The particular topic has recorded over 3,000 viewings so the subject must be of considerable interest to people. For those that have not read this thread go to page one.
For those that have been following my reports you will al note that Ghurd's modified circuit works fine on all cells one to five counting from the Positive battery post. The sixth cell containing the Negative post seems to be a gremlin and the LED fails to extinguish when the probe is inserted. Whether this is an electro chemical problem or not is beyond my knowledge.
Ghurd's circuit takes its power from the battery under test and uses a single probe. I have trawled the Internet for hours looking for ‘water' level test circuits and there are plenty of them BUT most involve two wire probes and nothing would induce me to insert two wires into a battery cell. I err on the side of caution and am not keen on making myself as test guinea pig for a battery explosion.
In industrial and commercial operations there are indeed very nice LED sensors that are bi-polar but these are not inserted in each cell. This quote from a man in Australia sums things up quite well - “In industrial applications, we put the electrolyte sensor on the middle cell as this cell gets the hottest and has the greatest fluid loss. In the Industrial division we do not put electrolyte sensors on Block batteriesâ€. I do not know what Block batteries are but it makes little difference to the comment. What this means is that a Red LED showing on the sensor cell is a signal to re-water and check all the other cells at the same time.
Trying to find anything on the Internet that can establish the electrolyte level (not the SG level) is like looking for a needle in a haystack and the only ‘ancient' guidance I can find lies on the Powerstream website at this URL
http://www.powerstream.com/1922/battery_1922_WITTE/batteryfiles/chapter09.htmBasically the test machine is a glass pipette and if it is suitably graduated to suit the battery under test it should work.
There is another way which anyone can replicate at zero cost. Unscrew and remove the cap from any cell. Place a clean piece of wood over the cap hole so that it extends over the side of the battery where the maximum and minimum levels are marked. Measure the heights and then write the details onto the side of the battery for ready reference. Obtain some clean white paper, scissors, and a pen and ruler. Mark a line from one edge of the paper to – say – the maximum level depth (in my case 26 and 34 mm on two separate batteries). Then cut the paper into strips of – say – 10cm by 1cm. If the battery is at floor level this test is very awkward, but if it's more than 600mm above ground level its much easier. Rip off one piece of test paper and insert it in the cell until your eye sees the line at the top edge of the cell plug hole. Remove the paper and see if the bottom edge has touched the acid – I'm sure most of you have seen what happens when dry paper touches a liquid so I will not explain further. Anyway, if the paper is dry – add electrolyte and keep checking with same test paper until a wetness can be seen on the bottom tip. Then carry on to the next cell. Simple.
When searching the Internet I came across countless web sites which mention “check the electrolyte level†but they make no mention of the methodology of doing it. It's quite laughable that even premier battery manufacturers follow this practice and I quote from one of them - “Remove the vent caps and place them upside down so that dirt does not get on the underside of the cap, or, for the -------- series batteries, simply flip open the cap. Check the electrolyte levelâ€. That's all there is from a very respectable battery manufacturer “Check the electrolyte levelâ€. Nothing about how to do it.
What next? Ghurd's circuit works well, but is it worth the effort? Or, should I just stick with the paper method? The wet lead acid battery must have been around for about 150 years now, and much must have been written about the subject, but where is all the information?
I hope I have saved all readers some time and brought everyone up-to-date on the subject as I know it to be in May 2010. If I have written anything that is wrong or unclear, please make a comment.
I will follow up with the result of an enquiry with a USA sensor maker when I receive a reply.
David in HK