Solar-powered lights - recommendations please ??
Adrian
Another of those projects that's been on the back-burner for a while is
devising 'something' to finish off the stone-built gateposts at the
entrance to our place.
Suddenly - bright idea <g> - literally !
Considering making a couple of 'lanterns' with stained glass - powered
by solar-recharged high intensity leds (it's a long way to run a mains
cable down to the gates from the house).
Mostly for decoration (and for a bit of fun!) - not expecting
quartz-halogen-style illumination !
So - any recommendations for solar lighting kit that people have
actually used and found to be effective. I can see that prices range
from the ridiculously cheap up to 20 quid or so for something that's
probably a bit more useful like this from CPC
http://cpcireland.farnell.com/lloytron/l980/solar-led-shed-light/dp/LA03127
I'm guessing that the cheapest devices are going to have very
short-lived batteries in them... what's a sensible price-point for a
decent solar lighting kit ??
Thanks
Adrian
zaax
Solar lights doen't work in the UK, too dark in the winter.
Tony Bryer
> Solar lights doen't work in the UK, too dark in the winter.
IIRC also a function of low temperature
--
Tony Bryer, 'Software to build on' from Greentram
www.superbeam.co.uk www.superbeam.com www.greentram.com
Andy Dingley
> I'm guessing that the cheapest devices are going to have very
> short-lived batteries in them... what's a sensible price-point for a
> decent solar lighting kit ??
"Decent"? No idea - too subjective.
24 quid gets you a "Tritronic" PIR security light with two nice 3-LED
lamps, a 6" square panel and 3 C-cell NiCds. PIR doesn't work in cold
weather, but it's quite a good set of parts for a lighting set
Otherwise Maplin's January sale for panels (excellent deals last year)
and Ultraleds.co.uk for the LEDs themselves.
meow...@care2.com
Correction: inadequately designed solar systems dont work in winter.
Just design the system to give enough output under winter conditions.
NiCd and NiMH have significant self discharge, the cheaper lead acid
will work better.
Some diffuse concentration on the panels for winter only can make a
big difference to how much panel you need.
Forget about cheap £20 kits, they're only rated for summer use, and
power collection, storage and light output are all fairly pathetic.
NT
Dave Liquorice
> 3 C-cell NiCds. PIR doesn't work in cold weather,
Niether will the NiCds. Really need Li-Ion but I don't think the charging
requirements for those are quite as easy as NiCd.
--
Cheers
Dave.
pete
experience to it.
The OP says he'll use high-intensity LED. Let's say that's a 1 Watt type
and that it'll be asked to provide, worst case, illumination from 4pm to
midnight in the winter. (After that presume it doesn't matter if it runs
out of puff - there won't be anyone around to appreciate it).
That's 8 Watt-hours per day - so the solar panel should provide (say)
10 WHr daily to charge it.
Now, today is a perfectly clear winter's day and the sun is about as high
as it ever gets (at 51 degrees north) in the winter. A quick measurement
with a 6cm x 4cm solar panel gives me 3.7 Volts across a 1K resistor - or
about 14 milliWatts for a 24 cm2 area.
On the outrageously optimistic assumption that during the winter, you'll
average ONE HOUR of charging at this rate per DAY, you'll need about 700
times the surface area of solar panels that I used, i.e. 17,500 cm2.
That's 1.75 square metres of panel to provide enough charge to keep 1 LED
lit for 8 hours.
A quick shufti on eBay throws up a 1 square metre (1.49 * 0.67) panel for
grabs at £360. Interestingly, this is rated at 100 Watts - gotta love
that sense of humour! So it looks like we're talking about £500 just for
the solar panels. However, I can't see this being a starter: once the OP
realises just how much acreage is involved, and (due to it having to face
the sun) the near impossibility of disguising the panels, or siting them
discretely so they aren't an eyesore.
