. They meant little but were cool for sports car enthusiasts. Along came volt meters and I was like - thank goodness someone had a clue.
The volt meter in my SX4 will tell me more about that car's electric systems than the AMX cluster in my Javelin with ammeter could ever tell.

Anyway, my point is that a volt meter won't test a battery, but will give an indication of SoC and how well it handles a load. Is it handling it well enough for the rating/size of that battery or not?
It's a tool once one knows what to watch for.

This is how you test a battery and charging system ->

Ok, but I was referring to using a battery tester to also read the voltage, not using a voltmeter to test a battery.

 

[ShadowsPapa]

Ok, but I was referring to using a battery tester to also read the voltage, not using a voltmeter to test a battery.

LOL - I don't consider that a tester, it's a volt meter. That's where it gets goofy - people say "hey, I bought a battery tester". No, you bought a volt meter. (although with a dry cell that's about all that's needed)

 

[jebiruph]

LOL - I don't consider that a tester, it's a volt meter. That's where it gets goofy - people say "hey, I bought a battery tester". No, you bought a volt meter. (although with a dry cell that's about all that's needed)

It's a battery tester because it has the circuitry required to calaculate the internal resistance of a battery that a voltmeter doesn't have. Is there a modern battery tester that works on a different principal than calculating the internal resistance of the battery?

 

[J Sierra]

The new battery testers give the internal resistance.

 

[ShadowsPapa]

The new battery testers give the internal resistance.

(not the professional testers - it's only one piece of the puzzle. PRO testers, and testers like I'd use, still load the battery)

Do the "new battery testers" test resistance, or conductance?
They would either need a shunt (for resistance) or send an AC or high frequency signal through the battery to determine conductance. However, that's a "maybe" method because things take place inside batteries that can either increase or decrease resistance/conductance. It's possible for the number to not shift much at all but the battery still end up leaving you stranded.

Is there a modern battery tester that works on a different principal than calculating the internal resistance of the battery?

Yes, in fact most REAL testers don't rely on resistance alone, if at all. They still load the battery and look at the response.
The internal resistance method is only good if you start when the battery is new and track it over time, but even then, the battery already has diminished load capacity when you start to see a change in resistance - it's already gone. Prices have really come down but still - $50 and up is for decent ones.

Here's some support for my contention -

starter batteries fail mainly due to capacity fade rather than low CCA or elevated internal resistance. This characteristic is visible with most lead- and lithium-based batteries. A capacity measurement is more meaningful than measuring the internal resistance, but estimating capacity on the fly involves higher complexities than simply taking an ohmic reading.

To study the correlation between capacity and internal resistance, Cadex tested 175 aging starter batteries by measuring the CCA and capacity according to SAE J537. In this lengthy test, Cadex found that the correlation between capacity and CCA is only 0.55 (1 would be a perfect match). This led to the development of capacity estimation technology, as relying on the internal resistance, or CCA on a starter battery is unreliable.


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Battery testers work by applying load and monitoring the voltage and current of the battery.

Note that most real battery testers run into the over $50 range. Really nicer ones, over 100. Look up "car battery tester" and see that almost all have thick cables and clamps and load the battery to some extent.

And I ran into another road block for knowing based on resistance or conductance - you need to know very specific information on YOUR battery. The charts I found rely on knowing the details of the battery's internals, size and more. And that includes details of the plate design. it's laid out here in a way -

Different conductance testers use slightly different methods to compensate for the inductance and capacitance of a battery, so different testers can give different results, depending on how they were designed and calibrated. Conductance testers must also make complicated calculations, which may not give accurate results, because battery resistance is affected by its electrolyte/dissolved compound condition, the condition of the plates, the size of the plates, the plate layout, and the battery’s temperature. Given that most users do not have access to detailed design information about a battery (aside from rated capacity, size, and cold-cranking current), you should be careful in selecting a conductance tester, and even more careful in interpreting the results.

All of the info I have says it's an indicator, but isn't something to rely on. Battery internal resistance can change due to a lot of factors but too often, the battery is already diminished by the time you see the difference in resistance.
Pros still use the method of loading the battery to a known discharge rate and observing the voltage.
The battery testers used by Jeep shops are pretty complex and load the battery. The battery must be at a certain level or above before the testing can be performed.
Just like in the past - ideally the battery is charged, then load tested and voltage observed.
And that's modern testers.

Here's one description of many simple or basic "battery testers' (the sub-$100 type)

Capacity readings are outside the capability of most battery testers. Capacity is the leading health indicator that governs end-of-life when the battery has faded. Loss of energy storage goes mostly unnoticed while the readings on a battery tester remain unchanged.

Battery performance and symptoms also change with temperature and SoC level. A good battery with a partial charge performs similar to a fully charged battery that is weak. A battery tester should identify these conditions, but most cannot do this.

And here's support of my bottom line -
Most battery testers measure Ri by applying a calibrated discharge pulse and observe the voltage drop. Ohm’s Law (V=I x R) provides the Ri by dividing the voltage drop with the applied current.
The Ri of a battery does not correlate well with capacity. Tests at Cadex labs reveal a correlation between capacity and Ri of only 51%. Ri alone does not provide the full picture.
(Ri is internal resistance)

So, rely on a cheap "tester" but it's not going to do what someone like me wants - true indicators, real tests that give a bigger picture.
If you start from day 1 with a very accurate internal resistance and see it changing, especially larger changes, it's a possible indicator but real testing should still be done.

