In article ,
The Other Mike wrote:
The other half of the site has 5ft T5's with magnetic
ballasts fed by a Honda EU20i generator which despite being a quiet
suitcase model and loads of additional soundproofing is still way too
noisy. Near silent operation is essential. Hauling fuel is also a
PITA as its a long way from the road.

So I need a way of powering the 5ft T5's (58W) from a low voltage DC
supply. IOTA only make ballasts up to 40W and they need a circa 50v
supply, realistically I need to keep to 12v to keep the solar array
price down.

My feeling is that magnetic ballast mains florries fed via an inverter
would be very little more efficient than 12 volt halogen lighting.

--
*Save a tree, eat a beaver*

Dave Plowman London SW
To e-mail, change noise into sound.

On Jun 23, 12:11*am, "Dave Plowman (News)"
wrote:
In article ,
* *The Other Mike wrote:

The other half of the site has 5ft T5's with magnetic
ballasts fed by a Honda EU20i generator which despite being a quiet
suitcase model and loads of additional soundproofing is still way too
noisy. *Near silent operation is essential. *Hauling fuel is also a
PITA as its a long way from the road.
So I need a way of powering the 5ft T5's (58W) from a low voltage DC
supply. *IOTA only make ballasts up to 40W and they need a circa 50v
supply, realistically I need to keep to 12v to keep the solar array
price down.

My feeling is that magnetic ballast mains florries fed via an inverter
would be very little more efficient than 12 volt halogen lighting.

electronic invertors get over 90% efficiency, the difference between
the 2 is huge

On Wed, 22 Jun 2011 17:51:40 -0700 (PDT), Tabby
wrote:

On Jun 23, 12:11Â*am, "Dave Plowman (News)"
wrote:
In article ,
Â* Â*The Other Mike wrote:

The other half of the site has 5ft T5's with magnetic
ballasts fed by a Honda EU20i generator which despite being a quiet
suitcase model and loads of additional soundproofing is still way too
noisy. Â*Near silent operation is essential. Â*Hauling fuel is also a
PITA as its a long way from the road.
So I need a way of powering the 5ft T5's (58W) from a low voltage DC
supply. Â*IOTA only make ballasts up to 40W and they need a circa 50v
supply, realistically I need to keep to 12v to keep the solar array
price down.

My feeling is that magnetic ballast mains florries fed via an inverter
would be very little more efficient than 12 volt halogen lighting.

electronic invertors get over 90% efficiency, the difference between
the 2 is huge
I agree - if the inverter is run in it's "sweet spot" - but if,
say, a 1200 watt inverter is used to power a 13 watt load, the
efficiency drops WAY DOWN because the quiescent load (what it takes to
run the inverter with no load) becomes a sizeable percentage of the
total power consumed. - and just how efficient IS a magnetic ballast??
Likely something closer to 80 than 90 - so combine that (let's say
80) with the (possibly) 70% efficiency of a lightly loaded inverter,
and you are down to about 56% efficiency - where, particularly for
task lighting, a low voltage halogen is DEFINITELY worth considering.
(and an LED positively SHINES.) (pun intended)

On Jun 23, 3:54*am, wrote:
On Wed, 22 Jun 2011 17:51:40 -0700 (PDT), Tabby
wrote:



On Jun 23, 12:11*am, "Dave Plowman (News)"
wrote:
In article ,
* *The Other Mike wrote:

The other half of the site has 5ft T5's with magnetic
ballasts fed by a Honda EU20i generator which despite being a quiet
suitcase model and loads of additional soundproofing is still way too
noisy. *Near silent operation is essential. *Hauling fuel is also a
PITA as its a long way from the road.
So I need a way of powering the 5ft T5's (58W) from a low voltage DC
supply. *IOTA only make ballasts up to 40W and they need a circa 50v
supply, realistically I need to keep to 12v to keep the solar array
price down.

My feeling is that magnetic ballast mains florries fed via an inverter
would be very little more efficient than 12 volt halogen lighting.

electronic invertors get over 90% efficiency, the difference between
the 2 is huge

*I *agree - *if the inverter is run in it's "sweet spot" - but if,
say, a 1200 watt inverter is used to power a 13 watt load, the
efficiency drops WAY DOWN because the quiescent load (what it takes to
run the inverter with no load) becomes a sizeable percentage of the
total power consumed. - and just how efficient IS a magnetic ballast??
*Likely something closer to 80 than 90 - so combine that (let's say
80) with the (possibly) 70% efficiency of a lightly loaded inverter,
and you are down to about 56% efficiency - where, particularly for
task lighting, a low voltage halogen is DEFINITELY worth considering.
(and an LED positively SHINES.) (pun intended)


That's miles out.
T5 tubes 74-105 lumens/watt, ave 90
Magnetic ballast @80% efficient - 72 l/w
70% efficient invertor - 50 l/w
12v Halogen 24 l/w

LED would be good for inspection lamps, desk lamps etc


NT

In article
,
Tabby wrote:
My feeling is that magnetic ballast mains florries fed via an inverter
would be very little more efficient than 12 volt halogen lighting.

electronic invertors get over 90% efficiency, the difference between
the 2 is huge

That may well be their peak efficiency. But driving an inductive load
which requires a decent sine wave? And the efficiency of the fittings is
likely poorer too if not getting the correct waveform.

It would be very interesting to know the actual efficiency of this setup
in practice. I'd say you'd be surprised.

--
*Did you ever notice when you blow in a dog's face he gets mad at you? *

Dave Plowman London SW
To e-mail, change noise into sound.