Andy Burns
> On Sat, 3 Jan 2009 03:01:39 -0800 (PST), Andy Dingley wrote:
>
>> 3 C-cell NiCds. PIR doesn't work in cold weather,
>
> Niether will the NiCds. Really need Li-Ion
My laptop won't allow itself to be powered-on (even when plugged in)
when when the li-Ion battery is cold, no doubt the battery has internal
protection, not sure whether it doesn't want it to be charged while it's
cold, or that it doesn't it want to supply power.
The Natural Philosopher
actually, they are easier.
Basically the same as lead acid. Limit the current, to no more than the
one hour rate, and limit the voltage to about 4.2v per cell.
They are still crap in sub zero conditions though.
ARWadsworth
"Adrian" <adr...@ambquality.co.uk> wrote in message
news:6s6ruqF...@mid.individual.net...
Solar powered cats eyes?
http://www.astucia.co.uk/default.aspx
Adam
meow...@care2.com
> On Sat, 3 Jan 2009 04:07:57 -0800 (PST), meow...@care2.com wrote:
> > zaax wrote:
> >> Adrian wrote:
> >> > I'm guessing that the cheapest devices are going to have very
> >> > short-lived batteries in them... what's a sensible price-point for a
> >> > decent solar lighting kit ??
> >> >
> >> > Thanks
> >> > Adrian
> >>
> >> Solar lights doen't work in the UK, too dark in the winter.
> >
> > Correction: inadequately designed solar systems dont work in winter.
> > Just design the system to give enough output under winter conditions.
> >
> > NiCd and NiMH have significant self discharge, the cheaper lead acid
> > will work better.
> >
> > Some diffuse concentration on the panels for winter only can make a
> > big difference to how much panel you need.
> >
> > Forget about cheap �20 kits, they're only rated for summer use, and
> > power collection, storage and light output are all fairly pathetic.
> OK, here's a strawman spec. - hopefully other people will add their
> experience to it.
ok :) Lets see if we can tidy it up some.
> The OP says he'll use high-intensity LED. Let's say that's a 1 Watt type
ok
> and that it'll be asked to provide, worst case, illumination from 4pm to
> midnight in the winter.
ok, you could but I'd sooner say no to that. Solar power is a premium
resource, especially in winter, so we dont want to waste 90% of it.
Instead we go for a PIR light, set to run for say 3 minutes. Say there
are 6 in&outs after dark per day on average, so thats a total of 18
minutes run time per day.
That's 0.3Wh/day, down from 8Wh. A factor of about 25 right there.
> (After that presume it doesn't matter if it runs
> out of puff - there won't be anyone around to appreciate it).
> That's 8 Watt-hours per day - so the solar panel should provide (say)
> 10 WHr daily to charge it.
25% loss is standard for the lead acid, but you've also got to take
into account the charge controller and LED ballast.
Lets say 5% loss on charge controller, 10% on the ballast and 25% in
the battery. Now for 0.3Wh per day we'll need 0.3Wh x 1.4 = 0.42Wh/day
> Now, today is a perfectly clear winter's day and the sun is about as high
> as it ever gets (at 51 degrees north) in the winter. A quick measurement
> with a 6cm x 4cm solar panel gives me 3.7 Volts across a 1K resistor - or
> about 14 milliWatts for a 24 cm2 area.
Why have you used a 1k resistor? Can you seriously get no more current
out of it?
Have you not used a low level of concentration - god knows the panel
needs it at this time of year.
> On the outrageously optimistic assumption that during the winter, you'll
> average ONE HOUR of charging at this rate per DAY,
I dont see any basis to assume the rest of the day will deliver zero.
> you'll need about 700
> times the surface area of solar panels that I used, i.e. 17,500 cm2.
> That's 1.75 square metres of panel to provide enough charge to keep 1 LED
> lit for 8 hours.
well, by now of course this is miles out.
> £360.
> £500
if you make up some basic concentration and see what current you can
get out of it we can recalc what's needed and add a margin.
NT
PS if the OP has a tree anywhere nearby we could go with a power
source that gives more output at much less cost.
