Motor fading at WFO

[MG1234]

Don't know if this is what cap banks are for but finally got my Zonda to fly ,using Vant lipos 6500 mah 65c,in series for 5s per motor ,at full trigger only on some passes you can hear one motor fade in and out ,I'll try different mix of lipos today ,but is this what cap banks are for ? To keep the motors humming at full tilt ? I read the thread on caps and understand them just don't yet have the practice app figured out ,thanks

[z400]

So you understand what capps are for but aren't sure what..they are for?


Wait, what?

[kfxguy]

If you hear one motor fade in and out, does it veer off one way? Maybe you have an esc issue.

[MG1234]

I have RCBB -ESC ,I'm thinking it's the ESC ,just checked out the radio ,a Devi extension wire was bad ,radio worked good on the bench and it runs 9 other cars and boats that work fine ,but just now it made 2 really fast passes then one motor cut in and out so I set it on my stand and that same motor started running wide open ,hard to remove the hatch with the prop spinning ,then it was starting and stopping fast ,then broke the shaft and strut just about the time I got it unplugged ,I had sprayed some corrosion X around each side of this ,it's wrapped and has sealer on each end ,but I put a little in there because I was running in salt water ,their web site said to use it ,so now I have a bunch of repair to do and test these ESC ,maybe I can send them to someone ,

[tlandauer]

So you understand what capps are for but aren't sure what..they are for?


Wait, what?

Would it not be more helpful if you shared your knowledge with him??

[tlandauer]

OP, the capacitor is used to absorb the current/energy that is flowing between the batteries and the "gate" ---ESC. It is like a miniature battery that charges and discharges real quick. This current is called the "ripple current".
When you open the throttle the current gushes thru, if you close it the ESC "gate" has to block it, this constant ''slamming" is hard on the components and failure will result. Hence the application of capacitor.
The addition of a cap bank is to help the capacitors already on the ESC, another situation is that when you have relatively long wires between the battery and the ESC, and sometimes the battery is not up to the task of discharging the current that the motor is demanding, the "back side" of the ESC is experiencing a "vacuum" that will heat up and heat is the No.1 enemy of electronic components. By having a larger capacitance, you have a "bank" that temporarily stores the energy to be used in such an instant.
This is of course an over simplistic explanation.
For my first point, you can look at it another way; if you have a long hi pressure water pipeline , you open the end valve wide and then slam shut, the pipe will burst, fortunately most valves close gradually, there isn't a way to slam shut them, even then, in critical pluming work there are valves along the pipe to be shut off sequentially for this very purpose.
For an in-depth study of capacitor and cap bank, there is the excellent write up by DrWayne. http://forums.offshoreelectrics.com/...emptive-answer

[iridebikes247]

I haven't heard of Vant lipos are they hardcase car packs?

Boats pull way more current than cars sometimes a manufacturer can make something that works great in cars but in a high current boat, not so much.

This spring I had the same problem with my mystic, bigger hull but also higher voltage. The motors would go in and out of sync at top speed, the lipos were sagging bad on one side. Changed packs problem went away, also picked up 7 mph.

I don't think caps are the problem you would have probably cooked an esc by now. Whats your motor kv, also what esc?

[MG1234]

Capacitors store power and can discharge very quickly ,we use them in industrial to start motors and compressors,I've learned that they save ESC from brown out when the lipo is supplying less power,this is what I ment when I said I understand caps,what I was asking is what are the symptoms of brown out when you need more caps ,in my case one motor was fading in and out ,i was trying to figure out a problem but to late now ,It destroyed the out drive while on a bench trying to un plug it ,it started hitting reverse so I pulied it out of the water and once I set it down ran wide open with some hic cups in reverse ,it took maybe 10 seconds to remove the hatch and un plug with the prop going crazy ,but not fast enough ,only one ESC was acting up ,I had removed and tested the radio ,so that leaves that ESC as being the problem ,ran the same radio with other boats and cars and it's fine ,I'm bummed because that Zonda was like a Ferrari ,that's my story ,

[MG1234]

I bought it used but was told they are 2100 kv TP motors ,the ESC is from RCBB its 2 molded into a tray with shrink wrap and sealer,so maybe my 60$ lipos ruined my 300$ ESC, these vant lipos are the same grade as a zippy or other China brands ,I have a Spartan and genesis and the really work these lipos ,learned here not to run to lipo cut off but to stop early ,the Zonda has been perfect all summer ,but in my box of 16lipos some are less than perfect ,I've sent back 4 this summer for warrantee ,this is my last weekend for boats ,came up to the bay for a few days ,our racing season for trucks and buggies has started along with the desert season ,so this is my last run ,what a giant learning curve this year ,thanks for the help

[Flying Scotsman]

Hmm, a bit lost here...not unusual for me ....You destroyed one drive, motor started to hit reverse in the water, was it turning normally initially? it ran in reverse at full bore on the bench. What was the other drive doing during this mishap? What was destroyed, I presume it was the motor. Were you bath testing one drive at a time?
Sorry to hear about you loss, but it sounds really weird.

Douggie

[MG1234]

I made 2 passes then one motor stopped ,the boat was near me ,that same motor glitched backwards twice and stopped so I grabbed the boat and set it on my stand to remove the hatch when that same motor and only that motor ran wide open and then reversed a few times ,so as fast as I could without getting chopped up I removed the hatch and unplugged but just before I unplugged it reversed again from full forward to reverse and broke the strut and flex drive ,thanks

[kfxguy]

Sounds like a defective or wet esc.

[ray schrauwen]

The esc in your boat is a Rcboatbitz brand esc correct?

Their brand escs are rebadged Flier rc escs. These are similar if not the same as older Fighter cat escs. This specific esc is called a dual esc or twin. It is two fet boards with one control board or just two escs gooped together. When these go they can do funky things. The esc only costs $300 because its two in one. Go get a pair of decent escs and this craziness should not come back.

The escs are only rated at 150amps each at best and can not dissipate heat like two separate escs can.

Sorry it caused so much damage. External safety loops may have saved you some damages because they are very quick to remove power without removing canopy.

. I bet your battery system only connects one pack to one esc. Many people running twins will make a wire harness that makes both packs be connected in parallel. Why do this? Doing this let's both packs drain EQUALLY and IDENTICALLY!
Running packs separate will show which pack is weaker or had more load when you come back and check voltage.

It is my opinion that one pack drained more than the other and caused one esc to fail. Flier escs fail in strange ways!

Since they are Siamese, the other esc may not ever be able to be used again????

[ray schrauwen]

Hopefully link works. This could be your esc. Rcboatbitz doesn't sell it anymore, nuff said!?

http://fightercatracing.com/index.php?page=shop.product_details&flypage=flypage.tpl&product_id=212&category_id=48&option=com_virtuemart&Itemid=97

[kfxguy]

Ahhh flier escs. Yes. Makes sense now. The cooking block on the ones with cooling blocks blow the sal out and leak once you exceed about 60-70mph. They only seem to live a short life for the most part.