Re: Battery Boxes...What One Company Designed

[Marc F Hult <MFHult@xxxxxxxxxxxxxxxxxxxxx>]

On 17 Sep 2005 07:46:48 -0700, "Too_Many_Tools" <too_many_tools@xxxxxxxxx>
wrote in message  <1126968408.243469.263290@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>:

>I think that is the path I may take...in the past I have found that
>since the electronics continue to get "better" it is usually not worth
>trying to design in old stuff....and sometimes "old" means just a few
>years old.
>
>My cost for the UPS equipment I am able to find is nil but one needs to
>factor in long time power usage (idle current), ability to replace it
>when it fails and suitability for the home enviroment. It is a fool who
>designs a system around a surplus component that when it fails, you
>have to toss the whole system. This battery box in question is a
>component that can be useful as my system evolves as it will.
>
>This is one reason for the question of "what voltage" since it is
>apparent that the trend is to different voltages than in the past.
>
>TMT

FWIW, here's what I do (use fixed-spacing font to view ASCII diagram):


Internet
 |
Home Automation Control System
 |
Genset controller
 |
 +-----------------+
 |                 |
 |                 |
28vdc NG Genset -->| Switch over------+
                                      |
                                      |
AC line --+--60amp charger/converter -+-- 14vdc batteries ---o 28vdc
          |                   |       |        |
          |                   +-------+--------+
          |                           |
          +--80amp charger/converter -+-- 14vdc batteries ---o 14vdc
                              |       |        |
                              +-------+--------+-------------o vdc 'grnd'

In words:

A bank of deep-cycle lead batteries is series connected to provide 14vdc
(nominal 12vdc) and 28vdc  (nominal 24vdc).

Most loads including home automation computers, UPS, and low-voltage light
dimmers are connected to the 28vdc output.

Home control and other devices that can run off 12vdc (security panel, home
automation controllers, video modulators multiplexors, cameras, audio
equipment) are connected to the 14vdc  rail.

Devices that need other voltages are supplied via DC-DC converters (eg 5vdv
for microcontrollers, router, switches and so on) or  DC-AC inverters (eg
24VAC for HVAC)

The 'lower' (0-14vdc) bank of batteries is recharged and powered by a
UL-listed 80 amp Inteli-power (one "l") charger/supply

http://www.progressivedyn.com/Products.php?ProductID=76

The 'upper bank' (14-28vdc) is recharged and powered by an 60 amp
Inteli-power charger/supply.

Together they provide nominal 60 amps at 28vdc and 20 amps 14vdc =~2000 watts.

A Baldor natural gas 28vdc genset has been purchased (not yet installed) to
kick in during power outages that has additional capacity for additional 28vdc
and 120VAC UPS needs. Controller is a Bouchette A120

http://www.bouchette.com/Products/A120C.htm

The choice of 28vdc was driven in large part because this the highest nominal
voltage that meets the requirements of the under-30-volt sections of the
National Electrical code (NEC). A 14vdc system would require conductors
(wires) with twice the cross-sectional area to have the same distribution IR
losses.

This provides isolated, UL-listed, NEC-compliant single-conversion power for
the most/all of critically  needed devices including lighting. There is no
interruption whatever if line power goes down because the system is connected
directly to batteries at all times. A power outage simply changes the charging
source from line AC to genset.




The system can be expanded to higher voltages or currents with additional
batteries and chargers. and additional charging sources (eg photovoltaic)
merged.

DC Grounding and maintaining isolation of subsystems that need to have
separate "grounds" is _very_ important and a whole 'nuther topic.

HTH ... Marc
Marc_F_Hult
www.ECOntrol.org