• Who

  • Daniel Puratich idea

  • Tim Gu looking into it

• What

  • Take in 12V and output 24V

  • For powering our 24V battery charger

    • would be massive help at comp and flight tests to be able to charge faster

  • Supply enough power for the charger

    • if the current is really high then this project is going to be waaay out of our skill range

• Why

  • We have 12V server PSUs that are CSA approved

  • We get more power capability out of the charger at 24V

  • we could also just buy this? not sure if it maths out.

Initial Requirements:

12V - 24V @~40A Boost Converter PCB

• Input 12V from PSUs, output 24V

• Output Current

  • 7A of current x 4 batteries was recommended - targeting 28A output current (672W output power)

• Cost

  • Not sure if this is that much of a concern

  • The COTS option we identified was ~$100 off AliExpress, we can aim to do lower than that, but not a primary goal

• Timeline?

Topology:

• Due to the high power requirement, it may be best to design the board using the interleaved multiphase boost topology:

  • Essentially several boost convertors operating in parallel, out of phase with each other (their on/off switching alternates)

  • While one phase ramps up current, the other phase ramps it down.

  • Output current being split between multiple phases reduces power losses, which makes this more efficient than a single phase boost convertor. We may not need a heatsink

• Example of a six-phase interleaved boost convertor: PMP31073 reference design | TI.com

Important components/features:

TODO: Research for component selection

• Switching regulator/controller IC

  • to generate the PWM signals to control the MOSFETs

  • should find one that supports the multiphase boost topology

  • This will determine how we choose some of the other components

• Inductor

• Capacitor

• MOSFET

• Diode

• Current sense (probably copying Hall effect sensor from other boards)

• Overvoltage protection?

Research for COTS options:

Details

Battery charger: HotA F6 Quad Battery Charger (4 x 15 A)

...

• 1000 W output power limit across the 4 channels, with max current 4 x 15 A.

PSU:

Supermicro PWS-741P-1R Datasheet

...

• DC output: 740W, 12V/61.7A

  Assuming our boost groundside convertor supplies 24V DC to the charger:

  If we charge

What convertor to buy?

...

• Suggestions from Jerry Tian and Ryan Scomazzon : Charger should be able to charge 5.5Ah batteries at 1C. 7A of current per battery was recommended.

  • If charging 4 batteries at once, the current will max out at 10.4 A per channel (each channel is 250 W / 24V)

  • Alternatively we could just not use max power, and just charge 2 batteries at once with lower power/current.

How much power/current do we need to charge these batteries (how fast do we want to be charging them)?

COTS options:

• AliExpress seems to have the most amount of options and is well priced (but might be a bit sketchy?)

...

Product

...

Price

...

Specs

...

Notes/Features

...

Datasheet

...

Szwengao WG-12S2450M

...

134.68 (AliExpress)

...

24V 50A

0-1200 W

• • charger must supply 4 x 7A at 24V = 672 W.

  • Ideally the convertor should be rated for well above 672 W (it should have some headroom)

COTS options:

• The product from the following brand is the best I could find in terms of price and provided specifications. Most other products don’t have a datasheet

  • Though it is from AliExpress, is it sketchy to buy this from there?

• Couldn’t really find anything good on Amazon or Facebook Marketplace

Product	Price	Ratings	Features	Datasheet	Notes
Szwengao WG-12S2420M Image Added	50.36 (AliExpress)	24V 20A 0-480 W	High efficiency: 96.6% (@12Vin, 25℃) Non-isolated between input and output 100% full stable current output Support -30 °C environment 100% full load burn-in test OT, OL, LV protections Waterproof level IP67 1 year warranty	https://proa2427b-pic7.websiteonline.cn/upload/WG-

12S2450M

12S2420M.pdf	Not enough power if we want to charge 4 batteries at once
Szwengao WG-12S2430M Image Modified	77.99 (AliExpress)	24V 30A 0-720 W	High efficiency: 95.6% (@ 12Vin, 25℃)

For the rest, same as WG-12S2450M

Non-isolated between input and output 100% full stable current output Support -30 °C environment 100% full load burn-in test OT, OL, LV protections Waterproof level IP67 1 year warranty	https://proa2427b-pic7.websiteonline.cn/upload/WG-12S2430M.pdf	Load is 672W, at 95% efficiency this convertor would have to handle ~707 W input power Theoretically possible but it would be operating near its limit, would leave very little headroom
Szwengao WG-

12S2420M

12S2440M ✅

Image Removed

Image Added

50

100.

36

68 (AliExpress)

24V

20A

40A 0-

480

960 W

High efficiency:

96

97.

6%

8% (

@12Vin

@24Vin, 25℃)

For the rest, same as WG-12S2450M

https://

Non-isolated between input and output 100% full stable current output Support -30 °C environment 100% full load burn-in test OT, OL, LV protections Waterproof level IP67 1 year warranty

proa2427b-pic7.websiteonline.cn/upload/WG-

12S2420M.pdf

12S2440M.pdf

More expensive than the 720W option Load is 672W, at 97% efficiency this convertor would have to handle ~693 W input power If charging 4 7Ah batteries at 1C, this convertor would be operating at 693W/960W = 72% capacity, leaving plenty of headroom

• The WG-12S2440M should suit our needs

Usage

...

• Uses screw terminal connections

  • Is there any designing that has to be done for wiring/harnessing? Diagrams?

• On the output side: 672 W load at 24V - output current is 672/24 = 28 A

• On the input side: Assuming 97% efficiency, input power is ~693 W at 12V - input current is 693/12 = 57.7 A

  • 4 AWG wire?

• Do we need a fuse for the wire carrying high current between the PSU and the boost convertor?