Model Boat Mayhem
Technical, Techniques, Hints, and Tips => DC Motors (Brushed) and Speed Controllers => Topic started by: flybobby on July 12, 2006, 03:51:56 pm
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I am looking to use the above mentioned ESC with 12v supply (2x 6v gel cells).
The guy in the shop said that it would be fine, but on reading the spec sheet, it gives 4.8-9.6v input.
This is the first time I have used ESC and am a trifle wet behind the ears on the subject; can this unit be used with a 12v supply? ???
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Hi Fly hobby
the speed controller you have bought is a car one and yes the voltage on the sheet is maximum 9.6V you will fry it at 12 volt? ?there is no reason it wont work in a boat but maximum 9.6 v? the 27 bit stands for the number of turns on a car motor and as such there is no correlating graph with boats as they generally have motors that are anp rated. If you told the shop it was for 12volts then take it back you need an mtroniks Viper 15 at the very least,? this will run 4.8 to 12 volts the 15 in this case stands for amps which I cannot answer with the info given as to whether 15 will be enough amps
The eco 27 is now old stock incidentally as it is all viper nowadays trust this helps it wont be branded viper and eco or it shouldnt be??
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Thanks for that, the shop has mis-sold me that then, will be taking it back. :o
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Make sure you get a Marine model - car ones don't always have reverse!
Barrie
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Get the Viper 15, Pete M
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Just read the spec on the viper 15, what does it mean by capable of 4500mAh cells? If i were planning on 2x 6v 4ah gels in series for 12v, would this exceed the vipers limits?
May seem like a dumb question, but I want to make sure I have everything right to avoid expensive mistakes!!
Thanks all ;)
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Make sure you get a viper that is new stock and has a rapid astern ramp up speed. I have a shed load of the early vipers, and the astern apears very slow as the ramp up speed is restricted, or that is what the helpful man at Mtonics told me!? A slow astern respons speed can certainly put a dent in ones pride! :-\? ? ?PIT
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flybobby,
"Capable of _ _ _ _ mAh"? No idea why that would be included since a battery's capacity wouldn't mean anything as far as the ESC is conserned. The amount of current draw, yes. How much current is in the battery, no. Sort of like telling you a fuel pump's rating in fuel tank size. Meaningless.
- 'Doc
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flybobby,
"Capable of _ _ _ _ mAh"?? No idea why that would be included since a battery's capacity wouldn't mean anything as far as the ESC is conserned.? The amount of current draw, yes.? How much current is in the battery, no.? Sort of like telling you a fuel pump's rating in fuel tank size.? Meaningless.
- 'Doc
Thanks Doc, put my mond at rest :)
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Not sure that it is meaningless myself........
Nothing to do with the capacity of the battery driving it. I have thought about this a bit after getting my three brand spanking noo Vipers.
It is, I think, a guide to the average draw that you can pull from the thing without overheating it. Effectively if you are drawing more power from it, you can only run it for a shorter time before letting it cool down, or before it goes into thermal shut down. 4500mAH gives a 100% rating - it will happily pull 4.5A continuously. If you want to pull 9A, you have to do it with a 50% duty cycle (e.g. 5mins on 5mins off). If you want to pull 15A you have to do it with a 30% duty cycle (e.g. 3mins on 7 mins off). I guess you could up the AH rating by forced cooling the module - say water pipes in the fins at the bottom of the module, or a more efficient heatsink.
I think it is done this way rather than a power rating because the power rating in any specific configuration is indeterminate once you start to factor in varying battery voltages and motor back-EMFs. The power dissipated in the controller depends on the FET on resistance and the current (I^2*R), so to specify the power as an AH rating gives a more meaningful and usable measure.
Tim (the Wombat)
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The amperage of the unit is 15 amps for the viper 15? ?they do have a slight overrun on that but that?s not to say you can run 17amps through it, 15 is the lot they do produce a 20 and a 25 for that purpose
The batteries and speed controllers referral to 4500 mah is really nothing to do with the rating of the speed controller on the amps side as above 15 20 25 and so on.
