Conductance test

[Kakalina]

Can you do a test with a conductance meter on a deep cycle battery?

[tkeithlu]

Did you inherit some lab equipment? No. I cannot think of any practical way of getting useful information from that. Even a $10 hydrometer would tell you more.

[Wotname]

Originally Posted by Kakalina

Can you do a test with a conductance meter on a deep cycle battery?

If by the term "conductance meter" you mean "electrical conductivity meter", then the answer is NO.

If you mean "low ohm meter", the answer is also NO.

If you mean something else, you might explain more .

[tkeithlu]

I've watched other people (way out of my area of interest) use a conductivity meter to measure soil moisture. My suspicion is that if you put the probes across 12V DC your biggest challenge would be getting to a fire extinguisher in time. I hope you find some alternative good use for your meter. It's good to find neat new uses for surplus stuff. I have used an instrument usually found in a proctologist's examination room to check out the inside of a motorcycle engine cylinder. I still have it, in the bottom of a tool box, 30 years later. It might still work.

[john61ct]

in the bottom!

https://youtu.be/BxuCeHUxoBY

[Kakalina]

A conductance meter measures the resistance in a battery. Nigel Calder explains it in his book.
Go to u tube and do a search.
You input CGA of the battery and it shows the resistance.
A deep cycle battery does not have a CGA rating so I wanted to know if you could still use it.

[tkeithlu]

Ahh, the plot thickens. We're talking about two very different pieces of test equipment. Good luck with it.

[Wotname]

Originally Posted by Kakalina

A conductance meter measures the resistance in a battery. Nigel Calder explains it in his book.
Go to u tube and do a search.
You input CGA of the battery and it shows the resistance.
A deep cycle battery does not have a CGA rating so I wanted to know if you could still use it.

What is the CGA of ANY battery??

Maybe you mean CCA???

[StuM]

I wasn't familiar with the technique, so did a bit of quick googling and found this:

CONDUCTANCE TESTING QUESTIONS AND ANSWERS
Three relevant quotes and a conclusion:
"Q. How is the conductance test performed?
A. Simply by connecting the two test set leads to the positive and negative posts of the cell or battery under test, a measurement is taken in a matter of seconds. There is no need for additional leads to be connected to the ends of the string, or for clamp-on current measurements. A conductance measurement is displayed in Mhos or Siemens, sometimes abbreviated with a "G".

"Q. Since the qualitative conductance test requires a standard, how can that standard be established?A. The most effective method for the establishment of a standard requires the performance of a timed discharge test to locate a cell or battery that performs to 100% of the rated discharge capacity. A conductance test can then be performed and a reference established. A sample of 30 or more new batteries can also be used to establish a standard. Without a set reference value, conductance testing can still be utilized to trend state of health, as batteries can be monitored through periodic conductance readings and the observation of deterioration over time."
[emphasis added]


"Q. How can conductance readings be used?
A. A significant number of tests on a variety of valve regulated lead acid (VRLA) batteries demonstrate that conductance is predictive of battery state-of-health. Since conductance is directly related, and very nearly linear with timed-discharge capacity, a reading of the percentage of a known conductance reference value is a reliable predictor of a capacity test result. "

Conclusion:
ISTM that you could take the meter to a store and slap it on a series of similar batteries on the shelf to establish a base line for new batteries. Then compare your reading to that baseline for a straight percentage capacity remaining.

[Kakalina]

Sorry a typo

[Wotname]

Originally Posted by Kakalina

Sorry a typo

No problem , at least we are on the same page again. It would probably help if we knew the make and model of the meter but as a basic guide, the CCA isn't critical for using the generic meter, a reasonable guess will give you a guide.

As long as you use the same figure each time, you will get a trend.

If you carried a full and proper capacity test and also used the conductance meter shortly after, you will have a base line to use when testing the battery again in the future with this meter.

[btrayfors]

A dedicated inductive/conductance meter like those in the Midtronics series is the defacto industry standard for measuring battery health.

Problem is, these are pricey ($500 and up) and while they work fairly well with automotive batteries while measuring CCA (cold cranking amps). However, they work less well with deep cycle batteries trying to estimate CA (i.e., amp-hour capacity).

I've used one of these testers with marine deep-cycle batteries for years (Midtronics MDX-650), as have others, including MaineSail who's written about them.

I believe they are useful in providing general information about battery health IF YOU KNOW WHAT YOU'RE DOING and don't expect too much. You cannot expect them to directly read residual deep-cycle battery capacity.

I've found these testers to be helpful in detecting changes in battery capacity (battery health) over time, i.e., months and years of use.

The ONLY way to know actual residual capacity is to carry out a controlled 20-hour test and measure how many AH the battery is actually able to deliver. To be accurate you need to control ambient temperature, start with a 100% fully charged battery, and apply a constant current C/20 resistive load (which will remain constant as the battery voltage drops). This takes a special load testing device.

All other testing methods are less accurate and/or they measure something else, not residual capacity (battery health).

Bill

[Kakalina]

Thank you that is what I was looking for.

[john61ct]

Originally Posted by btrayfors

The ONLY way to know actual residual capacity is to carry out a controlled 20-hour test

I believe under the right conditions over time the Merlin/Balmar SmartGauge does internally gather an accurate estimate of this, but trying to think of a way for the user to extract that value.

Let's first assume it works (2-3% accuracy, maybe 5% while charging) and accept that few other than Gibbo knows exactly how: there are many threads where that's been debated before.

Right conditions:
compatible chemistry (not LFP, all LA far as I know, not sure re Firefly?)
continuous usage deep cycling over a period of time, at least a few days

Get charge to true 100%, then ensure no charge sources active.
Hook up a device that measures power consumed by loads.
Draw loads until SG says say 80% SoC. Let it rest a few hours, confirm, yes 80.0%
Read from counter total AH drawn
multiply times five

Thoughts?

[btrayfors]

Haven't had time to puzzle that out, but one thing it wouldn't do is to give you the actual capacity of the battery unless Peukert were accounted for. If the applied load were much less than C/20, then you'd get an over estimate of the total capacity of the battery. Similarly, if the load were much more than C/20 you'd get an underestimate.

And, all that is assuming the 80% SOC is correct.

Nope, I'll stick with the C/20 constant resistive load applied over a 20-hour period in order to estimate the true capacity of the battery.

Bill

Originally Posted by john61ct

I believe under the right conditions over time the Merlin/Balmar SmartGauge does internally gather an accurate estimate of this, but trying to think of a way for the user to extract that value.

Let's first assume it works (2-3% accuracy, maybe 5% while charging) and accept that few other than Gibbo knows exactly how: there are many threads where that's been debated before.

Right conditions:
compatible chemistry (not LFP, all LA far as I know, not sure re Firefly?)
continuous usage deep cycling over a period of time, at least a few days

Get charge to true 100%, then ensure no charge sources active.
Hook up a device that measures power consumed by loads.
Draw loads until SG says say 80% SoC. Let it rest a few hours, confirm, yes 80.0%
Read from counter total AH drawn
multiply times five

Thoughts?