I have a dozen very nice solar lawn lights that I'd like to convert to
AC power. The conditions, both solar exposure and temperature here in
Wisconsin mean that these things run out of juice before the morning.
Sure seems like it shouldn't be rocket science to convert to AC power.

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Clarification of Question by juststeve-ga on 11 Oct 2006 02:40 PDT

Sry to not be clearer...no, all i want to retain the existing
LEDs....my only goal is that they have enough juice left in the
morning as winter encroaches. Not only are nights getting longer...in
Wisconsin they get ....ummm....cold. I have zero confidence in
batteries.

The lights are close enough to the house that it is reasonable to wire
them together and run a line from indoors. Even if a battery sits
inside providing the juice. But i'm betting the problem here would be
that i'd have to run a dedicated line from the to each individual
light. That case would kill any further attempt to repurpose these.

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Clarification of Question by juststeve-ga on 13 Oct 2006 08:53 PDT

Thankx inventorbob-ga....i'm inclined to go with 1). I haven't put a
voltage tester on a connector yet but given each light holds 2 AA
batteries, i'm dealing with 3 volts, yes?

The physical layout of the lights would be most natural to run as 4
different spokes of 3 lights each. Would I be ok to split the dc line
4 ways from the central point?

From the interior outlet to that center point is about 12"...then each
spoke is around 10".

Hello Steve

             You did not expired the question, so I will (after
reading the suggestions in the comments) summarize what is the (only
sensible) solution:

 You burry a cable connecting (in parallel) all lamps to a one spot, preferably
 inside the house or in a sheltered spot. At that spot they will be connected to
a 3 V DC power. 

 This is basicaly   inventorbob-ga's solution 1). I discourage
solution 2) since it is not a 'low voltage' solution. There are safety
and code problems with solution 2).

 The cable which can be burried is sold in an Home Depo and similar
stores (which carry automatic sprinklers). They can be used for 120V
and of course for any lover voltage. There are however some local
ordonances  (if I remember correctly, there is a  minimal depth (about
10") )

 Make and keep  drawing of the curcuit (for case of future digging ..)

 You can add a central recharchable battery  and a simple regulator
circuit which will charge it (from your power supply) only when
needed.

You can add such regularor to each local battery in circuit 
 circuit in From: inventorbob-ga on 11 Oct 2006 08:28 PDT  case 1)

With such regulator you can have several branches connected to your power supply
or central batery.
Regulators  prevent the local batteries from discharching by any other
path than to their local LED light (eliminating possible local loops).

Regulator can be just a diode (allowing the current to flow only one way) or
a slightly more complex circuit which will enable charging only when the
voltage of local battey drops to certan level.

 There are codes which cover outside wiring. Your 120V AC to 12V DC converter
and eventual central battery should be inside or conform.

http://experts.about.com/q/Electrical-Wiring-Home-1734/Low-voltage-landscape-lighting.htm

http://www.codebookcity.com/codearticles/nec/necarticle225.htm

http://www.eng-tips.com/viewthread.cfm?qid=70587&page=8


 I would let a local electrician or garden landscape contractor to install
it, since they know the local codes.

http://landcarenetwork.org/planetFile/pdfs/AE_LoVoLightingStudyGuide.pdf

 http://en.wikipedia.org/wiki/Voltage_regulator

Hedgie

Do I understand correctly:  you want to lay underground cable to the
lights and convert them to 120 volt ac wiring and screw light
fixtures?

LED lights consume much less electricity than incandescent of
fluorescent lamps.  That is why they are used on solar lawn lights. 
The other two types of lights will deplete the accumulators' dc power
much faster.  "Rocket science" isn't going to change that.
Supplementary solar panels might help, if the specifications for the
existing lamps indicate that rechargable cells will provide enough
power to let the lights "burn" all night  -  and the nights are
getting longer.

I think you could probably run them off an ac adaptor that has the proper voltage.

I think you would be much better off just buying a new set of
low-voltage wired garden lights. It would end up costing less, and
would be designed to resist the elements better than any
do-it-yourself modifications to your existing stand-alone,
solar-charged/DC-powered LED lights.

yes it would be possible, but as mentioned above, for the cost you are
better off getting purpose built mains powered lights. depending on
the design of the lights you MAY be able to fit more batteries in it
to add to the stored power but it isnt clear whether you are running
out cos you cant store enough (i.e. need more batteries) or that you
are running out because the batteries you have don't charge fully cos
of a fault with the panels or there not being enough daylight to
charge them before dusk.

HI Steve,
You have mentioned one serious problem, the effect of cold on the batteries.
There isn't much you can do about that.  You've got everything working
against you:  shorter days with weaker sunlight to charge;  longer
nights;  and the cold.

What about a voltage ac/dc converter in the house and a line to the
lamps, wired in series.  I seem to remember that low voltage dc
current gets used up by the resistance in long wiring (but may be
wrong), so you should looking into that as a potential problem.  If
so, maybe heavy duty speaker cable is the answer, or ac cable to the
nearest or to all the lamps and converters at the first one or at each
of them.
Maybe someone can tell you here.

Good luck, Myoarin

2 good ways:

1) Measure the voltage at the internal battery when fully charged. 
Find an AC/DC converter of similar voltage.  Wire up the AC/DC
converter on the DC side to where the battery plugs in.  If the lights
don't light up, then switch the polarity of your wires.  Wire all of
the other lights off of the same converter in parallel.

DC __+_________________
         |      |      |
         +batt  +batt  +batt
         -batt  -batt  -batt
DC __-___|______|______|


2) wire the AC directly.  This needs to be done more carfully, because
of the higher voltage.  You will wire up the LED's directly

Black Pwr___~~Resistor~~___(|>)___(|>)___(|>)___(|>)___(|>)___ White Ntrl

Resistor = (120 - (0.7 x number of LEDs))/0.014

Note: the LED's have a direction.  You can look inside the plastic and
see two metal plates. one is shaped like a T and one like an I.  Hook
the T of one LED to the I of the next.  If you hook a T to a T, they
will block each other.

___(T I)___(T I)___(T I)___(T I)___

As for your spokes,

just tap off of the + of your DC power supply to each light's +.
Tap off the - of the DC power to each light's -

As long as there is an electrical path from the DC power+ to the
light+ and DC power- to the light- then it should work.


_________________DC _+_____________________
|      |      |          |   |      |      |
+batt  +batt  +batt      |   +batt  +batt  +batt
-batt  -batt  -batt      |   -batt  -batt  -batt
|______|______|__DC _-__ / __|______|______|
                  |      \
                  |-batt+|
                  |      |
                  |-batt+|
                  |      |
                  |-batt+|