Little Big Project

[fasteddie600]

were the fets heatsinked ? dropping small volts at high current amounts to a lot watts dissipated as heat

No, just the little one that runs up the back of the FET. I didn't anticipate the amount of heat at the loads it's running. It's only really 100W+ it's getting hot.
I have been looking at fitting a little heat sink but there really isn't a deal of room to work with, I have a couple of screw on type little FET sinks that would be idea but they are too big.

Not a big deal really, 70W safe is plenty for me and everything stays nice and cool. I am only usually around 10-20W and I can get huge clouds and silly builds with 70W. I may look at doubling up the FET's on the big box that should hopefully allow 140W whilst staying cool?

 

[sparkyjuice]

If you can bleed off the heat I think you'll find the FET will give nearer rated current
But parallel fets should work


Sent from (who cares) using Planet of the Vapes

 

[RicModMaker]

Inspired by @Seedy and the pocket rocker mod, the good lady was going to get a wee box mod today. Unfortunately that box got ruined when I drilled the wrong side so that ruined my plan for a tiny box mod with a single battery.
So instead I built this with the time today.

It's a bit of a plain jane on the outside except for the brilliant FDV 510 which is fantastic having sprung centre post.
Fitted inside it has 4 Turnigy Lipo power packs each rated at 35C continuous 100C pulse. Wired in parallel that gives over 100A handling continuous. 750mAh each gives it 3000mAh and an onboard 1A USB charger.
Switch is wired via 68A(continuous) MOSFET and 2.5mm wire.
Unfortunately no room for a fuse or a power switch, but I can live with that as it's only for me to use. I wanted an LED in there too but I gave up figuring out how to make a neat job of that with so little space.

Interestingly this has a much lower volt drop than my big power project box mod running 2xVTC5's! Aprox 0.3V better in the Lipos with a 0.13ohm coil running around 80-90W.

I am happy, for a box that took 6hrs to build and cost under £30

Turnigy Batteries from Hobbyking @£1.90ish each
Box from maplins £3.09-not the greatest!
FDV 510 from Modmaker £5.99
Switch from RS £8.99 I pushed the boat out a bit there!
Mosfet about £1.50 from RS
USB board from Modmaker £1.99
Resistor about 2p and some wire.
£29.18

Not sure how many box MOD's I need but it is definitely more!

Lovely little thing. Very nice work. I must get my harris in gear with some lipos.
Good work fella
Ric

 

[fasteddie600]

Lovely little thing. Very nice work. I must get my harris in gear with some lipos.
Good work fella
Ric

Lipos seem to be the way forward! I am really enjoying using them and they are nice and cheap from Hobbyking. Early days but the performance looks excellent.

 

[RicModMaker]

Lipos seem to be the way forward! I am really enjoying using them and they are nice and cheap from Hobbyking. Early days but the performance looks excellent.

I'll be getting some tomorrow. Just a thought on heat and MOSFETs, do you think attaching one to a strip of metal would do the trick or even attaching it to the case if its Ali?

 

[fasteddie600]

I'll be getting some tomorrow. Just a thought on heat and MOSFETs, do you think attaching one to a strip of metal would do the trick or even attaching it to the case if its Ali?

That thought had crossed my mind but in the big box it will be easier to add another 1 or pos 2 FET's onto the board. I am thinking of possible trying to add another into the little box too but that will be a challenge.

 

[Hammy]

That thought had crossed my mind but in the big box it will be easier to add another 1 or pos 2 FET's onto the board. I am thinking of possible trying to add another into the little box too but that will be a challenge.

I think i've found a fet that would be better than the one you're using Fast Service Unavailable, not had a look for availability or price yet.

 

[Chegs]

That thought had crossed my mind but in the big box it will be easier to add another 1 or pos 2 FET's onto the board. I am thinking of possible trying to add another into the little box too but that will be a challenge.

My MOSFET's have sod all onto which I could attach a heatsink,my solution to the legs breaking off was to buy some small-bore brass fuel pipe from the model shop and solder the legs on the MOSFET into small pieces of pipe(just enough to cover each leg)The extra metal was enough to stop the wires detaching from hot MOSFET and took up just the same amount of room.So far,4x 1000 MaH lipo cells in parallel has survived down to 0.03 ohms effortlessly,though the tiny sized MOSFET melted the insulation tape I had thrown on it to test(mosfet rated at 80A)a twisted coil of 2 x 0.5 mm kanthal

 

[fasteddie600]

I think i've found a fet that would be better than the one you're using Fast Service Unavailable, not had a look for availability or price yet.

nice find, they can be had here. I am no expert but it looks good.
Buy MOSFET Transistors IRLB3034PBF, N-channel MOSFET Transistor 343 A 40 V, 3-Pin TO-220AB International Rectifier IRLB3034PBF online from RS for next day delivery.

My MOSFET's have sod all onto which I could attach a heatsink,my solution to the legs breaking off was to buy some small-bore brass fuel pipe from the model shop and solder the legs on the MOSFET into small pieces of pipe(just enough to cover each leg)The extra metal was enough to stop the wires detaching from hot MOSFET and took up just the same amount of room.So far,4x 1000 MaH lipo cells in parallel has survived down to 0.03 ohms effortlessly,though the tiny sized MOSFET melted the insulation tape I had thrown on it to test(mosfet rated at 80A)a twisted coil of 2 x 0.5 mm kanthal

Nicely done chegs, nice solution! Personally tape melting would be too hot for me, that would literally have the little box as a pool of plastic as it is very heat sensitive.



I have doubled the FET on the little box, and all looks good so far. Well as good as another FET crammed in there can look!

 

[RicModMaker]

nice find, they can be had here. I am no expert but it looks good.
Buy MOSFET Transistors IRLB3034PBF, N-channel MOSFET Transistor 343 A 40 V, 3-Pin TO-220AB International Rectifier IRLB3034PBF online from RS for next day delivery.




Nicely done chegs, nice solution! Personally tape melting would be too hot for me, that would literally have the little box as a pool of plastic as it is very heat sensitive.



I have doubled the FET on the little box, and all looks good so far. Well as good as another FET crammed in there can look!

Noobs question here but does double up the FETs share the load between them?