I'm determined to make an underhood worklight/lightbar. Looking for input.

I have one of these currently:

It was cheap ($20 after coupon) and for what it is, it’s not awful. But it’s also not good enough for me to enjoy using it unless I’m really desperate.

Here are some pictures of the internals of this light, highjacked from this thread. I will post my own pics tonight.

Issues with this light include:

1. Poor runtime (with included single 1800mAh 18650 battery)
2. Poor beam pattern (narrow “strip” of light, does not illuminate entire engine bay)
3. Ugly blue tint from 5mm LEDs
4. Potentially dangerous charging circuit?

I really want to mod it into something useful. I’ve had a few ideas and I’d like to bounce some of them off of you all.
Option A:

1. Install a 26650, 32650, or 3Px18650 (about 38mm diameter) battery for increased runtime.
2. Frost the plastic tube housing to diffuse the light
3. Deal with the tint
4. Install TP4056 charging circuit


Option B:

1. Install 2Sx18650 batteries so I can use this 12V driver :

2. Install six of these 12V COB strips. I would mount them to a strip of aluminum that replaced the stock 120mm LED board.

4. Not sure how to charge this 8.4V configuration - open to input.

I really like Option B, even though it is obviously more work. I like using the LD-51 driver because it gives me 3 modes (1500mA, 375mA, and 30mA) which would be 250mA, 62.5, and 6mA at each COB when wired in parallel. Each COB is rated 12V, 3W, so it seems like that setup would work well. A simpler solution to drive the LEDs would just be a CC/CV DC-DC convertor like this, but then I don’t get modes.

The thing I have not figured out is how I would charge Option B. I want to be able to charge the light by plugging it in. I do not want to disassemble the handle and remove the batteries to charge them outside of the light. (Basically, onboard charging is required.)


Comments from the peanut gallery?

I was planning on building a similar light, however I thought 12V LED light strips offer
a) cheap price
b) wider availability
c) better tint than comparable lights (no high CRI or anything but at least neutral white)
d) 12V means it could also run from a car battery (even if you’d have to clean up the voltage first)
e) the LED light strips I have are quite reliable and durable

a couple 12V strips could be placed next to each other for a decent amount of light.

MILSPEC: I also thought about 12V LED light strips, like this right?

Maybe I could do that, I’ll need to read up on what kind of amperage/power they need.

One thing I’d love to do, but don’t know how - make the light capable of dual power sources: Li-Ion built into the light, AND have some leads on the light so that it can be directly connected to the vehicle battery.

5m strips are typically 12V/2A approx 24W. this varies depending on model/brand/manufacturer

Since 12V is still a voltage which is used for emitters the right driver must be out there.

Most of the dimmers that I’m seeing for LED strip lighting are large and meant to be installed permanently in a home, not in a portable device. Maybe something like this or this be used to achieve variable light levels out of the LED strip lights, in a portable form factor?

So what about something like the dimmer switch from above, attached to a buck/boost controller like this buck/boost convertor :

…which could be connected to either Li-Ion battery, or the vehicle battery?

Check out illumn’s light pods, they have one on sale for $15. I’ve bought several and there real nice

Thanks for the suggestion. But I’m not sure the Light Pod will be best for me, it appears to be a spot light meant to wire into a vehicle’s 12V system as an accessory exterior light, and I’m specifically wanting a light bar meant for underhood mechanic work.

I have modded a handheld umteen LED rechargeable on NiMh. Put 2X capacity cells and kept the individual 5mm LED side but removed the paper inside tube revealing the other side…
Mine has a plastic, “reflector” and does not have the pins exposed on the back side of LED board. On the back side I ran 3 strips of the 12V 5050 SMD, stuck on. I use this side as direct Car battery connection. I have 2 panel mount 5.5X2.1mm connectors in the base. Power to one connector runs One of the 3 strips as Low mode. Second connector runs 2 of the 3 strips as High mode.

Original side still functional but with 2X capacity batteries.

5050 SMD side with 3 strips.

soldering strips.

Base has a threaded cap to cover connectors. Center is the original charging port. Outer are my 12V DC connections.

Also check these cheap COB 3X AAA little lights. Bright and have strong magnets… Cheap, but work well. Aluminum versions are better IMO. Have gifted many to automotive enthusiast friends.

Buddy gave me an old BluePoint rechargeable that needed batteries and he lost the charger for it. I have swapped in some good cells in a pack I made, plus another NiMh in series for brighter use. I have that one in my shop and using my Horrible Freight charger on it from another LED handheld. It’s back in service and going strong.

If you fill that with 12V COBs you won’t need any other lights on in the shop. :smiley:
Would like to see where you go with this.

Oh, got one of those black inline dimmers…. Don’t work well at dimming, bad delay and not exactly variable.

These are better and have the POT separate from board inside the box if you want to gut the box. There is a ribbon cable to the POT with a connector on the board.

vw, thanks for the input.

Regarding those 3x AAA COB lights you mentioned - I like them too, and they were the reason I first thought about using COBs for the underhood light instead of SMD strips.

Nice idea to have the light dual sided by removing the paper in the back half - the HF light design could definitely do that.

I have the white box dimmer in several places inside my house (undercabinet lighting, pantry, etc) and didn’t consider them due to size - good to know the guts are discrete and might be able to be repurposed.

So for your 12V SMD side of the light - does it just run direct drive off of the car battery? Or do you have a dimmer pot in there somewhere to give you variable output?

the 5050 SMD are direct drive. My variable is either connector, one strip or 2 strips at a time. Thinking while writing the last post I have a few splitter wires in the 5.5X2.1mm connector. Guess I could also have a third mode using both connectors, lighting all 3 strips at the same time.