Adrian
Thanks for all the comments so far.....
fwiw, I _do_ have trees nearby - and I'm intrigued to see what you were
thinking of doing with them <g>
Adrian
pete
I used a 1k resistor, as the load (i.e. 1K) should be the same as the
internal resistance of the panel (in this example, 800 Ohms) to transfer
most power into the load. In practice, the load used by the OP will be different,
however the power per square centimetre will be the same - presuming he
uses the same solar panel technology.
> Have you not used a low level of concentration - god knows the panel
> needs it at this time of year.
>
What is this "concentration" thing?
>
>> On the outrageously optimistic assumption that during the winter, you'll
>> average ONE HOUR of charging at this rate per DAY,
>
> I dont see any basis to assume the rest of the day will deliver zero.
True, however the output drops _very_ quickly when the sun goes in. Also
the position of the panel will (probably) be fixed, whereas for maximum
output it should rotate to follow the sun, otherwise its output will depend
on cos(angle) between the panel and the sun. When the voltage from the
solar panel drops below the battery voltage, it won't charge the cells
even though it's still capable of supplying power.
Jules
> PIR doesn't work in cold weather
I think the ambient temperature only changes the field of view, doesn't it
- they don't just stop working altogether. We've had many a cold evening
here recently where it's hit -30C (I'm a brit living in the wilds of
Minnesota these days) and the PIR sensor on our porch security light has
been just fine.
cheers
Jules
The Medway Handyman
> HI Folks
>
> meow...@care2.com wrote:
>>
>> PS if the OP has a tree anywhere nearby we could go with a power
>> source that gives more output at much less cost.
>
> Thanks for all the comments so far.....
>
> fwiw, I _do_ have trees nearby - and I'm intrigued to see what you
> were thinking of doing with them <g>
http://www.treehugger.com/files/2006/03/the_new_power_p_1.php ???
I'm intreegued as well :-)
--
Dave - The Medway Handyman
www.medwayhandyman.co.uk
Jules
>> PS if the OP has a tree anywhere nearby we could go with a power
>> source that gives more output at much less cost.
>
> Thanks for all the comments so far.....
>
> fwiw, I _do_ have trees nearby - and I'm intrigued to see what you were
> thinking of doing with them <g>
Hmm, the gadget that ET built to phone home was powered by a tree branch,
wasn't it...
Aha: tree branch -> dynamo -> light bulb -> solar panel -> solar lighting? :-)
J. (in an inefficient mood today)
meow...@care2.com
He's close... tree movement will never drive a dynamo though. You need
a mini gen that will produce useful power at under 100rpm, ie a
stepper motor from a 5.25" floppy drive or a printer.
Attach plastic string to tree 3/4 way up.
String comes down at 45 degrees and is looped once over motor shaft.
End of string has a weight on, needs to be sufficient to drive the
motor as the tree comes back.
Now, the wind blows the tree, the tree sways, and the stepper produces
pulses of relatively high current low voltage output. Pick a stepper
that's not stiff, many of the printer ones are very stiff.
Parts cost: a bit of string and a few diodes to rectify the output
Advantage: no cost, more output in winter than summer, and with nylon.
fishing line its almost invisible.
NT
Richard Russell
> The OP says he'll use high-intensity LED. Let's say that's a 1 Watt type
He also said "mostly for decoration". A 1 watt high-intensity LED
would be far too bright for that application, IMHO. My assumption is
that what he really meant was 'high efficiency', not 'high intensity'.
I've made basically what he described, except that rather than being
for decoration they are to show where the pillars are at night (no
street lighting in the vicinity). I bought, very cheaply, a couple of
'solar powered shed lights' similar to the ones linked to in an
earlier post. They're designed to give out a reasonable amount of
illumination for a short period, so I modified them to give out much
less light for a much longer period (five white LEDs at about 1mA
each, I think). I also converted them to turn on automatically at
night and off in the day (don't ask for the circuit; it relies on
germanium transistors I happened to have in the junk box!).
They're working well at the moment. In the depths of winter the solar
panels don't provide enough charge to keep them lit all night, but for
most of the year they do.
