German S-100 Class Schnellboot (Fast Boat)



The SBoot Electrics

I recently (2015) bought three 120Amp waterproof brushless speed controls:

These seem to work OK and have reverse which starts from about mid stick position, however they don't seem all that smooth at the low end of the revs but we'll wait and see if that is an issue or not. Having the same amount of reverse as forward is not a good idea in a boat as it will "dig in" going backwards and swamp the boat, even in a car you only have 1 reverse gear, I'd prefer to have more forward stick and a smoother start with only about 10% reverse speed but getting a speed controller with reverse at all seems to be a bit of a trick so lets not be too choosy.

 I also tried one of these speed controllers on the 1/35th Schnellboot model with three much smaller brushless motors all wired in parallel to see how that works, could have been a disastrously short trip as I wasn't sure what the speed controller would make of the signal back from all three motors but as long as the motors can run freely they seem to sink up ok and all run at the same speed and quite controllable so this is the path I will take for the 35th scale models, i.e. one battery, one speed controller. The 35th scale props for the Schnellboot that I bought from G-Force have counter rotating wing propellers so one motor needs to be running in a reverse direction to the other two, to achieve this, two wires of the reversed motor need  to be swapped over.

This is the 35th scale Schnellboot hullframe with three small AXI brushless motors installed all wired in parallel running on one 120Amp HobbyKing brushless speed controller. So now when I come to put the three controllers in the 20th scale boat one of the speed controllers doesn't seem to work properly and I don't know if it's the same one Itried this experiment with?


I bought four of these Turnigy 5,000mAH Lipo batteries a few years ago and made sure they were kept charged, these have only been used for the odd experiment so far. two of them have expanded and split.

So being the electronics engineer and the mad experimenter I decided to see what happens when they are discharged by a big fat 1 Ohm resistor, so 15Volts equals 15 Amps, not a huge current I thought! Anyway look what happened! I did this in the safety of my brick bunker with the hose on standby just in case. The question is "Is it relatively safe now that it's discharged fully"? Certainly there is no electrical energy in there. How do I dispose of them? How do we dispose of camera, phone, laptop Lipo batteries, these have Lithium in them which is very toxic, especially to fish and groundwater. I may go back to NiMH batteries, having spent many thousands of hours building the boat do we really want it to catch on fire in a spectacular way?


Make sure you have one of these fire resistant bags to charge your Lipo batteries in, they are not expensive and your life may well depend on it, This one has a velcro tab that closes over the wires easily. Charge your batteries somewhere safe. There are plenty of examples on the Internet of what happens to Lithium based batteries when they explode.


These are the two remaining 5000 mAH Turnigy batteries in the forward battery box, which is mounted under the bridge housing.


Before the above split 5,000mAH batteries were noticed I purchased another Turnigy Graphene 10,000 mAH battery for the mid motor so that I can get good operating times, I did plan on buying two more of these but I shall play the waiting game now and see how it survives first because I am not happy Mr Turnigy. You can see a cell voltage siren fitted to this battery, this is a safety device that plugs into the balance charging socket and sequentially monitors each cell, there are settable voltage points that operate a loud siren if any of the cells fall below the set point, so this can live in the boat and let us know if the battery is getting low or if something worse starts happening. This is from Radient - - it is model RDNA0326 and I bought it from the local hobby shop.



This is the aft battery box for the 10,000 mAH battery. I built these with a numer of notches on the bottom so they lock into the ribs but can be moved back and forward for weight balancing.


This is an XT90 connector, as fitted to the 10,000 mAH battery, these are the best connectors that I have found so far and I will change all of them to this type.



I have purchased a 2.4Ghz Futaba 7 Channel radio system:

This is awesome, I can use all 7 channels to control various functions! One paddle (and one hand) could control steering and speed so the other paddle can be used for gun altitude / azimuth or similar and there is another rotary knob to proportionally control a servo which I may use to experiment with the "Llursen" effect, this then leaves two toggle switches to turn things on/off or launch torpedo's or similar. So five proportional controls and two switches.


I also bought a number of 5000mAH Turnigy Lipo batteries a while ago and recently a Venom balance charger:

I've had these batteries for well over a year and had no effective way to balance charge them until I bought the Venom charger in early 2016 and I was surprised how well the batteries have kept their charge.

Balance charging is so important for Lithium batteries as all of the cells are in series and if they are not balanced (in voltage and therefore charge level) one cell can become discharged before the others, especially at high loads (and I am planning very high load currents) and then that cell will reverse polarity with disatrous results.


(C) Copyright 2016  - John Drain