How to build a $20 47A power supply

[Ola]

Originally Posted by snellemin

27.6V......sweet.


This is what I was pulling this morning charging my ebike batteries.

Thats so cool! :D Couple years ago, i would laugh at you if you said that you`re going to charge batteries with 1150w power


Btw, i love youre e-bike project..!

[BrianG]

FYI: These supplies generate quite a bit of heat when driven near its max for a while. Despite the high efficiency of these supplies (~85%), outputting ~550w generates close to 100w. So, that fan is needed when they are driven hard.

If you are enclosing them in some kind of charger station case, you could probably use a larger fan (which doesn't need to spin as fast for the same CFM) as long as the air is directed through the power supply. Then you could do that fan speed reduction mod. IIRC, you can't simply remove the fan because the supply needs to see some rpm or it won't function.

[Ola]

I do agree.. But i`m wont be pulling full amps for that long time with every charge..
I also have max 5s batteries, so the charger will charge at 850w maximum.. Thats approx 970w at 0.85, so theres still a good margin up to the 1150w maximum on the PSU`s.. And thats at stock 24v... Wouldnt it be producing less heat at 27v, being more efficent?

I`ll do some testing and measure temps to see how it works out..
I think i will be installing a switch for the fans as well.. for minimum + maximum settings, in case i want more cooling :)

At 20A charging, the air coming out of the psu`s are cold as the outside air hehe..

[snellemin]

It's just crazy at what power level we can charge batteries now. Would be nice if I had 230Vac in my garage, so I could use all three Powerlab8 at the same time. Oh well, maybe one day.

My ebike is nice to commute with. Very low key. Most people thing that the ESC is a audio amplifier. Currently running 16s2p lipo(32mph max). Just too cold at times to go 40mph.

[Ola]

Originally Posted by snellemin

It's just crazy at what power level we can charge batteries now. Would be nice if I had 230Vac in my garage, so I could use all three Powerlab8 at the same time. Oh well, maybe one day.

My ebike is nice to commute with. Very low key. Most people thing that the ESC is a audio amplifier. Currently running 16s2p lipo(32mph max). Just too cold at times to go 40mph.

I got 3x32A 230v to my garage heheh.. And we have several 10-16A circuits 230v at our hangar at the airstrip, so were all good

I modifies the PSU`s this evening I didnt have resistors to make absolute max output voltage, but i did make 27v still.. I reckon it drops some at load though, but alot better than the 24.3 i had.

i also soldered a 13Kohm resistor on the fan control circuit to slow down the fan`s.. I tried to shorten those pins, but that made the fans run WAY to slow.. I think i found a good mid level, and its very easy to put a switch into the circuit to make full fan speed if its necessary.. Test`s at 40A will show

The aluminium suitcase i`m using for charge-box, is vented in both ends of the PSU`s now, and all thats left to do with it, is making a 230v input socket for the PSU`s on the outside of the box.. Pic`s will come when i get my PL8

[Ola]

Originally Posted by Ola

Pic`s will come when i get my PL8

Well, here`s my take on a portable charge case :)

[ANGRY-ALIEN]

Nice ... that looks pretty good...

[RC toy]

How big is the power supply? (one PS LxHxW )

[phildogg]

Originally Posted by RC toy

How big is the power supply? (one PS LxHxW )

12x3x2.75

[bruce750i]

The fan may need to be a high pressure fan at any cfm. The cases are very constricted. A 2-sp switch would be nice like mentioned above.

[josh9mille]

Im planning on doing the dual power supply, but I have a question: In my garage (where i plan to use the power supply) the neutral and ground is bound together in the pannel box. So is removing the ground prong on one of the power supply cords going to even do anything?

[BrianG]

Neutral and ground are electrically the same point in any US panel box for 120v mains, so that's nothing new. However, if you don't float the ground wire in the PS units, you get problems because you are paralleling the input, but series connecting the output.

[josh9mille]

Cool, thanks Brian

[mistercrash]

I made a 12V/24V power supply from two HP PSs. I installed an ON/OFF switch on the little wires I used to connect the three little pins of each PS and it worked fine. Then I decided that instead of having two power cords (one for each PS), I wanted the two to merge as one so I did that. I made sure to have one PS grounded and the other ungrounded. So now the switch doesn't work. Is there a way of wiring the switch so it can turn the power supplies on or off when the two power cords are merged together.

Thanks

Oh yes, the pics. Some in here like pics. I went for the compact look.

[mistercrash]

Here is how it was wired with the switch. It worked fine shutting off and powering on both PSs. But when I merged the power cords together, the ungrounded PS would always stay on and the grounded PS would always stay off no matter where the switch was.