Richard.
http://www.rtrussell.co.uk/
To reply by email change 'news' to my forename.
meow...@care2.com
Ah. True for an ohmic source, but a solar panel is a very different
animal.
> In practice, the load used by the OP will be different,
> however the power per square centimetre will be the same - presuming he
> uses the same solar panel technology.
>
> > Have you not used a low level of concentration - god knows the panel
> > needs it at this time of year.
> >
>
> What is this "concentration" thing?
1 sun's fine in summer, but in winter concentrating the light hitting
the panel makes a major difference. A _very_ shallow cone that doesnt
block skylight can add some diffuse skylight, or a reflector can add
more direct sunlight when available. Remove the reflectors when the
sun gets hot.
> >> On the outrageously optimistic assumption that during the winter, you'll
> >> average ONE HOUR of charging at this rate per DAY,
> >
> > I dont see any basis to assume the rest of the day will deliver zero.
>
> True, however the output drops _very_ quickly when the sun goes in.
The sun's up for more than 1 hour round here - though it can feel that
way some days!
> Also
> the position of the panel will (probably) be fixed, whereas for maximum
> output it should rotate to follow the sun, otherwise its output will depend
> on cos(angle) between the panel and the sun. When the voltage from the
> solar panel drops below the battery voltage, it won't charge the cells
> even though it's still capable of supplying power.
Well, that depends on your charge controller. For such tiny powers I
doubt its worth using a charge controller, in which case yes, as you
say. Since this is a real issue in winter, you could maybe pick a
battery with a bit lower voltage than usual for the panel, eg 9v
battery on a 12v panel. That would give a little more dull day
tolerance. Battery capacity will be the main defence against dull days
though.
NT
Jules
> He's close... tree movement will never drive a dynamo though. You need
> a mini gen that will produce useful power at under 100rpm, ie a
> stepper motor from a 5.25" floppy drive or a printer.
The power source seems analogous to a tidal plant - strong, but
intermittant, slow and variable over a short range of movement. Can't help
thinking that there must be inherent inefficencies in involving the tree
though, and there must be far better ways of capturing the wind energy
that's moving the tree in the first place...
meow...@care2.com
In terms of energy efficiency it makes no attempt to be efficient -
but thats not the issue. Its the classic mistake of alt energy types
to concentrate on energy efficiency when the real deal is actually
financial efficiency.
The treegen has zero visibility, unlike all other wind collectors. It
uses almost zero materials, needs no support structure, there are
masses of natural collectors already in place, and it costs a few
pence. How can you beat that?
Oh, one last plus point. Due to the weight on string mechanism its
possible to connect a whole handful of trees up to one generator,
which incidenitally will then run more or less continuously.
NT
Adam Aglionby
Naturally growing windmill , like it a lot.
Adam
Adam Aglionby
>
> Another of those projects that's been on the back-burner for a while is
> devising 'something' to finish off the stone-built gateposts at the
> entrance to our place.
>
> Suddenly - bright idea <g> - literally !
>
> Considering making a couple of 'lanterns' with stained glass - powered
> by solar-recharged high intensity leds (it's a long way to run a mains
> cable down to the gates from the house).
>
> Mostly for decoration (and for a bit of fun!) - not expecting
> quartz-halogen-style illumination !
>
> So - any recommendations for solar lighting kit that people have
> actually used and found to be effective. I can see that prices range
> from the ridiculously cheap up to 20 quid or so for something that's
> probably a bit more useful like this from CPC
>
>
> I'm guessing that the cheapest devices are going to have very
> short-lived batteries in them... what's a sensible price-point for a
> decent solar lighting kit ??
>
> Thanks
> Adrian
For the naysayers who say solar power is only good on the Equator ,
dont get much more north in the UK than northern tip of the Shetland
Isles or more mission critical than a lighthouse , Northern Lighthouse
Board have 121 solar powered lighthouses:
http://www.nlb.org.uk/ourlights/solarisation.htm
Smaller ones LED, bigger ones use 35W metal halide lamp not unrelated
to car headlight lamp. Very big solar arrays and batteries though.
