Thanks for the quick reply tex, did you see the video i linked? With a 4s lipo it doesn’t ramp, but will happily go full power till heat cut off. I’ll be able to sort out a step up dc dc converter of adequate wattage but if like for it to still have the ramping ui. Any thoughts as to what might be the issue here?
I didn’t watch the video the first time.
What cells are you using? They don’t appear to be high drain cells? Have you tried using some high drain cells?
The driver could be hurt, I have run into odd issues like this during prototyping when a driver was hurt due to excess voltage spikes etc.
The voltage reading the driver sees will also be a momentary reading on that driver IIRC, later we updated the firmware with a crude low pass filter to help mitigate this by spreading out the voltage readings over time. Basically if the voltage drops during the time the PWM is on, the driver can see this and think the voltage is low. Using high drain cells that don’t drop as much can take care of that.
The updated firmware might also be able to help, this should be the GT4 firmware which should work on the GT70 driver as well and has the low pass filter: GT4 firmware
The no ramping issue with the lipo is a reverse issue if I had to guess, the ultra high current capability of that battery combined with the wires that act like inductors can cause big voltage spikes that freak out the driver and can even damage it (did that when testing with a bench power supply a few times). For this better filtering could possibly help but the driver was not designed for this use case as it is hard to mitigate.
A simple option would be to add another 10uf cap to the empty C3 or C4 pad on the driver IIRC (it is at the top above the wire pads). Could even double up those caps if you wanted, they help control the voltage ringing but are not perfect.
The GT4 driver was updated to help with this issue due to the higher currents it deals with but not sure it would be enough for your use case.
Without a scope to see what is going on, it is all just guessing. It is possible that a large electrolytic cap added to the battery carrier just before it goes to the driver could help control the voltage ringing the driver sees but it is a bandaid fix at best. It is cheap though and would not hurt anything if you wanted to try it. I would get the largest cap(s) you could fit in the space rated for 20v+ (25-30v is better) if you tried this.
Yeah I have always been suspicious of the cells. Supposed to be 3500mah ncr18650ga but ebay can be very unreliable.
I have not been kind to this light or the driver i would not be shocked if it was hurt.
Ill try the updated firmware, add some caps and locate a good dc dc converter.
Thanks again for your help
Edit:
Can I get a second opinion on this dc dc converter? They’re saying 720w, but I’m not sure it looks beefy enough …
https://www.fasttech.com/product/9664388-dkp6012-720w-programmable-digital-constant
That converter appears to be a buck converter, it can only lower the voltage, so it won’t help you.
The important thing you want to look for with boost converters is the input current limit. if you feed it 12V and output 15V @ 8.5A, this means you will need:
15v * 8.5a = 127W of power
127w / 12v = 10.6A of input current before efficiency losses in the converter itself. These can range from 10–30 or more in lower quality converters.
So actual input current would be between: 11.6A - 13.8A
Basically, you would want a boost converter with a 15A input current limit to handle the GT70 at full power. This is hard to find as most cheap units top out around 10A. You can beef up the cooling on the converter in some cases to get more output though, sometimes just attaching a fan will do it, others it needs a larger heatsink. Might be worth trying a$5-10 converter with a 10A limit and beefing up the cooling vs spending $50 to get a 15A converter.