[time-nuts] Oscilloquartz BVA has been sold. Thank you all who expressed an interest.

[Mark Spencer]

For what it is worth I ran two identical AGM 12 volt batteries for approx 7 years or so in my home lab.   

I carefully adjusted the terminal voltage while float charging them via a blocking diode and checked the voltage every few months.   I also confirmed that the terminal voltage of each 12 volt battery was essentially the same.   The manufacturer provided data re suitable float voltages at various temperatures.  The temperature in my time lab is fairly stable.

  After over six years of service they powered two of my OCXO's for approx 48 hours during a lengthy power outage when I was not home.   It all worked as I expected (I had chosen the batteries to provide at least 48 hours of run time with some margin) and after approx 7 years I had to replace the batteries when it became apparent they were not charging (the power supply I charge them with has an ammeter which helped me realize there was an issue.)   I expect to get a similar life span from the replacement batteries.  The second set of batteries at first had a significantly higher voltage difference when being float charged, the battery vendor replaced either one or both of the batteries and all was good.

I would not be surprised if the deep discharge of the first set of batteries contributed to their subsequent demise.

The experience of others may differ from mine (:


Mark Spencer
mark at alignedsolutions.com
604 762 4099

> On Sep 25, 2020, at 2:06 PM, Poul-Henning Kamp <phk at phk.freebsd.dk> wrote:
> 
> --------
> Bob kb8tq writes:
> 
>> Two basic types of SLA / VRLA batteries out there: AGM and Gel. For the AGM 
>> variety, you want a bit more to your charger.
> 
> Yes, if you buy batteries for N * 100K $money, spending more money
> on your charger is a good investment.
> 
> But if you have two batteries doing float-charge/long-run/tiny-load,
> in a benign environment in a corner of your lab, the internal
> variance between batteries in that same production lot, will
> overshadow any imaginable benefit a fancy charger could bring.
> 
>> I haven't worked with Gel cells in a while so they may indeed be easier.
> 
> They are for the same reasons they suffer cyclic use better.
> 
> But for a float/long-run application, it makes absolutely no difference.
> 
> -- 
> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
> phk at FreeBSD.ORG         | TCP/IP since RFC 956
> FreeBSD committer       | BSD since 4.3-tahoe    
> Never attribute to malice what can adequately be explained by incompetence.
> 
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