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Old Sep 21, 2010, 06:55 PM
Registered User
Newfoundland, Canada
Joined Mar 2010
13 Posts
Help!
Lead acid Battery with ESC and Motor??

I posted this is a tread earlier but it was a old one so i figure i would try my luck here as well.
i want to build a lobster boat, and i have everything. did have everything i should say since i fried my esc. i connected a 12V SLA battery to my esc and motor. it provided 5 volts to my receiver, and that worked fine, which ran my servo fine. However the motor was a random dc toy motor i bought at a surplus store, and when i looked up the ratings for the model, it was rated for 8-20Vdc and roughly 1 amp. the esc was a brushed and so was the motor,and the esc was rated for 12 volts/20 amps. The receiver had 2 jumpers on it, one for brake on/off and the other for Li-xx/Ni-xx. so my questions are: what should i have had my esc jumpers too, and as a future reference, i am going to get a brush-less esc and motor and use a 12V SLA battery on it for my boat, what ratings and size should i look for, while keeping in mind that i am very new at this and i am not looking for a speed daemon, its a 40 inch lobster boat, and i am looking for a somewhat cheap solution. if anyone can help me with regards to the connections and what to use in the future, it will be greatly appreciated. thanks
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Old Sep 21, 2010, 09:37 PM
Nickel Belter
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Northern Ontario
Joined Jun 2009
865 Posts
Jumpers?

So you had the two wires from the battery going into the input terminals on the ESC, and the two motor wires going to the terminals on the motor, right?

If it fried the moment you plugged it in, there was a short in the system or you attached it backwards to the battery (+ to - accidentally)

If it fried when you started up the motor then whatever you have the motor attached to is too big and the motor drew too much current.

More information such as the ESC make and model and a picture of the mystery motor would be helpful.
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Old Sep 21, 2010, 09:54 PM
Sea Dragon-Lover
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PDX, OR
Joined Dec 2002
10,274 Posts
Neither jumper setting should have created an issue that would have fried the ESC.

I imagine that the jumpers would be set to "brake off".
And the second set to Ni-xx. Since you are running an SLA battery,
there should be no reason to use the Li-xx, because you won't need to
worry about a low voltage cut off that LiPoly batteries require.

If the motor ratings were accurate, the ESC should have been able to handle the power.
Definitely sounds like there was a short somewhere...
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Old Sep 22, 2010, 05:51 AM
Registered User
Blackpool, Lancs
Joined Feb 2006
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Either the ESC had an internal short on its output, or the motor and/or its wiring was giving the short. Before frying the replacement ESC, I would check the motor's actual current draw just connected to the battery. Typically, the "brake" function causes the ESC to short the motor windings out when the stick tells the power to be off. If this function was being applied at the wrong time, there could be a problem. I would look for actual marine ESCs, where the braking function doesn't exist to give any problems in the first place.
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Old Sep 22, 2010, 06:53 AM
Registered User
United States, ME, Bar Harbor
Joined Sep 2005
440 Posts
A 12 volt SLA battery will not provide the amps required to a brushless set-up. Read very carefully the specs on the battery you propose to use. A 7amp/hr SLA is usually rated at a 24 hr rate. That means it will supply 1 amp/ hr for 7 hours( or there about) The point being that brushless motors draw huge amp loads, lipos can supply that, SLA's can not.
cheers
Jonathan
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Old Sep 22, 2010, 07:06 AM
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United States, ME, Bar Harbor
Joined Sep 2005
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I have to swallow some of what I just posted. I checked the Powersonic site and looked at specs for their batteries, each manufacturer is different be advised< and their batteries will handle a high discharge rate, That said, they also make a special series of high discharge rate batteries that handle an even higher rate of discharge. Just be sure to match the specs on your motor to what your battery can provide.
Jonathan
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Old Sep 22, 2010, 07:26 AM
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Backwoods Alabama
Joined May 2000
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Quote:
The receiver had 2 jumpers on it, one for brake on/off and the other for Li-xx/Ni-xx. so my questions are:
That jumper arrangement sounds suspiciously like that of a Jeti ESC. FWIW.

