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Forum Index : Electronics : voltage control

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jonopy

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Joined: 13/05/2011
Location: United Kingdom
Posts: 7
Posted: 04:23pm 12 May 2011
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Hi can someone help an old thickie from the UK
I HAVE A BUGGY USING A TRANSAXLE 3-12 VOLT -110 AMP BATTERYS IN SERIES 36 VOLT
BUT i ONLY NEED 24 VOLTS TO RELEASE BRAKE AND SUSPECT I COULD DAMAGE BRAKE IF I USE 36 VOLTS CANNOT GET INFO FROM MANUFACTURER IN ITALY THE CONTROLLER IS 36 VOLTS BUT WILL NOT SUPPLY ENOUGH AMPS TO RELEASE BRAKE SO FITTED 24 VOLT RELAY TO RELAESE BRAKE BUT UNFORTUNATLEY OUTPUT FROM RELAY STILL MEASURES 36 VOLT IS IT POSSIBLE TO GET 24 VOLTS TO THE BRAKE AND HOW PLEASE. CHEERS JONOPY
jonopy
 
VK4AYQ
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Joined: 02/12/2009
Location: Australia
Posts: 2539
Posted: 08:50pm 12 May 2011
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Hi Jonopy

You could connect your supply across 2 batteries to get 24 volts to your brake.

Check your brake as to how many amps it draws as it should open on 36 volts, you may have faulty wiring to it.

Bob
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jonopy

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Joined: 13/05/2011
Location: United Kingdom
Posts: 7
Posted: 07:32am 13 May 2011
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thanks for the reply bob,the brake will release with 36 volts but it should have only 24 volts, you said connect to 2 batteries to get 24 volts, Which 2 batteries can I connect it to to obtain 24 volts with the 3 batterys in the circuit ?
hope you can explain that bob I did say I am a thickie , cheers jonopy
jonopy
 
VK4AYQ
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Joined: 02/12/2009
Location: Australia
Posts: 2539
Posted: 10:43am 13 May 2011
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Hi jonopy

In your string of batteries it should be the positive terminal on the center battery assuming it has a negative earth. The next battery up the string is the one that the 36 volts positive to all your other odds and ends, so check the negative terminal of this battery with your voltmeter it will be 24 volts also as it is connected to the positive terminal of the prior battery.

All the best

Bob
Foolin Around
 
jonopy

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Joined: 13/05/2011
Location: United Kingdom
Posts: 7
Posted: 02:54pm 13 May 2011
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thanks Bob you are a star cheers jonopy

tried it bob but i still got 36 then I realised what you said providing I have NEGATIVE EARTH well I have not got an earth the controller manufacturer is 4QD and they state not to earth their controller or wiring system am I goosed is it not possible without a negative earth ?
the problem and I think it may be a problem is I am running 36 volts into a 24 volt motor with a 24 volt brake on the end of the motor my controller only allows 1 amp to the brake which is not enough power to release it. so I have 36 volts going to a relay which is 24 volts in and 24 volts- 30 AMPS out
I Have had a problem recently when the brake got very hot when the controller was not responding and I released the brake using 36 volts I presumed this was too much voltage or ampage I do not know but it cost me a recondition of the controller as I said earlier I am clueless as regard relays, wiring, etc any suggestions please it is driving me round the twist thinking about itEdited by jonopy 2011-05-15
jonopy
 
VK4AYQ
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Joined: 02/12/2009
Location: Australia
Posts: 2539
Posted: 11:22pm 13 May 2011
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Hi jonopy

It sounds like you have an integral brake system in the controller and that may be the problem. what is the purpose of the brake, is it to hold the buggie in one place or to slow down and stop it?

I sounds like it is a waste of electricity to hold the brake off all the time. You could have a relay connected between the terminals of the motor to short them out and have regenerative braking, this will stop the motor but will not be a positive lock in one place type brake, also this would require removing the existing brake.

You could also use a separate switch to control the brake direct from the positive terminal of the second battery where you will have 24 volts, there must be an earth wire going into the controller or it wouldn't work at all. Remove the brake wire and run a wire from the 24 volt terminal through a separate switch to the brake, this will get the 24 volts direct to the brake, the only thing is then you would have to be sure the brake is off before moving as it will stall the motor if its not disconnected.

When you connect 36 volts to the brake it will draw extra current and get hot and will burn out the controller, thats why I would look at ways to make the brake work without involving the controller.

