12v lighting for my house powered by my van

[12vshocker]

hello all is this possible????

I drive a van around all day, I want to use the van to charge up a 110ah Agm battery, I then want to use this battery to power up a 12v led lighting circuit in my house. I also want to use the 240v supply as a back up to the same lighting circuit, with some sort of switch over device for when the agm battery voltage gets low.

Essentially I will have 2 batteries in rotation, charging one all day why the other is being used

Any idea if this set up is used any where and how well it works, or where to find the calculation to see how long a fully charged 110ah battery would last

I don't want to use a inverter, just the transformers already build into the Selv lighting, and diodes to stop the 240v system back feeding into the 12v system.

Is this possible, (not too bothered about it being economical)

Let me know your thoughts and criticisms

 

[Deuce]

Why even bother.

It does seem like a lot of effort to swipe a few AH each day from a van..

 

[davesparks]

I would assume the led circuit in question only requires 12v at source, why would it be a problem if the power comes from a 12v battery or the typical psu?

It will require 12V at the lamp rather than at the source. Led psus are normally located very close to the lamp, here the battery will be relatively far away.
Percentage volt drop is far worse at 12V than it is at 240V, dropping 2 volts in a 240V circuit is no problem, but losing it from a 12V circuit could stop a 12V Led from working.

 

[Deuce]

It will require 12V at the lamp rather than at the source. Led psus are normally located very close to the lamp, here the battery will be relatively far away.
Percentage volt drop is far worse at 12V than it is at 240V, dropping 2 volts in a 240V circuit is no problem, but losing it from a 12V circuit could stop a 12V Led from working.

I know... but why would the battery be further away than the mains>elv psu? The OP hasn't said it would need to be.

I may have missed something, feel free to point it out if so.

EDIT: Also I was once told most 12v leds will run down to about 9.5v anyway. We have run 3m ribbon from approx 10m, reading ~11v at the end of the run using 2.5mm.

 

[davesparks]

I know... but why would the battery be further away than the mains>elv psu? The OP hasn't said it would need to be.

I may have missed something, feel free to point it out if so.

EDIT: Also I was once told most 12v leds will run down to about 9.5v anyway. We have run 3m ribbon from approx 10m, reading ~11v at the end of the run using 2.5mm.

The battery would be much further away from the LED than the PSU would be because he is wanting to light the whole house from one battery, so for an average house you could be looking at maybe 40/50 metres of cable to some lights. Also the OP mentions SELV transformers at light fittings so this could be 50W MR16s rather than LED lamps.

My personal experience of volt drop in 12V circuits comes from fitting lights to landrovers where experience has shown that 4mm is necessary for even relatively short distances.

 

[Deuce]

The battery would be much further away from the LED than the PSU would be because he is wanting to light the whole house from one battery, so for an average house you could be looking at maybe 40/50 metres of cable to some lights. Also the OP mentions SELV transformers at light fittings so this could be 50W MR16s rather than LED lamps.

My personal experience of volt drop in 12V circuits comes from fitting lights to landrovers where experience has shown that 4mm is necessary for even relatively short distances.

But why do you assume the battery would be further away? He can't energise a circuit using a 12v battery that then feeds PSU's that have 240v on the primary. Surely the battery will go wherever the PSU(s) currently reside, whatever the actual arrangement/distance is.

I agree that in automotive voltage drop can be a killer, for various reasons. But most LED kit that is sold as 12v can run between 9-20v no issue at all. I'm not saying voltage drop doesn't occur, I'm simply saying it's often not an issue.

 

[12vshocker]

Ok so the plan is: to power the the lighting circuit using a car battery via a pcu, that connected the the a/c via timer circuit, fit a diode to the battery pos, so not to waste electricity recharging the battery with a/c power supply.

Is there a better way to click over to the ac power? I.e. Monitoring the battery status and some sort of automatic switch over once the voltage drops?

Also how do you calculate how long the battery would last, I know I'd need to find out the consumption of that circuit per day, and battery ratings etc but what would the formula look like?

And if I connected the neg post of the battery to the met bar would it tap into the unused neutral current (probably not the right word). Also I suspect something terrible would happens under fault conditions.

 

[12vshocker]

Sorry I meant UPS not PCU, stupid TLA's

 

[davesparks]

But why do you assume the battery would be further away? He can't energise a circuit using a 12v battery that then feeds PSU's that have 240v on the primary.

Because there is only one battery which he wants to feed the whole circuit from directly and he wants to install a diode to prevent the 240AC getting to the battery, he clearly hasn't got much of a clue.

From what I can understand of the OP this is exactly what he is intending to do, feed a whole lighting circuit at 12V directly from a battery.

 

[Deuce]

Because there is only one battery which he wants to feed the whole circuit from directly and he wants to install a diode to prevent the 240AC getting to the battery, he clearly hasn't got much of a clue.

From what I can understand of the OP this is exactly what he is intending to do, feed a whole lighting circuit at 12V directly from a battery.

I just... Can't believe that. He must surely mean the elv circuit on the secondary side of the PSU. not the entire lighting circuit the PSU is on..

 

[davesparks]

I just... Can't believe that. He must surely mean the elv circuit on the secondary side of the PSU. not the entire lighting circuit the PSU is on..

I may have misunderstood completely but what I got from the first post is that he wants a 12V lighting circuit, doesn't want to use an inverter, wants to keep the existing transformers/drivers in place and use a diode to prevent the 240V AC getting to the battery.

 

[Richard Williams]

I got a headache reading that lot

 

[DPG]

I bet the novelty of swapping batteries between house and van every day soon wears off.

 

[PJElectricalSW]

Just use a 12vDC to 230vAC inverter, no worries about any DC volt drop, LED gubbins and secondary lighting circuits. Use existing cabling with a switch over rotary switch to go from 'mains supply' or from the invertor supplied juice.

Economy 7 users do not know what they are sitting on...

 

[Deuce]

Just use a 12vDC to 230vAC inverter, no worries about any DC volt drop, LED gubbins and secondary lighting circuits. Use existing cabling with a switch over rotary switch to go from 'mains supply' or from the invertor supplied juice.

Economy 7 users do not know what they are sitting on...

So this is where we're at.. the op is gonna drive his 12v DC van to power an inverter to charge a 230ac battery to then power 230ac psu's to power 12v DC lights?

This has reached insanity level. I invite the op to post again and let us all know what the hell their motivation is! I can only assume it's stealing power... Which is fine, I don't care - on the basis that in this case stealing the power seems to be at least as much effort as earning it legitimately

 

[12vshocker]

To carify I will be using an inverter of some sort, but how do I get it to switch over automatically to mains supply if the voltage drops?