<h1>It will come with issues</h1>
<ol>
<li>Efficiency of good step down converters is 90%. Cheap ones used to start at 70%. What that means is:
<ul>
<li>Additional strain on your PSU and control board.</li>
<li>More heat to dissipate, that'll go to waste unless you have a closed chamber and print in things that requires high temperatures.</li>
<li>Higher electricity bill than it needs to be.</li>
</ul>
</li>
<li>Additional point of failure:
<ul>
<li>You will spend more time building and debugging your device.</li>
<li>Higher risk of failed prints in the future.</li>
<li>More difficult repairs.</li>
</ul>
</li>
<li>Lower voltage means thicker or hotter cables.
<ul>
<li>Hotter is wasteful and can be dangerous.</li>
<li>Stiffer is bad for bedslinger designs.</li>
</ul>
</li>
</ol>
<p>It is your choice if you are OK with these drawbacks. I would not, but none of these screams <em>&quot;don't do it!&quot;</em>. It's quite probable that you will be able to pull it off and make a decent printer.</p>

CC BY-SA 4.0
2023-04-21T18:54:00.587Z
good points, thanks. currently in a HEVO, which is a corexy, so not too much strain on the 16 AWG solid wire.  i'm probs just gonna get a 24V,  to be safe.
4m1r
CC BY-SA 4.0
2023-04-21T19:46:32.407Z
@4m1r With 16 AWG solid cables and corexy you can safely ignore point 3.
Mołot
CC BY-SA 4.0
2023-04-24T09:42:08.160Z
Let's add there's a reason why people get heat beds that run on 230V AC. Startup time. Stemming from all the mentioned limitations, the 12V bed will heat up much slower than a 24V would (and vastly slower than a 230V one would). It's the pre-heat/start-up time, adding sometimes good 10 minutes to each print at the beginning - meaning you need to wait the 10min before 1st layer starts printing and you can verify adhesion is alright and leave the print alone and go do something else.
SF.
CC BY-SA 4.0
2023-04-25T14:20:44.393Z
yep.  found an mk2b 24V for about $12. worth it.  thanks!
4m1r
CC BY-SA 4.0
2023-04-21T14:42:28.160Z
2023-04-21T14:42:28.160Z
Mołot
<p>I've got a 12 V bed (MK2A) and a 24 V PSU (Meanwell 350). I've also got a 12-24 V Einsy Rambo controller, and I'd like to run my hotend at 24 V. My HEVO is still in development, so when I tested the bed, anything over 32 °C restarted the board (I forgot it was 12 V).</p>
<p>Must be a voltage drop from the bed draw? The Einsy has a dedicated rail for the bed, so I was thinking I could use a dropdown converter between the PSU and the board rail. So I could continue to run the 24 V PSU for everything else and 12 V for the bed. Is it a bad idea from a safety perspective to run a simple 24 V-&gt;12 V converter in line there?</p>
<p>Also, what would that do to my amperage, I read something about converting volts down causing high amps and wattages requirements. Is that true?</p>
<p>UPDATE:</p>
<p>I wanted to check if changing the bed config in Marlin would allow me to reduce the voltage and it appears that if I change MAX_BED_POWER to 127 (half) I can indeed run the bed as is.  I can bring it up to 70 degrees at least at the moment. Admittedly I'm not sure what this does exactly and if this is safe.  Thoughts?</p>
<p>This thread appears to discuss exactly my problem and my temporary solution with MAX_BED_POWER limit too.</p>
<p><a href="https://reprap.org/forum/read.php?4,252638" rel="nofollow noreferrer">https://reprap.org/forum/read.php?4,252638</a></p>
<p><a href="https://reprap.org/forum/read.php?4,851922" rel="nofollow noreferrer">Here's a similar discussion</a></p>

CC BY-SA 4.0
2023-04-20T23:44:34.930Z
Just wanted to ask why. It seems to me that 24V bed cost about as much as a decent step-down with power headroom.
Mołot
CC BY-SA 4.0
2023-04-21T02:10:39.053Z
Yeah, just about.  I think I can get step down for about 15 to 20 bucks on AMZN and about $25+ for 24 V bed.  But then I have to get new flex plate, magnet, etc. and about an hour or two of extra work.  ;).  Also, just curious to see what folks here say.
4m1r
CC BY-SA 4.0
2023-04-21T12:27:57.360Z
It depends on how much the amperage is of the bed and how much the step-down converter can deliver. Could you add what 
converter you'll be using?
0scar
CC BY-SA 4.0
2023-04-21T18:49:47.043Z
like for example, this one seems reasonable. https://www.amazon.com/EPBOWPT-Converter-Regulator-Voltage-Transformer/dp/B07V6X6L89 I think I'm using the original mk2a which should be about 10A https://reprap.org/wiki/PCB_Heatbed#MK2.2C_MK2a Einsy has 15 A fuse for the bed.
4m1r
<heated-bed><power-supply>
Is it a bad idea to run 24 V to 12 V step down to heated bed?
4m1r
# Is it a bad idea to run 24 V to 12 V step down to heated bed?

