[time-nuts] OT Gel Cell question

Ed Palmer ed_palmer at sasktel.net
Mon Jul 28 13:12:48 EDT 2014


As I understand it, the only time that any sealed lead acid battery will 
vent is in the case of gross overcharging.  The battery is designed so 
that normal charge rates and correct float voltage will result in 
recombination of any hydrogen and oxygen produced.  Was there a fault in 
the charging circuit or perhaps, the charging circuit didn't have proper 
temperature compensation of the charge voltage?

Ed

On 7/28/2014 10:56 AM, Brooke Clarke wrote:
> Hi:
>
> Using lead acid batteries and a precision frequency standard is not a 
> good thing if they are too close together.
>
> A number of decades ago (before the Time Nuts or the internet) I was 
> able to purchase a rack mount Gibbs 5 MHz double oven frequency 
> standard that used a very nice Bliley glass tube crystal because it 
> was not as precise as is was supposed to be.  It used GelCell backup 
> batteries that were physically in the same rack chassis as the oven.  
> The fumes from the batteries when charging etched some traces off the 
> PCB inside the oven defeating the temperature control but leaving the 
> oscillator.  It took a long time to reverse engineer and repair it.  
> I've added a photo of the cord wood construction of the cylindrical 
> oscillator.  The core of the cylinder holds the glass bottle crystal 
> and the glass piston coarse tuning capacitor, surrounded by the first 
> heater, circuitry for the oscillator and dual temperature control 
> circuits on ring shaped boards.  These fit inside a cylindrical cavity 
> which is the outer oven.  I've added a photo of the inner assembly at:
> http://prc68.com/I/office_equip.html
>
> Have Fun,
>
> Brooke Clarke




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