Re: Battery Boxes...What One Company Designed

[Marc F Hult <MFHult@xxxxxxxxxxxxxxxxxxxxx>]

On 21 Sep 2005 05:09:19 GMT, ddl@danlan.*com (Dan Lanciani) wrote in message
<1331592@xxxxxxxxxxxxxxxxxxx>:


>I was really trying to frame some simpler questions.  What is it that you
>are allowed to do by remaining < 30V that you would not be allowed to do if
>you used, say, 48V?  Similarly for using DC instead of AC.

IOW, get back to the Q&A that might have transfer value to other folks.
Thank you ;-)

Allow me to assert that, side for legacy requirements for some thermostats
and HVAC controls, nearly all home automation/control/measurement electrical
power needs are intrinsically  DC. (Air conditioning, heating, large motors
etc are beyond our scope here.)

The system I've described and shown in schematics consists in building blocks
in increments of nominal 12vdc (~13.8 vdc. One can easily add additional
voltages in series on _top_ of the 0-12-24vdc voltage, 80/60 amp
configuration.

So I could create a 1.25 amp 48vdc supply with two 1.25amp 13.8vdc Powersonic
wall-wart chargers and two 7AH sealed lead cells (the most cost-effective
size) that I have on hand and move around for various projects. I have been
using this particular combination from this supplier for isolated  power
supplies for environmental monitoring for at least 20 years.

This would provide a system with 0-12-24-36-48vdc at 80/60/1.25/1.25 amps

48vdc just doesn't happen to be needed in my case right now, which (based on
the devices I have) _does_ need ~40 amps at nominal 24vdc to power the DC
dimmers that I happen to use. Requirements of other folks will vary. Point is
that the approach is modular, and one can move things around as needs change,
which in a experimental/hobbyist environment, they inevitably do.

Recognize that if the battery bank  weren't there, and aside from the
specific listing issue, the 80-amp 12vdc "tap" is Class 1-compliant so one
could partially "de-build" to reach a particular code goal/requirement should
it come to that.

Using a 40 amp instead of 60amp charger/supply would make the 24vdc tap also
Class 1 (same provisos).

>Don't the DC/DC converters take up about as much space as the wall warts
>they replace?

No, in part because the DC-DC converters can be internal to the devices they
power. Compare the hodge-potch of wall-warts, power strips, surge protectors,
and local UPS's that conventionally are used to power a pc and associated
accoutrements with these:


http://www.mini-box.com/s.nl/sc.8/category.13/it.A/id.356/.f
http://www.mini-box.com/s.nl/sc.8/category.13/it.A/id.300/.f
 (the 12vdc on the latter is pass-through, not regulated.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=7546712441&rd=1&sspagename
=STRK%3AMEWN%3AIT&rd=1

Which, *inside* an (eg)  low-power PC such as VIA EPIA is smaller, more
energy efficient, has fewer connections to fail, and has longer battery
backup among other things.

A standard/conventional hermaphroditic connector for DC connectors are the
Anderson Powerpole series

http://www.andersonpower.com/index.html
which have been adopted by hams as informal quasi standard for Radio Amateur
Civil Emergency Service (RACES) among others

Purchased inexpensively here:

http://www.dcpwr.com/products/productlist.php?id=32&PHPSESSID=b2fc5d42026
3007049701b9f1764ba4d

And recognize -- importantly! -- that the short back-up time on under-desk
UP's don't actually solve *anything* if the PC is supposed to stay up
permanently which is often the case in HA applications. So the conventional
under-desk AC-based tangled jumble fails and the almost invisible, internal
DC solution elegantly and dependably meets the needs.

Depending on the specific CPU requirements (part of this approach involves
getting real with what we actually need in terms of computational horsepower)
sufficient 5vdc and(or) 12vdc power may be available from the same DC-DC
converter to supply a router or other gizmo. If not, add another DC-DC
converter, perhaps within the same case, but certainly not on the wall or on
an AC power strip.

>Or do you have enough consumer devices that require neither
>voltage conversion nor isolation nor class 2 current limitation that you
>come out ahead?

I think that you are asking whether I use devices that can use unregulated
nominal 12vdc or 24vdc. Yes. 12vdc devices abound. And this is a factor in my
purchasing decisions. It also prompts me to take the covers off devices to
see what their internal power supplies _really_ need.

... Marc
Marc_F_Hult
www.ECOntrol.org