Modern real battery testers actually test the battery, loading, and so on and that's what pros use.
If FCA replaced batteries based on internal resistance, they'd go broke. That's why their testers are big and cost the big bucks.
And it's why I say - don't rely on parts stores to test batteries unless they fully charge it, then load test it as well as other testing (or at least 12.45 volts before testing)
Driving to a parts store with your battery at 12.2 volts is going to give you bad information.

 

[J Sierra]

They use small load then bigger load, measure the delta V and the delta I. Then divide delta v by delta I and that is the internal resistance.

 

[Jefe1018]

Papa, love you as much as the next guy but sometimes I question the amount of free time you have to live a life full of so much experience and write out a few dissertations a day.

 

[ShadowsPapa]

They use small load then bigger load, measure the delta V and the delta I. Then divide delta v by delta I and that is the internal resistance.

In a real sense, there are 3 resistors in parallel:
The aux battery
The crank battery
The truck's electronics. (which is a load on the batteries at all times, and thus a resistance)

Any 'load' is drawing from the aux and crank battery be it the truck or any test equipment.
You can't measure anything about one without the other skewing results unless they are untied.
So if these are checking the internal resistance of "the battery" - the result is from both.
How is that accounted for?
It can't happen while it's running of course because the voltage is constantly shifting, and both batteries are tied together. (mine was constantly changing today)

As the temps were in the upper 30s and as I'd driven my truck quite a bit lately, the voltage while running finally dropped down to about 13.2-13.3 while cruising.
While going down hill or mild braking, the voltage jumped up again to ~ 14.4 an then back down to the lower 13s as I hit the gas again. So with the moderating temperatures and the fact it was driven quite a bit lately, it finally got out of that 15.0 volts thing.

Parked the truck at 12:30 today, went and checked voltage at 5:30 and it measured 12.67 by Fluke at the battery terminals.
Pretty much fully charged. (close to it anyway)

 

[J Sierra]

The battery tester is not to be used in circuit, or connected to another battery.

 

[ShadowsPapa]

The battery tester is not to be used in circuit, or connected to another battery.

I thought you were using 2 of those $25 testers in the truck.

If you are changing gears and talking REAL testers and not your "testers" in your truck, no, not all do it that way. There's still the load then measure voltage. Good testers do more than just check resistance of the battery. Read what I posted - that's today's testers, and proof that resistance alone is only about 50% reliable.

 

[J Sierra]

Two different thing battery monitor just a volt meter. Battery tester you program with battery type and it runs load tests.

 

[ShadowsPapa]

Two different thing battery monitor just a volt meter. Battery tester you program with battery type and it runs load tests.

But Jerry said you had a battery tester.
I tried to say it was only a volt meter or monitor thing and then it went from there.
I was trying all along to say what you are running is basically a volt meter with some extra features.

The $25 devices are not battery testers.

Jerry said they were -

I'm not sure I agree with your assesment of the value of a Bluetooth battery testor for the purpose of this thread. If your goal is to test "Your battery voltage - truck off and at rest", then having the BT battery testor hooked up allows you to read the voltage without touching the truck.

While you can do the same thing with a Bluetooth OBD adapter, do we know if the BT OBD adapter is reading voltage directly or reading it from another module? If reading from another module, does having a BT OBD adaptor plugged in have any impact on the resting state of control modules it may communicate with?

As for the value of the BT battery tester's starting and charging tests, these tests aren't intended as battery tests, they are testing the external systems related to the battery, how low does the voltage drop when starting and how high does the voltage go when charging. One thing that the BT battery tester can do the the BT OBD adapter can't is test the aux battery.

It went from there. REAL battery testers measure more than voltage and more than internal resistance.

In the quote below Ri is internal resistance -

.....test by applying a calibrated discharge pulse and observe the voltage drop. Ohm’s Law (V=I x R) provides the Ri by dividing the voltage drop with the applied current.
The Ri of a battery does not correlate well with capacity. Tests at Cadex labs reveal a correlation between capacity and Ri of only 51%. Ri alone does not provide the full picture

Testing has shown that 48% of car batteries fail due to capacity fade. That happens when they are drained and left not fully charged, or frequently under-charged. That's what happens a LOT with these.
Only 12% fail due to high internal resistance, further proving it's not a good way to judge.
Loading the battery and measuring voltage under that load (some now say 2x AH rating) and watching voltage - over 9.6 is ok, under that it's lost capacity.
Most actually fail before the internal resistance is even a thing.
If someone is relying only on that, they may be disappointed.

I like the load testing, it's tried and true but you need a battery that's over 60% or so charged.
The newer hand-held testers do not require a fully charged battery because it only applies a small amp load to the battery. The electronics in the tester monitor how the battery responds to the load, and then the tester decides if the battery is good or bad.

 

[J Sierra]

I thought he was talking about a proper battery tester, they are not the same thing at all. The monitor is just a voltmeter. The testers are larger do bunch of other functions.

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