Type of solar panel make a difference as well, poly crystalline
cheapest but only really works well under direct Sun, mono crystalline
and amorphous will charge in cloudy conditions but cost more.
1W LED is fine if you want to illuminate the gates not just the house
number, 1W LED run at less than 1W, 350mA, gets very efficient.
If it dosent need to be white, green LED is the most efficient
colour , have an old Maplin LED solar light that dosent receive direct
sun for 8 months of the year, fitted with 3 off 5mm LEDs was lit for
couple of hours over Christmas day evening.
Adam
dennis@home
"Adam Aglionby" <ledl...@gmail.com> wrote in message
news:9be279a9-b59c-4828...@x16g2000prn.googlegroups.com...
Which ius a killer as far as being green goes.
It is a low maintenance reliable energy source they put in, not a green
solution as doing the maths will demonstrate.
If the OP is going to use batteries and LEDs then as they run for ages from
a couple of nicads I would do away with the charging bit and just charge
them in the house from a mains charger.. you know it makes sense.
Adam Aglionby
> "Adam Aglionby" <ledli...@gmail.com> wrote in message
Very true, embodied energy is probably quite lot higher than a 3
cylinder Lister, but a demonstration of the ability of PV arrays if
you have the budget.
> If the OP is going to use batteries and LEDs then as they run for ages from
> a couple of nicads I would do away with the charging bit and just charge
> them in the house from a mains charger.. you know it makes sense.
Run a 24V line in reasonably heavy 2 core, speaker cable is good,
then tap off for path lights and gatepost lights as required. LED with
appropriate drivers or resistors at each point, 24V usually means that
V drop at currents involved is negligible up to few `00metres. Add
dusk and PIR sensors to taste.
Adam
meow...@care2.com
I wondered about that, burying it just 4" deep using only a blade to
push it under the grass, no other protection. But how long would it
last? FWIW only one core needs to stay serviceable, the ground can be
used as a return if necessary.
NT
Jules
>> If the OP is going to use batteries and LEDs then as they run for ages from
>> a couple of nicads I would do away with the charging bit and just charge
>> them in the house from a mains charger.. you know it makes sense.
>
> Run a 24V line in reasonably heavy 2 core, speaker cable is good,
> then tap off for path lights and gatepost lights as required. LED with
> appropriate drivers or resistors at each point, 24V usually means that
> V drop at currents involved is negligible up to few `00metres. Add
> dusk and PIR sensors to taste.
I'd wondered before about running 12VDC everywhere - I've got all sorts of
stuff I can usefully run off 12V (both lighting and equipment), and in
theory it lends itself to easy battery supplementation using a bank of car
batteries, rather than relying on the 'green' source being available 24x7.
24V might actually be better and still have handy "off the shelf" charging
properties.
but,
a) I'm not sure how car batteries would fare for a moderate, constant load
(given that car use is generally a short, high-current draw and then a
charge cycle),
b) The transmission losses involved might just be too great for a
low-voltage DC system to really be viable.
(obviously car/truck batteries would need to be outdoors, but we've got a
spare shed tht's got some useful ventilation, so that'd do I think)
cheers
Jules
meow...@care2.com
I think all the points you raise are dealt ith fairly well on the
uk.d-i-y wiki. This would be a good place to look:
http://www.wiki.diyfaq.org.uk/index.php?title=Category:Low_Voltage
articles:
low voltage wiring
lead acid battery
cables
backup power
I'd also suggest one other possibility. If you'll run the 12v system
off mains normally, then an iron carbon battery might be a good option
for you.
Btw theres no need to put lead acids outside.
NT
Jules
> I think all the points you raise are dealt ith fairly well on the
> uk.d-i-y wiki. This would be a good place to look:
> http://www.wiki.diyfaq.org.uk/index.php?title=Category:Low_Voltage
Heck, ta - I shall have a good browse through that.
> I'd also suggest one other possibility. If you'll run the 12v system
> off mains normally, then an iron carbon battery might be a good option
> for you.
