Model Boat Mayhem
Technical, Techniques, Hints, and Tips => Batteries & Chargers => Topic started by: peter61_uk on January 16, 2014, 09:42:57 pm
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Ok guys........ I've read some of these threads and I have to admit I'm proper confused about types of batteries, cells, chargers, wiring in parallel or series, run times and the whole enchilada.............
So fo a simple soul. I'm building a tug (it's my first go at this) ...... 84 cm Long, 18 cm Beam ....... I have Permax 600 motor with a 3:1 Gearbox ...... Running a 45mm prop. (It was suggested that I change the motor for a 12v. But I have this one so that's what I'll use if I can).
So what type and size battery (voltage, amps etc) do I need that will give a reasonable run time in the pond ????
Thanks
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If it is a 6volt motor 2 x 6 volt 12 amp gell cells should be somewhere near.
You would need to ballast the hull and weigh the ballast and convert to the individual battery weight.
I do use gell cells as tugs require lots of ballast and these batteries supply power and ballast.
Bob
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If it is a 6volt motor 2 x 6 volt 12 amp gell cells should be somewhere near.
You would need to ballast the hull and weigh the ballast and convert to the individual battery weight.
I do use gell cells as tugs require lots of ballast and these batteries supply power and ballast.
Bob
Thanks Bob.......... The motor is rated for 7.2v. So, and excuse my absolute ignorance here, that'll give me 12v? or two lots of 6v??? ....... But I've seen some threads online where some run this Multiplex Permax Motor on 12v ????
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You can get 7.2v NiMH batteries in a couple of odd shapes and sizes.
Take for example this one:
http://www.componentshop.co.uk/7-2v-3300mah-sc-nimh-battery-pack.html (http://www.componentshop.co.uk/7-2v-3300mah-sc-nimh-battery-pack.html)
A 3000mah battery pack, so technically at 7.2v you can draw 3.0 Amps from your battery for an hour. Obviously in the real world, you probably won't get this unless all your running gear is very efficient, or say you take it easy and draw less than 3.0Amps.
The higher the Mah of a battery, the longer it will last. If you have a 6000mah battery, and still draw 3 Amps, you can techincally get 2 hours of running. Make sense?
I don't think you would need to worry about running in series with a 7.2v motor. Series just means that you wire another battery directly in line with another. So the red wire from your ESC goes to the 1st batteries red wire. the black wire from this battery goes to the red wire of the second battery, and the black wire of the second battery goes to the black wire of the ESC. If you were using two 7.2v batteries, this would give you 14.4v, which is far far too high for what you want! Wiring in series keeps the Mah the same
Running in parallel means literally connecting the red wires to the red wires, and black to black. This increases your Mah, so two 3000mah batteries would give you 6000mah. Some people seem to recommend avoiding wiring in parallel like this, never tried it myself! Wiring in Parallel keeps the voltage the same however.
I hope this helps, if not, give us a shout and I'll try and explain it different. Once you get your head round it, it seems simple!
Steven
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6 volts should be fine.
But ensure that the ballast to the waterline will support 1 or 2 batteries.
Minim batteries are fine but you will need lots of fixed ballast.
Bob
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You can get 7.2v NiMH batteries in a couple of odd shapes and sizes.
Take for example this one:
http://www.componentshop.co.uk/7-2v-3300mah-sc-nimh-battery-pack.html (http://www.componentshop.co.uk/7-2v-3300mah-sc-nimh-battery-pack.html)
A 3000mah battery pack, so technically at 7.2v you can draw 3.0 Amps from your battery for an hour. Obviously in the real world, you probably won't get this unless all your running gear is very efficient, or say you take it easy and draw less than 3.0Amps.
The higher the Mah of a battery, the longer it will last. If you have a 6000mah battery, and still draw 3 Amps, you can techincally get 2 hours of running. Make sense?
I don't think you would need to worry about running in series with a 7.2v motor. Series just means that you wire another battery directly in line with another. So the red wire from your ESC goes to the 1st batteries red wire. the black wire from this battery goes to the red wire of the second battery, and the black wire of the second battery goes to the black wire of the ESC. If you were using two 7.2v batteries, this would give you 14.4v, which is far far too high for what you want! Wiring in series keeps the Mah the same
Running in parallel means literally connecting the red wires to the red wires, and black to black. This increases your Mah, so two 3000mah batteries would give you 6000mah. Some people seem to recommend avoiding wiring in parallel like this, never tried it myself! Wiring in Parallel keeps the voltage the same however.
I hope this helps, if not, give us a shout and I'll try and explain it different. Once you get your head round it, it seems simple!
Steven
Thanks Stephen ............... So, I'f I were to buy two of these 3300 batteries.......... I could run one in the boat and one as a spare ???
