Hi

Looking for a DC-DC  converter to get 5VDC from my 48 volt battery string.

This is to power a Raspberry Pi / Venus box.

I could use a regular 230VAC adaptor, but if the inverter shuts-down due to battery low-voltage, I lose the connection.

 

 

 

Look for a LM2596HV module

https://www.aliexpress.com/item/32270826168.html

I have not seen the HV variant available locally, only the normal LM2596, which only goes up to 36V.

Thank you Mr P.

I'm hoping for something local.

7 minutes ago, Crankshaft said:

Thank you Mr P.

I'm hoping for something local.

https://www.communica.co.za/products/bmt-adj-dc-dc-module-3a-4-5-60v

Thanks, will check it out.

What concerns me is this:

"(Note: Higher than 50v can not work for a long time)"

 

MEAN WELL SD-15C-05

https://www.mantech.co.za/ProductInfo.aspx?Item=372M0042

DIN rail version is DDR-15L-5

 

42 minutes ago, Crankshaft said:

Thanks, will check it out.

What concerns me is this:

"(Note: Higher than 50v can not work for a long time)"

 

I saw that. It is very strange wording - I think as long as you stay well below 3A, you should be fine. A raspberry pi 2 should not be a problem, but the option in the post above is better.

The DIN version looks nice.

Can't find it on Mantech's site.  Have these been spotted in SA?

https://za.rs-online.com/web/p/din-rail-power-supplies/1757776/

Thank you.

Will probably try the R30 cheapie from Communica first, and if that fails, upgrade to the Meanwell.

@Crankshaft I'm all for getting a cheapie rather than buying some expensive kit if the same can be done.

My concern here for your part is what happens if that DC-DC fails.

Many Voltage regulators will simply pass input through if they blow/fail. (Internal short circuit)

Lost a couple of pieces myself with the older LM3xx series. Luckily all during development phases, so no real biggies.

My concern if that happens you buy a new Pi which makes the Meanwell or even PULS seem fairly priced.

Alternatively maybe clipping with Zener or some quick protection circuit?

3 minutes ago, Riaanh said:

My concern here for your part is what happens if that DC-DC fails.

Many Voltage regulators will simply pass input through if they blow/fail. (Internal short circuit)

Lost a couple of pieces myself with the older LM3xx series. Luckily all during development phases, so no real biggies.

The older technology linear voltage regulators that you refer to could short but the switched mode DC-DC converters die with no output when they fail.. 

5 minutes ago, Richard Mackay said:

The older technology linear voltage regulators that you refer to could short but the switched mode DC-DC converters die with no output when they fail.. 

Mosfets like to fail short-circuit. In this case that would result in full power to the output.

Current Automation has both the regular and DIN mount Meanwell units.

@Crankshaft I got one of this for my setup https://www.aliexpress.com/item/4000054986071.html?spm=a2g0s.9042311.0.0.43404c4dKKqWpW

On 2020/02/06 at 12:00 PM, Crankshaft said:

Thanks, will check it out.

What concerns me is this:

"(Note: Higher than 50v can not work for a long time)"

http://archive.communica.co.za/Catalog/Details/P1028682385
 

 

To get 5V from 48V

Use the above DC/DC from Communica (~R80.00) and get a 1.5KE6.8A Transzorb at the same time.    In its protection direction,  it has a ~7V voltage drop and can handle 400mA without getting to warm.   Wire it in serie in the postive 48V supply line, with the cathode band facing the 48V battery.
This drops the 48V  (can be up to 57V when charging), down to less than 50V.   

Lastly put one of the RPI stick-on Heatsinks on the LM2596 chip to ensure it runs cooler.

Works great for a few extra sents        

Edited November 12, 20213 yr by Randmental
Spelling

Hey Crankshaft, i know i came some years late but, did you tryed the DIN rail DDR-15L-5? Did it work? I tried with a Buck Converter on PCB 60 to 5 VDC but it overheats (Same system 48V battery for a 5V PI), so im looking for a more robust option, the DIN one looks nice, but i dont have suppliers for that in my country, so im looking for comments before ordering something from outside (Because i will pay like double the cost just in shipping). Hope i can get an answer over here and thank you!