# current limiter for led lights

#### thatguy98

Joined Dec 15, 2020
13
hi,
i have 4 led lights designed to work in ac but i want to use them in a garage that doesn't have power.
The lights consist of just an led strip without any resistors, have a forward voltage of 60v and draw 300mA.
I thought of removing the ac/dv converter and just use a 60v battery to power them, connecting all of them in parallel.
The problem is that they don't have any protection, so i would like to use a current limiting circuit in series with each light. Any suggestions?

#### ronsimpson

Joined Oct 7, 2019
2,627
60V battery? Can you rewire the LEDs so the will work at 11 to 12 volts. Car battery?

#### crutschow

Joined Mar 14, 2008
31,570
The power supply may be constant current so you would have to add some limiting.
Do you have a DC power supply you can use to test their actual operating voltage at 300mA current?

What about using a 12V to AC inverter operating from a car battery?

#### thatguy98

Joined Dec 15, 2020
13
60V battery? Can you rewire the LEDs so the will work at 11 to 12 volts. Car battery?
unfortunately no, it's a pre made led strip

#### thatguy98

Joined Dec 15, 2020
13
The power supply may be constant current so you would have to add some limiting.
Do you have a DC power supply you can use to test their actual operating voltage at 300mA current?

What about using a 12V to AC inverter operating from a car battery?
i don't have any way of testing them other than plugging directly to ac at home.

i thout of using a 12v battery and a dc/ac converter but wouldn't that waist some of the battery power, resulting in less operating time?

#### crutschow

Joined Mar 14, 2008
31,570
i don't have any way of testing them other than plugging directly to ac at home.
Then we have no way to make a good recommendation about how to power them directly from DC.

Can you measure the DC voltage across them when they are operating?
i thout of using a 12v battery and a dc/ac converter but wouldn't that waist some of the battery power, resulting in less operating time?
Yes.
It's a trade-off been simplicity and battery life.
How long would you likely use the lights in a month?

#### Tonyr1084

Joined Sep 24, 2015
7,251
Can you give us a link to the LED strip? Model number? Any information so we can look the information up. Seems you might have a supply capable of 60V @ 300mA. Or take a picture(s) of what you have and post that please.

#### thatguy98

Joined Dec 15, 2020
13
Can you measure the DC voltage across them when they are operating?
When I measured the voltage across the led strip it gave me 110v, I think it's because the rectifier circuit is a cheap one.

How long would you likely use the lights in a month?
I intend to use the garage as a home gym, so I'd be using it 3/4 hours a day 6 days a week.

Can you give us a link to the LED strip? Model number? Any information so we can look the information up. Seems you might have a supply capable of 60V @ 300mA. Or take a picture(s) of what you have and post that please.
I couldn't find anything on the internet becous they're brandless lights.
I'll attach some pictures and the Amazon link I bought them from.

https://www.amazon.it/dp/B08NSKCX5F/ref=cm_sw_r_cp_apa_fabc_.UK2Fb9QDAJYB?_encoding=UTF8&psc=1

#### crutschow

Joined Mar 14, 2008
31,570
I intend to use the garage as a home gym, so I'd be using it 3/4 hours a day 6 days a week.
If it's 3 or 4 hours, that's a lot of time, which will require a large battery.
How often were you thinking you'd have to recharge the battery?

How about just running an extension cord from the house to the garage?

#### thatguy98

Joined Dec 15, 2020
13
If it's 3 or 4 hours, that's a lot of time, which will require a large battery.
How often were you thinking you'd have to recharge the battery?

How about just running an extension cord from the house to the garage?
Maybe 2/3 times a week. I know it's a long time but I thought a 15ah would last at least 2/3 days

The extension cord is not an option because the garage is detached from the house, and the only way to do it is to run it from the neighbors above the garage

#### RIKRIK

Joined Oct 11, 2019
146
Okay the calculations you need.
60v x 0.3ma = 18w
So say if you used a cc boost converter , lets just say it 100% efficient and I'm using a 12v battery.
18w÷12v= 1.5A being drawn from the battery. So 10hours of run time 15ah battery. But with losses less.

Let's do the same but with a 2 12v battery's @24v. As getting 60v of batteries is 5 batteries. Quite a hassle to charge.

18w÷24v = 0.75ma. So 20 hours of run time. 15ah battery.

