On Nov 11, 10:38*pm, Darryl Ramm wrote:
On Nov 11, 10:14*pm, JS wrote:
[snip]

* Are Sonnenschein batteries the best way to go? Tom Knauff stocks a
couple of sizes, but not all. Many web searches come up with
substitute batteries of lower quality.
Jim

being a battery geek I'll bite...

Unlikely - Sonnenschein are Gel cells (electrolyte in fused silica)
and Gel really just do not offer significant advantage over VRLA. If
they did there would not have been an almost total move in the sealed
lead acid battery market from Gel Cell to VRLA technology. Go for a
good quality brand name VRLA (Valve Regulated Lead Acid, aka starved
electrolyte lead acid battery, aka recombinant gas valve regulated
lead acid battery). Panasonic, PowerSonic, etc. Most are made in China
but the brand name still matters. Buy from a distributor with good
turnover, charge with a battery charger specifically designed for VRLA
batteries, don't charge at high temps, and select a charger with a
bulk charge specs to ~ C/10 to C/5, disconnect from the charger when
complete (unless you really know and trust the charger has a proper
float mode), charge as soon as possible after use - don't leave flat
for long periods of time, discharge test once a year and write the
test date and capacity on the battery and toss when capacity starts to
fall significantly. VRLA are very low cost and very effective for what
they do.

Disadvantages of gel cells are higher cost for no real benefit, maybe
prone to damage from high charge currents (formation of voids in the
gel) - but VRLA are prone to evaporate off electrolyte from
overcharging. And a general benefit of VRLA is the broad industry
investment in VRLA technology.

Unfortunately many people call any sealed lead acid battery a "gel
cell" not realizing almost all are VRLA.

Darryl

Grrr !@# automatic spell checker. Gel cells have electrolyte in "fumed
silica" not "fused silica". To see what this means see
http://en.wikipedia.org/wiki/Fumed_silica.

BTW VRLA batteries have electrolyte suspended in fiberglass mats
packed tightly between the plates. They are barely damp hence the
"starved electrolyte" terminology. The tight packing between these
mats makes the batteries very robust. Because the plates no longer
have to be as rigid/robust by themselves as in an old style flooded
lead acid battery the plates can be purer lead and don't need alloying
for strength/rigidity. That results in chemistry that give much lower
self discharge rates (why you do *not* need to leave a VRLA battery on
a charger over winter etc.) and better internal resistance properties
compared to flooded lead acid batteries. There is a slight
overpressure on the battery managed by neoprene vents and a close
cycle chemical reaction where gasses are recombined with help from a
catalyst. Hence the "recombinant gas" terminology sometimes used.

Gel cells share some of these features as well but its been exploited
more in VRLA designs.


Darryl