On Jun 23, 10:53*am, "Dave Plowman (News)"
wrote:
In article
,
* *Tabby wrote:

My feeling is that magnetic ballast mains florries fed via an inverter
would be very little more efficient than 12 volt halogen lighting.
electronic invertors get over 90% efficiency, the difference between
the 2 is huge

That may well be their peak efficiency. But driving an inductive load
which requires a decent sine wave? And the efficiency of the fittings is
likely poorer too if not getting the correct waveform.

It would be very interesting to know the actual efficiency of this setup
in practice. I'd say you'd be surprised.

A switche dmode generated sine is highly efficient. If it wasnt, the
invertor would cook itself.


NT

Tabby wrote:
On Jun 23, 10:53 am, "Dave Plowman (News)"
wrote:
In article
,
Tabby wrote:

My feeling is that magnetic ballast mains florries fed via an inverter
would be very little more efficient than 12 volt halogen lighting.
electronic invertors get over 90% efficiency, the difference between
the 2 is huge
That may well be their peak efficiency. But driving an inductive load
which requires a decent sine wave? And the efficiency of the fittings is
likely poorer too if not getting the correct waveform.

It would be very interesting to know the actual efficiency of this setup
in practice. I'd say you'd be surprised.

A switche dmode generated sine is highly efficient. If it wasnt, the
invertor would cook itself.



Plenty of camping style 12v fluorescents available, and I can totally
confirm the battery lasts about 5 times as long as using normal 12v
bulbs, since I have both.

Generally 8 or 16watts fittings are less than £20.


http://www.the12voltshop.co.uk/Shop/...escent-lights/


NT

In article ,
The Natural Philosopher wrote:
It would be very interesting to know the actual efficiency of this
setup in practice. I'd say you'd be surprised.

A switche dmode generated sine is highly efficient. If it wasnt, the
invertor would cook itself.



Plenty of camping style 12v fluorescents available, and I can totally
confirm the battery lasts about 5 times as long as using normal 12v
bulbs, since I have both.

Sigh. But that's a custom made 12 volt fitting. Not a low efficiency mains
one run off an inverter. Big difference.

--
*The man who fell into an upholstery machine is fully recovered*

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Plowman (News) wrote:
In article ,
The Natural Philosopher wrote:
It would be very interesting to know the actual efficiency of this
setup in practice. I'd say you'd be surprised.
A switche dmode generated sine is highly efficient. If it wasnt, the
invertor would cook itself.



Plenty of camping style 12v fluorescents available, and I can totally
confirm the battery lasts about 5 times as long as using normal 12v
bulbs, since I have both.

Sigh. But that's a custom made 12 volt fitting. Not a low efficiency mains
one run off an inverter. Big difference.

i was merely pointing out the obvious way to avoid having to do that.

On Jun 23, 3:40*pm, "Dave Plowman (News)"
wrote:
In article ,
* *The Natural Philosopher wrote:

It would be very interesting to know the actual efficiency of this
setup in practice. I'd say you'd be surprised.

A switche dmode generated sine is highly efficient. If it wasnt, the
invertor would cook itself.

Plenty of camping style 12v fluorescents available, and I can totally
confirm the battery lasts about 5 times as long as using normal 12v
bulbs, since I have both.

Sigh. But that's a custom made 12 volt fitting. Not a low efficiency mains
one run off an inverter. Big difference.

Put the figures to it, then you'll know


NT

In article
,
Tabby wrote:
Sigh. But that's a custom made 12 volt fitting. Not a low efficiency
mains one run off an inverter. Big difference.

Put the figures to it, then you'll know

That's the point I'm making - any figures are likely just a guess when
dealing with this unknown. Quoted efficiencies are always under ideal
circumstances.

Of course it would be better to use proper low voltage florries or decent
LED lighting - but the OP has ruled this out on cost grounds.

--
*I'll try being nicer if you'll try being smarter

Dave Plowman London SW
To e-mail, change noise into sound.

On Jun 23, 6:49*pm, "Dave Plowman (News)"
wrote:
In article
,
* *Tabby wrote:

Sigh. But that's a custom made 12 volt fitting. Not a low efficiency
mains one run off an inverter. Big difference.
Put the figures to it, then you'll know

That's the point I'm making - any figures are likely just a guess when
dealing with this unknown. Quoted efficiencies are always under ideal
circumstances.

We dont have precise figures on the invertor, but low loading isnt
going to make a big difference. One can work this out from
understanding the way they operate. It is possible to find figures for
smpsus.


Of course it would be better to use proper low voltage florries or decent
LED lighting - but the OP has ruled this out on cost grounds.

Short tubes and LEDs both significantly have lower efficacy, and low
quality 12v ballasts aren't models of anything. Assuming a mains
invertor gets lower total lumens per wattt just isnt logical.


NT

In article ,
Tabby writes:
On Jun 23, 10:53*am, "Dave Plowman (News)"
wrote:
In article
,
* *Tabby wrote:

My feeling is that magnetic ballast mains florries fed via an inverter
would be very little more efficient than 12 volt halogen lighting.
electronic invertors get over 90% efficiency, the difference between
the 2 is huge

That may well be their peak efficiency. But driving an inductive load
which requires a decent sine wave? And the efficiency of the fittings is
likely poorer too if not getting the correct waveform.

It would be very interesting to know the actual efficiency of this setup
in practice. I'd say you'd be surprised.
A switche dmode generated sine is highly efficient. If it wasnt, the
invertor would cook itself.

It's efficient into a resistive load.
A magnetically ballasted fluorescent lamp isn't a resistive load.
Even if it has a power factor correction capacitor (and most
don't nowadays), that can only correct the inductive component
in the power factor, not the contribution from the tube, which
amounts to about half of it.

The inverter cannot recover the excess energy borrowed from it
and returned each half cycle due to the phase shift, so the load
on the inverter is much nearer to the (higher) VA rating of the
lamp than the power rating. (That's why inverters are rated in
VA and not Watts.)

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]