This relates mainly to the battery capacity mah stands for milli amps per hour so if you had a stick pack rated at 3300 and 12 volts its absolutely fine likewise you can have a lead acid (or better still 2 X 6v gives better boat balance) rated at 4.5 this = 4500 mah, its usually quoted on lead acids as the shorter figure as they go so high?we are only moving the decimal point ?but using two 4.5 (4500) mah at 6 volt run together to make 12 volts will still only have a 4500 mah and again this is fine but to be honest with that weight of about 2Kg in the boat it is likely to be a larger boat and I would advocate going for an electronize then.? ?
Without making this post extremely complicated the potential chance of blowing the esc at say 7.2 mah does exist but first of all you would be better with an electronize here as its going to be a bigger boat but if you used a viper you would still be OK if you were just light running, it is whem you are flat out and/or full duration of the run of the battery when you would cause harm to the ESC
Trust this helps also we have had a couple of PM?s on this but for others wiring 2 X 6 v to 12 easiest way to remember is join one batteries + terminal to the other batteries ? terminal, this leave a negative terminal on one battery and a positive on the other battery which is now the 12volt + and -
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The batteries and speed controllers referral to 4500 mah is really nothing to do with the rating of the speed controller on the amps side as above 15 20 25 and so on.
This relates mainly to the battery capacity mah stands for milli amps per hour so if you had a stick pack rated at 3300 and 12 volts its absolutely fine likewise you can have a lead acid (or better still 2 X 6v gives better boat balance) rated at 4.5 this = 4500 mah, its usually quoted on lead acids as the shorter figure as they go so high? ?but using two 4.5 (4500) mah at 6 volt run together to make 12 volts will still only have a 4500 mah and again this is fine but to be honest with that weight of about 2Kg in the boat it is likely to be a larger boat
Thanks for that useful info, you answered another question I were pondering, that is if I were using 2x 6v in series, would the capacity be doubled too.
Thanks again ;)
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Running batteries in Series increases the voltage but not the capacity (amps). Running in parallel increases the capacity but not the voltage.
HTH
Doug
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I need a couple of speed controllers for tug I am building - I always intended to get Vipers ( mainly because they are guarranteed waterproof) but could anyone tell me what the advantages of Electronize controllers are?
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Running batteries in Series increases the voltage but not the capacity (amps). Running in parallel increases the capacity but not the voltage.
HTH
Doug
Top info, thankyou ;)
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Hi Rats
The Mt'S are good and yes they are fully waterproof but generally in the larger tugs you will be on 12 volts and drawing a decent amperage at times now whilst the MT's are OK for this the electronize have a couple of benefits here (yes they are not waterproof but your hull should reasonable be) they will run at higher voltage up to 24, some 12volts batts with an ammeters will register 12.7 12.8 volts MTs will be Ok with this but its safer with an electronize added to which many of them now have variable speed so you can turn them down somewhat, yes the same can be achieved with the throttle, they are also now coming in with auto set neutral so if you are on a ratchet control you can set neutral at ? eg ? forward ? reverse and the last benefit they are repairable bust an MT and that?s your lot but they are both good escs it generally depends on size of tug the bigger lean more towards Electronie
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Thanks Model World will check out Electronize !
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If the longer run times of larger capacity batteries is a problem the first step is in providing a little cooling. If the ESC isn't too small, and you really aren't pushing it too hard, air cooling would probably do fine (vents front and rear mean air flow. Enough? Beats me, but shouldn't hurt anyway.). Next step is forced air cooling, fan. Then water cooling. Then a refrigerated system (that I wanna see!). I know it isn't the 'correct' way of thinking about it but, I figure if an ESC is getting too hot it just isn't big enough (large enough current capacity) or the heat sink is too small. And I have a phobia about circulating water inside a boat (knowing how I do things, that ain't a phobia, it's smart!). Oh well, 'nuff of all that...
- 'Doc
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Ok I am really confused. I was planning on getting a Mtroniks Viper 25 working off a 6v 12AH gell cell (lots of run time and I will have other working features running off the same battery). The boat manufacture says I need a 15amp ESc so I thought I'd play safe with the 25 Amp version. Does this mean that the Mtroniks is not going to be suitable??? Still not sure how a high capacity battery will damage a ESC when its drawing the same number of amps as when its connected to a lower capacity battery.