Not sure what I'll do as power input yet; solar's obviously a bit
unlikely (it doesn't make much sense to go solar -> electricity -> motor
-> alternator -> batteries -> electricity ;)
There's some scope for a wind turbine* here, and I'm on the look-out for a
diesel genny too (our water's from a private drilled well, so of course
the pump doesn't work if the power goes out!)
* I don't really like the things, and certainly wouldn't buy a commercial
one, but I think I can homebrew one and can get about 50' of height if I
put it on the barn roof, so that might be just enough to do something
vaguely useful.
Can't move for trees around here either, but I'm not sure if using them to
raise steam and generate power that way is particularly sensible (although
the wood's rather good for house heat!)
> Btw theres no need to put lead acids outside.
Hmm, I thought car batteries were prone to venting (potentially) nasty
stuff - sealed lead-acids are another matter, of course.
cheers
Jules
Adam Aglionby
wrote:
> On Mon, 05 Jan 2009 08:16:43 -0800, Adam Aglionby wrote:
> >> If the OP is going to use batteries and LEDs then as they run for ages from
> >> a couple of nicads I would do away with the charging bit and just charge
> >> them in the house from a mains charger.. you know it makes sense.
>
> > Run a 24V line in reasonably heavy 2 core, speaker cable is good,
> > then tap off for path lights and gatepost lights as required. LED with
> > appropriate drivers or resistors at each point, 24V usually means that
> > V drop at currents involved is negligible up to few `00metres. Add
> > dusk and PIR sensors to taste.
>
> I'd wondered before about running 12VDC everywhere - I've got all sorts of
> stuff I can usefully run off 12V (both lighting and equipment), and in
> theory it lends itself to easy battery supplementation using a bank of car
> batteries, rather than relying on the 'green' source being available 24x7.
>
> 24V might actually be better and still have handy "off the shelf" charging
> properties.
>
> but,
>
> a) I'm not sure how car batteries would fare for a moderate, constant load
> (given that car use is generally a short, high-current draw and then a
> charge cycle),
Probably less than ideal, deep cycle batteries are always a better
bet and not ludicrously more expensive.
Traction batteries on other hand....
>
> b) The transmission losses involved might just be too great for a
> low-voltage DC system to really be viable.
24V is popular for that very reason, half the copper of 12V for a
given load or double the load. Vehicle makers were very keen on
changing everything over at one point.
For LED lighting makes wiring very simple with adequate headroom for
voltage drop.
PVC insulated cable tends to survive the outdoors fine, especially
buried out of the Sun , no UV, containment not really neccessary
apart from perhaps mechanical protection in some areas.
>
> (obviously car/truck batteries would need to be outdoors, but we've got a
> spare shed tht's got some useful ventilation, so that'd do I think)
Wouldn`t neccessarily need to be outdoors, lot of public buildings
have cabinets full of the things somewhere for emergency lighting.
Adam
> cheers
>
> Jules
Jules
>> a) I'm not sure how car batteries would fare for a moderate, constant load
>> (given that car use is generally a short, high-current draw and then a
>> charge cycle),
>
> Probably less than ideal, deep cycle batteries are always a better
> bet and not ludicrously more expensive. Traction batteries on other hand....
Yeah, I've not looked into cost yet. A quick google seems to indicate
somewhere in the $90-$140 range for car batteries, which is probably about
60-100 quid or so. That's probably about what I remember them being in
England, too.
>> b) The transmission losses involved might just be too great for a
>> low-voltage DC system to really be viable.
>
> 24V is popular for that very reason, half the copper of 12V for a given
> load or double the load. Vehicle makers were very keen on changing
> everything over at one point.
I think I remember when my dad's old Beetle had 6V electrics...
But yeah, I'd be as happy dealing with 24V as 12V I think.
> PVC insulated cable tends to survive the outdoors fine, especially
> buried out of the Sun , no UV, containment not really neccessary apart
> from perhaps mechanical protection in some areas.
