Electronics > Projects, Designs, and Technical Stuff
Seeking info on a giant battery charger
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edpalmer42:
These batteries are sealed AGM batteries.  Trying to add anything to them would be difficult at best.  But, before adding anything, remember that they are telco-grade batteries with a 20 year design life.  They've spent their entire life in a temperature-controlled environment with precisely monitored and temperature-compensated charge voltages and have rarely, if ever, seen any significant discharge.  They've lived a perfect life and, depending on their age, they could all be in excellent condition just as they are.
tautech:

--- Quote from: TerraHertz on October 19, 2019, 09:32:03 am ---
--- Quote from: tautech on October 17, 2019, 11:47:31 pm ---... you might want to consider getting some phosphoric acid for your old cells and give them some love like outlined here:
https://www.instructables.com/id/Lead-Acid-Battery-Care-and-How-to-Restore-Them/

--- End quote ---

I have doubts about the worth of that article. Zero mention of sulfation as a factor in Lead-acid battery demise (and the major cause of plate swelling.) Also his talk of adding phosphoric acid... hmm, if that was such a great idea for battery improvement, why isn't it done by battery manufacturers as standard?

--- End quote ---
It is and has been for some 100 years.
A little Googling of 'phosphoric acid lead battery' reveals this.
However the process is only really useful for FLA cells.

This 1977 paper is worth a study:
http://jes.ecsdl.org/content/124/10/1478.full.pdf
TerraHertz:

--- Quote from: tautech on October 19, 2019, 08:05:45 pm ---This 1977 paper is worth a study:
http://jes.ecsdl.org/content/124/10/1478.full.pdf

--- End quote ---

That makes much more sense. From the abstract:

--- Quote ---The  effect  of  phosphoric  acid  on  the  positive  electrode  reaction  in  a  lead-
acid  battery  is  studied  by  cyclic  voltammetry.  It  is  proposed  that  phosphate
reversibly  adsorbs  on  the  PbO2  during  charge,  and  modifies  the  crystal  growth
of  PbO2  on  the  lead  grid.  The  form  of  PbO2  produced  in  the  presence  of  phos-
phate  is  not  easily  reduced  to  lead  sulfate  and,  therefore,  the  positive  grid
does  not  become  insulated  from  the  active  material.  The  limit  of  this  effect  is
reached  at  a  low  concentration of  phosphoric  acid.
--- End quote ---

So, it somewhat inhibits the formation of lead sulfate. Nothing like what the first article claimed.
Thanks for that link.

However, as edpalmer42 pointed out, these are moist glass mat batteries, so 'adding something' is not feasible.


Edit: Unrelated - OUCH! Remember that 'advertising photo-fails' thread, with the lady holding a soldering iron (not turned on) by the hot end?
Well I just did pretty much that, except hot. Stripping some axial-lead components off an old terminal strip board, needing lots of awkward fiddling with the iron and needle nosed pliers to unwind the lead ends wrapped around posts. Fumbled the iron; it ended up with the hot end between fingers as my grab reflex acted. Very briefly. Butter fingers, ending up with buttered fingers (it helps with burns.)
edpalmer42:

--- Quote from: TerraHertz on October 20, 2019, 01:41:34 am ---Edit: Unrelated - OUCH! Remember that 'advertising photo-fails' thread, with the lady holding a soldering iron (not turned on) by the hot end?
Well I just did pretty much that, except hot. Stripping some axial-lead components off an old terminal strip board, needing lots of awkward fiddling with the iron and needle nosed pliers to unwind the lead ends wrapped around posts. Fumbled the iron; it ended up with the hot end between fingers as my grab reflex acted. Very briefly. Butter fingers, ending up with buttered fingers (it helps with burns.)

--- End quote ---

Thankfully, it's been many years since I had such an accident.  When I did, I made an interesting discovery.  Pinching an ice cube between my poor burned fingers helped numb them and so reduced the pain.  However, I didn't expect that pinching the ice cube until I melted through it took away the pain permanently.  I was quite amazed.  Maybe the cold killed the damaged nerve cells.  Everything healed up without further discomfort or other issues.
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