Need some help: Fully custom build was fine, now having throttle range issues

[Smokytyrz]

I have a Savage .21 that I converted to electric using Kershaw direct drive, brushless motor, and 6S ESC and battery setup.

The truck was running perfectly for about a year since the build, then it sat for a couple months and now has this issue that I've been troubleshooting for a while.

When I first plug in and turn on the truck everything seems fine. FWD and REV are fine and I seem to have full power. Then within the first 5-10 seconds of runtime the max throttle output clearly starts being reduced. Then within 10-15 seconds the throttle only produces motion when the first 25% of the throttle travel is used. After that point on the throttle it is like the ESC prevents current from passing. It doesn't shut off. It just doesn't go. Doesn't make any sound.

Then slowly the throttle becomes less and less effective until the truck just won't go at all, at any throttle amount.

If I let the truck sit for a moment, it will go again, but the behavior resumes very quickly. And it is always progressive.


If I unplug and restart then the whole process starts over again, beginning with full power output.

I've been messing with this for a year trying to trace the cause. I've basically rebuilt the truck and still the issue persists!

I even use this radio for multiple vehicles so it shouldn't be the radio as it works fine in other cars and bikes.

I'm at a total loss and could really use some advice. I've been into r/c for decades and consider myself skilled, being able to fix 99% of what comes along. But this has me totally stumped.



As far as I can tell the direct drive is fine. Clutch is fine, alignment is fine, and everything turns as smooth and precisely as the day I installed it.

I've swapped motors (the original Medusa and a new CC, ESC's (both Mamba Monster), BECs (all 6V ParkBEC), and batteries (all MaxAmps 6S (2 x 3S).

Nothing is binding in the mechanicals. The ESC is programming fine. The motor seems strong. And the wiring is correct.


What could be causing this? I've replaced ALL the electrics. I thought surely that would fix it even if I never discovered the root cause, but no. Please help!


Thanks!

[_paralyzed_]

Solder connection, either on battery to esc, or esc to motor. Do you run 2x3s? Have you ever swapped out your series connector to rule it out?

Something is getting hot quickly and failing... feel connections separately for heat when this happens...

[_paralyzed_]

Deans plugs? I suspect a solder joint, or possibly a bad plug on the series connector...

[rcs2022]

Originally Posted by Smokytyrz

If I let the truck sit for a moment, it will go again, but the behavior resumes very quickly. And it is always progressive.


If I unplug and restart then the whole process starts over again, beginning with full power output.
Thanks!

I would check the batteries, could be the ESC is cutting the power when voltage is too low! one damaged cell? check the led lights on your ESC, when the lipo cut off kicks in certain lights will go on in different color. at least on the CC ESC, namely the MMM if you have that one.

[pinkpanda3310]

Originally Posted by Smokytyrz

I've replaced ALL the electrics.

Did you replace all the elec's one at a time or the whole lot at once? When I started reading I was thinking battery, same as rcs2022. Is this teh largest rc you have and therefore the most taxing on the batteries? Do you have a battery checker? I tend not to think it is a connection but then electricity does stuff that bends my brain, for example there might be a connection that'll get worse as it heats up.

[bdebde]

Originally Posted by pinkpanda3310

...electricity does stuff that bends my brain...

Electricity is magic,

Try different batteries (another brand?), especially if they are old.

[BrianG]

Dirty or poor connections would cause voltage drop, but may not be high enough to cause LVC when the pack is fresh, but as they deplete even a little, that coupled with voltage loss from bad connections could be prematurely tripping the LVC. However, any voltage loss due to connections would cause excessive heat at those points.

Seeing as you are using all MA batteries, I would suspect them as being the culprit, especially if they have been sitting for a while. I would see if maybe a friend or your LHS has some packs you can try to see if it does the same thing.

A single bad cell could make the whole pack(s) appear to be weak, but you'd think this would be readily apparent by the amount of balancing needed for a single cell.

[Smokytyrz]

'twas the batteries! And now I look at my other Maxamps batts and they are getting puffy. So that, I am guessing, means I'll be tossing all of my Maxamps batteries that are older than a year. A YEAR AND A HALF I got out of these. Seems kinda short for the price. And its use-it or lose it, because I don't have a lot of bashing time or flight time. Just a little here and there when I can sneak it in around family obligations. Yet they still died.

FOUR batts I was trying. And I tried in every combo so that means there are no good batts. I could test each cell and reassemble the "good" cells but how long till they go bad as well? Not worth the effort. No more Maxamps I guess? Kinda sucks because they do offer some nice choices and packaging options. But at the price it isn't worth it for not even making it two years.

Thanks to all for the excellent help!

[Bondonutz]

Originally Posted by Smokytyrz

'twas the batteries! And now I look at my other Maxamps batts and they are getting puffy. So that, I am guessing, means I'll be tossing all of my Maxamps batteries that are older than a year. A YEAR AND A HALF I got out of these. Seems kinda short for the price. And its use-it or lose it, because I don't have a lot of bashing time or flight time. Just a little here and there when I can sneak it in around family obligations. Yet they still died.

FOUR batts I was trying. And I tried in every combo so that means there are no good batts. I could test each cell and reassemble the "good" cells but how long till they go bad as well? Not worth the effort. No more Maxamps I guess? Kinda sucks because they do offer some nice choices and packaging options. But at the price it isn't worth it for not even making it two years.

Thanks to all for the excellent help!

Sad news but all to common, the rest of the RC community will figure out their stuff is garbage sooner or later. Unfortunately MA is laughing all the way to bank in the process, hard earned money to pay for their overzealous advertising to trick noobs with more money than sense.

Hyperion makes awesome packs and are availible here in the RCM store, support the forum !
If looking for something more budget minded check out Hobbypartz.com Gens Ace or Sky lipos.

[Smokytyrz]

I wouldn't say I was a noob, having been in the hobby for three decades now. But I do feel taken. I'd heard the good and bad about MaxAmps. But I like to support the small business, the new kid. Got burned this time.

Thanks for the Recos. I picked up some Reedy packs and so far I am enjoying them. Cheap. Good output. Fits well on all vehicles so far.

[rcs2022]

Could it be you are storing the Lipos fully charged?
Read somewhere storage for more than couple of days between usage should be at 50 to 70 % charge.

[_paralyzed_]

I want to go on record noting that the original post stated he had already tried different batteries, and my trouble shooting recommendations were based on that.

I hate being wrong

I'm glad you are up and running

[Bondonutz]

I wasn't insinuating you were a noob, sorry.

[_paralyzed_]

Originally Posted by Bondonutz

I wasn't insinuating you were a noob, sorry.

whatever Newbie McNoobersnatch

[Bondonutz]

Yeah I know, I don't know shit about these new fangled RC thingies. The only one I have I bought at Radio Shack and runs on Nicads but it's real fast.