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Thanks for that, the shop has mis-sold me that then, will be taking it back. :o
for 12v, you may be best with electronize, or if they are too heavy, the MPI Tornado 50esc. I have one for a robbe najade :)
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Hi Mankster
12ah is to much for an MT esc to handle I will try and explain but its not the easiest Think of electricity like water. Volts = pressure
Amps = flow
Volts is like pounds per square inch, psi. Says nothing about how much water is flowing, just how hard it is being pushed. You can have 100 psi with zero water flow. Say the tap is switched of.
Amps is flow, like gallons per hour. You can have flow at low pressure and you can have flow at high pressure. Now there is one last bit
Amp hours are how much flow can be sustained for how long. It is used as a way of measuring how much electricity is in the battery. Like how many gallons of water in a tank. It is a capacity number. Says nothing about flow or pressure, it is about capacity. Imagine if you were to release all the water from a tank down a light plastic hose that would handle a reasonable flow but you then turn the tap on higher it may split the hose just like it will blow the esc as there is too much capacity flowing over it
The amps is the need to buy a hose that will handle the water the amp hors means it will handle it at a constant
As regards the 7.2ah above we have used as an experiment for something else but we knew we were likely to blow it as the battery was delivering more amp hours than the esc could handle and I would not advise it, hence the suggestion to go for an Electronize which can handle 12ah (of Flow rate) and upwards easily. Hope this explanation helps and doesn?t confuse anymore I suppose another thing to say is there are 3 variables amps, volts and amp hours
If anyone is still confused I will get M V to come on and explain he is off today but may have a better way of explaining
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The water comparison example above works fine until you get to the part about opening the tap further and bursting the pipe. The water pressure is already applied to the pipe whether the tap is open or not. (So voltage is already applied to the escape no matter what hte current draw is.) The limiting factor in the water example is the capacity of the pipe to flow water (friction, or resistance for votage). Measure water pressure against the top edge of a swimming pool, it'll be the same as against the bottom of the pool. (Equal pressure in all directions in a body of fluids, if the fluids are not in motion.) So, the capacity of a battery shouldn't make any difference to the ESC as long as the current drawn, and the applied voltage are within it's ratings. Cooling an ESC shouldn't be a 'biggy' as long as you don't try to 'push' the thing further than it can be. How far is that? Depends on what the designer used as a margin of error ("fudge factor" = technical term). The published rating is/should always be lower than the absolute maximum, just good sense, which assumes the manufacturor has good sense...
- 'Doc
PS - Oops! After reading the above, the 'pressure already applied to the pipe' does depend on where the tap is, the top or the bottom of the pipe. I assumed the tap was at the bottom end. The electrical part still holds true though.
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Hi Mankster
12ah is to much for an MT esc to handle I will try and explain but its not the easiest Think of electricity like water. Volts = pressure
Amps = flow
Volts is like pounds per square inch, psi. Says nothing about how much water is flowing, just how hard it is being pushed. You can have 100 psi with zero water flow. Say the tap is switched of.
Amps is flow, like gallons per hour. You can have flow at low pressure and you can have flow at high pressure.? Now there is one last bit
Amp hours are how much flow can be sustained for how long. It is used as a way of measuring how much electricity is in the battery. Like how many gallons of water in a tank. It is a capacity number. Says nothing about flow or pressure, it is about capacity. Imagine if you were to release all the water from a tank down a light plastic hose that would handle a reasonable flow but you then turn the tap on higher it may split the hose just like it will blow the esc as there is too much capacity flowing over it
The amps is the need to buy a hose that will handle the water the amp hors means it will handle it at a constant
As regards the 7.2ah above we have used as an experiment for something else but we knew we were likely to blow it as the battery was delivering more amp hours than the esc could handle and I would not advise it, hence the suggestion to go for an Electronize which can handle 12ah (of Flow rate) and upwards easily. Hope this explanation helps and doesn?t confuse anymore I suppose another thing to say is there are 3 variables amps, volts and amp hours
If anyone is still confused I will get M V to come on and explain he is off today but may have a better way of explaining
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May be I not reading this right but now I am even more confused!
The way I understand it,? AH is a measure of the capacity of the battery (I know that larger capacity batteries have the ability to supply larger maximum currents) So a 6v 12AH battery can theoreticaly supply a constant 12 Amps for 1 hour before discharging completely. If the Current draw is 24 amps, the battery will discahrge in 30min. Similarly if the current draw is only 6amps then the battery will supply that current for 2 hours. I think this bit is well understood by every one.
