Model Boat Mayhem
Technical, Techniques, Hints, and Tips => The "Black Arts!" ( Electrics & Electronics ) => Topic started by: sailorboy61 on September 16, 2012, 08:13:08 pm
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I have a twin motor boat.
Question - Am I better with two separate batteries feeding the two separate motors, with the possibility of unequal discharge rates, or two batteries, via a balancing board, (Action), feeding the two ESCs for the motors both wired into the single output of the balance?
I presume the latter means I need to watch the draw current of the single output as a disadvantage?
Thanks to the experts!
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Unequal discharge should only be a problem if spending a lot of time running on one motor. of if one battery is not as good as the other or one motor a lot thirstier than its mate. Although it is by far the simplest option, it might be well worth considering using a separate battery pack for the RX/servos as well. Murphys law states that the ESC carrying the systems BEC will be the one to cock its toes up - this is aided by the fact that that one is doing that bit more work.
As per Action's drawing, you only need one main switch. Of course, the bit where the two supplies and the two loads are common could well need heavier wire unless the rest of the wire was heavy enough in the first place. This is especially important in the ground line as any resistance here will affect the switching voltages of the timers in whatever is being controlled.
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I have two twin screw boats that are both built with one battery/ECS for each motor, and in each boat one battery and ECS provides the power for the receiver and servo. One boat is a tug that has two 12V 7Ahr sealed lead acid batteries with an ECS each, the other is a warship that uses two 7.2V NiMh packs and with both of them I've never noticed any difference in the charge levels of the batteries even after serveral hours of running. The current load drawn by the receiver and servos is tiny, under 100mA, this is a negliable current load when compared to what the drive motors draw, I wouldn't worry about it.
The other ECS in each boat has its middle, 5V supply cable disconnected from the receiver because its not needed, but you can still put that 5V to good use if you know how. The voltage regulator in the ECS that supplies the 5V is capable of suppling up to a 1A load (Mtronics ECS are certainly capable of this), this is plenty for powering LED lights for example. In the tug I have this ECS connected to the receiver through a circuit board that I built that allows the black ground and signal cables to pass through to the receiver but terminates the 5V at some connectors that can be used to connect LEDS too. The circuit board has the correct resistors on it to protect LEDs and a relay switch circuit so that the LEDs can be switched on/off from the transmitter. The total current load of the LEDs and switch circuit is under 50mA (thats 0.05A), negligible to the battery.
Hope this helps.
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Go with ACTions advise I would,I have a couple of boast on this sytem and never have any problems with it.
Dave
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I've not had any problems with this setup, its always worked reliably.
Regards
Neil