I'm working on a power distribution board which is going to distribute to several other devices/boards. Due to the high current requierment of the all the devices in total (about 29A - mix of 5V, 12V, 3.3V - mainly most current at 12V), I've decided to have 3 inputs to my board from the same battery. (my connectors were limited to 13A each)

Now, the 4s 18650s (not sure how many in parallel yet.) will have a nominal voltage of about 14.8V. Thus, I need to buck this down to 12V for each of my inputs.

Now the issue I have is that I can't seem to find many buck converters that will operate with an input of about 14.8 and give me 12V out, they're too close.

So I'm thinking, if I go with a 5s instead and then I'll have 18.5V nominal, I can easily buck that down with an IC such as the MAX20745. Would that seem like a reasonable solution?

MAX20745: https://www.maximintegrated.com/en/products/power/switching-regulators/MAX20745.html

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    \$\begingroup\$ The idea of needing to put a buck regulator on a 29 ampere supply hints at a design that is not fully thought through. Motor drivers, for example, are preferably designed to handle a variation in supply voltage themselves, and effectively fold the "regulation" into their control of the motor itself. And any high current lower voltage regulators should be selected to tolerate your pack voltage variation directly. What are your actual loads, specifically? And what are their specifications? Have you ever designed a circuit board or regulator supporting even just a few amperes? \$\endgroup\$ – Chris Stratton Jan 6 at 21:04
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    \$\begingroup\$ Also, can any of your loads feed power back to the supply? For example a motor driver may end up doing so, and your buck regulator might not tolerate that. \$\endgroup\$ – Chris Stratton Jan 6 at 21:07
  • \$\begingroup\$ @ChrisStratton It's part of the FSAE Formula Student competition for an eV car. This board provides power to the low-voltage parts on the car. 5V loads would be two microcontroller boards running diferent sensors and a GPS module with a total load of just under 3A (from both). The 12V loads are high power LEDs (6W for one, 3W for the other). The main 12V loads are 0.68A fans (about 20). The remaining are 2 water cooling pumps at 12V (2.5A each) and 1 radiator fan at 7A. \$\endgroup\$ – AlfroJang80 Jan 6 at 21:09
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    \$\begingroup\$ Whoever is doing the motive power systems for your electric car would probably have a lot of relevant thoughts - you really shouldn't try to do this without consulting them, and it's a little bit odd that you want to run all of this stuff off a unique pack. If the motive team won't give you a power bus (think about how every production EV would have a 12v accessory supply...) you should probably consider your loads uniquely. For example, look at what that radiator fan's motor and or driver can actually take, or replace them with more flexible solutions. Consider a regulator per load... \$\endgroup\$ – Chris Stratton Jan 6 at 21:15
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    \$\begingroup\$ Yes. Big ones. And please have a fault protection right at the battery. \$\endgroup\$ – Chris Stratton Jan 7 at 3:37

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