Car charger DC-DC

I would like to build a car charger to be able to charge my board while on the road. At first glance it seems that a DC step-up should do it. Anyone that wants to drop some knowledge if I’m about to do something stupid?

Input voltage: 12V
Max input current (fuse): 15A
Output voltage: 42V (10S)
Wanted output current: 3A

If I charge at 3A it gives me 126W. At input side this will give me (including losses) 11-12A. So this should be OK.

  1. Converter:
  • Quite beefy and should have no issue with the needed 126W (Wouldn’t push it above 500W)
  • Big plus: Interface with screen and 10 modes can be saved. So I can charge 10S, 12S and at different Amps.
  • Big downside: It seems like there is no safety for inrush current at the charging side. I’m not an electronics guy but since they warn for it I’m not eager to try. This means I always have to plug it in before connecting it to the board.
  1. Cable plug to charger: I had some 1,5mm2 (±16AWG) cable which is perfect for the amps. I’m also keeping it short, 500mm.

  2. Cable charger to board: Only 3amps so the 18AWG cable that I have is perfect. This one can also be longer for convenience.

  • Some pins to stack under the interface module (2x 8p on each side). This makes the screen pop higher then the heat sink. Makes it easy to design an enclosure for it.
  1. Enclosure:

This gives me exactly what I wanted: A small (130x110x53mm) charger that I can simply plug in my car. And charges at 3amps for 10s. Not bad :slight_smile:

Just buy a car inverter. It converts 12v dc to 120vac. Turn just plug your regular house charger into it and go. As long as the car is running, efficiency doesn’t matter. It will charge just fine as long as you dont have some massive beast of a charger

As I mentioned I’m not really interested in an DC-AC converter. Simply because I don’t want a bulky mess in my car. On top of that I really don’t want to go DC-AC-DC :stuck_out_tongue:

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I.bought this for a road trip this summer and wouldnt power my 12s8amp charger =\ thought it would have been enough but maybe I got my calculations wrong…

POTEK 500W Car Power Inverter DC 12V to AC 110V with 2 AC outlets and 2A USB Port

That’s too much for a normal cigarette plug. Then you need to hook it up directly to the battery. Or did you try that?

No… But someone else mentioned that might be the case BUT I could tap of the power lines to my sub woofer… No road potential road trip planned till october anyways =)

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Yea the lighter plug can only pull so many amps. You need to try directly to the battery.

First… spend more than the 12 bucks on devices like this… death is not really an option… or a fire…

For example… Murata has this solution Isolated DC/DC Converters 240W 11-13.2Vin 54.2Vout 4.44A is more what you wanna consider…

Next, at that amperage, run heavy gauge wire straight from your battery… buy a cheap set of jumper cables and reuse those…

I agree that electronics could be shady but I always inspect them and keep in mind that these things are not designed to push them, I keep a safety margin. So it’s a well thought and personal choice to tinker with them.

Your solution is typically for power over ethernet and outputs a fix 54V, not very useful for me but maybe they have one 12V to 42V, don’t know.

On the note of running heavy gauge wire straight from my battery: This is a typical (over)reaction I see so often on this forum. 15amps does not need a huge pair of 8AWG wires. I work with electronics and there is more then 15 amps flowing trough PCB’s from time to time… Just take length in account (which will be very short in my case) and set a margin, simple math.
On top of that my goal is to be not bulky at all, so definitely no big wire’s going to the inside of my car.

12 V cigarette lighter a rated 150w.
you can use it…


Seems like a good option, thanks!

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Found this too

Beast mode

Updated OP

Waiting for a friend to print the enclosure