[Boatanchors] GEL CELLS

[Brian]

Not that simple.

The gassing Voltage depends on the temperature, too.

Car battery charging systems often charge up to 14V5, in spite of the 
under-bonnet temperature. Why is it set so high? A couple of reasons - the 
battery can be fully charged, and first thing in the morning, when air 
temperature is usually low, the car's engine will start. This temperature 
cycling and operating at beyond gassing temperature are some of the reasons 
that car battery manufacturers only offer a one-year guarantee on car 
batteries. Where it is possible to alter the set point, I set it at 13V65 
which is below gassing Voltage for most operating temperatures.

Sealed lead-acid batteries (SLABs) and gell cells have even less room to 
manoeuvre than flooded cells (those in car batteries). With SLABs, there is 
only limited volume available for gas production. With gell cells, once the 
acid in the gell gasses out, there is no simple way to replace the lost 
water.

Another little point: many self-styled pundits - even among the ARRL 
editorial staff - warn of the dangers of charging batteries in confined 
spaces  "because they give off hydrogen which is explosive". Hmmm. Simple 
analysis of the chemistry of lead-acid cells' charging and discharging shows 
that the gasses given off are hydrogen and oxygen, in exactly the correct 
ratio to recombine explosively if there is a naked flame around, eg, welding 
in a motor mechanic's garage while charging batteries. Warm, concentrated 
sulphuric acid does wonders to your favourite radio equipment, your car and 
your bank balance.

73 de Brian, VK2GCE.


On Thursday, January 22, 2015 1:50 PM , Mac said:

"Float" a quality "12V" Gel Cell battery at 13.5 to 13.8 volts (2.25 - 2.30 
volts per cell) and it will last a minimum of 5 years.

Applying more than that 13.8 for much time will severely shorten its life!

Straight from Powersonic's user guide!

* * * * * * * * * * *
* 73 - Mac, K2GKK/5 *