High side switch

[ronv]

You might need a bigger diode and a small heatsink. The one you have looks like a 3 amp one? At 6 amps max load it will disapate almost 4 watts. So a TO 220 with a 10C/watt heatsink would be called for.
Don't forget to make sure the cap is charged before you hook up the battery for the first time.
Might want a little heatsink on the LM317 as well. It won't be out of spec, but will be 100C or so without it.
Here is a good diode that will only require a small heatsink.

 

[mmmalmberg]

OK Switching to a TO220 Schottky, already have heatsinks ordered for the mosfets, will order some small ones for both the diode and the LM317. I'll pre-charge the cap, that's going to be something to be careful about the whole time I'm working on them since I'll be taking apart & putting together a few times fixing this and that...

Thanks Ron.

 

[ronv]

Something like these:

https://www.aavid.com/products/standard/577102b04000g

https://www.electro-tech-online.com/custompdfs/2012/05/88724.pdf

You could maybe put the diode in last so you can test each section on it's own.

 

[mmmalmberg]

How substantial a heatsink should I have for the mosfets? The ones set up on my order right now are only 24.4 C/W.

 

[mmmalmberg]

Something like these:

https://www.aavid.com/products/standard/577102b04000g

https://www.electro-tech-online.com/custompdfs/2012/05/88724-1.pdf

You could maybe put the diode in last so you can test each section on it's own.

That's about like the heatsinks I'd lined up for the mosfets. I was going to flip all the heatsinks around so they point in toward the board, don't know if that's OK or not... The ones I was going to order don't have the solderable tab but I'm just remembering last time I used them the regulators they were on kept getting bent around so maybe a good idea for mechanical stability...

 

[ronv]

What FETs are you using?

 

[mmmalmberg]

What FETs are you using?

Haven't ordered any of these parts yet but this is what's on the mouser order so far - https://www.mouser.com/Search/ProductDetail.aspx?R=ZXM64P035L3virtualkey52230000virtualkey522-ZXM64P035L3

 

[mmmalmberg]

Maybe better https://www.vishay.com/docs/91092/91092.pdf

 

[ronv]

It the paper is blank how about this one?

https://www.electro-tech-online.com/custompdfs/2012/05/irf9204pbf.pdf

That heatsink is enough. Help keep the battery warm in the New Mexico snow.

 

[mmmalmberg]

It the paper is blank how about this one?

https://www.electro-tech-online.com/custompdfs/2012/05/irf9204pbf.pdf

That heatsink is enough. Help keep the battery warm in the New Mexico snow.

Oops too late just fired off the order with the Vishay's. True about the battery and the cold. 'Nuther good reason for the cap. With this setup, even if the battery dies completely everything will still work. Down the road if I wanted I could replace with some more contemporary sort of long-lived battery and appropriate charging circuitry but if they last long enough I'll stick with the SLA's.

 

[ronv]

That one will be a problem. It has Rds on (on resistance) of .14 ohms. At 6 amps thats 5watts (I^2R). With a 25degree C/watt heat sink thats around 150C in the shade. The other one has on resistance of .016 ohms so only .6 watts.

 

[mmmalmberg]

Cool I will see if I can find those... Thanks for watching my back

 

[mmmalmberg]

Both low voltage cutoffs working and dialed in. Haven't yet tested the current limiter for battery charging but it's there... View attachment 65246

 

[ronv]

Cool, Can you post a picture of the "big birds"? I am impressed with them.

 

[mmmalmberg]

View attachment 65260View attachment 65261View attachment 65262 They are currently completely disassembled, new electronics will go into new boxes, some structural changes, motor replacements, a few added feathers etc.

 

[ronv]

Thanks,

Hope the show goes well!

 

[mmmalmberg]

Thanks,

Hope the show goes well!

Thanks Ron, me too, your help has been deeply appreciated.

 

[mmmalmberg]

View attachment 67303

Thanks,

Hope the show goes well!

 

[mmmalmberg]

They're up and running, I had to pull out one of the LVC's that seems to not be working, possibly the last of all the damage done when I connected the output of one of them backwards and blew up a bunch of stuff when the sun came up that morning... Show opens tomorrow, should be ok for the moment, going to try to get some parts overnighted, will be $4. worth of parts plus probably $25 shipping

 

[ronv]

Really cool.

By the way, I see MikeML is back.