Are Zippy Lipos safe with a Castle MMM Speedy? - Page 3 - RC-Monster Forums

BrianG · 02.24.2009, 03:00 PM

Patrick, when the TVS fails, does it fail open or closed? Meaning, will the user be able to tell it has gone bad? I'm just thinking that if it was forced to dissipate too much power without sufficient cooling interval, it might pop and then allow the large spikes to get to the battery.

MrMin · 02.24.2009, 03:53 PM

Cool down..This is a heated thread! I've built a couple of 6 x 4700uF 50v SuperLowESR audio grade capacitors(thats 24mF 50v cap.) and placed then across mmm input. That should help the poor little ESC with its ripple current problem, maybe. Whats your throw on that one patrick? Kind of "band aid" - like BrianG said, but I've did it already a week ago. Not run it yet.. (have family) :-). Maybe some vendor will start selling big caps like for car audio for eg....

BrianG · 02.24.2009, 03:57 PM

Quote:

Originally Posted by MrMin

...Maybe some vendor will start selling big caps like for car audio for eg....

Mike does carry some low-ESR caps in his store already: http://www.rc-monster.com/proddetail...=35vcap&cat=21

MrMin · 02.24.2009, 04:06 PM

hee hee. I mean much bigger caps. Like the 1-2 Farad monsters for car.. coupled with low ESR they will cost more than the batts....Hey Mike, monster opportunity.. if you put a sticker on it, you can sell it for double the price and have some nice flashing leds on it...

...I think my overkill 23mF low esr should suffice - did not do the math - off the batt(pun intended :-) ) what do think brian?

Pdelcast · 02.24.2009, 05:08 PM

Quote:

Originally Posted by MrMin

hee hee. I mean much bigger caps. Like the 1-2 Farad monsters for car.. coupled with low ESR they will cost more than the batts....Hey Mike, monster opportunity.. if you put a sticker on it, you can sell it for double the price and have some nice flashing leds on it...

...I think my overkill 23mF low esr should suffice - did not do the math - off the batt(pun intended :-) ) what do think brian?

It would be hard to find room for a 1-2 farad 35V capacitor in an 1/8th scale.

But yes, extra capacitance cant hurt, and in some cases will be a very good thing.

HOWEVER, using it as a band-aid for insufficient batteries isn't a good idea -- just get batteries that can handle the load (better fix...)

Pdelcast · 02.24.2009, 05:09 PM

Quote:

Originally Posted by BrianG

Patrick, when the TVS fails, does it fail open or closed? Meaning, will the user be able to tell it has gone bad? I'm just thinking that if it was forced to dissipate too much power without sufficient cooling interval, it might pop and then allow the large spikes to get to the battery.

Usually, they fail closed for about 1/100th of a second, then they fail open. Seriously.

BrianG · 02.24.2009, 05:16 PM

Thanks for the info. So, the user might never notice it when driving around if it happens to go bad. They should be designed to emit red smoke or something equally cool and visible.

And yeah, a 1F cap would be "slightly" large and heavy. For the weight, might as well add more cells...

MrMin · 02.24.2009, 05:34 PM

Just triple up on caps. BTW: If you look at the specs, the ripple current of about 3A per 3300uF Cap 50V.... And if that does not work, use a bigger hammer. How much ripple-C are we expecting, patrick, brian??

No Really...1F is just a joke. red smoke is a good idea and TVS Transient Voltage Spikes are are real problem. That is why patrick said DONT USE THE NO SPARK THING.

Wink Wink Brian

Pdelcast · 02.24.2009, 05:38 PM

Quote:

Originally Posted by MrMin

Just triple up on caps. BTW: If you look at the specs, the ripple current of about 3A per 3300uF Cap 50V.... And if that does not work, use a bigger hammer. How much ripple-C are we expecting, patrick, brian??

No Really...1F is just a joke. red smoke is a good idea and TVS Transient Voltage Spikes are are real problem. That is why patrick said DONT USE THE NO SPARK THING.

Wink Wink Brian

The better the battery, the less ripple current ... so what we do is size the capacitors to something that is reasonable, and use a high switching frequency to optimize the capacitance (higher switching = lower ripple current.)

But, the enemy is ripple voltage -- and the better the battery, the less ripple voltage.

Pdelcast · 02.24.2009, 05:47 PM

And for those who are interested...

We've been struggling with whether or not to release a version of software that actually measures voltage ripple, and limits performance based on how the batteries perform.

On one hand, it would prevent a lot of damaged ESCs, and batteries -- when users are pushing batteries insufficient for the application.

BUT, on the other hand, a lot of people who are running "marginal" systems will see a performance decrease, and might yell "FOUL!" at us for releasing software that would actually lower the performance of their system.

As it is, very few controllers actually get damaged by ripple voltage/current -- but the people who damage controllers this way don't just do it once and then learn a lesson. They tend to destroy controller after controller with the same bad setups. And then they blame US for making a defective product.

Brian, and others, I'd be interested in hearing your thoughts on this...

phatmonk · 02.24.2009, 05:53 PM

What corners are being cut with these Zippy batteries that they can sell them so cheap?And cause these issues?

Arct1k · 02.24.2009, 05:54 PM

I'm for the software Patrick - I'd rather have something trip or lower (but i'm sure acceptable) performance than a smoking esc.

I toasted a couple of MM early on and paid for them to be replaced as used in 1/8th scale - Even though well rated batteries in reality I believe a component was ripple - since the failures I then added extra caps and never had a failure since.

johnrobholmes · 02.24.2009, 06:09 PM

I would rather see the ESC limit instead of have it slowly get killed from ripples.

e-mike · 02.24.2009, 06:11 PM

me too...+1 for the software....i take very care of all my mmm.....this kind of devise could it be a great solution for a bad set-up.....

02.24.2009, 06:17 PM

Quote:

Originally Posted by Pdelcast

And for those who are interested...

We've been struggling with whether or not to release a version of software that actually measures voltage ripple, and limits performance based on how the batteries perform.

On one hand, it would prevent a lot of damaged ESCs, and batteries -- when users are pushing batteries insufficient for the application.

BUT, on the other hand, a lot of people who are running "marginal" systems will see a performance decrease, and might yell "FOUL!" at us for releasing software that would actually lower the performance of their system.

As it is, very few controllers actually get damaged by ripple voltage/current -- but the people who damage controllers this way don't just do it once and then learn a lesson. They tend to destroy controller after controller with the same bad setups. And then they blame US for making a defective product.

Brian, and others, I'd be interested in hearing your thoughts on this...

An optional software updated for that would help the people who pay attention to their rigs know if they need to upgrade or not

The stubborn people will argue that their 2C 500mAh batteries can handle their 1/8th scale no matter what