[rescue] [Slightly OT] Smart-UPS 1400 Battery replacement

[BSD Bob the old greybeard BSD freak]

> Ok, I think I'm now truly confused.  I know of three types of batteries
> involved, Lead Acid, the old type that you have to add water to, Sealed
> Lead Acid, what I see in cars and upses, and gell cells, which I've only
> seen once in a Mazda Miata, which was expensive, and hard to charge.  Are
> sealed lead acid batts gell cells?  If so why are SLA batteries cheapish
> compared to gell cells?

There are others, for example Edison nickel-iron-alkaline batteries
(mostly similar to nicads, but based upon different electrodes chemistry).

SLA are the ``gel cells'' you usually get in the marketplace.
The real gel cells are few and far between (Gates etc made/makes them).
I have yet to see any in a ups.  All I have found in ups systems are
SLA types.  Gel cells can be used in any position, while SLA's should
be used in the usual vent-on-top position.

> > No, they didn't use "lead acid", and yes they did use lead acid.
> > 
> > explanation:
> > Gells are "gelled electrolyte lead acid" batteries. Same formula as "wet lead
> > acid", but the acid is gelled. If your ups used wet cells then someone did a
> > switcharoo on you.

SLA's are ordinary lead acid types with a sealing rubber vent top.
They don't vent much, under average use.  But, they will vent if
you boil them under overcharge.  They really are NOT sealed, in
the true sense.  The little rubber vent top valve holds in some
pressure, and most of the gassing, but will vent if it goes up
enough.

> > Why gelled electrolyte?
> > 1) they don't spill.

SLA's don't spill either.  The vent top prevents that.

> > 2) they don't gas (give off hydrogen while charging, a big boom potential).

Yes, they do.  They retain more pressure and vent less, but they do vent
under overcharge.  See the little rubber seal on the top of each real
gel cell?

> > 3) they don't need water added every week (the gassing causes the electrolyte
> > to boil off water).

SLA's are non-serviceable waterwise, unless you remove the vent tops
and rewater them with a syringe (difficult but it works).

> > 4) much less likely to have corrosion deposits around vents and terminals
> > (caused by gassing and condensing electrolyte).

SLA's are the same.

> > 5) they have a flatter discharge output (full charge to near discharge voltage
> > curve is flatter).

Yes and no.  It depends upon the battery design/construction.

> > Now, I am sure someone will ask... Can I switch cheaper wet cells with the
> > gells? The answer is no. Gells have different charging rates than wet cells.
> > Gells charge by current, wet cells charge by voltage (and charge much more
> > quickly). If you swap in wet cells you will find that your batts are always
> > hot, never fully charged and all the steel in your box will begin to rust
> > furiously within a month (from acid fumes). Take it from someone who tried.

Gel cells and sealed lead acids should be directly interchangeable.
Vented wet cells are another matter entirely.

All batteries can be charged by current (best) or voltage (2nd best),
if you know the proper parameters for a given type of cell.  There is
no magick involved, just know-how.  It all depends upon their usage
cycles.  Most ups will float across the battery, and that is what
eventually kills off the batteries....too much floating current over
time.  It is a design/manufacturing tradeoff, arbitrarily made by some
design engineer at the ups plant.

If you put vented wet cells in a box... no wonder you got rusting.
Vented cells always need air flow to remove any acid fumes, prevent
explosive air mixtures inside the box, etc.

> > Gells don't suck. Nicads suck (another story).

I will take all the wet nicads you wanna send me.  Dry nicads do suck.
I will take all the Edison nickel-iron-alkaline cells you wanna send me.
I will also chuckle all the way to the bank......(:+}}...

I have some big Edison nicads from stationary systems that I have
been running for well over 20 years, and they are still good as new,
except for some slight cracking around the cases where some were
just sitting out on the back porch.  They are lifetime batteries.
They are ideal for ups work, but way too expensive in commercial use.
Try 100 bucks per cell at 1.1 volts per cell, and see how expensive
that little ups would actually be.

Real Edison cells are the only things any better, and those are
getting to be unobtainium, but they should last 100 years.  Sadly,
they have not been made in some 40 years or so.  Those too, will
outlive me.....(:+{{...

Bob