36 volt to 12volt

[christopher]

my means of transportation on the small island where i live is a 36 volt golf cart, and one of my largest electrical draws. I am in the process of doing a motor conversion to charge this but have no suitable source as a dump load when not being charged or fully charged and hate to just waste the power.  perhaps some of you electrical guru's can either approve this idea that I have come up with or, shoot it down??  I have a few electronic speed controllers for these golf carts and was wondering if i used a second 36 volt battery bank as a dump load, could i use one of the electronic speed controllers to effectively reduce the 36 volt to 12 volt to use on my 12 volt inverter??

Thanks for any thoughts, good or bad.

Christopher

[tecker]

 What I would do is set up 3 12 volt sets and  put the bank into 12/ 36 configuration with a double throw disconnect.

[drdongle]

Using the controller may work, however you will simply have to experiment with it to find out. A DC to DC converter would be a better choice.

[scottsAI]

Buy a 36v inverter. They do exist. Much simpler.

Have fun.

[srnoth]

Hi there,

I know this is off topic, but just out of curiosity ('fas'ness'), where is this 'small island' you refer to?

Please tell me if I am being too forward ;-).

Cheers,

Stephen.

[christopher]

thanks, guys i guss i will get out the test meter and see what i can find out. just hate to see these things burnt at the dump.not at all forword Stephen i live on Elbow cay its in the northen Bahamas ( 6 miles long 1/4 mile wide )

Christopher

[christopher]

Hi Stephen.

The small island i refer to is Elbow Cay (Hope Town), Abaco.

go to www.abacos.net/elbow.html to see pics, info, etc.

Christopher

[FishbonzWV]

Hi Christopher,

A couple of questions.

From your posts you are working on a motor conversion for your genny.

Are you going to use a controller on it or just rely on monitoring the charge of the battery.

Second, Is your spare 36v bank another cart or just the loose batts.

If the batteries are loose just rewire them for 12v and hook them to the genny, they will charge but you will have to monitor for full voltage.

I know you have the wind for it! Atlantic side of the islands...non stop winds.

Been to quite a few of the islands myself but have not made the Abocos yet. Beautiful places.

Does Elbow generate it's own power or is it cabled in?

Bonz

[christopher]

Bonz,  Thanks for the reply. Sorry did not see your reply until now.

In answer to the questions: No controller, just relying on monitoring (very much doubt i will have get to a full charge, but when the cart is in use i will need to dump the power somewhere).

Loose batteries, i can reconfigure.

Power is cabled in from Marsh Harbour, approx. 5 miles away (quite a few poer cuts).

Still having fun.

Christopher

 

[srnoth]

Kool.

I will be staying by my aunt in Nassau some time in July, and we are going to spend a week at their house in Spanish Wells. I heard that golf carts are the main means of transportation there too. Sounds fun. Is their much in terms of RE going on in the Bahamas?

Anyway, back to your question. I suppose you could just reconfigure your batteries in 36v banks. I have a couple questions though:

*Are your spare batteries identical? Because if you do create a 36v string, the batteries in the string must be identical, or some will be overcharged, undercharged etc.

*How do your speed controllers work? Are they just adjustable resitors, or are they the fancy electronic type ones? I ask this because one of the simplest ways to charge a 12v bank with a 36v genny (or any power source for that matter) is to put a resitor in series with the power output of the genny. This drops the voltage, but also wastes a lot of energy. If your speed controllers are simply adjustable resistors, they should definately work. The only problem with using resitors is that quite a lot of energy is wasted.

If they are the electronic type, then I guess the only way to find out if they will work is to try. What I would do is connect the 12v battery bank to the output of the speed controller, with an ammeter in series to monitor the rate of charge. Then connect the input for the speed controller to the 36v source, and slowly increase the 'speed' on the speed controller, which, if it will work, should slowly increase the rate of charge on the ammeter. Hopefully this will work.

Anyway, having said all that, I have never used a golf cart speed controller to reduce voltage, so I make no guaranties. Someone please correct be if I am wrong.

Oh yes, by the way, what is internet access like in the Bahamas? Are there places I can go to connect? I heard there is no internet on Spanish Wells. Is this true?

Okay, I'm finished,

Cheers,

Stephen.

[christopher]

Hi Stephen!

These are the electronic controllers, and if I can't get them to work at least I will pull out all the good parts.

I would be very surprised if you would not be able to get internet service in Spanish Wells as my wife is into genealogy in a big way and talks with cousins there all the time. (She says we may even be family).

Seems to be very little interest in wind power in the Bahamas other than what you see on the sail boats.  Have seen some solar hook-up's on smaller remote Keys without grid power. A Lot of big noisy gas gens

Christopher

[Nando]

Christopher:

Please explain your conversion, I am really curious, please say the reasons, I am an Electronic Engineer.

The motor controller, most of them, have a high power semiconductor to ground the motor winding to complete the power connection to the battery, unhappily the frequency of operation is low ( 50 to 1000 Hertz).

There are other controller, more sophisticated some driving the positive side of the battery, so you may need to define what you have to be able to direct you to a solution.

There are some converters that take the 36 volts and converts it to the lower voltage but some are power limited ( 10 or 20 amps) and/or expensive.

How much power do you need for the 12 volts units ?.

You could get a Solar panel charge controller to charge the 12 Volts from the 36 volts, like the Xantrex C40 or C60 or the OUTBACK MAX60 ( this one is the best and more expensive).

C40 = 40 amps charging

C60 = MAX60 = 60 amps charging.

Regards

Nando