Bullet size vrs amp draw

[ezhitz]

I was wondering can the bullet connector size have any impacted on amp draw! Now I use castle 5.5 and want to know if going to 6.5 help lower amp draw. Currently on my 4s hydro I will peak at 255 amps and doesn?t seem to change much with smaller props. I ask only because I was told bullet size could be a problem.

Thank you

[fweasel]

Larger bullets will cause less resistance and allow larger amounts of current to flow, as well as decrease heat. Changing your bullets in theory could increase current draw if your system was previously limited by them and already maxed out. Unlikely though.

[RaceMechaniX]

The following link is to the German Eco racing site where several racers compiled connector contact resistance.
This is the best indicator of how a certain connector will be able to conduct current.
The lower the resistance the better. Size is not the best comparison, but consistency, fit of the pairs and cross-section are.
Notice that some of the smaller connectors have lower values compared to the larger diameter connectors which have poor fit.
Some of the connectors you just have to know have good or bad fits from experience to understand the table.

http://www.eco-idc.de/haupt.html

[larryrose11]

Tyler,
I cant seem to find the info about the connectors in the link.
Halp?

[RaceMechaniX]

Sorry, I thought the link would work directly. Here is a pic of the table.

Connector contact resistance.gif.jpg

[ezhitz]

Thanks Tyler for the info I’m currently using castle 5.5 connectors.

[fweasel]

I use Castle and LMT bullets. Well worth the extra price.

[eXoNerated]

Excuse me for asking but does the IMPBA and NAMBA still require connectors between the inverter and motor? If the total 3Ph motor current draw was 300 amps arbitrarily would that be 3 connectors capable of 100 amperes each?

Thanks,
Hubert

[RaceMechaniX]

Hello Hubert and welcome to OSE,
No, there is no requirement to have connections between the motor and ESC.
I am not sure there is a written rule about battery to ESC connections, but in the general sportsmanship to remain safe there should be a way to disconnect the battery from the ESC.
In the 3-phase connection to the motor, the current is not shared like a parallel battery connection. Each connection will see 300A.

[eXoNerated]

Hi Tyler,
I agree it is necessary and practical to implement some type of B+ disconnect however it seems soldering the the phases directly to the inverter would give the lowest voltage drop across them. How are you doing it in the SAW boat with LMT? Are you running the 6 wire versions?

BTW
Are you in North Carolina now? If so where do you run?

Thank You,
Hubert

[RaceMechaniX]

Hello Hubert,

Yes I am in the Asheville area here in Western NC. I have to travel to Atlanta just to run a model boat which is 4 hours away and travel about 7 hours to Huntsville to run SAW. The fast SAW rigger is a little too fast for Huntsville so it's pretty restricted on to only running at Munich for top speeds.

I am using Schulze controllers with direct soldered heavy wires on the ESC instead of the 6mm female connectors. On the motor end I am using either heavy wall 8mm bullets or 6mm LMT bullets.
I am using the 6 wire LMT motors in some of the boats, but not a requirement.

I hardwired the ESC to improve the packaging of the ESC close to the motor and reduce the possibility poor connection.

-Tyler

[eXoNerated]

Thanks for this Tyler. What american wire gauge are you using? Is there any particular brand you prefer based on solder ability, flexibility, oxgen free. etc? Any chance EC, N.C. can contain your boat? What solder and flux are you using? I hate to ask so many particulars but it matters.

Regards
Hubert

[RaceMechaniX]

I am using 8mm^2 wire from Nessel in Germany. https://nessel-elektronik.net/Siliko...schwarz-TypNEG I am using standard 60/40 rosin cored solder.

By EC you mean Elizabeth city? I have never run there, but I don't think it's long enough. The new boats are very slippery so once on plane they coast for a long length. I do not have air brakes on my SAW rigger so I need to length to coast or width to add rudder and make a wide arc scrubbing speed.