Building a Capacitor pack - What type?

[mikeshandssay]

So I see that everyone is putting cap packs in their high power rigs. I can solder like the best of them - and want to build my own.

What kinds of caps should I be looking at?

This is going into a Limitless build with a Mamba Monster.

 

[Overpowerrc]

@LibertyMKiii imo is a cap expert

 

[mikeshandssay]

@LibertyMKiii imo is a cap expert

Paging Dr. Cap Pack @LibertyMKiii

 

[LibertyMKiii]

Panasonic FM series caps are the ones to get.
I have a 3D print on thingiVerse if you are interested. It is a bit bulky and I doubt the MMX8s needs this much capacitance, but I tend to go over the top

https://www.thingiverse.com/thing:4347771

 

[mikeshandssay]

Panasonic FM series caps are the ones to get.
I have a 3D print on thingiVerse if you are interested. It is a bit bulky and I doubt the MMX8s needs this much capacitance, but I tend to go over the top

https://www.thingiverse.com/thing:4347771

Thanks! For a potentially 8S power system - which should I be looking at?

https://www.mouser.com/Panasonic/Pa...-Leaded/FM-Series/_/N-75hqw?P=1yzuxhaZ1yzvjj0

EDIT: Maybe this one - https://www.mouser.com/ProductDetai...=sGAEpiMZZMtZ1n0r9vR22ZGaUoI0JcRfgRpMIaLoxUc= ?

 

[LibertyMKiii]

Thanks! For a potentially 8S power system - which should I be looking at?

https://www.mouser.com/Panasonic/Pa...-Leaded/FM-Series/_/N-75hqw?P=1yzuxhaZ1yzvjj0

EDIT: Maybe this one - https://www.mouser.com/ProductDetail/Panasonic/EEU-FM1H821L?qs=sGAEpiMZZMtZ1n0r9vR22ZGaUoI0JcRfgRpMIaLoxUc= ?

If you use 820uF you would need at least 10 caps. I usually use 1,800 or 2200 uF caps.

These are the ones I used on the last build
https://www.mouser.com/ProductDetai...=sGAEpiMZZMtZ1n0r9vR22ZGaUoI0JcRfq6aa0k7ziXY=

 

[mikeshandssay]

If you use 820uF you would need at least 10 caps. I usually use 1,800 or 2200 uF caps.

These are the ones I used on the last build
https://www.mouser.com/ProductDetail/Panasonic/EEU-FM1V182B?qs=sGAEpiMZZMtZ1n0r9vR22ZGaUoI0JcRfq6aa0k7ziXY=

Can you go into what I would need... And why I would need 10 caps?

Engineering background here. Just new to caps in RC.

 

[LibertyMKiii]

Ideally you want at least 6,000 uF of capacitance. More is better but at the cost of space and weight...

In the most simple method you would need some wire, the caps, solder, and heat shrink.
I like to use liquid electric tape if going this method.

You can see here how I attached them to the wire and then the black is the liquid electric tape brushed on. Then covered in a clear heat shrink.

You can solder those wires direct to the battery leads of the ESC or you could add connectors. In this picture its hard to see but I used 6.5mm bullet connectors.

 

[mikeshandssay]

Ideally you want at least 6,000 uF of capacitance. More is better but at the cost of space and weight...

View attachment 80053

In the most simple method you would need some wire, the caps, solder, and heat shrink.
I like to use liquid electric tape if going this method.

You can see here how I attached them to the wire and then the black is the liquid electric tape brushed on. Then covered in a clear heat shrink.

You can solder those wires direct to the battery leads of the ESC or you could add connectors. In this picture its hard to see but I used 6.5mm bullet connectors.
View attachment 80054

Awesome! I was more wondering what math equations you use to calculate the amount of needed capacitance

 

[LibertyMKiii]

Awesome! I was more wondering what math equations you use to calculate the amount of needed capacitance

I am an EE myself but sometimes it's better to look at real results. If you have a MMX you should have the ability to pull data logs and see what your ripple voltage is. I did this and once I had a capacitor pack above 6000 uF the ripple voltage was in control for a 40x74 motor.
Some of the ripple comes from the batteries inability to supply strong power. I was using top of the line batteries, so lesser batteries might require more capacitance to achieve similar results.

I am now running 21,000 uF mainly just because I can, not because I needed that much

3D printing made the whole process much more controlled and neat.

 

[mikeshandssay]

Damn that's pretty sick work. I need a 3d printer! I don't have a MMX - just a mamba monster.

Do you have a special connector to discharge the cap pack once you are done running it and take the batteries out? Or would just turning on the ESC do the same thing.... hrm. Thoughts?

 

[mikeshandssay]

I am an EE myself but sometimes it's better to look at real results. If you have a MMX you should have the ability to pull data logs and see what your ripple voltage is. I did this and once I had a capacitor pack above 6000 uF the ripple voltage was in control for a 40x74 motor.
Some of the ripple comes from the batteries inability to supply strong power. I was using top of the line batteries, so lesser batteries might require more capacitance to achieve similar results.

I am now running 21,000 uF mainly just because I can, not because I needed that much

3D printing made the whole process much more controlled and neat.
View attachment 80056
View attachment 80057
View attachment 80058

What size heatshrink should I get?

 

[LibertyMKiii]

What size heatshrink should I get?

I tried looking back at my purchases but I must have bought the heat shrink way back... sorry man I am not sure.

Damn that's pretty sick work. I need a 3d printer! I don't have a MMX - just a mamba monster.

Do you have a special connector to discharge the cap pack once you are done running it and take the batteries out? Or would just turning on the ESC do the same thing.... hrm. Thoughts?

You could power on the ESC as an easy and safe way to drain the power from the capacitors.

 

[mikeshandssay]

I tried looking back at my purchases but I must have bought the heat shrink way back... sorry man I am not sure.



You could power on the ESC as an easy and safe way to drain the power from the capacitors.

Awesome, thanks for the response.

I still don't have a way to measure ripple voltage. :/

Taking a little bit of a shot in the dark capacity wise, but going to build a 8 Cap Pack of the Caps you listed.

 

[LibertyMKiii]

Awesome, thanks for the response.

I still don't have a way to measure ripple voltage. :/

Taking a little bit of a shot in the dark capacity wise, but going to build a 8 Cap Pack of the Caps you listed.

The older Mamba Monster and Monster 2 ESCs are pretty tuff. Like you said we don't know what the ripple voltage is, but a small cap pack wouldn't hurt and might extend the life reducing the stress of oscillating power levels. I know they don't have much capacitance and Castle ESCs have had issues with ripple voltage so it wouldn't be a bad thing to add capacitors.

 

[Joelk]

What size heatshrink should I get?

I used 30mm for 2200uf 35v caps and it fit well.

 

[jondilly1974]

If you want to hit the easy button, just grab a Ripple Killer from @phildogg

 

[mikeshandssay]

If you want to hit the easy button, just grab a Ripple Killer from @phildogg

I'm gonna take a stab at making them myself. Doing a Limitless build and want to make it a custom shape.

 

[Surchaufeur]

@LibertyMKiii i have found 470uf capacitors from panasonic on amazon. Was thinking making a cap pack myself than buying a tiny cap pack from hobbywing for 20$. What rating would you recommand for a 6s esc like the blx 185? Its really my last try to get my exb going. I was planning to drop back to 12T but my heatsink is going to hit the center diff outdrive. 14t is the only pinion that gives me the clearance.

The hobbywing cap pack is also 470uFx4

 

[iamsohai]

@LibertyMKiii I have a few 10000uf 35v from an old project. Think I can used them?