I bought the CW 5050 SMD strips a while back. Now 5630 are the new rage as they are claimed to be brighter than 5050. I have a roll of 5630 waterproof Warm white I got off ebay auction cheap. This roll is thin (less than 5mm wide) as the thin 5630 are running the long way with the strip allowing it to be thinner. Two of these thin strips can be used in place of the usual 10mm wide strip. Also got another strip of WW 5630 off amazon to use in other lighting to upgrade the CW 5050 I installed a whille back. I like the WW 5630 over WW 5050. I think its the brightness that makes it nice yet not harsh on the eyes as the CW. WW 5050 just seemed too dim and ended up using CW 5050 in the past projects.

There are also double density strips out there. 2X the LED in the same length, 5M roll.

I would keep the original configuration but stuff as many higher quality 18650s in parallel as you can into it. Do the 12V strips on the back side, direct to connector.
I have bought this Solar connector package from Horrible Freight.

Just BEWARE you will need to Verify all the POS and NEG connections are Correct. Cant remember what parts are wrong but use the 5.5X2.1mm connector as being Correct because you can not modify it. Connect the length of cable and work backward from there to make sure the other parts connect to it with correct polarity.
But it does give a nice bundle of premade options to use on a direct 12V light.

This is a tiny 1-3s charging circuit that I just purchased. I have not received it yet so I can’t comment on its capabilities. You can search for multi-cell lithium ion charging module and you should find some other options as well

Update: handle dimensions are smaller than I thought, 1x26650 is the most battery I can fit in one handle. (and I need the other handle for charging circuit and switch) Looking at the traces on the back of the LED board, it looks like all 120 5mm LEDs are in parallel, wired up in a 3Px40P arrangement. Not sure that matters, but I thought I’d say it.

Update pics:

Keep us updated. It is an interesting project.

Do you think a charging circuit like the one I posted would work with your setup and the ld-51 driver?

I think that yes, it probably would have worked - but now I have to revamp the plan for just one cell since I overestimated how large the handle diameter was. Actual diameter I have available is 35mm, or between 29 to 31 if I didn’t feel like removing material. Which means no 2x or 3x 18650 (36mm and ~36mm, respectively). So the LD-51 driver is out, and I’m not aware of any LED drivers that boost 3.7V to 12V for a simple solution. I’m probably back to looking at a standalone CC/CV module and some sort of PWM pot for variable output like I brainstormed above.

but the simple and reliable TP4056 charging circuit is back in play.

I’m considering keeping the 5mm LEDs, and adding basically an entire second light system on the back of it, as vwpieces did… but man these 5mm angry blue narrow beam LEDs are awful. I really want to ditch them completely.

I’m going to rest tonight and try to come up with another plan tomorrow, now that I’ve got some more info. Thanks to everyone so far.

If you still like to use 12v strips, the logical choice is to tap into the car battery as it’s sitting right there. A direct cable with clamps to grab onto the battery terminals. However, if it were me, I would not want the extra wires hanging there. I wonder how the driver from th utorch ut02 would work for you? I think I’m going to be swapping the driver in mine. Though I haven’t fully decided yet. It can be modded with a resistor to deliver 12v and just over 1amp from a single cell. I would think you would want more power than this though? If you are interested, there might be someone else on here as well who has no need for their ut02 driver.

I have debated ditching the internal battery, and just making the light run off of the 12V car battery only. But I would really like to also have internal battery available to give the light more flexibility.

I just had another thought - what about using LiPo packs for the battery instead of Li-Ion batteries? They might be a good solution because:

  • available in 2S config (good for the LD-51 3-mode driver I had in mind)
  • have chargers readily available (though the light would lose the on-board charging like the TP4056 chip could provide)
  • can be had in just about any size to fit in my light handle

Here one I found:

Capacity: 2100mAh
Voltage: 7.4v
Constant discharge: 6-10C
Burst discharge: N/A
Weight: 94g
Size: 59x35x27mm
Balancing plug: JST

Numbers in the dimensions of that Lipo look ok till you think about the square… Make a box that size to see what I mean.

I think I saw some tubular lipo on hobby king.

oh yeah…

edit: and I call myself an engineer to make it that much more embarassing. I know multiple roots of two by heart.

35mm / 1.414 = 24.75mm inscribed square

Using the LiPo finder on HobbyKing, this might be the largest 7.4V LiPo option I can fit, at 1500mAh, 32x13mm. The 7.4V is attractive, but a 3.7V 5200mAh 26650 has 70% more capacity.

But I’m having trouble finding boost circuits for 3.7V - most that are capable of 12V out require minimum 5V input. The only one I’ve found so far is this one, and it is limited to 2A.

edit edit: This one specs 2.5A, input down to 3V:

edit3: This one on FastTech uses a newer chip, the XL6009 instead of the older LM2577 above. Supposedly better low voltage performance and 4A capable.

edit4: Well, “4A” means 4A at 3V, so less than 1A at 12V after conversion. So even the (relatively) higher power 4A unit above couldn’t supply the 12V, 1.5A that the LD-51 driver can do on High. There are higher current options for DC boost convertors, but they are physically larger and I haven’t found one that looks like it would fit yet.

What do you think about this setup?

One of my main questions is:

Do I need a to disconnect the driver and Li-Ion side of the light, for the times I hook up the car battery?
Is hooking up 12V to the “other side” of the circuit going to damage it somehow?

I’m still considering a ~1500mAh 2S (7.4V) LiPo battery, it would make the boost circuit unnecessary, but it would have significantly less capacity. (19.24Wh for the 26650, 11.1Wh for the LiPo)