Hybrid Car – More Fun with Less Gas

Re: Battery Boxes...What One Company Designed

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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
low voltage.

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 ?

Cheers, J/.
John Beardmore

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 ;-)

... Marc

Posted by John Beardmore on September 16, 2005, 10:29 pm
 MFHult@nothydrologistnot.com writes

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...

Cheers, J/.
John Beardmore

Posted by John Beardmore on September 17, 2005, 10:45 am

But only you know what they cost YOU.

Personally I have done a lot of mobile stuff on 24 volts because that's
what trucks use.  I don't like 12 because the current requires huge
wires, though I've done a bit of that.  If it was for home / stationary
use I'd expect to see some efficiency advantages by going to higher
voltages, but if you charge from PV for example, will you be able to get
say a 96V OPT regulator off the shelf ?  And what if one battery or PV
in a string fails ? Probability goes up as strings get longer.  Lots to


None really.  The inverters we have used have been cheap, modern, fairly
efficient, fragile, small, switching technology, square wave out and
nasty, or have been hugely heavy, inefficient thyristor fired 50Hz 1960s
technology with massive transformers and sin wave output.  All down to
what has come out way.

We also have a huge, and I suspect fairly inefficient 7kW UPS inverter
lurking around but there isn't much point in telling you about that.
One day it will come in handy though.

But given the price of modern inverters, is it worth your just going out
and buying what you need when you know what you need ?

Cheers, J/.
John Beardmore

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