12v battery discussion

[Nate]

OK the questions tell me you are thinking and want more info.

Example:
1975 Caroche Club Car with aluminum dump bed, I added that to let you know it weighs a little more than a standard Caroche.

GE motor wound for torque with a 4" case (smallest motor I have ever seen in a golf cart). It is a quality motor though.

Standard gearing for a Caroche, 8:1
72 volt conversion using Sam's Club cheap 12V group 24 deep cycle batteries.
Top speed 25 MPH, it will go faster than 25 MPH if conditions are right but it will most always hit 25 MPH so to me that is the real number.
Range was 25 miles at 25 MPH when batteries were new now two years later it will go about 15 miles. The batteries just do not have the capacity they once had but then these were the cheapest group 24 batteries I could find.
This cart has a LOT of torque, hit the throttle and you swap ends. It will tow a 7000 lb Dodge diesel 1 ton truck without too much trouble. The motor gets warm but never too hot to touch.
This cart was also at the 06 Bonanza in Kentucky but most folks wanted to see the 120V competition cart so they didn’t pay much attention to this Caroche.

[Nate]

Scotty, there are many opinions on paralleling batteries or running a single string. I personally prefer to run a single string. I like to figure out my amp usage then find a battery at that amp rating then string them in series. The problem with golf carts is battery trays. A group 31 would be much better than a group 24 but they don't fit the trays.

You can't extend range with only some batteries in parallel and other in series. You run all in series or all in parallel. 48V with 12V batteries would require eight batteries.

The reason people go for 64V is you can get that with eight 8V batteries. 8V batteries are a lot better for range than 12V batteries and they have a longer life.

Basically more lead more range.

[Nate]

Oh yea almost forgot.

I have run across a few motors that do not like more voltage than 48V.
I tested a D-310 on 72V and it arced the comms because the armature insulation broke down. This was a used but rebuilt motor with less than 10 miles on it. If you have a quality motor you are probably OK. How do you know? If you can service the brushes without dismantling the motor it is probably a quality motor. Still use at your own risk.

[scottyb]

Nate, the 25 mile range of the CC seem impressive to me. What is typical range on say 48v? I have heard 90 minutes peddle time for a full pack. Is that assuming wot @ 14 mph? 21 miles?
Is there a simple formula for us non-electrical engineer types ( or should I say electrically - challenged) to figure out what the requirements for a given combination of motor/controller comdination will be? And what is actually available from each voltage battery? (6,8,12) a %?
And, finally, eight 12v batteries to make 48v? In series 8x12 is 96? So what are you saying? A sieries... of pairs? Confused, still

[Nate]

Typical range of a stock cart 36V or 48V at stock speeds in good condition is about 35 miles.

Low RPM torque motors can get away will a lot less controller than speed motors. If you have a heavy load the low RPM torque motor will still need some amps though. You can't go too big on a controller other than spending too much money. Motors will only draw as many amps as they want unless the controller limits them. Controllers cannot force amps through a motor, only limit amps.

A single 48V pack would consist of four 12V batteries. Make two 48V packs and parallel them and your amps add. Put them is series and your voltage adds.

Take the battery amp hour rating and divide by two, this will get you closer to real power.
Example: Group 24 deep cycle 12-volt battery rated at 80 amp hours (80 Ah) is really closer to 80 amps for a half hour to a realistic discharge voltage.

[scottyb]

Nate, I really appreciate you dropping by & sharing knowledge with myself and others here. There is much to learn about these simple (stupid) carts.
One more Q.....is there..a formula that I can use to calc loads and or draws for a GC motor.(and) What about caculating the losses from cable and conrller system...Thanks

[Nate]

Ohms Law is what I use to learn the electrical characteristics of a motor.

A good DC shunt would tell you a lot. Not to be confused with motor shunt, do a search for "Shunt" on eBay and you will see what I am talking about. I would get 500 amps minimum. A good Fluke meter with data logging would help a lot also. This is a bit extreme but if you want to get good data....

Look up basic resistance for copper to calculate wire loss but a meter will show you actual loss across a connection. How serious do you want to get with these carts?

My competition carts are fine tuned, more than just connecting the wires. I try to get every amp to the motor and not loose it in heat.

If wires are getting hot the losses are way up.

[scottyb]

Okay,
I'm just trying to wrap my brain around this electrically impulsed contraption!
It's nearly impossible to improve something until you can atleast understand how it works.
If resistors regulate current by wasting it. Then conrtollers regulate current by what - metering? ( ie: no waste)
But are controllers able to tap into or meter out more amps faster than say WOT on a resistor cart?

Alright off to my homework, I shunt return till it's done......
]

[scottyb]

Okay,
Which one do I want???
And...can I put this one on the dashboard and watch the draw?

http://cgi.ebay.com/3-1-2-DC500A-LED...QQcmdZViewItem

[scottyb]

I found this tutorial.....make your own shunts.

http://www.uoguelph.ca/~antoon/gadge...ts/shunts.html