How RC Boats and EDF Jets can pull 120A+ reliably

RC boats and EDF jets come to mind when it comes to the top performance vehicles in RC and the most demanding on it’s components. Pulling 120A+ reliably is not as easy as plug and play. Especially if you are operating an RC that you had built. Even ready to run or fly RC’s have “watch outs” to them that will help increase reliability. Keep in mind we are talking about 120 amps continuous. Let’s look at what we can do to make certain we maintain maximum reliability in these high power demand systems.

RC LiPo battery vs High Demanding Power Systems

Every single RC vehicle (120A+) that is sold to my knowledge, does not provide a battery pack included. These are purchased separately. It is critical to the completion of the RC, to purchase a battery that can handle the load. Pulling 120A+ reliably on any battery pack is a significant load.

Generally speaking, a high demand power system that is capable of pulling 120A or more continuously will have a larger battery pack. The battery packs tend to be in the range of 4000mAh to 5000mAh in capacity. These higher capacities increase the continuous current draw of the pack in our favour. Picking the correct C rating of the battery pack to give you lots of head room will increase the reliability. For example, a 4000mAh battery with a 120A continuous current draw, selecting a 45C pack or better is ideal. A 45C battery pack will provide 50% head room in terms of the loading. The maximum continuous current draw for the battery pack is 180A. Visit the battery C rating page for more information on battery packs.

LiPo Battery Run Time

A critical component to maximum system reliability is limiting your run time correctly. A lithium polymer battery is best kept above a capacity of 20%. You can read more on maximizing the lifespan of the LiPo here. As the battery’s capacity drops less than 20%, the amount of heat that builds in the pack increases. Heat build up in the battery pack can permanently damage the pack. Avoid discharging in to this critical zone to maintain reliability.

Maintain ESC Reliability on High Powered RC’s

If you are selecting an ESC for a build, selecting an ESC is actually quite easy. Just make sure you select an ESC that can handle the correct cell count (obvious point here) and the current draw. Selecting an ESC and getting the cell count incorrect will leave you with a dead ESC immediately on power up. However, selecting an ESC incorrectly for the load that you place on it may not be immediate destruction. You may be flying your EDF jet at 100mph when all of a sudden on the 4th flight the motor shuts down when you are 600ft away and you can’t see it to land safely.  This results in a near total loss.

Even after running the calculations and doing all the research you could make a mistake. Grab a data logger and record your first run. Understand what kind of loading is placed on your power system and then compare against specifications. You never know when something might be binding and is not immediately figured out on the bench. This will show up on the meter.

ESC Temperatures vs Reliability

It doesn’t matter if you have selected an ESC that can handle 10 000A for your 100A load and the ESC is running too hot. Temperature is the ultimate killer of electrical components. Review the maximum continuous temperature that your ESC should reach in the instruction manual that came with it. Tweak your setup to be certain you can run your setup as cool as possible. Temperature is another parameter that can be logged.

Can a weak LiPo place more load on your ESC, Destroying it?

The short answer is, yes it can.  Drawing over 120 amps of power is quite significant for any power system in RC. A weak battery pack will create a more significant voltage drop for every pulse of power that is sent from the ESC to the motor. The ESC in the system sends these pulses at a high frequency. Each pulse that is sent to the motor results in the voltage sagging as the pack is under load. The amount of voltage that the battery pack sags, is dependent on the batteries specification and condition. It is this voltage difference that is known as ripple voltage within the ESC. Significant ripple voltage will place extra strain on the ESC. This strain can lead to failure within the ESC. On high powered radio controlled models, be certain to use a healthy battery pack.

Maintain Motor Reliability on High Powered RC’s

Very similar to the above, maintaining reliability on the motor is very much related to the temperature. It is best to keep motor temperatures below 60C or 140F for optimal reliability. If you are selecting a motor for your own build, you will want to size it correctly to be able to handle the load. Larger motors that can dissipate more heat will help reduce the running temperature.

 

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