Homebrewed Electricity > Storage

lead acid battery chemical analysis results

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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.

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