Free trickle charge from the phone co ?

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Tubetec

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Nov 18, 2015
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A buddy of mine bought a small house in the middle of nowhere , mains power was disconnected at some point , he's planning to live without the creature comforts or standing charges associated with mains supply . There is however a phone line remaining connected to the exchange , most likely supplied with 50 or so volts dc . He has a bank of 12 volts gel cells which he needs to dismantle and take to a friends place to charge every once in a while ,its just to run led lights and a small invertor for low wattage 240V appliances like mobile phone charge etc
From a recent previous discussion about telephone mics I found out a single old style carbon mouthpiece could draw upto 100ma at 50 volts , in the event of two recievers off the hook thats 200ma potentially . A trickle charge of 200ma at 50 volts across four lead acid 12volt batteries would do nicely to keep things topped up .

When I mentioned this potential source of power his eyes lit up , lets set any possible legal implications aside and consider if this is feasible , would a simple resistance in series limit the current to a reasonable amount and still keep the batteries topped upto 12.8 or so volts? Of course the man in the telephone exchange may notice the voltage drop if he comes along with his meter to the local connection box ,but more than likely he'll think its bad insulation due to moisture ingress into the cableing . Inevitably the phone supply is made to withstand an almost dead short although the resistors in his junction box might be running a bit hot ,ahahahaha

Tomorrow I may perform some load tests on my own redundant land line just to see whats possible current wise ,of course out in the back arse of nowhere you've potentially miles of cable so things might well be different .
 
Yeah course , youd need to make sure the batteries are fully float charged and allowed to settle to 12.8v before hooking up and include a resistor so your not drawing power from the line when the batteries are in use . At the moment the guy runs an invertor off the cells in parralel to power 240v leds , instead you could connect the cells in series and have several 12 volts supplies to volt automotive led lamps and ditch the invertor .
 
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0.1 amps at 50 volts over 24 hours , thats around 125 watts , times 365 , 45kw per year , half of that probably ends up wasted as heat in the charge process , still if you could light a modest dwelling and run a few low powered devices , you still save on the standing charge ,4 or 5 hundred euros per year with mains supply before you consume a watt of power . Of course no reason not to suplement things with photovoltaic or mini windturbine too .
 
a petrol powered chainsaw is still going to be required to chop wood for the stove to heat the place and boil water , but I can cut a weeks timber for 75 cents with my Stihl , then I need to split it with an axe old style , we have a very temperate climate here in the Emerald isle though . Food for though anyway .....
 
I would get a solar panel battery charge controller. Some can accept up to 100VDC input and autodetect a 12V or 24V battery setup. I got a good one for two big panels and a cheap one for a single 180W panel. The cheap one was $20.
 
There is no free lunch... here for POTS (plain old telephone service) the phone company detects if a phone is sitting off the hook for a while and first sends out a loud alarm signal, then disconnects.

My land line is fed from a DSL modem that plugs into mains power so I am not sure if off hook voltage is still present on the phone line..

Good luck...

JR
 
...12 volts supplies to volt automotive led lamps and ditch the invertor .
We have outdoor lighting systems here that run off 12v too. I guess the bulbs themselves house the drivers to convert from AC 12v but, seems they would work without the drivers if fed dc..maybe flickery if not regulated?
Come to think of it, I wonder what the AC compatible residential led bulbs are doing inside their housings . What voltage are the leds ultimately running at.?
 
LEDs operate at low single digit DC. Low power lighting fed from AC could wire the LEDs anti-parallel so they alternately conduct during positive and negative swings.

JR
 
Here when you lift the reciever you hear a steady dial tone , if you dont dial a number after a little time it goes to beep beep beep , same as engaged tone . With the phone on the hook I measure 56v dc on my line , when I lift the reciever it drops to around 12v . When I put an 820 ohm resistor across the line it drops to 21 volts , so around 25ma flows , not much use really .
 
There's always some current detection in the phone xchange, as John already pointed out. Sometimes there's a fuse that doesn't get reset automatically if there's no number attached to the line.
 
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