Daygreen DC-DC Converter Testing (24v to 13.8v)

Crimp Daddy

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I'm testing this DC-DC buck converter for a project and wanted to share the results. Let me know if you guys/gals see anything funny.

The main thing I noticed is the unit doesn't start working until you give it at least 21.40 VDC (Specs show 18v on the low side). Once it fits that voltage you can turn it down and it keeps working. Is that normal?

Low Voltage shutoff was 17.07 VDC

Voltage Drop @ 5A load at 21.4 VDC Input
13.78 Idle to 13.54 under load.

I did test thing thing at a full 30 amps and it handles the load pretty well, butit starts to heat up... if you want to manage heat I would say 10-15 amps RMS at most.

https://www.aliexpress.com/item/24V...13-8V-30A-DC-DC-Charger-2018/32267954153.html


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I have a sister version of this unit, the 48V > 12V one.
Yes, mine ran hot too, even with light load (a few amps).
So I moved it so it's mounted vertically & attached a heatsink & it runs much cooler now.
I attached the heatsink with a U shaped strip of 1mm aluminium strip - made this a tiny bit short each side to give a bit of tension.
The strip fitted nicely under the unit - its brackets give a few mm clearance.
I put several of those grey siliconetransistor heatsink pads underneath the heatsink for better heat transfer.

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PS: if you open it, it's "potted" in some grey rubbery stuff - can't see anything ;-)

Looks like Daygreen have another case style that should run cooler:
https://www.aliexpress.com/store/pr...nverter-Apply-To-48V/1487825_32911310159.html

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Redpacket said:
PS: if you open it, it's "potted" in some grey rubbery stuff - can't see anything ;-)

No wonder it gets hot, are the FETs or VRs mechanically in contact with that fancy heatsink case ?
 
Sean said:
Redpacket said:
PS: if you open it, it's "potted" in some grey rubbery stuff - can't see anything ;-)

No wonder it gets hot, are the FETs or VRs mechanically in contact with that fancy heatsink case ?

If the outside of the case is hot, (before my mod)it's academicif the FETs, etc were in contact or not? Sure they'd be hotter inside (not so good) but the net result is exterior heat dissipation either way.
Daygreen say they fill the units with "heatconducting ethoxyline" (ie the potting compound)so it's not all bad.


CrimpDaddy said:
The main thing I noticed is the unit doesn't start working until you give it at least 21.40 VDC (Specs show 18v on the low side). Once it fits that voltage you can turn it down and it keeps working. Is that normal?

Low Voltage shutoff was 17.07 VDC

I think they have designed in some hysteresis so it doesn't "flap around" if you're close to the under-voltage limit eg, thisgap of 21.4 startup vs 17.07 would make for clean startup/shutdown.
That said, might be better if it started up at 18V & shutdown at something like say16V to better matchexpectations from the spec?
 
Ethoxyline is a resin, rather like epoxy - it'll likely be a better insulator than a conductor.
 
Well they're saying it's heat conducting - maybe they added something like they do with "silicone" heatsink washers - silicone is a bad heat conductor yet the washers work well?

Bottom line is adding a heatsink to the case helped heaps.
 
Redpacket said:
Well they're saying it's heat conducting - maybe they added something like they do with "silicone" heatsink washers - silicone is a bad heat conductor yet the washers work well?

Silicone heatsink washers are used to electrically isolate the devices tab from the heatsink, mica does the same thing. They don't aid heat dissipation, or conduction to the sink - ideally the tabs would be in direct contact with the sink (via paste), but that's not always possible.

I agree increasing the surface area of the case will help, it's just an odd design that seems to encourage heat to build up within.
 
Its a design that works well for humidity protection and stops insects from being toasted, two of the largert failure reasons in some countries..

I have one of the black DayGreen units, the case does not seem to get wam and it's easier to add a fan to the front of the case as I think it was M4 screws I used to attach a fan...
 
Sean said:
Silicone heatsink washers are used to electrically isolate the devices tab from the heatsink, mica does the same thing. They don't aid heat dissipation, or conduction to the sink - ideally the tabs would be in direct contact with the sink (via paste), but that's not always possible.
Actually most "silicon" heatsink washers are quite good heat conductors & do aid heat transfer to the heatsink & yes maintain electrical isolation at the same time.
Agree it's not as good as direct metal to metal contact.

Mica is a poor heat conductor but good insulator - better in toasters that modern electronics!

For my sink solution above, the silicone washers helped by "conforming" to the rough surface on the converter while conducting heat to the heatsink nicely.
 
i have one of these as well a 30A versions, main problem i have with it is that using it with asolar panel at 36v I(which works btw) it does not use the full 10A the panels are giving out(250w x2) so when i checked with my wattage meter at full sun was giving out 30-50w.
 
I just ordered a 60a unit with a different case design from alliexpress. Will let you know if it suffers the same fate.
 
These units are not really designed to be fed from a solar panel. They don't have eg MPPT on the input to adjust the current drawn from a solar panel as clouds go over or morning > midday > evening changes, etc. The current drawn at the input of these will be whatever it takes to hold the output at its rated voltage, eg 12V.
They will work from a solar panel only as long as you draw less watts than the panel can make.
 
I would not run this directly off solar... but what I also originally thought might be a con, is actually a pro. It's good the device needs a minimum voltage to start so it does not cycle the load on/off constantly.

So far from my limited testing this is one of the better DC-DC options on the market until you step into more mainstream brands like Victron and Samlex DC-DC converters. I will be buying a Victron DC soon too for testing... some of their units look pretty great.
 
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