Hi

Probably an important question to ask - how much current does this sub-species 
of the Z series pull off of 24V?

My *guess* would be it pulls a couple of watts  (say 6W) per box once the OCXO 
is warmed up. If so, that would be just under 1/4 A on the 28V supply and just 
over that as the battery crossed 24 V. 

If you have the full dual box setup, that would be 1/2 A on battery. A 7A SLA 
would get you 14 hours of run time. At least around here, that’s a long (and 
unusual) outage. There’s nothing in the house (except the Honda generator) that 
will run that long in an outage. I’d be quite happy with a 1-2 AH setup that 
gives me 2 to 4 hours (or half that if my power estimates are bunk). 

The 7AH’s are already dirt cheap. They make a ton of them. I’d save some money, 
but not a lot. The main thing I’d save would be space. 

Bob


> On Oct 25, 2014, at 9:54 PM, Tom Miller <[email protected]> wrote:
> 
> I really don't disagree with you. I did say run the supply at 28.0 and use a 
> diode off the supply to the battery. That would place the float voltage at 
> 27.3 or so. Best would be to follow the manufacturers float service 
> recommendations. Ideally it should also be temperature compensated with a 
> -2.4 mV/°C slope. Not a problem with how we use these in the lab though.
> 
> And yes to get the longest run time, just power the main unit from the 
> battery as Bob suggested.
> 
> Now I am just waiting on some DB-9 connectors. I ran out of them and the 
> local RatShak went TU.
> 
> Tom
> 
> ----- Original Message ----- From: "Christopher Brown" <[email protected]>
> To: <[email protected]>
> Sent: Saturday, October 25, 2014 5:32 PM
> Subject: Re: [time-nuts] Lucent KS-24361/Z3812A GPSDO initial setup
> 
> 
>> 
>> Might want to dial that back a bit.
>> 
>> Since 12V/7ah batteries are mentioned I am assuming standard small
>> gelcell units.
>> 
>> Proper float voltage for a deep cycle is lower than a SLI type, and
>> gellcell even lower.
>> 
>> Generally 13.6 - 13.8 would be the gellcell range, with 13.6 being right
>> on for long life use of _small_ batteries.  Equalizing charge wold be 14
>> - 14.2.
>> 
>> Floating a small gelcell at 13.6 (27.2) v.s. 14 can mean the diff
>> between 12 - 24 months v.s. 5 - 7 years service life.
>> 
>> On 10/25/14, 11:39 AM, Tom Miller wrote:
>>> These units are ideal for powering via a float charged lead acid battery.
>>> Use two 12 volt / 7 AH batteries in series and adjust the regulated float
>>> power supply to 28.0 volts. Be sure to use a diode from the supply to the
>>> battery just in case the supply can't be back fed during a power fail.
>>> 
>>> Tom
>>> 
>>> 
>>> 
>>> ----- Original Message ----- From: "Bob Camp" <[email protected]>
>>> To: "Bob Stewart" <[email protected]>
>>> Cc: "Time Nuts" <[email protected]>
>>> Sent: Saturday, October 25, 2014 3:01 PM
>>> Subject: Re: [time-nuts] Lucent KS-24361/Z3812A GPSDO initial setup
>>> 
>>> 
>>>> Hi
>>>> 
>>>> Spend the effort, get an antenna outside the house. Beg / borrow / steal a
>>>> UPS. Even a brand new one is less than you paid for the 3812.
>>>> 
>>>> 
>>>> Bob
>>>> 
>>>> 
>>>> 
>>> 
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