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6 volts should be fine.
But ensure that the ballast to the waterline will support 1 or 2 batteries.
Minim batteries are fine but you will need lots of fixed ballast.
Bob
I quite like the idea of the Nimh battery thing.......... and I was thinking, for ballast maybe using plasticine moulded into the inside edges of the hull and under the tray that'll hold the receiver and the one for the esc............... then paint it over.
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Thanks Stephen ............... So, I'f I were to buy two of these 3300 batteries.......... I could run one in the boat and one as a spare ???
Yeah, that's what I do, but I don't have a tug boat :-))
Also with NiMH batteries, the larger the Mah, the heavier battery is. Take a look at some of those on the component shop website and see whats best. For example a 5000mah is 450 grams, where aa a 3300mah weighs 396 grams.
Obviously the larger mah the price goes up aswell!
Steven
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Thanks Steven ....... big help.
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Peter,
In a tug you will need something far more dense and therefore heavy than plasticine.
Tugs require a lot of ballast to ensure the large prop is deep enough to not suck air from the surface.
What you use is immaterial as long as you can get her down to her waterline.
With a heavier battery this is removable so making the model that much lighter for recovery and transporting.
Bob
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if you want to learn more about any type of battery, I would add this site to your reading list - http://batteryuniversity.com/
Grendel
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Hi Peter, I have three tugs and the only one with a NiMh battery is the St Canute which is quite small. The other two, Smit Nederland and Sun XX1 both use the gel lead acid batteries. Judging from the size description of your tug I would think it will need a lot of ballast and therefore a 6v 12h battery weighing in at approx. 2kg would seem to be a good starting point. Whether two are needed will depend on what amount of ballast you need in total and how much running time you want. Try putting the hull in the bath and loading it with bags of, say sugar, to see how much you need. I am not familiar with your motor and the current it draws at 6v or the rpm it does but I assume it is only a couple of amps even when turning that 45mm prop so I would expect 1 battery to be sufficient in terms of capacity for running time. It helps to know the current draw of you motor particularly under load as this helps you decide on the rating of the speed controller. Finally I would only ever use lead as extra ballast. I hope that helps. Graham.
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it may be worth putting the bags of sugar inside plastic bags to avoid the sugar getting wet first - just in case - just to maintain family harmony.
Grendel
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it may be worth putting the bags of sugar inside plastic bags to avoid the sugar getting wet first - just in case - just to maintain family harmony.
Grendel
:-)) :-)) Thats's why I use Canned Food {-) {-)
Ned
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Maybe I'll use the cat.........????? If I weigh him first, that'll give me a benchmark :}
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Just remember you don't need to put the cat in a plastic bag like the sugar!
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This cat was happy to act as ballast on the half built battleship until we got to the bathroom. {-) Graham
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At this stage of a build cat ballast is too late. {-) Graham
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Random Caption Competition!
http://www.modelboatmayhem.co.uk/forum/index.php/topic,17267.msg466096.html#msg466096
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In my tug, Model slipway Envoy I have two, 6 volt gel batteries. I still had to add a fair amount of lead sheet ballast under and around them too.
I managed to wire my batteries via a double pole, double throw switch so you can decide if you want the batteries connected in series giving 12 volts to the speed controller or in parallel giving 6 volts operation. In small areas it's far more controllable on the lower voltage setting and the 12v gives you another turn of speed when you want to race about in open water.
You do need to make sure the switch is in the right position when charging though so an interlocking mechanism was made ensuring you can only connect the 6 volt charger when the switch is in the 6 volt position.
Craig.
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I managed to wire my batteries via a double pole, double throw switch so you can decide if you want the batteries connected in series giving 12 volts to the speed controller or in parallel giving 6 volts operation. In small areas it's far more controllable on the lower voltage setting and the 12v gives you another turn of speed when you want to race about in open water.
.....but perhaps not really needed with a 7.2 volt motor.
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Thanks all for your replies. It has helped a great deal toward me understanding this......... One thing that I'm still not sure about though...... I can understand the 6v lead acid / gel battery route. As well as powering the motor it'll provide some ballast...... But, will the 6v battery on a 7.2 volt motor mean much of a drop in power to the motor ???? Or is the 1.2 volt drop insignificant ???
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It's hard to say unless you try it with a 6v then try it with 7.2v.
On my fireboat I had a 6v SLA battery, the boat didn't quite plane, changed it for a 7.2v NiMH, and it did make it up on the plane. It all depends on the boat and what you want out of it!