Well out here in my area of USVille there's no building code (no building
regs or planning permission) but there is an electrical code, and I
know that specifies conduit for outdoor wiring. Of course they assume
that's at domestic AC rates, not LV-DC, but I don't think they make the
distinction. I'll have the check though, as it's possible that the
rules only apply for things directly connected to the house fusebox -
maybe if it's downstream of a transformer or off-grid altogether (e.g.
solar) then I can do what I like.
>> (obviously car/truck batteries would need to be outdoors, but we've got
>> a spare shed tht's got some useful ventilation, so that'd do I think)
>
> Wouldn`t neccessarily need to be outdoors, lot of public buildings have
> cabinets full of the things somewhere for emergency lighting.
>
> http://www.batteryfaq.org/
Hmm, I've seen sealed ones in telcos before, but haven't ever had a
change to see a battery-noly emergency setup (we had a diesel genset at
one site, but of course that just needed a single truck battery for
starting purposes, rather than a big bank).
That site still seems to say (I've only had a quick flick through so
far) that ventilation's vital when charging car batteries due to the gases
given off. Of course "how much is enough" is the vital question... maybe
it's only an issue if you have the battery in a tiny box and go stick your
head right in there :-)
cheers
Jules
meow...@care2.com
> On Mon, 05 Jan 2009 19:56:28 -0800, Adam Aglionby wrote:
> >> a) I'm not sure how car batteries would fare for a moderate, constant load
> >> (given that car use is generally a short, high-current draw and then a
> >> charge cycle),
> >
> > Probably less than ideal, deep cycle batteries are always a better
> > bet and not ludicrously more expensive. Traction batteries on other hand....
>
> Yeah, I've not looked into cost yet. A quick google seems to indicate
> somewhere in the $90-$140 range for car batteries, which is probably about
> 60-100 quid or so. That's probably about what I remember them being in
> England, too.
30Ah used car batts are a tenner here, though not very good for
offgrid use. For deep cycle types you can always make your own.
> >> b) The transmission losses involved might just be too great for a
> >> low-voltage DC system to really be viable.
> >
> > 24V is popular for that very reason, half the copper of 12V for a given
> > load or double the load. Vehicle makers were very keen on changing
> > everything over at one point.
>
> I think I remember when my dad's old Beetle had 6V electrics...
> But yeah, I'd be as happy dealing with 24V as 12V I think.
Dont overlook the 3 wire system. May do a wiki article on it some time
Its only vital if enough hydrogen is given off to potentially reach
explosive levels, and thats rarely the case.
NT
Adam Aglionby
wrote:
> On Mon, 05 Jan 2009 19:56:28 -0800, Adam Aglionby wrote:
> >> a) I'm not sure how car batteries would fare for a moderate, constant load
> >> (given that car use is generally a short, high-current draw and then a
> >> charge cycle),
>
> > Probably less than ideal, deep cycle batteries are always a better
> > bet and not ludicrously more expensive. Traction batteries on other hand....
>
> Yeah, I've not looked into cost yet. A quick google seems to indicate
> somewhere in the $90-$140 range for car batteries, which is probably about
> 60-100 quid or so. That's probably about what I remember them being in
> England, too.
Shopping around on batteries always pays off, like lamps can see quite
some cost spread even on same brand, try looking for "leisure
batteries"
> >> b) The transmission losses involved might just be too great for a
> >> low-voltage DC system to really be viable.
>
> > 24V is popular for that very reason, half the copper of 12V for a given
> > load or double the load. Vehicle makers were very keen on changing
> > everything over at one point.
>
> I think I remember when my dad's old Beetle had 6V electrics...
> But yeah, I'd be as happy dealing with 24V as 12V I think.
6V electrics earned Joe Lucas , maker of 6V British bike electrics,
the well desrved title as The Prince of Darkness.
> > PVC insulated cable tends to survive the outdoors fine, especially
> > buried out of the Sun , no UV, containment not really neccessary apart
> > from perhaps mechanical protection in some areas.
