[time-nuts] OT Gel Cell question

Alexander Pummer alexpcs at ieee.org
Mon Jul 28 13:44:28 EDT 2014

as long as it is not a gals/ceramic seal, there is no way to stop 
sulfuric acid to get out from the cell, just imagine the dilatation 
diffrence between plastic and metal...

On 7/28/2014 10:12 AM, Ed Palmer wrote:
> 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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