42-88V variable current/volts charging. Poor fan flow design choice?

[marka-ee]

I have an AliExpress battery charger that does 10 amps and has variable voltage and variable current. I think it's a pretty good charger overall so far because it can charge my 10S batteries and also 20S. Or anything in between. My question though is how they implemented the cooling. There is a fan on the back and the fan is sucking air out of the electronic case. Whereas then the cold air flows in through a front grill. The front grille is near the front display which consists of a neat little circular blue LED dot chaser that indicates the charge and then also indicates the battery voltage and the current being charged. It's my understanding that having a fan try to suck the hot air out of an electronic case is not optimal. This is because the hot air is thinner and thereby harder for the fan to propel out. I'm wondering if I should reverse the flow of the fan to suck fresh, colder air into the cabinet and then have it flow out of the front grill. Going across the various heat sinks inside. What do you guys think? Unfortunately, it doesn't have variable fan speed according to load. It's either on or off, but I guess that's okay. I'm just wanting to optimize things. It's my hobby

 

[docw009]

You could always add a second fan on the intake side, Also good for redundancy., Who knows. Someday, you might wind up staying someplace in the mountains, More airflow needed at 10,000 feet,

Last year, the charger fan on on one of my chargers stopped, I wouldn't have noticed except I was travelling and had the charger in the bathroom of the place we were staying, Hey, this thing is hot. I popped it open and found the fan connector had fallen off.

 

[99t4]

Forced cooling airflow direction is not the main cooling issue in these chargers. Main problem is the poor quality fan itself (specifically the bushings) which is often the first item to fail, causing cascading component failures.

Worthwhile to replace the fan with a better quality item. Since it's easy to flip the fan orientation, you could perform controlled experiments with each direction, measuring component temperatures with each method (fan as intake fan vs. exhaust fan). I suspect you won't find much difference.

 

[fechter]

The density difference between incoming and outgoing air will be so small that it would be hard to measure. Reversing the fan will change how the air flows through the supply a little.

If you have a thermometer you could try measuring the heat sink temperature with the fan in either direction and see if there’s any difference.

 

[Chalo]

The density difference between incoming and outgoing air will be so small that it would be hard to measure.

This. Air density/pressure is a function of absolute temperature. The percentage difference in Kelvin or Rankine degrees is what you're fussing over. Not worth worrying about.

It reminds me of folks who deflate their tires for airline travel, when the maximum pressure gradient between sea level and deep space is only 14.5 psi. And your passenger plane won't be dropping to deep space vacuum in the baggage compartment.

 

[docw009]

I 'll keep my position on reduced cooling with forced air at higher elevations, It's real.

 

[amberwolf]

in my long experience with optimizing cooling in my various audio=recording computer systems (and other related and unrleated projects), sucking air thru works better than blowing it, depending on where the fan is vs where the parts are that need cooling.

But you need to ensure the air goes where it's needed. Sometimes that requires a bit of baffling or ducting to make sure the air goes onto and "thru" the hot stuff. There will be plenty of parts inside that don't need cooling (or not much) vs things like the FETs, diodes, transformer, etc., that definitely need it, and if they haven't already optimized the airflow (unlikely) you can do this with bits of plastic or cardboard.

Often you can even reduce the fan speed to reduce noise once the air is going where it needs to.

If you want noise redcution and don't need to protect fingers or noses or paws or wahtever from fan blades, removing any grillework near the fan or in front/behind it will usually make a huge difference.

 

[Chalo]

I 'll keep my position on reduced cooling with forced air at higher elevations, It's real.

Sure, there's less than 70% as much air density at 10k feet than at sea level. My VW camper van sure noticed the difference when doing Rocky Mountain passes.

But really hot air in a charger at say 80C (way hotter than anything I've noticed) is still about 85% as dense as 20C ambient air, and I very much doubt the temperature gradient would be remotely that much if the fan is moving air through.

 

[Papa]

Whereas then the cold air flows in through a front grill.

Heat rises... so when the charger is in use, position it so the cooling air flow travels vertically through the charger's guts (inlet at the bottom, outlet at the top).