speedracer1129

How do you figure 20C rating is low??

ryan_t888

The A123 pack linked was rated at 30C discharge. There are plenty of 30C rated LiPo's as well. All with 60C burst.

speedracer,
I'm currently looking at LiPo's for 1P race setups, and 20C @ 5000mAh for example would be far too risky/low.

Ryan

nuts5000

ok what prop are you using on the stock BJ ????
and is this with turn fins?????

thanx from a BJ owner

oh and i have been having problems with my reciver
any body else??

speedracer1129

Hey Ryan,

First I am assuming that by "1P" you mean a single pack?!? Now, a Lipo pack of 5000mah with a 20C rating means 100amps continuous. We all agre?? OK, now here is the info off that same link posted:

6.6V 4600 Li-Ion Nano Phosphate Hypersonic Pack

Key Features
Inherently safe chemistry will not explode or catch fire
Twice the cycle life of competitive Li-poly batteries
50% more power (up to 60C burst) than competitive Li-poly batteries
Fast charge capable - reach 100% state-of-charge in 15 minutes using the Hypersonic ChargeSafeâ„¢ balancing fast charge system.
Balancing connector (compatible only with Sonic Charge (AQR400088))
Overview
Hypersonicâ„¢ is a high power density battery pack safely providing up to 30C continuous output and 60C burst rates. Unlike traditional lithium-ion, Hypersonicâ„¢ packs have exceptional safety characteristics with no risk of spontaneous combustion. All component cells are UL-1642 compliant. Deans Ultra connectors are standard.

Designed for exceptional power output, durability, and safe operation, Hypersonicâ„¢ Lithium Ion is the next generation battery for the R/C market. Using a unique, patented, revolutionary lithium-ion chemistry developed at A123 Systems, Hypersonicâ„¢ packs provide high performance and abuse-tolerance unmatched by any other battery chemistry.

With its ultra low-impedance design and high power capability, Hypersonicâ„¢ offers high performance and long cycle life characteristics in a robust, safe package, able to deliver up to 60C burst rates.

Hypersonicâ„¢ packs can also be connected together to create custom configurations for almost any electric propulsion application.

Experience a new level of battery performance in R/C vehicles with A123 Systems Hypersonicâ„¢ Lithium Ion.

Specs
Type:Lithium Ion
Capacity:4600 mAh
Voltage:6.6v
Connector Typeeans Ultra (wsd1300)
Maximum Continuous Discharge :30C
Maximum Burst Discharge :60C
Maximum Continuous Current :69A (138A Pulse)

It is clearly showing that this type of battery chemistry has a 1C rating different than Lipos cause it states 69amps continuous. So please explain how a pack rated with lower continuous amperage and voltage is better performance wise?? Is there something I am missing??

Lastly, the C rating is irrelevant. If you have a 2000mah rated at 20C and you have a 4000mah rated at 10C you still have 40amps continuous out of both packs. So why shoot down a lower C rated battery as long as you have the capacity to compensate??

Luis

Luis

ryan_t888

speedracer,

I'm not for or against the A123 cells and certainly not defending them. I was just saying that 5000mAh @ 20C LiPo would be far too risky for my planned race setups. I'm hoping to pull around 90-100A continuous, this does not leave any room for error on a 20C battery. I need at least 25C or 30C to be "safe." This was in reference to your quote asking why 20C would be too low.

As far as the 30C discharge vs 69A stated continuous dicharge, there must be an error somewhere in those specs. C meaning capacity is 4.6Ah. Multiply this by 30 and it should be a continuous discharge of 138A.

Ryan

speedracer1129

I understand what you mean. I tried to go to there site but it seems partially down. Never the less, just because a 20C pack does not meet your needs doesn't justify that it is no good as Taylor implied!! Also, if you went to a 6000mah/20C pack you would have a 20% that would work for your application. So it really is all relevant to what you need! However, I still don't understand why go with that pack if you are losing power due to much lower voltage. Just because a pack takes a higher voltage, doesn't mean it continuously gives it to you. Otherwise, the pack would be rated at a higher voltage.

Still, I recommend that if anyone really wants to use the A123, then to take full advantage, get them through MaxAmps only because they can build you a pack to meet your needs for capacity AND voltage. I definately would like to see heads up numbers between lipos and A123 cells to get a better idea.........but that is for another forum!!!

Lets keep those BJ/SV27 battles and comparisons going!!

Luis

ryan_t888

In other setups I would 2P the LiPo's. With only a maximum of 10 000mAh allowed, I will not purchase anything larger than 5000mAh. This is why C ratings are very important for certain applications.

