Cap pack?

[LibertyMKiii]

Just out of curiosity, do you, or anyone else, have any data on the maximum current pulled by the motor? I'm wondering if my third assumption of 150 A is anywhere near realistic?

I have not logged the BLX but I data logged the castle 1515 which has similar dimensions of 40x75 (but 2200kv).
It logged 180 amps on the Mamba monster X esc. (Gearing was 25/29). I would estimate in the 140-180 range for the BLX but likely only if geared high enough to create a big amp load.

 

[L0stB1t]

Wanna melt your brain? Go have some fun poking through this mess: https://onlinelibrary.wiley.com/doi/full/10.1002/ente.201600154

Whoah ?

The only reason I was willing to make some conclusions at all was in the hope that it would help you understand that batteries are not easy to figure out. Without some serious science chops and an oscilliscope, your best bet is probably just to guess and check: if you have a power problem, add a cap pack and see if it helps!

Thank you for your summary, it's very intriguing how complex it really is!

 

[L0stB1t]

I have not logged the BLX but I data logged the castle 1515 which has similar dimensions of 40x75 (but 2200kv).
It logged 180 amps on the Mamba monster X esc. (Gearing was 25/29). I would estimate in the 140-180 range for the BLX but likely only if geared high enough to create a big amp load.

Great information. At 150Amps a 5000 mAh battery would be empty in two minutes, but I'm sure everything would go up in smoke if you tried to actually maintain that kind of load for the full two minutes Crazy to realize it's possible to push 3 to 4000 Watts through these machines!

 

[phildogg]

Great information. At 150Amps a 5000 mAh battery would be empty in two minutes, but I'm sure everything would go up in smoke if you tried to actually maintain that kind of load for the full two minutes Crazy to realize it's possible to push 3 to 4000 Watts through these machines!

We for very short times push alot more than that.. ive logged some crazy data before..

 

[phildogg]

 

[LibertyMKiii]

I got one also with less than Phildogg but still "up there"

 

[gibawatts]

Hi guys, I decided to make my own cap packs also. Panasonic have a new FS series of ultra low ESR capacitors. I ordered a bunch of caps rated for 50v at 1200μF, it's the highest capacity for capacitor at this voltage in this FS series.

I don't know much about all this data but as I've been reading, what matters the most is the low ESR value, because it can define the rate of speed the capacitor can charge/discharge.

Some more data about the capacitor:

I will adopt the same concept with an XT90, so i can share the same cap pack between my Kraton and my BigSenton. I'm no electrical engineer and don't know much about electronics, but I can do some comparisons like temperature, acceleration, speed with/without the caps. Unfortunately I have no logging tools since I'll be running it with a MAX6 on the Kraton and the stock BLX-185 ESC on the BigSenton.

 

[sadlerbw]

Ooooo, shiny! Those are some NICE electrolytic caps there.

Just make sure that, however you end up attaching them, they aren't hanging by the leads. With the ratings for those things, about the only way you would kill them is through vibration and the wire leads bending back and forth. As long as the body of the cap is secured to something and isn't relying on the two little wire leads to hold it in place, they should be fine. I mean, 5000hrs at 105C? Yeah, you should never be anywhere close to either of those ratings!

Also, just FYI, assuming you weren't going to go bigger than a 6S lipo, the 35V versions would also be perfectly fine. Honestly, they would probably even be fine for 8S, which maxes out at 33.6v, but I like a little more wiggle room than that.

 

[gibawatts]

Ooooo, shiny! Those are some NICE electrolytic caps there.

Just make sure that, however you end up attaching them, they aren't hanging by the leads. With the ratings for those things, about the only way you would kill them is through vibration and the wire leads bending back and forth. As long as the body of the cap is secured to something and isn't relying on the two little wire leads to hold it in place, they should be fine. I mean, 5000hrs at 105C? Yeah, you should never be anywhere close to either of those ratings!

Also, just FYI, assuming you weren't going to go bigger than a 6S lipo, the 35V versions would also be perfectly fine. Honestly, they would probably even be fine for 8S, which maxes out at 33.6v, but I like a little more wiggle room than that.

I'm going to shrink-wrap them and fix the pack somewhere around the cage.

Yes, I thought of getting the 35v, but then, as the Max6 can handle 8s, I'll be safe with some slack then. I never like too have things to tight!

 

[LibertyMKiii]

I have always used 35v Panasonic caps for 8s use with no issues at all. Typically they are a good bit smaller in size.

 

[gibawatts]

Another question I have, does it make any difference if, instead of soldering the caps as a piggy back to the ESC wires, I put it like a filter between the ESC and the battery? Something like this: http://www.espritmodel.com/jeti-high-voltage-capacitor-module-addcap-1640-63v-300a.aspx

 

[LibertyMKiii]

Another question I have, does it make any difference if, instead of soldering the caps as a piggy back to the ESC wires, I put it like a filter between the ESC and the battery? Something like this: http://www.espritmodel.com/jeti-high-voltage-capacitor-module-addcap-1640-63v-300a.aspx

The packaging there looks different but in reality its not. Just shorter leads so it appears like it is inline. The small capacitor leads couldn't support the total current of the system if built as an inline configuration. While I don't know exactly how they built this product I'd be willing to bet it is still a piggy back off the main current wiring with clever packaging.