(Asked by: username_0 on 2023-04-20)

I've got a 12 V bed (MK2A) and a 24 V PSU (Meanwell 350). I've also got a 12-24 V Einsy Rambo controller, and I'd like to run my hotend at 24 V. My HEVO is still in development, so when I tested the bed, anything over 32 °C restarted the board (I forgot it was 12 V).

Must be a voltage drop from the bed draw? The Einsy has a dedicated rail for the bed, so I was thinking I could use a dropdown converter between the PSU and the board rail. So I could continue to run the 24 V PSU for everything else and 12 V for the bed. Is it a bad idea from a safety perspective to run a simple 24 V->12 V converter in line there?

Also, what would that do to my amperage, I read something about converting volts down causing high amps and wattages requirements. Is that true?

UPDATE:

I wanted to check if changing the bed config in Marlin would allow me to reduce the voltage and it appears that if I change MAX\_BED\_POWER to 127 (half) I can indeed run the bed as is. I can bring it up to 70 degrees at least at the moment. Admittedly I'm not sure what this does exactly and if this is safe. Thoughts?

This thread appears to discuss exactly my problem and my temporary solution with MAX\_BED\_POWER limit too.

<https://reprap.org/forum/read.php?4,252638>

[Here's a similar discussion](https://reprap.org/forum/read.php?4,851922)

**Tags:** heated-bed, power-supply

> **Comments:**
> **username_1**: Just wanted to ask why. It seems to me that 24V bed cost about as much as a decent step-down with power headroom.  
> **username_0**: Yeah, just about.  I think I can get step down for about 15 to 20 bucks on AMZN and about $25+ for 24 V bed.  But then I have to get new flex plate, magnet, etc. and about an hour or two of extra work.  ;).  Also, just curious to see what folks here say.  
> **username_2**: It depends on how much the amperage is of the bed and how much the step-down converter can deliver. Could you add what  converter you'll be using?  
> **username_0**: like for example, this one seems reasonable. https://www.amazon.com/EPBOWPT-Converter-Regulator-Voltage-Transformer/dp/B07V6X6L89 I think I'm using the original mk2a which should be about 10A https://reprap.org/wiki/PCB_Heatbed#MK2.2C_MK2a Einsy has 15 A fuse for the bed.  

---

## 1 answers

### Answer by username_1 on 2023-04-21. Score: 1 | Accepted answer

# It will come with issues

1. Efficiency of good step down converters is 90%. Cheap ones used to start at 70%. What that means is:
   * Additional strain on your PSU and control board.
   * More heat to dissipate, that'll go to waste unless you have a closed chamber and print in things that requires high temperatures.
   * Higher electricity bill than it needs to be.
2. Additional point of failure:
   * You will spend more time building and debugging your device.
   * Higher risk of failed prints in the future.
   * More difficult repairs.
3. Lower voltage means thicker or hotter cables.
   * Hotter is wasteful and can be dangerous.
   * Stiffer is bad for bedslinger designs.

It is your choice if you are OK with these drawbacks. I would not, but none of these screams *"don't do it!"*. It's quite probable that you will be able to pull it off and make a decent printer.

> **Comments:**
> **username_0**: good points, thanks. currently in a HEVO, which is a corexy, so not too much strain on the 16 AWG solid wire.  i'm probs just gonna get a 24V,  to be safe.  
> **username_1**: @username_0 With 16 AWG solid cables and corexy you can safely ignore point 3.  
> **username_3**: Let's add there's a reason why people get heat beds that run on 230V AC. Startup time. Stemming from all the mentioned limitations, the 12V bed will heat up much slower than a 24V would (and vastly slower than a 230V one would). It's the pre-heat/start-up time, adding sometimes good 10 minutes to each print at the beginning - meaning you need to wait the 10min before 1st layer starts printing and you can verify adhesion is alright and leave the print alone and go do something else.  
> **username_0**: yep.  found an mk2b 24V for about $12. worth it.  thanks!  

---