So say I have a 6v motor that I connect directly to this battery and I measure the current with an ammeter and find it draws a constant 12 Amp, so theoretically anyway it should run for 1 hour. No lets say I connect the a Mtroniks Marine viper 25 between the the battery and motor. and run the mator at full pelt. It is still drawing 12 amps and should still run for 1 hour on a fresh battery. So are you saying this speed controller will blow (dispite being rated at 25amps) if I do this? All the other speed controler I come acreoss make no mention of the maximum battery capacity anywhere in the specifications. Is this a particular to the Viper range? I dont remember the the old Mtroniks ESC's making any such claim.
Surley the current draw on a battery for any one given motor will be the same regardless of the capicty of the battery. And the only 2 variables in an electical circuit is Voltage and current (amps) so why do Mtronik mention battery capacity when no other ESC manufacturer I can find does the same?? ???
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Easy,
go for the electronize 30 Amp job, if it blows electronize will repair it for a tenner return post paid (UK) did mine.
Biggist tug of mine 44" ish is running a big 30 volt motor [bought surplus one day] at 24 volts and it goes a damn sight faster than it oughter.
cheaper than binning one and buying a bigger one next time. Tug
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The only reason an ESC may blow due to a battery being of too high capacity would be due to it heating up during extended use. I think that if you are geneous with your current rating, you should not have any problems.
Neil
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Yes Doc the tap was at the top of the pipe restricting flow.
To answer Mankster Mtroniks who we have spoken to put the rating on the esc as they wanted to assure everyone that these esc's would handle that size of battery as most of their esc's are used by stick pack users in the fast electric categories or speed boat style
Fast electrics is quite right you shouldn?t blow the esc at a somewhat tootling around speed its when you are flat out for as long as the battery can handle that you will cause it to go into thermal shutdown e.g. to hot, however there is a point in between flat out and tootling where shut down will not happen and where it will. This us the hard thing to calibrate as each boat is different so to be safe 4.5 was tested flat out OK we have tested 7.2ah and we were Ok though we were not flat all the time. 12ah you may be OK but we cannot really say you are ok as we would open the flood gate to people complaining if it shuts down so we have to err on the side of caution you can of course look at water cooling of the esc or air cooling but its each boat that is different. Mtroniks put the 4500 ah label on to really just say these esc's will handle that run time they are now testing how much higher they can go.
There is no hard and fast rule here give it a go check it after 20 or 30 minutes see how warm/hot it is then check again
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Ok this makes sense now. So a 15 amp Viper ESc can't actually handle 15amp continous indefinately without heating and possibly shutting down. So if you have a 4500mah battery back and running flat out with motor drawing 15amps, a 15Amp ESC will be safe for running this way for roughly 20min before the pack is exhausted. If you had a bigger capacity battery and ran it for longer at 15 Amps, you risk over heating. So If I got the 25amp ESC instead, I would still only be drawing 15amps so the ESC would be running cooler as its well within its design limits and hence I could run flat out for much longer than 20min ( assuming I had a bigger capacity battery) without risk of over heating?
I don't think scale boats will be running flat out for so long anyways.
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Even I can make sense of that. ;D
Good work all ;)
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Yep and me, maybe I'm not too old to get some of this new-fangled radio stuff ::)
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I said I wasnt perfect at explaining in type form Mankster but yes we got there I imagine Mtroniks will have an answer by weekend even though it will err on the side of caution as to how long. I would still bang an electronize 30 in a tug though as you have the higher amps and variable speed so you can stop whine and adjust the esc to lower output
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If anyone is worried about overheating ESC, you can now buy small electric fans from maplin and most RC Shops that sell RC Cars. The RC Car fraternity use these fans to blow air over the motor to stop it overheating during races.
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so just to be clear on this where do i stick the croc clips and bits of silver foil ? do i stick these in between the motor and ESC or the battery and ESC and at what point does the whole model go up in flames ????? ;D
sorry could not resist !
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Guy,
The silver bits are stuck to your forehead. The 'clips' to your ears or eyebrows, unless you really wanna be 'there', then you clip them to your nose. At least that's what's common around here. Me? Ain't gonna do it...
- 'Doc
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dont knock it until you have tried it !