lead acid battery chemical analysis results

[joestue]

Friend of mine has a lab, had an employee run positive grid plate samples from 3 different AGM batteries, CSB, BB, Genesis. we have more to run.

Won't have the calcium standard for the ICP machine till the end of this week but so far there is zero/zilch antimony in the remains of the positive grid plate, when it is dissolved in nitric acid and hydrogen peroxide.

did get results for copper in one battery but not so much in the others, but until a better method is developed the results are suspect.

anyhow it seems consistently some cheap agm's last 3 years others last as long as 7, when floated continuously at 13.8 volts. but the results don't really have a pattern.

one method i want to try is to setup a relay and a diode, such that the relay opens and the battery is at rest, but can still discharge into the UPS. when the power goes out, so will the timer opening the relay, so it will charge the battery, for say 2 days. then float for say, 28 days. 

[clockmanFRA]

Love the lab results.

In this day and age the chemical composition of the positive lead dioxide is very difficult to confirm as each manufacture have their own mixes.

It should be also noted that the Grid matrix design and thickness of the commercial plates is very, very important to hold the lead dioxide in position correctly. This lead matrix is another whole bag of worms regards the thickness and the holding capacity of each grid hole with lead dioxide in, ie, its proportionality.  But then get the matrix grid to heavy and thick and then 20% or more of each plate becomes a semi-PLANTE battery and will need charging and discharging to form correctly.

For my modern version of the PLANTE battery, I am using as pure as possible lead at 99.81 % purity, however the surface once in contact with air soon degrades at this purity.
Still testing and now sorting out the plate separators systems to be as efficient and safe as possible, and that’s another story.

[joestue]

I found a company claiming a lead calcium alloy for the negative grid and a lead tin calcium alloy for the positive plate.

https://www.sciencedirect.com/topics/materials-science/calcium-alloys#:~:text=Lead%E2%80%93calcium%20alloys%20with%20tin,type%20and%20grid%20production%20process.

Looks like the amount of tin and calcium could be the problem.
That book mentions tin preventing the formation of lead sulphate, which could be the real reason for the "open circuit effect" spoken of on the internet a decade ago, not the calcium

[Bruce S]

Since we have more than one UPS provider here, I have found that sometimes the early degrading is due to the physical design of the UPS itself.
APC's are horribly built when it comes to the batteries. The batteries are basically roasting inside the lower priced ones. The larger Martix ones are only marginally better. We have yet to have any last more than 3 years. Our maintenance spreadsheet actually starts warning us when they reach the 30th month.

Eaton's are a bit better and minuteman units are so under-powered when charging they last longer than the APCs but take 3x longer to recharge the batteries.

Hope this helps
Bruce S

[Jackir]

Sounds like an interesting experiment with those AGM batteries. It's always a bit puzzling when some last longer than others, right?

Your idea with the relay and diode setup sounds like a cool way to potentially extend battery life. It's worth giving it a shot and seeing if it makes a difference in longevity.

[dnix71]

I used to work for a commercial printer that used cast lead alloy type to imprint napkins, match covers and items like those that would not feed through a regular offset press. Management was cheap. We recycled and recast the alloy until it was neccesary to buy more.
Antimony was the one element that just had to be right. It hardened the cast so that we could get more impressions from a set of cast type. Too much made the type brittle and not fill the mold crevices correctly. We could get lead locally from ship builders, but keel lead can be pot metal if necessary.
People who reloaded bullets also need a certain hardness, too.
Too much antimony makes battery plates brittle and subject to breaking if the battery is mobile.

[Mary B]

I used to work for a commercial printer that used cast lead alloy type to imprint napkins, match covers and items like those that would not feed through a regular offset press. Management was cheap. We recycled and recast the alloy until it was neccesary to buy more.
Antimony was the one element that just had to be right. It hardened the cast so that we could get more impressions from a set of cast type. Too much made the type brittle and not fill the mold crevices correctly. We could get lead locally from ship builders, but keel lead can be pot metal if necessary.
People who reloaded bullets also need a certain hardness, too.
Too much antimony makes battery plates brittle and subject to breaking if the battery is mobile.

Tin was also used, helps mold fill out/adds toughness. Foundry type(individual type letters that got set in rows) is 60.5% lead, 25% antimony, 12% tin and 2.5% copper.(copper is up for debate, I have never measured it in it). Tin makes for sharp clean corners and a tougher alloy.

[joestue]

The problem is the antimony has a 50mv difference in voltage, causing self discharge and water loss.

We did get a tin standard so will run more tests.

I have read of attempts to make a lead antimony positive plate and a lead negative plate, but apparently it plates over to the negative plate and you get the water loss problem again.

[joestue]

Ran the same battery samples again (a chunk of positive grid plate is dissolved in nitric acid) and the tin results came back with significant variation.

The genesis battery was .14% tin. it allegedly lasted 7 years in an APC ups

the CSB was .3% and the BB battery was .08% -these batteries lasted a couple years.

this is all noise until more samples are run from dozens of batteries and correlated with the different environments.