Posted by Too_Many_Tools on September 16, 2005, 7:23 pm
Since I am starting the homepower/automated house journey, I have been
collecting surplus commercial equipment that might prove useful. One of
those items was a surplus Best battery box for a large UPS. Some
comments on the construction and design follows.
The box is designed for sealed 6v batteries (two banks or four) with
the second bank located above the first. The cabinet is metal with
galvenized trays for the batteries to sit in. The box was wired for 12v
at 200 amp with commercial welding cable. There are two in line fuses,
one per bank. The cabinet is on wheels. The cabinet has two vents
located on the back of the cabinet, one lower and one higher. The
cabinet is NOT actively ventilated but relies on natural convection. On
the front it has a single heavy duty switch to switch the direct
current. The switch has a ceramic resistor on it (to quench arcs when
Several things caught my attention. The use of metal throughout the
box...I would have expected fiberglass or plastic for corrosion
resistance. Next was the absense of an active ventilation system.
Third, the lack of an integrated charger for the battery box. I assume
the batteries are charged through the UPS.
I plan on making some mods to this box for my home system.
One is to make plastic tray inserts to keep acid at bay.
Next is an active ventilation system.
Third is to consider doing some type of a sliding tray on the bottom
level to allow one to access the batteries easier during maintainance.
Fourth is to incorporate a charging system.
Fifth is to place meters on the front to monitor voltage and amperage
and add the option for remote sensing.
Sixth rewire it for a different voltage (it was 12v at 200a)...any
I would be interested in any suggestions or comments as to what you
have added to or wish you had designed into your system.
Thanks for any and all suggestions.
Posted by Marc F Hult on September 16, 2005, 8:00 pm
Assuming that you are in US:
Check the National Electrical Code (NEC) which addresses both batteries and
Make sure that the DC/charging system is isolated from the AC, draws not more
than 20 (IIRC) amps source AC, is UL-listed and is not connected to earth
Above 30 volts, or if the system is not isolated, the NEC is more restrictive.
(FWIW, I have some of your questions. I have a growing 28vdc system.
A natural gas-powered 28VDC generator awaits installation. )
Posted by John Beardmore on September 16, 2005, 8:22 pm
How should we know ? Did you have any particular load in mind ?
I suspect most of us select components and design systems in response to
some particular need or requirement.
You seem to be coming at this the way a sculptor approaches a block of
You sound like you've found an interesting item, that requires a total
overhaul to be made stunningly excellent, to greatly exceed the spec
required to meet some undefined purpose.
What are you actually wanting to achieve ?
Posted by MFHult on September 16, 2005, 9:13 pm
My sons call this a " hood ornament project" Finding a neat hood ornament,
they say, I would be inclined to build a car under it...
I can't answer for the original poster, but some projects, especially DIY home
automation projects, can be driven by what one can do rather than what needs to
be achieved. That's often OK.
(Ooops... I jist realized how cross-posted this thread is . Oh well)
A common constellation of reasons that do have specific, useful and attainable
objectives (which also happen to be mine) is to provide a power system that
1) protection of devices in the home/office/farm/cabin that contain
semiconductors and so may be damaged by lightning and possibly other power-line
2) a useful amount of back-up power for lighting, electronic, and other
electrical equipment devices that are needed in emergencies
3) some personal outlet for frustration over 'energy dependence' in all its
Gotta go! -- Lightning and thunder as I type this ;-)
Posted by John Beardmore on September 16, 2005, 10:29 pm
Yes - I've got no problem with that, but asking us what voltage to wire
the bank to seems silly. Likely to be determined by available cable
lengths and thicknesses, surplus or cheap inverters etc...