How do I make my battery last longer?

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4 July 2010 at 20:31 #3592
David Reeves
Participant
@davidreeves52100
I’m having trouble with my first model boat
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4 July 2010 at 20:31 #27485
David Reeves
Participant
@davidreeves52100
I’m making a really simple non radio control model boat, however when I came to connect the battery to the motor it ran like the clappers for 2/3 minutes until the battery was completely drained, How can I make the battery run the motor slower and therefore last longer? The boat is a semi scale warship so doesn’t need to be fast. the motor says it will run between 4-9v and the battery is a 9.6v rechargable ni-cad.
4 July 2010 at 20:48 #27486
Colin Bishop
Moderator
@colinbishop34627
I don’t think there is any easy way to do this on a free sailing model. With a radio controlled boat you would use a speed controller which would allow varying speeds and supply the motor with the appropriate amount of power. Of course if you ran it flat out all the time then it would still only last for a few minutes. Introducing a resistance in the power to the motor would slow the boat down but simply bleed off the extra power as heat so you would not get a longer running time.

You are running the motor at the top end of its speed/power range so it will drain the battery very quickly as you have discovered. I think your only real alternative would be to use a lower voltage higher capacity battery, say 6 volts, This is likely to give you a more scale speed and last longer but you may have to experiment a bit.

Colin

Edited By Colin Bishop, Website Editor on 04/07/2010 20:49:06
5 July 2010 at 06:34 #27488
David Meier
Participant
@davidmeier28154
Hi David.

If your model has twin motors you could wire the motors in series which would halve the voltage to each motor and make them run slower.

I think this would help. What do you think Colin?

David.
5 July 2010 at 10:00 #27489
Colin Bishop
Moderator
@colinbishop34627
I get the impression that the boat just has the one motor. If it had two then wiring in series would not necessarily work as unless the motors are perfectly balanced electrically, one always tends to run faster than the other. I think a lower voltage higher capacity battery is the way to go.

Colin
5 July 2010 at 16:15 #27494
60watt
Participant
@60watt
What information do you have on the prop,motor and battery?

If you get 2/3 minutes then your current drain is about 20-30 times the battery amp hour figure. I suspect using a smaller prop will increase speed and duration.
5 July 2010 at 23:21 #27502
Dave Milbourn
Participant
@davemilbourn48782
One of these might be worth considering

http://www.mfacomodrills.com/speed_regulators/voltage_regulators.html

I would, however, first change to a much lower voltage battery and also maybe a smaller prop.

Dave M
7 July 2010 at 20:40 #27517
Kevin Flack 2
Participant
@kevinflack2
I have seen in our local RC Component catalogues a small manually adjustable DC motor speed control like a RC type in pulse control. this would enable setting the speed at a realistic one with the benefits of the RC systems?

Just a thought?

Kevin
7 July 2010 at 21:03 #27518
60watt
Participant
@60watt
Possibly the very same mfacomodrill one.

£1 will cover a vero circuit consisting of a 10% to 90% mark/space speed control based on a common 555 timer circuit beefed up up with a power transistor and diodes.

http://www.google.co.uk/search?hl=en&as_q=555&as_epq=speed+control

Circuit diagrams on the internet

Example:-

http://www.simplecircuitdiagram.com/2009/05/04/motor-speed-control-using-pwm/
8 July 2010 at 18:42 #27524
ashley needham
Participant
@ashleyneedham69188
need more info from the poster I think.

He could have a Purple Avenger 3000W cnd300+ series hot motor and a 25 yr old 900MaHr Ni-cad battery with 50mm 6 bladed prop for all we know and a simple change of motor battery and prop would sort hm out, eh?

Come to think of it, that sorts out most things!

So…David…motor type/any markings…battery type/markings hull and prop sizes all required for the electrical experts arrayed thus in the forum to advise.

(but dont expect a consensus of opinion)

Ashley
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