Re: Battery Boxes...What One Company Designed

[Marc F Hult <MFHult@xxxxxxxxxxxxxxxxxxxxx>]

On 18 Sep 2005 02:52:12 GMT, ddl@danlan.*com (Dan Lanciani) wrote in message
<1331585@xxxxxxxxxxxxxxxxxxx>:

>In article <as8pi1da45o1psehe0s983ql7439j8k3ek@xxxxxxx>,
MFHult@xxxxxxxxxxxxxxxxxxxxx (Marc F Hult) writes:

>|
>|
>| Inteli-Power PD9180 and PD9160 (now Progressive Dynamics) as I wrote in my
>| previous post. See
>|
>| http://www.progressivedyn.com/power_converters.html
>
>Interesting.  I had no idea that you could get class 2 supplies with such
>high power output.  Maybe I'll have to reconsider my low-voltage distribution
>analysis...
>


They have gotten very much cheaper, smaller, cooler, more robust, more powerful
-- and Ul. and ULc. What is not quite what I'd like is efficiency for this
particular family of devices. They are rated at  ">80%" at unspecified load. In
real world, this might mean 60% under low load. Course they may just be rating
conservatively.

The RV market is big enough to the create volume needed to avoid niche-market
pricing. This particular design (sold under at least three names) has been
around long enough for the engineering to tested and solid. I imagine RV owners
as a group are not the most gentle on equipment.

IMO, Key here is UL and internal transformer isolation. But I haven't probed to
see whether it is specifically UL for Class 2. I am satisfied that it means
engineering needs.

The other important part of a distributed DC system is use of isolating DC-DC
converters. There are plenty of NOS devices to be had in a variety of Vin and
Vout, nominal telco 48vdc being especially prevalent on the resale market.

I generally assume that all equipment that came with a wall wart and is located
more than  ~10m from the primary battery bank should be isolated (again) unless
known otherwise. DC-DC converters also provide the current limiting to 'convert'
the battery into Class 1. The NEC specifically states that a plain old zinc dry
cell is Class 2 (not 1) because the potentially high current capabilities. I
wonder how many door bells of yesteryear, connected with 20AWG bell wire, were
in violation ? ;-)

Marc
Marc_F_Hult
www.ECOntrol.org