Want to see some real performance from a heavy lifter?

RTRyder

Merlin of Multirotors
Sorry, no video here. I found out quite by accident how to get stunning performance from a heavy lift hex, feed it 32 volts! I got the two 4S 5000 packs I've been waiting for on Thursday, Friday I put connectors on and did the first test flight, still had 40% battery capacity after 10 minutes with the packs wired in parallel.

Late yesterday I decided to give it a go at 12 minutes to see what was left in the packs then. Quickly grabbed the TX and a connection harness off the bench and went out in the yard, connected the batteries, initialized and then started the motors. I noticed the motors seemed to be idleing a bit fast but didn't think much of it, then I gave it some throttle. HOLY CRAP!!!

You would not believe how fast a 7 1/2 pound hexa can climb if you give it enough voltage, I mean it was crazy, like the thing had JATO motors attached and that was at less than 1/2 throttle. Immediately I knew something wasn't right so I gingerly brought it back down from orbit and just as I landed the cap on the F/C blew, I yanked the plug just as that was happening.

Wasn't until I got back in the house and put my glasses on that I could see my mistake, I grabbed a series connection harness instead of a parallel connection and was feeding double the voltage to the MK electronics, approximately 32 volts at full charge on both packs. No wonder it had stunning performance the motors were supercharged!

I definitely have to give Holger and company credit for building the electronics robust enough to survive a bonehead move like this. I could easily have fried just about everything in the stack if it hadn't been able handle the volts, but all that happened was a blown capacitor, everything is still working normally, thankfully.

Also a lesson learned, don't assume that I have the correct power connection in hand when I use both parallel and series connectors that at quick glance look almost exactly alike, put the D**m reading glasses on and look at it before plugging it in!

So now I have to pull the boards off the stack and replace the power cap on the flight controller, but that's a cheap price to pay for what could have been a many hundreds of $ mistake. That little project will have to wait though, in a couple hours I'll be settled into a 737 winging my way to Texas for the week on business.

I'll be checking in as time permits but this is going to be a very busy week with a lot of meetings, so you probably won't be seeing me here much until next weekend.

Have fun and keep flying, I'll be back soon...

Ken
 
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FOX222

Member
Man you are lucky! I can believe the fc can take it as the recom data sheet indicates up to 34 volts but the bl's, I don't know how they survived 32 volts. What about your led strips did they cook?

You know I have worried from the first time I built the parallel connector that I would use the wrong one so I covered it with red heat shrink and the series connector with black. It,s not fool proof but So far so good.

John
 

Bartman

Welcome to MultiRotorForums.com!!
was there a little extra laundry to be done in the RTRyder household after that flight??
thanks for verifying the ability of the FC to handle 32 volts! you're fellow MK fliers commend you!
Bart
 

RTRyder

Merlin of Multirotors
Amazingly everything still works including the LED strip. I powered it up on one 4S and was able to initialize and start the motors so it appears to be fully functional even with the blown cap. Obviously the BL's have power regulation onboard as well, that was my first concern when I realized what had happend and I was VERY happy to see all green lights when I plugged that single pack in, even more so when it all worked.

Peering in at the bottom of the F/C board you can see the goo hanging down out of the top of the blown cap, that appears to be the only damage though all the boards will get a thorough examination during the teardown to replace the cap.

OK, I've got about 10 minutes before my flight boards so time to sign off...

Ken
 

Droider

Drone Enthusiast
Safe trip Ken... what a numpty.. I thought I was the only one who did tricks like that in a rush... may be you want to chip in on the 'PRE FLIGHT CHECK LIST' thread I started... Ill go and add to mine.... check the CORRECT adaptors are used!
 

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