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want to run two motors 1 esc

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mick31/08/2008 23:01:00
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i just wondered if i want to run two motors on one esc can i run the batterys running to the

esc without blowing it ? not very tech minded  be happy  to here your veiws 

thanks mick got two 777 motors and 6 to 12v esc and two 7.2v batterys

Modelman31/08/2008 23:13:00
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81 forum posts
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your esc has to be a bigger amp rating than both motors combined or it will pop or worse melt down and set fire.
JC Uknz02/09/2008 21:18:00
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141 forum posts
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If you have the motors in series you reduce the load.   powered from the two batteries in parrallel for longer performance at the  voltage of one battery 7.2v
Dave Milbourn05/09/2008 08:18:00
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4025 forum posts
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Mick

Excuse the blindingly obvious, but two motors and two batteries cries out for two speed controllers. Yeah - I know it's more expense but if you're not 100% certain of what you're doing then it's a darned sight easier to understand. It also makes fault-tracing easier as/when/if something goes wrong. There's an article here on some of your options, but it's not mandatory to purchase the actual products mentioned!:

http://www.action-electronics.co.uk/pdfs/Twins%20Ver2.pdf

I wouldn't recommend connecting two NiCad or NiMH packs together, especially in parallel.

As someone elsewhere says, suit yourself.

Dave M

JC Uknz06/09/2008 08:20:00
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I"" wouldn't recommend connecting two NiCad or NiMH packs together, especially in parallel. ""

Why and how are those batteries different to other batteries? Apart from the obvious.

If you are into electrics to a reasonable degree there are other ways of controlling two motors by using the extra movement of a servo arm to activate a switch to change polarity for manouvering a twin screw vessel.  One uses the steering servo for the job and the cost would be a pound or two.   It has been used for activating extra gadgets on a boat with a simple two servo R/C system but with a bit of thought changing a pair of motors so their props work against each other  is quite possible.

If you have things adjusted so the trim tab on the transmitter is at centre you can move it to get the extra servo arm movement to press a switch which can be either press to on or else press to remain on and press again to switch off.   The switch can be a DPDT switch to reverse polarity. There is some limitation that the vessel has stopped so the movement of the rudder doesn't affect things unduely.

mick06/09/2008 15:01:00
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127 forum posts
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 thanks lads  i get the point i will just run it on one but a better amp rateing

that way i cant get into trouble thanks again mick

Dave Milbourn07/09/2008 07:48:00
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4025 forum posts
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"Why and how are those batteries different to other batteries? Apart from the obvious".

Whoa there, fella!  I think you read a bit more than I intended into what I said . Firstly I only mentioned NiCad and NiMH because Mick specifically said he has 7.2v batteries and, as far as I know, you can't get SLA or LiPo batteries or packs which give that nominal voltage.

As to the "why" and "how", there's been a lot of debate about this elsewhere so I won't bore anyone with repeats. It would perhaps have been illuminating for you to have been in my workshop yesterday while I repaired a badly-burned PCB, caused by one battery attempting to charge up a parallel one with less charge in it. The copper land had been blasted off the epoxy-glass board and left a "trench" about 0.2mm deep. THAT'S why I don't recommend etc etc. The customer didn't say whether he'd been using SLA or Nickel-based batteries, but either type will do the same sort of damage under similar circumstances. Ref my presentation, I have to say that there's a world of difference between a bald "you must not" and a mild "I wouldn't recommend". I usually finish off my posts with either "Works for Me" or "Suit yourself"; maybe I should be more careful to do so on this Forum.

Finally I was conscious of Mick's statement about not being technical. Granted there is a time-honoured method of using microswitches to reverse the polarity of a motor at extreme rudder. The downside of this is that it's very fierce and that it only happens at full rudder. Maybe you could point out a suitable link where Mick and others could find such a circuit; that way he/they can make a more informed choice?

I'm afraid I don't understand your last paragraph in the context of controlling twin motors. If I read it correctly one stops the boat and applies full rudder and full trim, then proceeds with one motor in full reverse.........?? Who's to say? Maybe it works for you.

JC Uknz07/09/2008 20:50:00
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141 forum posts
11 photos

Dave Milburn,

It may be old hat to you but this is the first time that I have heard any reservations about the downside to coupling ni-cad and NiMH batteries in parrallel and more useful would have been links.   Also the description of your disaster may make sense to you but is way over my head as a non-technical enthusiast.   With little interest to me becuase such batteries are far too expensive since I get my batteries, sealed wetcells, for free after they are junked from their original purposes.**

You are definitely are mis-interpreting my final para because it is obvious to me that a limitation to the system is that you have the motor[s] not at 'full reverse'.   That it is a manouvering capability rather than perhaps reversal of motor thrust to assist a high-speed turn.     We have no information as to why Mick wants this system with its problems of balancing two motors being worked on two controllers.    I took his reluctance to use a second controller  as expense or room in the boat. 

**I am reminded of concerns about the mercury content of the energy saving light-bulbs and my wife saying how she and her sisters were permitted to play with the mercury out of a broken thermometer when she was a child ... lots of  fun as it moved around in little blobs.

mick07/09/2008 22:01:00
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127 forum posts
74 photos

i bought this boat with twin shafts fitted there is not a lot of room in the hull

so i thought i could keep the weight  down  as this is a fast planeing boat a 

rttl a s r l vosper at 1/24 scale  i have put  two 777 in  and have double rudders  a 

old mfa 12v  esc  but i was just asking about 2 7.2v packs in  but going by the feedback

i will use one maybe uprate the amphr thanks lads mick

JC Uknz08/09/2008 21:16:00
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141 forum posts
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MICK,  I think you are going to have to live with a relatively short running duration from a single battery and organise yourself a 12v car battery as a means of a fast recharge inbetween runs.   We have a couple of speedboats in our Club which work this way.     But it is not the way I work with my displacement boats so I can't help with details .. maybe Dave Milburn would help you ?.  

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