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I just found the spec on the Permax 600 motor:
SPECS: No-Load Speed: 17,600 rpm
No-Load Current: 1 Amp
Maximum Current: 28
Current at max efficiency: 10 amps
Typical operating voltage: 6-12
Shaft diameter: 3.2mm
Weight: 8.1oz
I have this on a 3:1 Gearbox.
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It's hard to say unless you try it with a 6v then try it with 7.2v.
On my fireboat I had a 6v SLA battery, the boat didn't quite plane, changed it for a 7.2v NiMH, and it did make it up on the plane. It all depends on the boat and what you want out of it!
Well, it's a tug ........... So planning wasn't really in my gameplan for it Stephen :}
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Hi Peter, If the 17600 rpm is when supplied with 12 volts then using a 6v battery would give aprox half that and the gearbox will take it down to a sensible speed for a tug. If its 17600rpm off 6v volts you well have the first planning tug on the lake. %% Graham
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Hi Peter, If the 17600 rpm is when supplied with 12 volts then using a 6v battery would give aprox half that and the gearbox will take it down to a sensible speed for a tug. If its 17600rpm off 6v volts you well have the first planning tug on the lake. %% Graham
Graham. If the motor gives out 17600 rpm at 12v, and I have a 3:1 gearbox ........ Then am I not putting 5866 rpm at the prop ??? .......and with 6v then it's 2933 rpm ......... With a 45mm prop I have know idea now how many rpm I need to get to the prop to chug this thing along at a sort of "tug like" pace?????
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Hi Peter, Yes you are right and I think 2933rpm on a 45mm prop will move your tug very well. Graham. :-))
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Hi Peter, Yes you are right and I think 2933rpm on a 45mm prop will move your tug very well. Graham. :-))
Thanks .......... So I'm on 6v Lead Acid or Gel ........Which will power the motor ESC, Receiver and Rudder Servo and give me some ballast .......... The only two questions remaing ???? 1) How many Ah for the battery ............ and 2) How long will the Tug run on the water ????
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A 3000mah battery pack, so technically at 7.2v you can draw 3.0 Amps from your battery for an hour. Obviously in the real world, you probably won't get this unless all your running gear is very efficient, or say you take it easy and draw less than 3.0Amps.
The higher the Mah of a battery, the longer it will last. If you have a 6000mah battery, and still draw 3 Amps, you can techincally get 2 hours of running. Make sense?
Steven
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Hi Peter, Well I use gel cells as they are a form of lead acid battery but unlike the car or motor cycle battery the electrolyte between the lead plates is not liquid but a paste. Therefore the battery can be used on its side without the acidic electrolyte running out. In most of my bigger boats I use a separate battery pack for the radio and do not use the battery eliminator circuit and the weight of the extra batteries is not a problem. In a couple of smaller boats where space is a problem the use of one battery can be useful. Its probably a bit old fashioned to use a radio battery and a motor battery. Basically the bigger the Ah the more running time you will get so 6v 12ah would be good. The running time will depend on the current taken from the battery when running under load so it would be good if you could measure the current drawn when running the prop in water. Your motor spec mentions 1amp but this could rise to 4 amps or more under load i.e with the prop in water. Even so with a 12AH battery you would bet approx. 3hrs running time. :-)) Graham
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Hi Peter, Well I use gel cells as they are a form of lead acid battery but unlike the car or motor cycle battery the electrolyte between the lead plates is not liquid but a paste. Therefore the battery can be used on its side without the acidic electrolyte running out. In most of my bigger boats I use a separate battery pack for the radio and do not use the battery eliminator circuit and the weight of the extra batteries is not a problem. In a couple of smaller boats where space is a problem the use of one battery can be useful. Its probably a bit old fashioned to use a radio battery and a motor battery. Basically the bigger the Ah the more running time you will get so 6v 12ah would be good. The running time will depend on the current taken from the battery when running under load so it would be good if you could measure the current drawn when running the prop in water. Your motor spec mentions 1amp but this could rise to 4 amps or more under load i.e with the prop in water. Even so with a 12AH battery you would bet approx. 3hrs running time. :-)) Graham
Good Stuff Graham ........ Component Shop have Sealed Lead Acid 6v 12Ah Batteries for £11.65 ....and with the dimensions, I can probably get away with one standing upright (and it'll give me 2kg of ballast :-)) ) .............. I'll do some mooching around on the net for gel batteries.
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Hi Peter, Just a quick point. By having the battery on its side you keep the centre of gravity as low as possible and thereby improve the stability of the boat and a sealed lead acid will be fine. 8) Graham
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Hi Peter, Just a quick point. By having the battery on its side you keep the centre of gravity as low as possible and thereby improve the stability of the boat and a sealed lead acid will be fine. 8) Graham
............ Result. Then I'm sorted in the battery dept. Thanks to all for your help on this. :-))