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

[John Ackermann N8UR]

I've had good luck with Iota brand chargers for 12 and 24 volt... I 
think they are "DCL" series or something similar.  They are available in 
various amperage and include a smart-charger circuit.  I know Amazon 
sells several models and the prices are in the $100-200 range.  One of 
their selling points is that they are electrically quiet, though I 
haven't done any real tests, and are designed to work as a regular power 
supply (ie, they don't flake out if there's no battery load attached.

John
----

On 9/25/20 1:22 PM, Bob kb8tq wrote:
> Hi
> 
> Properly charging batteries is a bit complicated. Why does “properly” matter? You want them to be fully
> charged, but not damage them in the process. That generally involves some sort of variable voltage
> for the charging source. If you decide to go with Lithium based parts, you can get BMS (battery management)
> IC’s that can help with the charging and the balancing ( = you want them all at equal voltages) of the cells.
> 
> If you look at older gear, this sort of thing didn’t get a lot of attention. Most of the backup battery setups
> worked poorly as a result.
> 
> ======
> 
> One “cute” alternative is to do a battery + boost converter ( = switcher) instead. If the device only operates
> during a power outage, noise is not a big deal. Everything that is attached to the OCXO output is dead anyway ….
> 
> The advantage of a switcher is obviously efficiency. A fully charged “12V” LiFePo4 stack could easily be at 14.8V.
> Fully discharged it might get down to 10.4V. Allowing for that 1.4:1 output ratio with a linear regulator means a
> lot of (expensive) battery energy goes up in heat ….
> 
> Bob
> 
>> On Sep 25, 2020, at 11:55 AM, Mark Spencer <mark at alignedsolutions.com> wrote:
>>
>> Pondering the backup power issues for my BVA a bit more,  I am thinking a dedicated DC battery bank (maybe 5 or 6 nominal 6 volt batteries in series) powering a suitable linear regulator circuit is probably the direction I will go in.  I suspect there are more elegant and or simpler approaches but I think from my perspective as a hobbyist this is probably the best direction for me.
>>
>> I like the idea of using a diode arrangement to facilitate changing the power source for the BVA.   I expect I will also add some form of over voltage protection as well.
>>
>> I need to ponder the likely voltage drops in the voltage regulator and diodes along with the voltages the batteries will provide as they discharge under load.
>>
>> It seems I have another winter project.
>>
>> Thanks all for the suggestions.
>>
>>
>> Mark Spencer
>> mark at alignedsolutions.com
>> 604 762 4099
>>
>>> On Sep 25, 2020, at 7:16 AM, Magnus Danielson <magnus at rubidium.se> wrote:
>>>
>>> Hi,
>>>
>>> On 2020-09-24 23:47, Tom Van Baak wrote:
>>>>> Next time I power down mine is to integrate a new supply and back-up
>>>>
>>>> May I recommend PowerPole connectors and frequent use of diode-OR. For
>>>> details see:
>>>>
>>>> http://leapsecond.com/pages/powerpole/diode-or.htm
>>>>
>>>> I got the inspiration when my Dad was in the hospital and I saw how
>>>> they did IV tubes with multiple injection points. It seemed so simple,
>>>> clever, reliable. Details [1] and graphic photo [2].
>>>>
>>>> So now I use diode-OR "Y" connectors on all my long-term standards. It
>>>> allows me to replace either power supply live without interruption at
>>>> any time. Come to think of it, they call it an IV in the hospital. And
>>>> here in my lab the I is about 0.18 and V is 24 so my IV is 4 watts. ;-)
>>> That's how we do it in Telecom, but on the 48V level. I managed to drive
>>> my company into do it with 48V all the way to the various boards,
>>> because that way the protection switching out there handled multiple
>>> faults. Also, for some reason there is this line of DCDC converters from
>>> 48V to about anything. We kept doing that since, even if the diodes now
>>> been replaced with MOSFETs to lower losses.
>>>
>>> If you look into say the 5065A that's how it's done there too.
>>>
>>> As for power-pole, those are great connectors, but I need to keep 12V,
>>> 24V and 48V in the lab, so I need to get the different color codes not
>>> to interchange them. You usually react when you see a yellow-black
>>> trying to mate with a red-black. So, I recommend folks to do the same.
>>> Once one got started with the Anderson PowerPole, it becomes more and
>>> more a solution.
>>>
>>> But yeah, thanks for reminding me that I need to progress on the
>>> power-pole and power supply projects. I'll do that after the PiDP-11
>>> project.
>>>
>>> Cheers,
>>>
>>
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