MEGAWATT Cooling Fan Questions

[MEXICOWANDERER]

It's cooling fan modification time.

The louvered cutout on the aluminum case has 4 spot-welds in the hub. Any idea why?

I am planning on full-circle cut-out the holes on both Megawatts, then use coarse, very coarse, screen to deflect junk from falling in. Seems these fans throw a flow restriction hissy-fit at the first sign of obstruction.

Tomorrow is the start of final assembly. I picked up killer heat-sink blocks for the sides. And yes I will re-thermal-grease the bi-polar power transistors.

There's going to be a lot of "stuff" inside that old Sola case. So much so that I am going to have to use 16-gauge wire on the high voltage from the terminal block. But I have a Huey-grade aux cooling fan inside and that'll have to do... (or not).

[MEXICOWANDERER]

Hammer & Chisel armor (armour for BFL) plating and mil spec is the thing for Mexico. Dirt salt air corrosion knocks, bangs and a poplace of sixth grade education is rampant. There are two Megawatts plus a 400-amp Shottkey dual rectifier to try and cool. I figure if I have to carry the charger, connect it, I might as well twist a timer knob. The key to this gizmo is flexibility. It can do ballet or sumo wrestling. I like the part about it being an adjustable 80-amp float charger - a real chameleon and I do not have to train a cutting torch on a nineteen cent chip so it agrees it really does have the ability to charge any battery. Backed down it can even power 700 watts of 10-volt vf LEDs. But it won't do windows or floors.

[Chris_Bryant]

NinerBikes wrote:

Whose budget is this coming out of, yours, or mex's? :h

For Mex it's not really a matter of budget- you can buy an Arduiono R3 with 2.4" touch screen for $12.99, and the ancillary parts would be in the $50 range, depending on how many parameters you wanted to monitor.

But- it's not the bullet proof solution that is required here, though I have had spring wound timers fail, not shutting off.

[NinerBikes]

Chris Bryant wrote:
A couple of comments- why no liquid cooling? If case space is a concern, liquid would certainly help, moving the radiators outside.
As to the whole design-

Two-stage charging presents a challenge to engineer when flexible voltage plus flexible time is involved.

This is taylor made for an Arduino- depending on the precision you need it would be trivial to measure current, voltage, temperature and whatever else you need to control a digital potentiometer controlling the megawatt.

Whose budget is this coming out of, yours, or mex's? :h

I bought a VW e-Golf last week.. 24.2kwh of lithium power. VW's clever engineers didn't see fit to water cooling either on the battery pack or the 7.2kwh chargers, but I assure you, it will suck down 30 amps of 240V for 3 to 4 hours to take the battery pack from empty to full, air cooled.

What is really bad for that battery is sticking a 50kwh DC charger and blast charging to 80% SOC in 20 to 30 minutes, with no cooling system present. Really, really not good for a very, very expensive Li battery pack.

A regular old EVSE for me, thank you.

DIY EVSE system for EV's.

[grizzzman]

Chris Bryant wrote:
A couple of comments- why no liquid cooling? If case space is a concern, liquid would certainly help, moving the radiators outside.
As to the whole design-

Two-stage charging presents a challenge to engineer when flexible voltage plus flexible time is involved.

This is taylor made for an Arduino- depending on the precision you need it would be trivial to measure current, voltage, temperature and whatever else you need to control a digital potentiometer controlling the megawatt.

LOL!!! You are a funny man!!!!!! A controller in the borg...... keep up the great work Chris! :R

[Chris_Bryant]

A couple of comments- why no liquid cooling? If case space is a concern, liquid would certainly help, moving the radiators outside.
As to the whole design-

Two-stage charging presents a challenge to engineer when flexible voltage plus flexible time is involved.

This is taylor made for an Arduino- depending on the precision you need it would be trivial to measure current, voltage, temperature and whatever else you need to control a digital potentiometer controlling the megawatt.

[MEXICOWANDERER]

Because of the "tall shoebox" size of this device, the Megas are bound to be stacked 2-story. Because of convection the upper of the two shall be the Alpha unit. Stack height is a definite issue. Plastered to the ceiling is that 400-amp Schottky dual rectifier and heat sink. I am hoping a great majority of the BTU generation is in the bi-polar transistors and the external heat sinks will help especially with external fan circulation.
It would have been easier of course to have housed all this "stuff" in a mid-tower PC size case. But then there goes the portability out the window.
The only thing I am not satisfied with is the need to go open-circuit to adjust the 10-turn pots. I am hoping against hope the units acheive some stability with regard to the vernier settings of the pot knobs 0-100
The next point would be a gross imposition for ninerbikes. Asking him to relay post an article about the manufacture of the BORG. Gets complicated. I cannot send more than one image with limited text on this smartphone or TelCel times-out. It would be an utter waste if none of you showed interest in seeing images along with reading text. For certain I have never seen a battery charger like this one.

