Has anyone modded a H1-A boost driver?

I can run more tests when I get a chance, this was mostly just to test the resistor change, and emitter numbers are accurate as they are regulated.

There were many input losses, with 3 ft 16AWG to each lead, the positive was an alligator clip on the stock spring (close to base), negative was an alligator clip held on the edge of the driver with my hand. So high connection losses. I will tack wires on for the next test. Also need to do the H2-C.

Keep in mind that even when the battery voltage is low, the output at the led is just like a fresh battery compared to a FET or CC driver where the light dims as the battery voltage goes down.

But yeah, 70% is kind of low in general. It’s probably like Jensen567 mentioned. With better connectors and shorter wires, efficiency will probably go up.

I am a beginner when it comes to buck and boost drivers, but I think the inductor causes a lot of the losses. The small ones that come on these drivers can have almost 0.1 ohms resistance, so with almost 10A that is a lot of heat.

When my H2-C driver arrives I’m going to experiment with replacing the inductor with a bigger, lower resistance one.

I have to agree with EasyB. This is how a driver with a properly sized inductor (and an oversized schottky diode) looks:


Ha ha, I guess you can use one 26350 battery to make room for all that. Lol

The inductor is definitely going to be the limiting factor, it basically always will be in a compact buck or boost driver. That said, these little drivers aren’t too bad!

Ran some new tests on stock and modded drivers with 4 wire input and output to read voltages at the board this time. My temp numbers aren’t perfect, just a thermocouple held onto the inductor, but decent ballpark. There is also no heatsinking at all, driver is just in open air, no fans.

H1-A Stock:

Input 3.58V 1.72A outputs 6.26V 0.94A, 95% efficient

Input 3.27V 6.11A outputs 6.37V 2.82A, 90% efficient, temps hit a bit over 50C after 2 mins.

H1-A with R100 added:

Input 3.54V 2.19A outputs 6.30V 1.18A, 96% efficient

Input 3.07V 8.71A outputs 6.48V 3.52A, 85% efficient, temps hit around 75C after 2 mins.

Based on the efficiency drop I think the inductor is saturated, this is probably as high as we want to push with a simple resistor mod. Overall I am very pleased with this H1-A.

H2-C results below are not accurate due to an unknown malfunction of the driver! New results in later post.

H2-C is not as good, or resistor moddable. Comes stock with 2 R100 stacked, I added a third R100.

H2-C stock:

Input 3.51V 2.62A outputs 12.45V 0.65A, 88% efficient

Input 3.29V 5.45A outputs 12.49V 1.10A, 77% efficiency, temps hit around 65C after 2 minutes.

H2-C with R100 added:

Input 3.39V 4.14A outputs 12.46V 0.99A, 88% efficient

High mode showed no change, output current actually went down a tiny bit to 1.06A. Tried lowering the output voltage, still no change. It appears a bit over 1A is the limit without more extensive modifications. I went back to stock resistors so the lower modes stay lower, as they did all move up despite no change on high.

Bigger inductor would probably help, and is certainly possible on both drivers, as the SMD inductor is on top of other components, connected with a large solder blob and jumper wire to the board, it does not sit on the board at all.

Thanks for your extensive measurements!

Now combine this with an XHP-70.2 to get an extremely efficient flashlight!

Well, I was going to make a comment with regards to the huge losses entailed with 6ft of AWG16 leads carrying 9A of current and the alligator clip contacts, but thanks for taking the time to read the voltage at the boards' input terminals, the figures make sense now.

Oh! If you need for these drivers to handle more power, upgrading the inductor is doable. On my above example, I literally milled the onboard one with my multitool, as desoldering those heat-sinking chunks of copper among the remaining board components can be tricky.

Jensen567, now that you're in, could you please test the maximum output voltage for the H1-A?

I ask this because with the newer configurable triple 3535 boards at Kaidomain, an in series configuration may be feed with a suitable boost driver.

