Cap banks - the pre-emptive answer

[drwayne]

Re the leads; OK bigger is better, but has it benefits to go thicker than the solid wire coming out of the cap itself, when mounting directly against the ESC ?:

The solid conductor eminating from capacitor has higher resistance than multistrand cable. To have a capbank connected a high demand circuit via a cable/conductor with avoidable resistance is poor design !

W

[viper1]

Sigh.... sorry, I understand your answer, but I'm afraid I didn't make my question clear enough. I didn't mean using the solid cap leads to connect the bank.
Let's say for example I have a cap bank, connected with e.g. 12 AWG wires to the ESC, does it have benefits to go to thicker, e.g. 10 AWG wires.
The chain is as strong as the weakest link is what I'm thinking, and in this case both the wire diameters far exceed the cap leads. so would it make a difference really?
All assuming this is on short lengths < 8 cm.

My wire examples are exaggerated but both are thicker then the solid cap leads

[drwayne]

Sigh.... sorry, I understand your answer, but I'm afraid I didn't make my question clear enough. I didn't mean using the solid cap leads to connect the bank.
Let's say for example I have a cap bank, connected with e.g. 12 AWG wires to the ESC, does it have benefits to go to thicker, e.g. 10 AWG wires.
The chain is as strong as the weakest link is what I'm thinking, and in this case both the wire diameters far exceed the cap leads. so would it make a difference really?
All assuming this is on short lengths < 8 cm.

My wire examples are exaggerated but both are thicker then the solid cap leads

The T180v3 external cap bank is connected by awg22 wires... very small by comparison the main battery leads.
However, the caps are also very small, and their charge/discharge is low yield.

Larger capbank charge(joule) movement will create a heat dynamic in the wire.
DeltaT in wires of AC is higher than it's DC rms equivalent..
Ive replaced many caps on escs where the cap leads have burned under load.
By provisioning the capbank with larger connect cabling, that temp dynamic is reduced... lower heat, lower resistance, better for all...

emoticons here are good. sigh ? ..try or

burn and learn, mate.

[viper1]

Got it ! Soooo Thick

Replaced the wires to 16 AWG while I had the ESC apart for my 'cooling mod' but still using original caps.
Kept 'm a bit shorter as well.

Thanks for your patience !

[drwayne]

If ever we meet face2face, Im rarely as cool or patient as here !
Saw the flyboy toys, nice.

Best of luck with boats.
DocW

[viper1]

If ever we meet face2face, Im rarely as cool or patient as here !
Saw the flyboy toys, nice.

Best of luck with boats.
DocW

If ever we meet face2face,....I'm more ugly, but not so dumb !

Thanks, gonna need all the luck I can

Salute

[Brushless55]

WOW!
my hopes are high for my T180 in my TP powered PMono now reading through this thread
I was unable to finish all six laps as I could only finish 5 1/2, now it may just be bad caps

[ray schrauwen]

Wish I read this before I made a cap bank for my SF200. The cap bank wires actually burnt open and esc died even after trying again with new caps. I didn't really think the wire guage mattered too much but, now I know it does. Thanks Dr.Wayne!

The T180v3 external cap bank is connected by awg22 wires... very small by comparison the main battery leads.
However, the caps are also very small, and their charge/discharge is low yield.

Larger capbank charge(joule) movement will create a heat dynamic in the wire.
DeltaT in wires of AC is higher than it's DC rms equivalent..
Ive replaced many caps on escs where the cap leads have burned under load.
By provisioning the capbank with larger connect cabling, that temp dynamic is reduced... lower heat, lower resistance, better for all...

emoticons here are good. sigh ? ..try or

burn and learn, mate.

[ray schrauwen]

This is a pic of what happened to my cap bank. I did shrink wrap the bank but, did not insulate the bare soldered leads.

Even if I had insulated the leads, the wire I used to connect them to the SF200 was too thin as well as you can see.

The boat runs dry so it wasn't an abundance of moisture that did it, more of an arc possibly from the AC but, I'm guessing at this point.

Anyway, thicker wire is better, closer to the esc is also better. At least no magic smoke, the driver Fets blew.

[drwayne]

Hey Doc,
Hows this info http://www.niccomp.com/help/ESR-Ripp...age-032012.pdf
Thanks Mike

Hiya
The main part of your quoted link appropriate to our use is the cap application to automotive audio power rails.
Although for my 12S setup..I didnt find any Sub-amplifier capacitor boost bank capable of 40k 50V 300A !
We are at an extreme of power demands not catered by any the 'domestic' boom box fraternity...

This is a pic of what happened to my cap bank. I did shrink wrap the bank but, did not insulate the bare soldered leads.

Even if I had insulated the leads, the wire I used to connect them to the SF200 was too thin as well as you can see.

The boat runs dry so it wasn't an abundance of moisture that did it, more of an arc possibly from the AC but, I'm guessing at this point.

Anyway, thicker wire is better, closer to the esc is also better. At least no magic smoke, the driver Fets blew.

The way you have soldered the caps, forces that last cap's leads to support the feed/discharge from the others.. this doesnt work well as it will likely burn ( see your pic )
Use a basic plain circuit (insulating) board to support your caps, and run the larger connection cable across the base of all the appropriate leads emanating from the caps.

Expect your cap bank to demand/supply the same ( or greater) power as supplied by your power source(batteries)
Logically if your battery/esc uses X-AWG cables..that is the same size required to/from your buffered power source/array ( cap bank )
A quality cap bank will emit a pulse 8x larger than the battery if you short the leads.. so why diddle with small cables when there is such a large discharge potential ?

Note of interest: it has been observed if my safety loop disconnects.. I have another 3 seconds on water run time before the cap bank is depleted and power stops.
3 seconds of 'full' power.. so please dont expect servo sized wires to support that power flow !

Pfft zap :

[rickwess]

For those building their own cap banks. Just cut it shorter to match the number of caps you want to use.

http://fightercatracing.com/index.php?page=shop.product_details&product_id=308&flypage=flypage.tpl&pop=0&option=com_virtuemart&Itemid=1

[drwayne]

For those building their own cap banks. Just cut it shorter to match the number of caps you want to use.

http://fightercatracing.com/index.ph...emart&Itemid=1

Head to RadioShack, Tandy, DickSmith, Force, Jaycar, RSI, Fallands, or whatever your country has in the way of electronics super stores and grab a piece of plain predrilled circuit board... 2 or 2.5mm spacing ..
The worst Ive seen was $3 for 4"x2"(100x50) !

The FC jobs are nice, but +$6 for their embossed name on a Chinese product? tsk tsk

[rickwess]

I like the substantial + and - buses on the PCB. It keeps it nice and clean. I'll spend close to $3 on the heavy awg wire to join the caps together and it won't look nearly as nice..

[ray schrauwen]

Yeah, you are right Wayne. I screwed up.

I have all the stuff to etch pc boards, should have done it in the first place, lazy, tsk tsk...

[drwayne]

Hmm

Yes, these FC labeled boards are a nice 'off shelf' item sourced from China.
The final connection from those boards to leads is via a 5mm solder pad... on 0.5mmX6.35 tracks.

Say a 6S setup.. some 22VDC with an expectation of some 250A peak .. ~5500W
Say an induced ripple of 2.2VAC = ~550W of heating..
Say 6S 1800Kv = 39600rpm = 118800hz ripple.
I say stand back !

This thread was initiated to circumvent people using rtr/offshelf fix-all solutions to our ever increasing demand for power and supply stability... without understanding the potentials and demands involved in their pursuits.
I applaud your enjoyment of the FC product.
Sadly they do not cater all needs presented at this forum.
cheers !