Hello,


I already use a Spirit System in my 450L Helicopter, everything fine. But I also think of using the spirit System in my big 700 Helicopter.
Actually I am using a HC3SX in the 700, now I am a bit afraid to replace it by the spirit system because of the few ports at the spirit System for power supply.
High Power Servos for a 700 Helicopter are drawing easily currents up to 20A...

I made some graphics:

HC3SX / BD3SX:


The HC3SX has three (!!!) direct Ports where power can be fed in (green arrows).
- the USB Port (thats allowed) => Greencap Buffer
- the output port for the ESC signal => Jive/Kosmik Master cable
- Battery port => Jive/Kosmik Slave cable

Apart from that, the three ports have different places, so the current flow is divided into two halves. One part of the current comes from the top of the unit and goes down to the servo ports and the other part comes from the bottom of the unit. So there is no place in the unit where the whole Servo current flows.



Spirit:


At the spirit System is only one direct port for power Supply and one indirect port for power Supply (over receiver PPM Cable) when PPM is used. If you use a Standard PWM Receiver then there is no port for direct power supply, then there are only two indirect ports.
The ESC Jive/Kosmik Master cable and the Greencap Buffer can't be directly connected to the Spirit. It is a pitty that it is not allowed to use the SYS Port for power supply.
Furthermore the two ports where power can be feed in are at the same place. So the whole current for all servos must pass one point. That means that the last servo (in this case the tail servo) gets the fewest power because of losses by Mr. Ohm.




Now I think of using a so called "power-bus" like that: http://www.mhm-modellbau.de/part-R2-POW-05.php
If you use this Powerbus unit, the servos are connected to this unit and the powerbus has an own big port for power supply. Then there is no current flow through the Spirit System.


What do you think?
Is it safe to use the Sprit System for High Power Servos without a "powerbus-unit"? Can the spirit handle high current?



Piotre

Hi

Spirit is tested for many years right now and is operating very well in even 800 size helicopters without any issues.
I recommend to use PWM connection if you are worrying about power slots.

Spirit cables are capable of delivering 20A continuosly and 40A in peaks.
You can fly without any doubt (if receiver is not a cheap clone) with BEC leads connected "indirectly" to your receiver.

Whats more, connecting one power lead to receiver and one to the unit causes unbalanced loads in the cables.
In case of failure there are very same chances for succesfull landing.

UPDATE: For such short cables resistance losses are relatively very small. Its resistance could be gradually higher with higher temperatures. For the resistance difference, you have to reach temperatures mostly bigger than 200°C. So until your cables aren't so hot, your model is safe.

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Spirit System developer

Thanks for the answer.

I am using Jeti, so no cheap clone receivers. Right now i use a Rsat2 receiver with the HC3SX, but actually I cannot use the Rsat2 receiver with the Spirit because the Spirit has no Signal out for the ESC. The Rsat2 receiver has only two Ports, PPM and EXT.

I already had to change the receiver in my 450L to a R6, there also worked a Rsat2 in the past.

I will think of power ports...perhaps I use some Y-cables at the Servo ports to get more power supply ports. In my opinion the power should be fed in at the place where it is needed.

Piotre

No problem.

It is absolutely not needed to connect BEC drirectly to the unit. You will need to secure connectors only to get same safety level with for example hot glue.

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Spirit System developer

Tomás,

The cables that come with the Spirit are seem to be 24AWG. A foot of 24AWG has a resistance of 0.025 ohms. If such wire carries 20A of current continuously, the total power dissipation will be 10watts. At 10watts, the wire temperature will rise very much up to the point the insulation will melt, and the wire itself will be very hot! Moreover, the connectors used in the cables are rated for much less than 20A. So according the analysis, the cables won't be able to work at 20A.

I can understand the Spirit cables can withstand a current of 20A of short duration, but not continuous.

Please, correct me if I'm wrong, or if I'm missing something in my reasoning.

Thanks,

David

Hi

Our cables are tested for 20A continuously (1 piece for 10A) and 40A for 3s peaks. There are more types of cables so it is not so easy to determine which one can handle such current without actual tests.
With cheaper cables it caused abnormal heating. Main difference is in wire threads.
These tests were performed with special equipment directly for this kind of measurement.

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Spirit System developer

Do I understand correctly youre saying not to connect one bec lead to the unit and the other one to your receiver? I hate Y cables and thats the only option until more ports are added. Is it bad?

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[b]-TT E700 V2-Spirit Pro-mks950-980-Kontronik Kosmik 160 HV -Pyro 700 rewound by PD / Voodoo 600 -PD-MX700-470kv--BLS255hv-VBAR 5.3+- Gaui X3+ Spirit Pro

Well, none is bad. I recommend to power the unit through 2 cables. Simplest solution is that which is used in e.g. PWM scheme.

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Spirit System developer