The motor will be quite happy on the 36 volts as it only sees the full voltage at full throttle but the brake will use more power as it is at full voltage all the time.
One other solution that you could use is a down converter, it is a small module that converts 36 volts down to a selected voltage in your case 24 volts they are available in ebay. They only convert 2 to 3 amps though so that may be a problem if the brake draws more.

Have fun

Bob
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jonopy

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Joined: 13/05/2011
Location: United Kingdom
Posts: 7
Posted: 10:29am 16 May 2011
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Thanks fo going to so much trouble bob i do appreciate it I posted a reply but it was disallowed for some reason by the site. going back to what you said ie
check to see how much ampage the brake draws, How would I do that bob ?
another question I would like you to answer please I have a 24 volt RELAY 4 contacts on it
12 -0 clock 3 o clock 6 oclock 9-o clock
I have not a clue how the wiring should go , should the negative and posititive from the batterys go to 9 and 3 o clock and the 6 - o clock go to the brake if so what should go to the 12 o clock pin ? i did say I was a thickie lol

what I started with was 2 very thin wires coming from the controller neg - going to 3 o clock pos + going to 9 o clock
a neg- from the battery going to the 12 o clock and a positive + from the battery going to the 6 o clock.
when I needed to use this wiring to release brake I bridged 12 + 6 o clock because I was stuck and the brake released but got very very hot and my controller was duff I have hed the controller sorted but warned to rectify wiring fault that caused problem can you help me with this one bob? chers jonopy
jonopy
 
VK4AYQ
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Joined: 02/12/2009
Location: Australia
Posts: 2539
Posted: 02:13pm 16 May 2011
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Hi Jonopy

I would suggest that you buy a multimeter do do some testing with as at the moment you are shooting in the dark, you can buy a multi meter on ebay very cheap and thats better than burning your controller again.

When you get a multi meter read the instructions as to how to read amps with it, set it on the 10 or 20 amp scale and put the leads red + to the battery side and black - to the brake, it will then read how many amps the brake draws, do this on the 24 volt position and the 36 volt position and note the difference.

The meter has a ohms setting that can be used to measure resistance and continuity, however be careful to use the ohms setting only with the batteries as you may get a back feed and burn out the meter.

Practice using the meter until you are familiar with its functions.

Then disconnect your relay from the circuit and test it on ohms setting, use the lowest setting on the meter, the control coil will show a resistance, probably between 20 and 40 ohms that should be 3 and 9 oclock positions, check that the relay is open circuit and when you activate it it goes to closes circuit.
The negative and positive should not go to the relay as you describe as when you activate the relay that would be a dead short.

I would suggest that you isolate both wires to the brake and connect one to the battery negative and the other one to the battery 24 volt position using the relay, first check that the relay activates when you activate the brake on the controller, after checking this, check that you have negative to the brake wire no 1 then connect the 24 volts to one side of the contact on the relay and run a wire to the other wire no 2 on the brake.


If you can do this it will isolate the 24 volt circuit from the controller, if you do not feel confident doing this, it would be better to get a auto electrician to have a look at it rather than burning anything out.

Hope that helps

Bob
Foolin Around
 
jonopy

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Joined: 13/05/2011
Location: United Kingdom
Posts: 7
Posted: 03:02pm 16 May 2011
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for a change bob I can say fully understand what you are telling me to do I have a meter but I did not know exactly where to check I have only used the meter for continuity and measuring voltage and a couple of times measuring the resistance on a potentiometer.
I have spent hours browsing the net hoping something would indicate 12 o clock positive and 6 o clock posiitive to brake on relay it seemed logical, as green as I am,
but I would not try without being sure cheers bob I will let you know how I go on thanks again. jonopy
jonopy
 
jonopy

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Joined: 13/05/2011
Location: United Kingdom
Posts: 7
Posted: 08:29pm 18 May 2011
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Thanks Bob you have been a great help job sorted I ran a lead from the Negative to the top of relay 12 o clock then a lead from 6- o clock on the relay to brake which is performing fine on 24 volts. It took me some time to realise that I was running a 24 volts from a negative it didn't seem right to a thickie . I managed a round of golf with buggy today worked fine it was . much appreciated bob wish there were a lot more in the world like you. cheers jonopy.
jonopy
 
VK4AYQ
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Joined: 02/12/2009
Location: Australia
Posts: 2539
Posted: 10:02pm 18 May 2011
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Hi jonopy

That is good to hear I am glad that I could help you, as many forum members have helped me in the past, cause thats what we are really about.

All the best

Bob
Foolin Around
 
jonopy

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Joined: 13/05/2011
Location: United Kingdom
Posts: 7
Posted: 10:03am 19 May 2011
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cheers Bob. jonopy
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