I can also hope the Lifelines appreciate the effort. This thing is bound to far outlive me and will be a pro-active memorial given to Jesus when I am gone. Soon I am going to repair to the work bench, sit down and start scratching my ah, er, head, how to make all this stuff into the case and then actually work. More Coffee!

[westend]

About air transfer volume in electronic chassis': I was challenged by finding solutions for air transfer with some cases I built. Adopting screens to keep out debris restricted flow too much. Drilling/punching holes was less restrictive but not well received, aesthetically. I ended up suspending a top panel, dimensionally the same as the chassis footprint, 1/4" above the chassis. On a 15" X 12" case, that resulted in a port of approx. 13 sq. in. The suspended panel works good as dust won't settle into the case, and cooling flow isn't restricted.

You guys with these small case power supplies may be able to do a similar construction by suspending a plate 1/2" or so above the fan chassis. Use longer bolts and a nut to hold the panel in place. Heck, a bean can lid with the edges dulled may fit an 80mm fan exactly, lol.

[landyacht318]

HECk, if you have the room inside the Borg for externally mounting a fan to the lid of the Megawatt, then do not limit yourself to a 60mm fan.

Not even sure why the lids are needed if they are inside another metal casing whose vents will be chickenwired to prevent debris intrusion.

Put a screened 120MM fan blowing in on Borg case(exterior?) and one 120MM sucking air out. This might negate the need for any internal fans which would be a PITA to replace, or hear if they get noisy.

I do have some ball bearing fans whose bearings make noise. They are better than sleeve bearing, but not bullettproof either

[MEXICOWANDERER]

Arghhh! Yes! Sleeve bearings. That slipped right on by me. Thank you Landy! You saved my rear-end!

Time to play musical muffins when I get home. I have benefit of the pair of in-bred brother power supplies to help in any potential bar fight so if one approaches theoretical max, I'll volt up it's brother.

Lots to play with if no mushroom cloud rises over the work bench. Tweaking a soft ramp-up with the Harbor Freight beer can 900-watt 2-stroke will be one of the exercises. Theoretically, this critter will work with the smallest generator. Right down to the last tenth of a watt. The "T" struts are being migged on as I write, for winding the power cord and the cables.

Beats watching Mexican soap operas or wasting money on Frankencerveza.

Film at Eleven...

[MEXICOWANDERER]

Senor Golden HVAC, the fans in question are the OEM Megawatt fans. Playing around with the forty or so different models of fans I have I hammer and chisel discovered it takes very little circulation blockage to significantly raise fan speed (measured stroboscopic-ally). A wire surface (radius) presented to the air-flow results in a surprisingly high disproportionate decrease in airflow disruption - on the order of almost 200 RPM! This is significant to no small measure.

The heat-sinking is accomplished with salvaged 1-1/2" X 3" sections of TO-3 black anodized material, plus a number of modified individual TO247 heat sinks. They are going to be applied using thermal adhesive. Some rough calculations reveal a @ 215% increase in BTU shedding (using a 120 MM high capacity fan). I have heard of only one failure of the Megawatt unit and that was jim-in-denver. Cause is unknown but the unit's application to many hundreds of amp hour capacity AGM batteries cannot be discounted.

Alas, finding dual pickup dual readout 12-volt panel meter and thermocouples, came late in the game. But the unit is bound for unsupervised operation so an IR scan shakedown will have to suffice.

One last thing needs to be done, which will require a minor tear-down:

A pushbutton reset 15-amp breaker needs to be installed in the rear panel and I do not have one. If the shakedown reports a 10-amp breaker will suffice, then so be it. A flashing 5 MM LED adjacent to the breaker will announce a fault. It's the inrush current that is an unknown.

Two-stage charging presents a challenge to engineer when flexible voltage plus flexible time is involved. Couple this to where I am doing all this creates the challenge. One-handed makes it an eye-roller.

[landyacht318]

Perhaps the spot welds are not that, and just marks from the stamping machine that punched out the holes for the fan's flow.

These fans do poorly with a restriction behind the impeller. I know room is tight but they will move a lot more air if you place them on the outside of the casing with no restriction behind.

Did you get 60mm ball bearing fans to replace the junky sleeve bearing fan provided?

The hole needed for least restriction, is not round.

From my Cheapowatt, may its rest in smoky fried pieces.







That 60mm Noctua fan is now on my Meanwell's Lid blowing inward, along with a 80MM fan sucking air outward, and the stock 40MM fan Meanwell provided.

Glad you did not want my heatsinks, as I am using them for a lighting project with halogen bulbs, but I woulda liked to meet you in person.

[Golden_HVAC]

I am confused, perhaps a picture of the fans or a link to where to buy them would help grasp what they look like.

But I trust that you know what you are talking about, and will get it done and make it better than stock.. .


Fred.