>
> Well out here in my area of USVille there's no building code (no building
> regs or planning permission) but there is an electrical code, and I
> know that specifies conduit for outdoor wiring. Of course they assume
> that's at domestic AC rates, not LV-DC, but I don't think they make the
> distinction. I'll have the check though, as it's possible that the
> rules only apply for things directly connected to the house fusebox -
> maybe if it's downstream of a transformer or off-grid altogether (e.g.
> solar) then I can do what I like.
Convoluted and variable are US Electrical codes , but would guess they
mostly use a definition of Safety Extra Low Voltage, in Euroland below
50V, that should mean you can do pretty much what you like at 24V.
Think Malibu lights and IDC connectors;
Just remember that though voltage is low , available current can be
quite high and put fuses in all the sensible places.
> >> (obviously car/truck batteries would need to be outdoors, but we've got
> >> a spare shed tht's got some useful ventilation, so that'd do I think)
>
> > Wouldn`t neccessarily need to be outdoors, lot of public buildings have
> > cabinets full of the things somewhere for emergency lighting.
>
> >http://www.batteryfaq.org/
>
> Hmm, I've seen sealed ones in telcos before, but haven't ever had a
> change to see a battery-noly emergency setup (we had a diesel genset at
> one site, but of course that just needed a single truck battery for
> starting purposes, rather than a big bank).
>
> That site still seems to say (I've only had a quick flick through so
> far) that ventilation's vital when charging car batteries due to the gases
> given off. Of course "how much is enough" is the vital question... maybe
> it's only an issue if you have the battery in a tiny box and go stick your
> head right in there :-)
Its hydrogen build up thats the risk , but batteries that need to
breathe have vent pipes that can be led to fresh air and regularly
inspected.
Need a bit of care charging and maintaining multiple batteries,
available current is , er, quite a lot, dead short will have several
`000 amps run through it.
It isn`t rocket science but it is worth respecting having several
litres of sulphuric acid sloshing about and enough current to vaporise
copper tube...
Cheers
Adam
>
> cheers
>
> Jules
Jules
> Shopping around on batteries always pays off, like lamps can see quite
> some cost spread even on same brand, try looking for "leisure
> batteries"
Will do...
>> I think I remember when my dad's old Beetle had 6V electrics...
>> But yeah, I'd be as happy dealing with 24V as 12V I think.
>
> 6V electrics earned Joe Lucas , maker of 6V British bike electrics,
> the well desrved title as The Prince of Darkness.
Same Lucus of the car world? I've owned numerous Triumphs over the years
with Lucas bits and they certainly weren't premium quality :-)
> Convoluted and variable are US Electrical codes , but would guess they
> mostly use a definition of Safety Extra Low Voltage, in Euroland below
> 50V, that should mean you can do pretty much what you like at 24V.
>
> Think Malibu lights and IDC connectors
Yeah, I wasn't sure if a commercial system goes through extra testing
which somehow certifies it whereas a DIY approach wouldn't - but I
suppose that makes life messy, so it'd be far easier to declare anything
under a given voltage as free from inspection.
> Just remember that though voltage is low , available current can be
> quite high and put fuses in all the sensible places.
Absolutely :-) I've seen the results of dead-shorts and overcharging in
car batteries and it ain't pretty...
cheers
J.
Andy Champ
>
> Its hydrogen build up thats the risk , but batteries that need to
> breathe have vent pipes that can be led to fresh air and regularly
> inspected.
>
shouldn't need an awful lot of ventilation to get rid of it though, it
isn't going to do the butane trick of collecting in a pool in the corner.
Of course, if it is bubbling away and making gas you'll need to keep an
eye on the fluid level and top up with distilled water as necessary.
Andy
unop...@mail.com
>
> I'd wondered before about running 12VDC everywhere - I've got all sorts of
> stuff I can usefully run off 12V (both lighting and equipment), and in
> theory it lends itself to easy battery supplementation using a bank of car
> batteries, rather than relying on the 'green' source being available 24x7.
>
Some people have used old Nickel-Iron (NiFe) batteries. They may not
be commercially available now, but they seem to have a reputation of
surviving abuse quite well. I have not used them myself, but filed
their existence away as something to investigate when time allows.
Cheers,
Sid