 

[sadlerbw]

That’s exactly what it is. I took a look at some of the product pictures, and the caps are attached to a circuit board that has big honkin’ pads on it that you solder to the battery wires. It’s all tidy and hidden inside the heatshrink when you are done.

 

[MtnBkr]

Great info guys! I'm in the midst of some "real world" testing on a speed run build. I'll report back my logs before and after.

 

[Don mercier]

ok,... There are two main factors contributing to the voltage drops at the ESC. the Resistance and the Inductance. The resistance is a combination of the resistance of the wire and the ESR of the lipo pack itself. The inductance which is mostly the wires though there is some inductance in the pack and the cells themselves.

The resistance.

Resistance drops the voltage relative to the current through it. So (V) volatage drop = CUrrent (I) x Resistance(R). For example say you have 50A current draw and overall resistance of 10mOhms. this means you will see a voltage drop equal to 0.01(R) x 50(I) of 500mV or 0.5V! at the ESC. during the startup of the motor they have a much higher and short duration startup current. for example, say you have a 300 amp start up current. so you will see a voltage drop of 0.01(R) x 300(I) of 3V at the ESC. now these numbers are all hypothetical at this point.

The inductance.

Ill leave out the math here. Think of your wires as inductors. Inductors store energy in the form of magnetic fields. while the field is charging the voltage at the other end drops. your battery can only deliver so much current and some of that is being sucked up by the inductance. once the field charges fully this effect goes away and only the resistance drop is present.

To counteract these effects you can do a number of things. the best is to shorten the wires and make them bigger. this lowers their resistance and their inductance. they have less resistance and cant store as much magnetic energy. The other thing to do is to provide a current supply right at the load (the ESC). This is where caps come in. they supply low esr/inductance current during the inrush and while the inductance is charging. if your caps are connected via big wires then they are much less helpful as you are adding back in inductance and resistance to those current supplies. they still help because they are in parallel with the battery and helping to supply some of that current. with the case of electrolytic caps their ESR plays a much bigger role as well as they tend to be in the 100mOhm range compared to the 6-10mOhms of your Lipo pack. Since these spikes tend to be short you don't need a ton of capacitance to absorb them. its better to have much lower esr and Inductance. this is why smaller polymer caps placed right at the ESC would be much more usefull and compact. Polymer caps are in the 15-30mOhms range.

Ok I've been trying too follow all this and I'm no electrician, so I just want to ask. I'm running a blx 185. It comes with 3x 390uf caps on it... I bought two 1000uf 35v caps would these work on this application

 

[L0stB1t]

Ok I've been trying too follow all this and I'm no electrician, so I just want to ask. I'm running a blx 185. It comes with 3x 390uf caps on it... I bought two 1000uf 35v caps would these work on this application

2000 µF is on the low side (6000 µF is recommended: https://www.arrmaforum.com/threads/cap-pack.5613/post-132459) but if those are good quality low-ESR caps and you can safely connect them close the ESC, it might still be worth it; you're essentially tripling the total capacity.

But if you're not doing anything too crazy with that Senton, I wouldn't really bother. See the summary in one of my older posts (before I jumped into this thread): https://www.arrmaforum.com/threads/new-esc-with-additional-external-capacitors.11577/post-133495

 

[godfella691981]

Not sure if it is relevant or not, when I picked up my Max8 it came with an optional cap pack, I installed it anyway.
I'm with you on the 6 pack probably being a bit overkill, the 4 pack from killmode would probably be just fine in a 6s setup, I would think you would only ever see any befits from the 6 pack in a speed run car or a EDF plane/jet.

My MAX10 Sct came with those, I wondered what they were for. The manual says they are replacement caps for if the ones on the ESC burn out.

 

[arelee]

It was purely for piece of mind. If the current cap pack it is not enough capacitance it will be easy enough and estically pleasing to see a connector and not see cut wiring. Also, if I decide the esc/motor setup requires more capacitance I can just solder an xt90 connector on another cap pack and plug right in.

Hey joostin420,

I bought a 6S "Ripple Killer" cap. pack, to attach to my XL-X ESC. To save space, and keep the cap. pack as close to the ESC as possible, I want to solder the wires coming off of the cap pack directly onto the ESC. On top of the the battery wires connection on the ESC. I saw a youtube video where this was done.

In the instructions, Castle states NOT to do this, because It would damage the ESC.

However, if soldered at the correct temperature, and not directly onto the ESC itself, but on top of its battery wires, do you think that there would be any issues? I am using 60/40 rosin core solder. I don't know what the XL-X uses.

 

[joostin420]

I have seen it done, but I have not wanted to risk damage. I solder in as close to esc as I feel comfortable with and use xt90 connectors for removal when required.

 

[arelee]

I have seen it done, but I have not wanted to risk damage. I solder in as close to esc as I feel comfortable with and use xt90 connectors for removal when required.

That makes perfect sense. I won't chance damaging the XL-X.

Many thank's!