I'm on the process of building a new version of my ebike electronic systems and I'm searching for a way to lower the voltage of the battery (13s = 54,6v fully charged) to 12v/5v for the accessories and various electronics.
I would like to keep my main microcontroller (which is a STM32 based board) powered at all time (with sleep modes) to be able to get GPS, GSM and battery monitoring running when necessary, and then switch (with mosfets/relays) the bigger loads if needed. Given that I would like to keep the thing connected all the time, because my battery box is screwed, I would like the quiescent current to be as minimal as possible, to avoid any unnecessary current consumption.
So i started to dig up in my boxes to excavate various DC to DC converter I have, and found 3 of them which I tested on my PSU at 54,6v input :
- RCNUN E-Cart Fixed 12v, 10A : 15mA quiescent current
- SUKUZU Fixed 12v, 10A : 8mA quiescent current
- LM2596HV variable buck 3v-48v, 3A : 5mA quiescent current.
Given that my battery bank is around 15Ah, 5mA would not be really dramatic, you could still run the thing for more than 4 months. But I'm trying to find a more efficient way to do it. So I looked at Ti's website and found this little chip : TI LM46002
Which provides pretty impressively low quiescent current : less that 30µA.
But I was wondering if it would be the correct way to go and if you had simpler way to get a 12 or 5v out of 60v max battery bank.
I hope my question is clear and that it's not a repost, I searched on the forums, schematics and stackexchange, but I might have missed the perfect answer.
Best Answer
I think this chip is a very good option if you always want an supply from 13s battery.
I'm seeing that the problem is to get a power supply with 60 V input (max) and low quiescent. Lower input voltage gives more options with low quiescent current.
With this in mind, a suggestion would be to use a second low power & low voltage battery (1s o 2s) that gets charged from the 13s, and supplies the low voltage electronics, and that totally switches on/off the higher voltage power supply that charges the battery. Its a bit trickier but could also work.