Boats What battery?

[Jon Schiff]

I have an RC boat with 2 motors, if I put 2 of the same motors in the boat should I double the voltage of the battery cause I doubled the motors?

 

[RandyDSok]

Your motors will be running in parallel.... so you'd double the capacity ( mah ) you'll need, not the voltage.

 

[Jon Schiff]

Your motors will be running in parallel.... so you'd double the capacity ( mah ) you'll need, not the voltage.

So what does that mean? I'm new to RC things. So I don't need to get a battery with a higher voltage? what do I need to get?

 

[RandyDSok]

So what does that mean? I'm new to RC things. So I don't need to get a battery with a higher voltage? what do I need to get?

It's not so much just an RC thing... it's a battery thing ( electronics )... which a lot of things use.

Batteries are rated with a few different specs... Primarily voltage and capacity ( mah or milli-amp hour )... mah is sort of like how big the fuel tank is, so think of it as how long it can run, voltage is what pressure it ( the fuel, electricity in this case ) is delivered. Another is amperage which is like what amount of current it has ( the volume of fuel that can be delivered at a time ). Wattage is the amount of power the voltage and amperage can deliver.

So what you get is a battery with the voltage that is recommended for the motor ( s ) and has a high enough capacity ( mah ) so it will run how long you want ( within reason since the weight increased with capacity ) and that can deliver at least as many amps as is needed.

 

[Jon Schiff]

It's not so much just an RC thing... it's a battery thing ( electronics )... which a lot of things use.

Batteries are rated with a few different specs... Primarily voltage and capacity ( mah or milli-amp hour )... mah is sort of like how big the fuel tank is, so think of it as how long it can run, voltage is what pressure it ( the fuel, electricity in this case ) is delivered. Another is amperage which is like what amount of current it has ( the volume of fuel that can be delivered at a time ). Wattage is the amount of power the voltage and amperage can deliver.

So what you get is a battery with the voltage that is recommended for the motor ( s ) and has a high enough capacity ( mah ) so it will run how long you want ( within reason since the weight increased with capacity ) and that can deliver at least as many amps as is needed.

oh i see, thank you

 

[Jon Schiff]

It's not so much just an RC thing... it's a battery thing ( electronics )... which a lot of things use.

Batteries are rated with a few different specs... Primarily voltage and capacity ( mah or milli-amp hour )... mah is sort of like how big the fuel tank is, so think of it as how long it can run, voltage is what pressure it ( the fuel, electricity in this case ) is delivered. Another is amperage which is like what amount of current it has ( the volume of fuel that can be delivered at a time ). Wattage is the amount of power the voltage and amperage can deliver.

So what you get is a battery with the voltage that is recommended for the motor ( s ) and has a high enough capacity ( mah ) so it will run how long you want ( within reason since the weight increased with capacity ) and that can deliver at least as many amps as is needed.

so if the voltage is 7.2 and that runs the 2 motors would adding another 2 motors require it to put out more voltage you run all the motors at the same speed as before?

 

[Smoggie]

No, of the motors are wired in parallel then you can have as many as you like, voltage doesn't change.

 

[RandyDSok]

so if the voltage is 7.2 and that runs the 2 motors would adding another 2 motors require it to put out more voltage you run all the motors at the same speed as before?

Think of it more like gas for a car/truck etc...

If it has one engine and that engine runs regular unleaded gas... so it uses 89 octane gas. If you have two or four engines... they still use the same gas.

Having more engines, you would want to probably have bigger gas tanks also. This is where you'd ( with a battery pack ) want to have a higher MAH.... since that represents the capacity of the battery.

 

[RandyDSok]

I hope this is just a hypothetical question... since you can't just add a motor/engine to a craft ( car, boat, airplane, heli etc ) without all of the the other engineering and technical issues that are involved. That amount of info requires a lot more knowledge than what a beginner will have to properly implement without causing other problems.

If you are building or getting your first boat ( or other craft ).... stay with the original specs and recommended equipment. Trying to overspec something is for advanced users only and even then, they will often make mistakes that will cause them to have to re-engineer the whole project to meet their intended goals.

 

[Jon Schiff]

Think of it more like gas for a car/truck etc...

