battery life

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7 March 2010 at 13:59 #25841
Kevin Flack 2
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@kevinflack2
Running 2x 540 motors in a PT boat what life from 2000mA or 2800mA nicd battery pack

anyone have ideas on this?
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7 March 2010 at 13:59 #1949
Kevin Flack 2
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@kevinflack2
7 March 2010 at 17:45 #25843
ashley needham
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@ashleyneedham69188
Kevin. Its a question bordering on the “how long is a piece of string” variety.

could be 2 hours for a pair of low drain 540/1 (MFA types) when poodling along gently all the time, or about 5 mins for full speed running with two “purple heat” super hot motors.

Or anything in between. I wouldn’t even like to make a guess . If nothing else, it would depend on your throttle hand (and it IS a PT boat dont forget).

The only way to even make a stab at this is to calculate, or better still, measure, the power drain at full throttle, and this would give you the least duration, and then calculate power consumption at ,say.1/3 throttle, and this would give you “best” duration….and so depending on the throttle useage, the ACTUAL duration will be somewhere in between, or less if not using a seperate reciever pack.

Possibly someone in the forum has a twin 540 engined boat and could say how long thier boat runs?

Ashley.

Edited By ashley needham on 07/03/2010 17:46:40
11 March 2010 at 17:06 #25874
Kevin Flack 2
Participant
@kevinflack2
Hi Ashley

I guess I rather asked for that one?

But I did have a 800mA old nicad pack that did not do 3 laps around the pool and was hot as anything, it did have a seperate receiver set also.

With that sort of performance it worries me to take it to the club.

It has a mechanical speed control which also does not help I suppose.

The PT boat will also encourage a heavy throttle hand no doubt, I may try it at the club with a lead battery but is rather heavy

I do get more than 1 hour on the other boats maybe even 2 or more but the are more sedate and have electronic controls.

I suppose a 20min time would be acceptable so if anyone has any similar setups/experiece?
11 March 2010 at 20:53 #25878
ashley needham
Participant
@ashleyneedham69188
Kevin. I dont know what size cells you had in NICac, but 800ma has been way surpassed in even AA cells,now offering 2800MaHr.

3000+ are easily available for Sub “c” cells, so your three times around the lake would become at least 12 laps, and if going for 4300mA cells….a good while longer.

Your Nicad cells are bound to be past their best. Splash out on the meatiest pack you can afford and I should think 45 mins would be yours for tne taking (not at full power of course!)

Ashley nb Ditch the mechanical speed controller, and you may get twice the current running time with no other alterations….
28 March 2010 at 12:44 #26144
Kevin Flack 2
Participant
@kevinflack2
After running at the lake on 1x motor to extend the life, speed was not too bad on the one anyhow!

Did some tests on the motors as fitted ran no load at 2.5A 2.7 with shaft and popped 8/10 fuses on the water.

Tried another of my motors it repeated at 1A at no load so fitted this instead, ran for 15 min + on the pool. A 2000mA battery pack giving the power.

So now will fit the 2nd motor only as an overdrive mode when I get a more efficient version.

Point is where to source the lower current types? So why is there no way of indicating the motor current etc I do see that the car motors have a huge selection of motor types and turn types. or am I missing something?
29 March 2010 at 15:44 #26159
60watt
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@60watt
Posted by Kevin Flack 2 on 28/03/2010 12:44:12:

After running at the lake on 1x motor to extend the life, speed was not too bad on the one anyhow!

Did some tests on the motors as fitted ran no load at 2.5A 2.7 with shaft and popped 8/10 fuses on the water.

Tried another of my motors it repeated at 1A at no load so fitted this instead, ran for 15 min + on the pool. A 2000mA battery pack giving the power.

So now will fit the 2nd motor only as an overdrive mode when I get a more efficient version.

Point is where to source the lower current types? So why is there no way of indicating the motor current etc I do see that the car motors have a huge selection of motor types and turn types. or am I missing something?

Kevin,whether you are trying to get more power,more efficiency or longer duration,the job is made easier if you understand the science.

The factors that determine current for a given motor are voltage and load torque (prop size,pitch)

Here is a Flash demo from Mabuchi
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