--Bill
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Old Sep 22, 2010, 09:39 AM
Registered User
Blackpool, Lancs
Joined Feb 2006
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Quote:
Originally Posted by jeno View Post
A 12 volt SLA battery will not provide the amps required to a brushless set-up. Read very carefully the specs on the battery you propose to use. A 7amp/hr SLA is usually rated at a 24 hr rate. That means it will supply 1 amp/ hr for 7 hours( or there about) The point being that brushless motors draw huge amp loads, lipos can supply that, SLA's can not.
cheers
Jonathan
A careful read of the original question will reveal-

Quote:
However the motor was a random dc toy motor i bought at a surplus store, and when i looked up the ratings for the model, it was rated for 8-20Vdc and roughly 1 amp. the esc was a brushed and so was the motor,and the esc was rated for 12 volts/20 amps.
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Old Sep 22, 2010, 09:42 AM
Registered User
Newfoundland, Canada
Joined Mar 2010
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sorry i just noticed a mistake in what my original message was, i stated "The receiver had 2 jumpers on it, one for brake on/off and the other for Li-xx/Ni-xx." i meant my "ESC"" and not the receiver. i will post a pic of the ESC as soon as i can and time permits as i am in the Canadian Arctic on a Ice Breaker and currently in a lot of ice which mean a lot of stuff for an Electronic tech to fix due to the banging around, and i have to take a pic of the odd polar bear, but i will post it later and thanks for the replies thus far.
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Old Sep 22, 2010, 12:38 PM
Registered User
Newfoundland, Canada
Joined Mar 2010
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The Specs of what i have

as for the motor;
Johnson Motor #9167AK. Motor: 37.5mm diameter x 57mm long. Shaft: 3mm diameter x 19mm long. 6600RPM @ 12Vdc, 330mA no-load. Operates on 8-20Vdc. Solder terminals.
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Old Sep 22, 2010, 12:56 PM
Registered User
United States, TX, Houston
Joined Jun 2010
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As jeno said, be sure and check the specs when buying SLA batteries, the advertised amp/hr rating is usually based on a 20 hour rate. They will supply current at higher rates than the amp/hr rating but for very short periods of time. Below is a spec sheet for a typical SLA 12 volt, 7 ah battery. Scroll to bottom of spec sheet to see discharge table.

http://www.jupiterbatteries.com/Data...JB12-007F1.pdf
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Old Sep 22, 2010, 01:05 PM
Timo2
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City of Glasgow
Joined Jan 2008
228 Posts
Hi Keeping84

You hve a PM

Timo2
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Old Sep 23, 2010, 04:49 PM
RELAX. You'll live longer
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Brisbane- Australia
Joined Jul 2007
3,088 Posts
I have three of the 30A versions of those ESCs in my Wallypower 118' & find them to be brilliant. Especially the slow revs.
I think that the problem is either the motor, or a short, or as previously stated a crossed connection on the input voltage.
If the motor is only rated to 1 Amp as you stated then I don't think it would power your model as it won't have enough power to turn a decent prop.
Does the motor still work if you connect it up to the battery directly?
Cheers.
Paul.
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Old Sep 24, 2010, 07:01 AM
Registered User
Newfoundland, Canada
Joined Mar 2010
13 Posts
Once again thanks for all the replies.

785boats:
the motor still runs fine when it is connected straight up to the battery. i have never put a motor in a boat before, so i have no ideal on what size to buy. i would be looking for a brushless motor and esc with reverse of the appropriate size. when i look on the hobby king website everything is measure in kv, but i have been told numerous times to get a 550 size motor. i cant seem to find it on their site, but that was when i was going to build a 24" model lobster boat, but the one i have in construction now is 40". do you have any ideal of what size of motor i should have for this boat in the kv scale, or a link to such a good motor and esc. i have lots of wiring diagrams on how to hook up the materials now, but i am not sure what size of motor/esc i should be dealing with
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Old Sep 25, 2010, 04:35 AM
Timo2
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City of Glasgow
Joined Jan 2008
228 Posts
Hi Keeping84

Ref Motor Type ? ?

Boat what Length , Beam , Weight , and Prop Size ??

"O" and Battery volt , Amp/hours

Timo2

p.s. Scale & boat speed
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Last edited by timo2; Sep 25, 2010 at 04:48 AM.
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