A program to log Specific Gravity.

[Simen]

A year ago i bought two new Rolls S530 batteries for half price, due to transport damage. They were a bit dented, and the top cover on the batteries had cracked some places in the seams, so some acid was probably lost, but the levels was well above the plates. When i brought them home i topped them up with water without thinking... (they didnt lack water; they lacked acid)

Oh, well; i figured that charging and discharging for a time would evaporate the water i added, but it seems that my solar controller are too nice to my batteries.

I have now started to run an equalize charge every day to get rid of the excess water, and see which cells really needs water. I am taking SG readings before and a while after each charge to monitor the progress, and a need for a logging program was born.

This program are simple, and written for my needs, but maybe others find it useful too.
It has two main screens; one where the specifics for the battery are entered, and a child window where measuremens are recorded/shown.

Most important for my needs are the temperature correction for the SG which are shown in the form of % State of Charge for each cell, since i live in a country where winters are cold. One measures the cells and temperature, enters the battery's temperature and SG readings, and the program shows the % charge for each cell. a % over 100 indicate lack of water; below 100% indicate not fully charged, or if SG has stopped rising during equalizing, it indicates too much water.

Here's a snapshot of the SG recording screen:


And here is the program:
http://www.mwlmf.net/prog/SG.rar

The rar file are 529kB; contains SG.exe, and can be extracted anywhere. the program will create 2 datafiles and one ini file, and doesn't do anything else...

Feel free to comment and suggest...

Edit:
The program uses comma as decimal separator. Sorry...

[SparWeb]

Hi Simen,

I take it you are measuring SG manually, and then entering the numbers into the table, correct?  Or have you found/invented a sensor that can read SG automatically?  If so, that would be very interesting, too!

I just have to ask the stupid question:  Why did you choose to track SG instead of voltage?  My guess is that under load (charging or discharging), the SG doesn't vary as much as voltage, so you can measure SOC without leaving the batteries to rest for several hours.  Do you have other reasons?

[Rover]

I see he also has voltage on his entry screen, unless that is somehow calculated.

If he is manually entering both then he can compare the 2 as well

[Simen]

Yes, i measure SG manually with a Refractometer. I wrote the program just to get an easy and precise way to see the real state of each cell, and help me balance them with water/acid after some equalizing.
Reading SG are, in my knowledge, the most precise way to find the real state for a FLA cell, regardless of load/charge. (Ofcourse, there's some variables, like stratification, history of the battery, but...)

The Voltage/amp readings are also manually entered, and just for reference. It'll give me an impression of the balance for each battery.

(Note: temp entry are in Celsius...)

Having a sensor to measure SG would be nice, but i haven't heard of one... There was a thread here i think that explored making one...

[tanner0441]

Hi

If you can afford it you can buy a state of charge meter which will give you the AH remaining. In the UK they come out at around £100 mark.

Brian.

[Simen]

My solar controller shows me that - in % SoC. (a Steca PR2020) But sometimes one just have to do things manually to get the best maintenance results.

[tanner0441]

Hi

Google this thing....Cadex CA-12 battery rapid-tester

Brian

[Simen]

Interesting thing - but it doesn't measure SG,and the price ($3000 ++) wouldn't suit most of us... :-/

[Simen]

I've no idea if anybody actually use my SG Log program, but i've just updated it with some bugfixes etc... The link in the first post will get you the updated version...

A small bug made it chaotic to add more than one battery bank and keep track of the readings, since the 'measurements' button showed the measurement readings for all batteries, regardless of which battery was selected; that is now fixed.
I also polished the SoC% readings for each cell, and added a SoC% for each bank (3 cells), and a SoC% for the entire bank (6 Cells).

[kitestrings]

Simen,

It sounds interesting. I tried to look at it, but can't seem to get anything close to your snapshot.  The table is there, but no data and I can't enter anything.  Is that what the file is, or am I msissing a step or two?

I also read SG using a refractometer.  They're a bit pricier, but so are the batteries your trying to care for.  I've been using a plastic '7-day' medicine dispencer and an eye dropper to retrieve the samples.  Then I can sit at the kitchen table to look them over.

~kitestrings

[Simen]

When the program starts, you'll get the screen where you have all your batteries registered. When you have registered a battery, you select that battery and press the "Measurements" button; There you can register your SG readings for that battery...

Also; remember that decimal separator are Comma...

Don't fill up that dispencer too often; those small samples adds up, and in a couple of years you'll have emptied your battery for acid...
I like those refractometers; they're a bit slower to use, but much more precise and easier to get the readings...

[kitestrings]

Simen,

The one thing I failed to try was the "+" insert button.  I think that is what I was missing.  I'll play with it a bit more, but it looks pretty cool.  Is the aH input intented to be for each battery or the bank as a whole?

I much prefer the refractometer.  I've probably broken 3 or 4 of the automotive types with the glass hydrometers over the years.  And, I haven't found them to be anywhere near as precise.

Thanks for sharing,

~kitestrings

[Simen]

The whole program assumes a 12V bank, so that "# of batteries" means how many single 'boxes' that are connected in series to make one 12V bank, so that Ah are for the whole bank...

A bit imprecise, i know...
The word 'battery' are usually describing a collection of cells, while a 'bank', a collection of batteries...

Tthe only field in the 'battery bank screen' that are directly used later, are the 'SG' field, which should be the manufacturers recommended SG @25deg. C. I use this to calculate the correct temperature compensated SG for 100% SoC, and as a baseline for the SoC for each cell...