Fix 2 problems with 1 project

[awol]

Problems-
1 - I have a 36v 20ah battery doing nothing
2 - I have a dark path down the side of my house where I can't really wire electric to.

A possible solution I can think of is use my 36v battery with some sort of dc-dc step down to 12v (powerful enough?) connected to 2 - 12v pir sensors (one pointing one way and one the other) like this:-

https://www.aliexpress.com/item/Vovotrade-DC-12V-IR-Infrared-PIR-Motion-Automatic-Sensor-Switch-For-LED-LightLamp/32626328170.html

which could power 2,3 or 4 12v led lights.
Like these:-
https://www.aliexpress.com/item/Excellent-Feedback-3W-Under-Groud-Light-12V-Garden-Light-IP65-Aluminum-Led-Lawn-light-With-Spike/1864456826.html

Sound a good idea?
Or would a couple of these work on a dc-dc stepdown?
http://www.ebay.co.uk/itm/12V-10W-PIR-LED-Flood-light-White-Warm-Floodlight-Motion-Sensor-85V-265V-LW41-/371576190163?var=&hash=item5683aab4d3:m:mKn5PJ4PQ7u8sEk0n5-Ip0g

OR any better ideas?
Would appreciate any help with the power ratings or number of lights etc and the wiring up.

 

[Tabs]

Just fit a light with a dusk til dawn sensor and either wire it in properly or just use an extension cable,jobs a good one.

 

[Deleted member 4366]

I've got a feeling that the dc/dc converters take power when they're connected, so will drain your battery.

You can make 36v lights out of the cheapo 1.2v (?) Ultrabright LEDs with a 400 Ohm resisitor in series. Multiply that for whatever brightness you need, i.e. one LED and one resistor times however many you need.

Alternatively, because the spec of LEDs is often unclear, get a 1k preset, turn it to max resistance and put it in series with your ultrabright LED at 36v, then turn down the resistance until it's nice and bright. Measure the resistance and get some equivalent fixed resistors.

Down the page, these guys mention running their PIR at 36v:

http://www.reuk.co.uk/wordpress/electronics/pir-sensors/

There's 36v PIRs on Amazon and Ebay, but I don't know how much current they draw. They might flatten yor battery.

 

[Danidl]

Problems-
1 - I have a 36v 20ah battery doing nothing
2 - I have a dark path down the side of my house where I can't really wire electric to.

A possible solution I can think of is use my 36v battery with some sort of dc-dc step down to 12v (powerful enough?) connected to 2 - 12v pir sensors (one pointing one way and one the other) like this:-

https://www.aliexpress.com/item/Vovotrade-DC-12V-IR-Infrared-PIR-Motion-Automatic-Sensor-Switch-For-LED-LightLamp/32626328170.html

which could power 2,3 or 4 12v led lights.
Like these:-
https://www.aliexpress.com/item/Excellent-Feedback-3W-Under-Groud-Light-12V-Garden-Light-IP65-Aluminum-Led-Lawn-light-With-Spike/1864456826.html

Sound a good idea?
Or would a couple of these work on a dc-dc stepdown?
http://www.ebay.co.uk/itm/12V-10W-PIR-LED-Flood-light-White-Warm-Floodlight-Motion-Sensor-85V-265V-LW41-/371576190163?var=&hash=item5683aab4d3:m:mKn5PJ4PQ7u8sEk0n5-Ip0g

OR any better ideas?
Would appreciate any help with the power ratings or number of lights etc and the wiring up.

The better idea is not to start from there.
1 Sell the battery to someone who needs it and replace it with 12v battery this will be a better match to those outside lamps you were considering.
2 split up the battery pack into a 60 amp hr 12v arrangement
All other arrangements waste more power in voltage reduction.
3 wire up the three 12v lamps in series so that the current from the first goes into the second etc. These lamps will have colour coded wires so that makes it easier to wire in series.
4 the PIRs absorb 15mA continuous, so with two of them your consumption is 30mA @whatever voltage thy are being run at. .. why not just use two switches at the end of the corridor

 

[awol]

The better idea is not to start from there.
1 Sell the battery to someone who needs it and replace it with 12v battery this will be a better match to those outside lamps you were considering.
2 split up the battery pack into a 60 amp hr 12v arrangement
All other arrangements waste more power in voltage reduction.
3 wire up the three 12v lamps in series so that the current from the first goes into the second etc. These lamps will have colour coded wires so that makes it easier to wire in series.
4 the PIRs absorb 15mA continuous, so with two of them your consumption is 30mA @whatever voltage thy are being run at. .. why not just use two switches at the end of the corridor

I was about to purchase all the gear I thought was correct with the help given but got thinking about what Tabs said above about a dusk til dawn sensor which made me realize I didn't want it activating during the day, so am now considering a plan-B which may be a 36v bike light and switch for the shed.
I like your 60a 12v idea though so may pursue that.

 

[soundwave]

a 100w led is 36v
http://www.ebay.co.uk/itm/100W-High-Power-LED-Beads-COB-Led-Chips-For-Floodlight-Lamp-Led-Spotlight-White-/302036076930?var=&hash=item4652c0c982:m:myb-UeR3K0rmKYJeog3oFVQ

you will need to limit the forward currant to 3000ma tho.

pmsl

 

[Danidl]

I've got a feeling that the dc/dc converters take power when they're connected, so will drain your battery.

You can make 36v lights out of the cheapo 1.2v (?) Ultrabright LEDs with a 400 Ohm resisitor in series. Multiply that for whatever brightness you need, i.e. one LED and one resistor times however many you need.

Alternatively, because the spec of LEDs is often unclear, get a 1k preset, turn it to max resistance and put it in series with your ultrabright LED at 36v, then turn down the resistance until it's nice and bright. Measure the resistance and get some equivalent fixed resistors.

Down the page, these guys mention running their PIR at 36v:

http://www.reuk.co.uk/wordpress/electronics/pir-sensors/

There's 36v PIRs on Amazon and Ebay, but I don't know how much current they draw. They might flatten yor battery.

Hi d8veh you probably knew it anyway but , the forward voltage drop on LEDs is only 1.8 V for red going up to nearly 3v for blue or 3.4v for UV types. The so called white LEDs are actually UV LEDs with phosphors, similar to those in flouresent tubes embedded in the plastic. The forward voltage drop must equal the emitted photon energy in eV.