If it has one engine and that engine runs regular unleaded gas... so it uses 89 octane gas. If you have two or four engines... they still use the same gas.

Having more engines, you would want to probably have bigger gas tanks also. This is where you'd ( with a battery pack ) want to have a higher MAH.... since that represents the capacity of the battery.

oooh i see, and the capacity can be as high as I want it to?

 

[Jon Schiff]

I hope this is just a hypothetical question... since you can't just add a motor/engine to a craft ( car, boat, airplane, heli etc ) without all of the the other engineering and technical issues that are involved. That amount of info requires a lot more knowledge than what a beginner will have to properly implement without causing other problems.

If you are building or getting your first boat ( or other craft ).... stay with the original specs and recommended equipment. Trying to overspec something is for advanced users only and even then, they will often make mistakes that will cause them to have to re-engineer the whole project to meet their intended goals.

No, I was actually planning on adding motors, the boat I have is a simple boat that turns on propeller speed, I'm just adding two more motors wired to the other motors. Really the only thing I could mess up here is the battery which is why I asked help on here and then accidentally buying the wrong propeller shaft/rod.

 

[RandyDSok]

If the boat is using standard brushless motors... each motor will require their own ESC to control them. If it's a brushed motor/controller... the controller will still need to be changed out to handle the additional amperage load that adding anything to it ( more motors, bigger motors, faster motors all increase amperage requirements )

It would probably be better to go with a bigger/faster motor/prop than to add an additional motor/esc with the added weight of bigger batteries... but even all of that will depend on the displacement of the hull and how it will handle that additional load... not to mention how all of this will affect the balance of the craft in the water.

And those are just some of the issues I can think of off the top of my head.

 

[RandyDSok]

oooh i see, and the capacity can be as high as I want it to?

No... the capacity is still limited to what the craft can handle... none of this comes without a cost and consideration in other areas. Remember... if you add weight to the craft... it will take much longer to get up on plane IF it can even get there with the added weight.

 

[Jon Schiff]

No... the capacity is still limited to what the craft can handle... none of this comes without a cost and consideration in other areas.

so if I have a battery that is 7.2 volts 1400mAH should I try to get one with 7.2 volts and 2800mAH?

 

[Jon Schiff]

If the boat is using standard brushless motors... each motor will require their own ESC to control them. If it's a brushed motor/controller... the controller will still need to be changed out to handle the additional amperage load that adding anything to it ( more motors, bigger motors, faster motors all increase amperage requirements )

It would probably be better to go with a bigger/faster motor/prop than to add an additional motor/esc with the added weight of bigger batteries... but even all of that will depend on the displacement of the hull and how it will handle that additional load... not to mention how all of this will affect the balance of the craft in the water.

And those are just some of the issues I can think of off the top of my head.

why would the controller need to be changed?

 

[RandyDSok]

so if I have a battery that is 7.2 volts 1400mAH should I try to get one with 7.2 volts and 2800mAH?

You are still not thinking about what all this added weight is going to do to the performance of the craft through the water.

 

[RandyDSok]

why would the controller need to be changed?

Because as I mentioned.... the amperage load would change which would require that you have a controller that can output that amount of amperage. The current controller is only going to be spec'd to support one motor... not more. And if they are brushless motors, they each require their own ESC to control them.

 

[Smoggie]

Randy has covered it all, but I'll run over the points again for clarity:..

In principal you can add as much mAh battery capacity as you like but the problem might be weight and space. Larger capacity batteries are physically bigger and heavier. In a plane or helicopter this is a big consideration, but on a boat it might be less of a problem as boats typically can carry a lot of weight and usually have more space too.

Are the motors brushed (two wires) or brushless (three wires) ? As Randy mentioned, brushless need an individual speed controller (ESC) per motor. Brushed can use a single ESC to control multiple motors, but it must have a current (Amp) rating equal to the total current draw of all motors added together.

 

[RandyDSok]

Where boats have problems with weight is getting them up on plane.... in otherwords, getting up enough speed to get them up out of the water and skim across on top of the water. I'd assume it isn't as critical as an aircraft, but still a pretty big consideration.