#### crutschow

Joined Mar 14, 2008
31,570
Maybe 2/3 times a week. I know it's a long time but I thought a 15ah would last at least 2/3 days
A 15Ah, 12V battery stepped up to 60V, would last for about 5 hours (at 50% discharge recommended for good battery life).
If you used five 15Ah, 12V batteries to get 60V that would give about 25 hours.

But how will you charge those batteries?
The extension cord is not an option because the garage is detached from the house, and the only way to do it is to run it from the neighbors above the garage
You don't have a straight shot from your house to your garage?

#### thatguy98

Joined Dec 15, 2020
13
Okay the calculations you need.
60v x 0.3ma = 18w
So say if you used a cc boost converter , lets just say it 100% efficient and I'm using a 12v battery.
18w÷12v= 1.5A being drawn from the battery. So 10hours of run time 15ah battery. But with losses less.

Let's do the same but with a 2 12v battery's @24v. As getting 60v of batteries is 5 batteries. Quite a hassle to charge.

18w÷24v = 0.75ma. So 20 hours of run time. 15ah battery.
The problem is not runtime nor battery size. I need something to regulate the current so that the lights don't burn out after a few hours of use

#### thatguy98

Joined Dec 15, 2020
13
A 15Ah, 12V battery stepped up to 60V, would last for about 5 hours (at 50% discharge recommended for good battery life).
If you used five 15Ah, 12V batteries to get 60V that would give about 25 hours.
Again the battery is not the problem. I can manage to find a 60v 15ah battery or just construct it myself with 4V lithium cells and a BMS.
My problem is with current regulation.

But how will you charge those batteries?
The garage doesn't get a lot of sunlight, I would just disconnect the battery, charge it at home and connect it back.

You don't have a straight shot from your house to your garage?
No I don't, the garage is at the first floor of the building across the street

#### crutschow

Joined Mar 14, 2008
31,570
I need something to regulate the current
Okay.
Below is the LTspice simulation of a simple current regulating circuit.
The LED current is shown for a 0V to 10V difference between the battery voltage and the 60V LED voltage.
If that voltage difference is more than about 5V, then Q2 needs to be mounted on a heat-sink.
The voltage difference will depend, of course, on the actual LED and battery voltages in the real circuit.

#### BobTPH

Joined Jun 5, 2013
6,317
Get a 25W or more 350 mA LED driver that is powered by 12V and can output more than 60V. They are available.

Edit: I say 350 mA because they are common. The LEDs ypu are using are most likely rated at that.

Bob

#### RIKRIK

Joined Oct 11, 2019
146
For portability and cost, I'd still keep it 24,36 or 48v. Just because the BMS systems and chargers are readily available.

A constant current boost converter, will give you constant current, can be picked up for less that $10. Also if in the future you want to change you lights, 12v and 24v are quite common. But obviously there's many ways of doing it. It depends on what's best for you. Thread Starter #### thatguy98 Joined Dec 15, 2020 13 Get a 25W or more 350 mA LED driver that is powered by 12V and can output more than 60V. They are available. Edit: I say 350 mA because they are common. The LEDs ypu are using are most likely rated at that. Bob i couldn't find any led drivers like that on the internet Thread Starter #### thatguy98 Joined Dec 15, 2020 13 For portability and cost, I'd still keep it 24,36 or 48v. Just because the BMS systems and chargers are readily available. A constant current boost converter, will give you constant current, can be picked up for less that$10. Also if in the future you want to change you lights, 12v and 24v are quite common.

But obviously there's many ways of doing it. It depends on what's best for you.
i hear what you say i just thought that a 60v battery with 4 corrent limiting circuits(since the 4 lights would be in parallel i would need one circuit each) would cost less and have a longher runtime than a 12v battery with 4 boost converters. And i would deal with lower current values drawn from the battery.( to power 4 20W leds in parallel at 60v with 300mA each i would draw around 7A from a 12V battery)

#### thatguy98

Joined Dec 15, 2020
13
Okay.
Below is the LTspice simulation of a simple current regulating circuit.
The LED current is shown for a 0V to 10V difference between the battery voltage and the 60V LED voltage.
If that voltage difference is more than about 5V, then Q2 needs to be mounted on a heat-sink.
The voltage difference will depend, of course, on the actual LED and battery voltages in the real circuit.

View attachment 225134
thank you. How did you calculate the resistors' values?