Battery Conductance Meter?

[Ron Swanson]

Do any of you field service people do conductance checks on medium-large (1000-2000) AH cells? 

There are quite a few offshore meters out there for car batteries but I don't know if they are any good to begin with, nor if they would be any good on larger 2 volt cells.

[Robin]

Are you talking about flooded cells? I am not aware that anyone in this industry does a conductance test. Everyone does a specific gravity test on their flooded batteries if they care about them. You can't do this on sealed batteries. Most people  then have fuel gauges to tell how full they are, but that doesn't give you the health of the battery. You do get to know your batteries though so after time you can tell how they are acting as to compared to new.
I'm not a good example of how to treat batteries though even though I know better. I've spent most of my life designing and manufacturing battery charges and fuel gauges.

My golf cart has flooded 6 volt batteries.
We make battery capacity meters. I don't have one.
We make battery chargers. I use the one it came with.
We resell a very nice specific gravity meter. I don't have one.
Flooded batteries should be equalized once in a while. I have never done this.
You need to check the water in your batteries on a regular schedule. I do this about every 3 years and then don't add water.
Scary huh!

[RossW]

Scary huh!

The age-old quote applies. "Do as I say, don't do as I do." 

[Ron Swanson]

We do all the tests you can think of, as necessary.  Specific gravity to my understanding is a measurement of state-of-charge and if there is a particular cell that is not functioning correctly, for whatever reason, it will be out of whack.

But we have noticed that lately, large industrial banks of flooded cells that have been installed for many years are starting to run hotter than they used to.

My hunch is that ohmic heating (E=I²R) is increasing in the cells.  Conductance decreasing.  Obviously you can't put an ohmmeter across them.

But not having used a conductance meter except cheap ones on car batteries, we don't really have any base line to work from.

I have seen conductance readings over time hand written on sealed telco batteries but can't remember where now.  It seems to be becoming more common these days.

[ClassicCrazy]

The fire alarm inspectors and electricians at work used to have a meter that supposedly told the capacity of a seal lead acid battery . I never trusted those. I only know that if their meter said it was below a certain capacity we had to put in new batteries.  I never did understand exactly how those meters determined capacity - maybe did a quick load test and conpensated for temperature ? Or if they somehow calculated the internal resistance too ?

There are expensive meters on the market that test internal resistance . Here is one that I just looked up on the web .
https://www.hioki.com/en/products/detail/?product_key=6382

Seems like I saw some kind of inexpensive battery tester on ebay that was supposed to test battery internal resistance.

If those batteries are getting hot then it seems like their internal resistance must be high and they are on their way out . Or out already! That is one way we found bad sealed lead acid in series - just feel them and if one was hot it was bad.

Larry

[Ron Swanson]

The way I understand they work is by hitting the battery with an AC signal low enough in frequency that any reactance does not come into play.

They measure the resistance to the AC current much the same way a regular DC ohmmeter would measure except the signal they are testing off is AC.  Blocked by a capacitor one would presume.

It should also be independent of state-of-charge which would be nice.

What I don't know is which (if any) brands are any good, or if they are all gimmicks, if they work on 2V cells, if they work on 1000-2000 AH cells, etc, etc.

It would seem the units sized for car batteries might tend to be out of range if testing large off grid cells.

[ClassicCrazy]

I would check with a battery dealer that reconditions fork lift batteries. Though the dealer I know out here - they load test and log the voltages of the cells to determine how good they are. Then they can repair a bad pack by replacing with cells that have similar load test ratings.  He said the cells in the center of the pack are the ones that usually  fail because they get hotter .

Larry

[CDN-VT]

Are you talking about flooded cells? I am not aware that anyone in this industry does a conductance test. Everyone does a specific gravity test on their flooded batteries if they care about them. You can't do this on sealed batteries. Most people  then have fuel gauges to tell how full they are, but that doesn't give you the health of the battery. You do get to know your batteries though so after time you can tell how they are acting as to compared to new.
I'm not a good example of how to treat batteries though even though I know better. I've spent most of my life designing and manufacturing battery charges and fuel gauges.

My golf cart has flooded 6 volt batteries.
We make battery capacity meters. I don't have one.
We make battery chargers. I use the one it came with.
We resell a very nice specific gravity meter. I don't have one.
Flooded batteries should be equalized once in a while. I have never done this.
You need to check the water in your batteries on a regular schedule. I do this about every 3 years and then don't add water.
Scary huh!

To Funny Robin !!

So to have fun
The pictures should bring a smile
& elly works well !!

[CDN-VT]

Sun Powered By midnite Components

VT
Nig`

[ralph day]

Ah, my old SW4048 still working away.  Glad to see it's not just a dock anchor somewhere.

Talk about remote power!  "How far away can my controller and inverter be from my solar panel?"  Rather How close?

Ralph

[CDN-VT]

They work very well in the spring & summer till Winter.
Then the system / Elly / Golf Cart is put away in the garden barn with the genie (man lift) and they are get hooked to the Midnight / Outback 24Vdc system (Elly is rewired for storage to 24Vdc 3 X 8vdc =24Vdc  . Then I just need to keep the garden shed panels clear because the power requirements over winter is nil . just to maintain all the tractors & batterys in float .

Wet Coast  Winter living gets 60% grey days , but i get to float once a week .

Come spring & towards summer all the equiptment is about to be pulled out mid FEB or just after.

We have logging coming before all the birds come back .

Ralph & Ms R , Yes the unit works well & thank you

VT
Nig`

VT 

[boB]

You could measure battery resistance (1/conductance) at various states of charge and various load currents...

Measure open circuit battery voltage and then load it down and measure battery terminal voltage again.

Conductance (Mhos or Seimens) = I (loaded) / [ E (unloaded) - E (loaded) ]

The larger the battery bank, the more load current will be necessary to get an idea of that resistance or conductance


I would think that resistance would be more useful though ?    R = [ E (unloaded) - E (loaded) ] / I (loaded)

Now, I have not had a good amount of sleep lately (busy) but I  THINK  that is correct.

Also, since it's electro-chemical, I'm not sure how linear that battery series resistance is with varying load. 

I wouldn't mind hearing about a few data points if you go through with these measurements.

boB  (in the air heading back to Seattle)

[Ron Swanson]

So it sounds like I will be the pioneer in this field.

It looks like Midtronics is the company who makes them.

Some look cheesy while others look quite good.

I have got to afford one when the money tree blossoms.

I highly suspect that this will be a very good metric for battery stage of life, if we can get repeatable results.

It will be 6 months to a year before I have good data but I will report it here.

[boB]

So it sounds like I will be the pioneer in this field.

It looks like Midtronics is the company who makes them.

Some look cheesy while others look quite good.

I have got to afford one when the money tree blossoms.

I highly suspect that this will be a very good metric for battery stage of life, if we can get repeatable results.

It will be 6 months to a year before I have good data but I will report it here.

I think it WILL be a nice metric.   I understand that most FLA's will have a higher resistance when brand new and will get better
after so many 10s of cycles (100 ?)  or so as the plates fully form.

Results will be interesting I'm sure.

boB

[CDN-VT]

I will try that formula boB .
I use a VAT 45  AVR unit . I can handle 24Vdc  @ 300 amps on a loaded carbon pile .
I have a Midtronics  unit also , I find It Swing & mis ..
Yes I reports bad cells , but I knew that  compared  on the VAT 45.

VT