Cheers ^:)

OCV on the H1-A output was a bit over 7.3V, so not really suitable for 3S emitters unfortunately.

The H2-C would probably work with a triple emitter setup, I will try this afternoon to see if the output looks better at around 9V than it did at 12V, because it was fairly disappointing at 12V.

Yes, 6ft of 16AWG on the input, and 6ft 16AWG on the output with alligator clips certainly leads to very high losses. Numbers definitely make much more sense and look better when taken at the board. I went from, eh, it’s OK, to wow, for 12 bucks this thing kicks butt.

Or I will try this morning. H2-C does NOT like going below about 11V on the output, anything less and we lose UI and only have high. It did push a bit over 2A into 9V though. I’m wondering if there are bias resistors for the DC-DC chip somewhere that could be changed to allow the H2-C to work for 3S emitter setups. Would be nice. OCV on the H2-C is around 15.9V.

Jensen567, thanks for the measurements. That is a bit disappointing about the max current of the H2-C. I notice in the specs it has a stepdown at 60s. Did you measure the output current before or after 60s? I’m asking because user Tjhosan resistor modded one with a R120 and got just over 2A to the emitter.

Before 60s. Not sure why mine did not respond to the resistor mod. It did increase output in lower modes, but on high it did not want to go higher than 1.10A. Did not even hit the stated 1.5A output. I will do some looking and try again sometime, probably won’t get a chance until Monday though.

Does anybody know what boost IC is used on either of the drivers?

According to RMM here it looks like at least the H1-A uses TI TPS61088. I’m guessing they are both the same but I haven’t taken the inductor off to check yet.

Also, it seems like after trying to run the output at 9V my H2-C has come back to life. I got close to the rated 1.5A output on stock resistors when I just hooked it up. Will re-test that and update.

Thanks Jensen567

from that datasheet:

OK, I edited my above post to note that the H2-C results are inaccurate. I still don’t know exactly what was going on, but after forcing the output to 9V it works normally again. New results!

H2-C Stock

Input 3.58V 2.48A outputs 12.03V 0.66A, efficiency 89%

Input 3.43V 5.60A outputs 12.06V 1.39A, efficiency 87%

H2-C with 2x R100 replaced with 2x R075

Input 3.52V 3.44A outputs 12.04V 0.90A, efficiency 89%

Input 3.24V 8.72A outputs 12.09V 1.90A, efficiency 81%

Input 7.01V 3.60A outputs 12.09V 1.93A, efficiency 92%

I now like both of these drivers quite a bit! I did not have time to take temps this test, and the readings are taken before the step down. Step down is also gradual over 30 seconds or so, not abrupt. It Also appears like using a 2S input with H2-C will result in a much better efficiency (not surprising at all). It still doesn’t like driving below 10.5V or so without losing UI.

Just to note, I used 2x R075 resistors as opposed to 3x R100 resistors because with the R100 setup my bench supply hit the 10.1A current limit, so I wanted to bring it below that.

With 1S input on H2-C I think around 2A output is about the best we can do, with 2S input I think we can push it further as the driver did not heat up nearly as fast.

Is the H1-A able to output 12V with 6V input? Or will that just fry it? I want a XHP35 in my L2, but I haven’t found a suitable driver yet (takes a 20mm)

I don’t think it would fry it, but it wouldn’t output 13V either. In post 47 of this thread EasyB linked to Tjhosan who got the H2-C to fit into an L2, might be worth asking him.

According to the datasheet the boost converter certainly has the ability. Whether or not the other components are up to it is the question. See my previous post concerning setting output voltage as well as the Datasheet

The H1-A, from the datasheet, can only go up to 12.6V, so not really suitable for a 4S emitter like the XHP35.

It could, however, fully drive in series triples (3S) providing up to 2.5A of output without much trouble, but seems to be MCU-gimped to ≈7.3V. Crap.

Cheers ^:)