Ryan.

needy4speed

the black jack is nice,but as i heard it does'nt handle nearly as good as the super vee which i am a proud new owner of...also checkout the hardware..i don't like all the plastic on the bj...if they had nice hardware as the the sv does it would be a closer contest..but i paid forty five bucks less for my sv and i feel i got the better boat hands down best price i found on bj was 289...but if you want 2 boats the bj would be a good second boat...but personally id rather buy another sv in another color

Avanti27offshore

best so far on GPS
BJ stock motor, hydra120 esc, prop?, 4200mah nimh 36mph
SV ammo 2300, stock esc, grim 42x55, 4200mah nimh 37.1 (but very unstable even with the batteries 3" fwd of stock so there is more to be had speed wise)

SV27dayton

Avanti,
Not sure why you think an unstable boat indicates it's capable of going faster? Also curious why you bumped up to the hydra 120. Is is thought that the stock ESC couldn't handle the ammo motor?

Avanti27offshore

the factory esc took a dump on the BJ that is why obrien did the upgrade

the reason I think there is more speed is the SV is because the boat is unstable due to the added power of the 4200mah batteries, so when I get the boat settled down by changing the set up I will be able to use the power that is there, hence faster run.

SV27dayton

So you are not able to hold it wide open long enough to top out. Do you have the adjustable trims? If not you need to get them and trim down 1/2 turn at a time.

obrien

Tabs are going to be his next purchase. We were talking about those last night.

Avanti27offshore

I am also going to try removing the star. turn fin and see what happens. (I have a port to install but I think it will just cause drag and want to test with no fins before I drill the transom)

adjustable trim tabs are high on this list of things to get SOON!

CadillacDTS2001

because when i run 30 C packs and 2P them
20C is just to low for what i do.

NitroNuisance

I thought they both had 45amp esc's

Avanti27offshore

obrien got his boat dialed in and went 42.9 so the BJ i sahead for now.

Easy rider

This is like comparing the taste of apples and oranges here.

You simply can't compare the handling of cat's and deep V's. Those are two totally different hull types with different purposes.

Generally speaking , a cat isn't as fast in cornering but they can be very very fast in straights. Do you want good handling or good speed ? A fast mono hull is a handfull to drive at top speed , cat's are easy in straights but tend to flip faster so you have to be carefull anyway. A bad flip can do some major damage to a hull.

The super V isn't a fast mono hull because it has no step in the bottom , so more water friction. And also because it's a V instead of a rather flat bottom. Deep V's handle GREAT in corners , nothing comes even close but have to give up speed in the straights.

An extremely well ready built shallow V mono hull is the Hot Shot from MHZ. All you have to do is add batteries , a prop , esc , receiver and obviously a motor.

here's a video I shot of my friends cat on 12 cells , just to show you how fast a BJ alike cat can be when well built.

http://www.youtube.com/watch?v=gLyBnkUxVTg

ryan_t888

What are you referring to?

I believe all mono's are the weakest in handling. The order of best handling, best top speed in my opinion from worst to best is a mono, cat, tunnel, hydro, rigger. This is said from experience with all hull types. The BJ, or all Proboat cats are an exception to this.

Ryan

Avanti27offshore

easy rider--
A step in a v bottom adds to acceleration and has nothing to do with top speed as it is not even in the water while on plane. the step also makes the boat looser in a corner.

we are not comparing cats to monos we are comparing the SV27 to the BJ26

Easy rider

Yes , this is comparing a cat with a mono. BJ vs. SV.

And the step does help with top speed because the hull rides on the rear edge of the step and the prop so the part of the hull from the step to the transom comes out of the water resulting in less friction / less water contact. This is theoretically on calm water. Most stepped flat bottom hulls like the Hopf Gozilla WE ( the best stepped mono1 hull on the face of this planet ) don't behave very good while cornering but are very fast in straights.

And indeed , steps help with acceleration allot too.

A non-stepped hull has a much bigger ride pad , more contact with the water resulting in better handling but giving up speed.

This is my RCMK deep V non - stepped mono1 , just see how fast it corners . Impossible with a stepped hull.

VIDEO : http://www.youtube.com/watch?v=-4XlVacW1JM

Avanti27offshore

yes A bj vs A sv, we are talking about two speciffic boats not the hulls in general.

I'm done talking about it. Thanks for your input, but when we run the bj and sv side by side they are close. There is no walk away winner.

SV27dayton

every time someone posts taht cats don't turn I have to post this video. He back off but it gets around quick.

http://www.youtube.com/watch?v=vGVdNT76M0w

SouthJerseyFe

Hmmmmm Cat dont turn hu..Well I'll be damned but look at my cat corrner like its on rails............... WOT is just over 40mph and I am holding it wide 99% of the time.. The cat is 34x10 on 4s-2p around 6 pounds.
[link=http://s42.photobucket.com/albums/e343/STOAK/?action=view&current=S2-1PX2.flv]Cats turn with the best of them!![/link]

SouthJerseyFe

Oh and BTW in IMO the SV27 is the better product. ProBoat blew it with the hardware selection.