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

[Bob kb8tq]

Hi

Two basic types of SLA / VRLA batteries out there: AGM and Gel. For the AGM 
variety, you want a bit more to your charger. I haven’t worked with Gel cells in 
a while so they may indeed be easier.

Bob

> On Sep 25, 2020, at 4:17 PM, Poul-Henning Kamp <phk at phk.freebsd.dk> wrote:
> 
> --------
> Bob kb8tq writes:
> 
>> Properly charging batteries is a bit complicated.
> 
> With VRLA lead-acids:  Not really, constant voltage 2.3V/cell, current limited to $Ah/10 and you're done.
> 
> For the tonnage of batteries relevant for us, when used indoors, temperature-compensation and all that is not relevant.
> 
> Charging Lithium on the other hand is several kinds of nightmares, many of them involving unquenchable flames.
> 
>> One “cute” alternative is to do a battery + boost converter ( = switcher) instead.
>> [...]
>> 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 ….
> 
> Yes, for most stuff I would just slap a good isolated DC/DC converter on a single 12V battery and be done with it.
> 
> But for a BVA I would choose more expensive batteries over switching noise any day...
> 
> -- 
> 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.