Odessy 925 Battery Cranking Amps

Andy4639

Member
Odessy 925's

925 cranking amps for 5 seconds
870 cranking amps for 10 seconds
765 cranking amps for 20 seconds
OK,
this may seem like a stupid ? to most but I think it's got some merit.
If you have 765 cranking amps per battery and you have 6 of these in series then it stands to reason you have 4590 amps too, correct? If not how do you figure the amps for the 11 second runs of the golf cart? :dazed:
 

Andy4639

Member
Frank thes are the ones I just bought. $945.00 for 6 of them. That was the best buy I could find. They are for Racing only but if you bought 2 set's then they might would give you a good enough run time for a regular cart. They only weigh 24 lbs each that is another reason the racing guy's like them!! :thumbsup:
 

StreetGlide

New Member
No...

With 6 batteries in series you would have ~72 volts, but only 765 "cranking AMPs".
In parallel you would have ~12 volts and 4950 "cranking Amps".

Ref 11 second runs for racing:
Take for instance the AGM (model # 680). Each battery only has an A/hr rating of 12.6 amps. So for 1 hour (60 minutes) the battery could provide 12.6 amps. For 1 minute, the battery could provide (12.6*60) which would equal 756 amps for 1 minute. For 1 second, the battery could provide (756*60) which would equal 45,360 amps.

Over 11 seconds, the battery could have provided (45,360/11) which would equal 4,123 amps for each second. About 10 times what would be needed with 400/450 amp motor controller.

Of course above doesn't take into effect battery voltage drop, efficiences of controller, etc.

Hope that didn't add to confusion.....
 

Andy4639

Member
So your saying for 11 second run I should have 45,360 amps to use. My controller is a 700amp controller which according to the builder it will handle 1000 amps.
This should be way more than needed for the 11 second's hopefuly 10 second times I need. Is this correct TOM?
 
925's will have a short circuit current over 2400 amps, the trick is how to short circuit the system to max out the amps to the motor without the brush pack being cooked! Good luck and yes it can be done.
 

StreetGlide

New Member
You can look at it that way. But you have to remember that you use the batteries to get you to and from the start, to the bar, etc. The key is that if you only use the cart a minimum for other than racing you should be able to completely charge the cart in about 20 to 25 minutes.

Remember the example I used was 486s. Your present batteries, if I remeber correctly, are basically 2 486s in parallel, so your total amp hour capacity is twice example given. If you are only using 72 volts, (less batteries voltage drop at high current, your not getting near 72 volts to the motor. Voltage has to be there for speed.

Voltage is = to the pressure to a water hose.
Current is the amount of water flowing through the hose. The more pressure, the more water will flow. The higher the voltage, the more currect will flow if the resistance stays the same. The size of the hose, the amount of couplings, etc. is the limiting resistance to the amount of water that can flow.

With electric power the current (I, measured in amps) is equal to the voltage (E) divided by the resistance (R, measured in ohms). That resistance is the internal resistance of the batteries, the resistance of the wires, the resistance in the controller, etc, but most of the resistance comes from the carts weight, drag, rolling resistance, and "other" resistance the motor is working to overcome.

If I=E/R, the R=E/I and (as normally stated as ohm's law, E=I*R.

Power measured in watts is equal to the voltage multiplied by the current. Power used is equal to the volage multipled by the current, or P=E*I, so, since E=I*R, by substitution, Power is also calulated as P= (I*R)*I, or P=I "squared * R). ALL this just means is that actual Power used to move the car with accelleration is based on having a lot of water pressure forcing a lot of water through a hose as fast as possible. The less resistance you have to the water
flow the more water you have to make the water wheel turn the axle.
 

Andy4639

Member
OK how do I find out what kind of voltage and amps I'm pulling then?
I know how to see the voltage is with a meter hooked up that records the readings, right?
How do I get the amp reading though?

925 batteries have

870 cranking amps for 10 seconds
765 cranking amps for 20 seconds
 

GarageBuilt

Well-Known Member
You would simply short circuit the battery pack causing the amps to spike while bypassing the controller. And yes this can be done. I'm just not sure why you would want to. The correct way would be to series your pack till you reach your max voltage. And then parallel the pack untill you reach the max amps that the controller can handle.
 

Andy4639

Member
How can you series batteries and also have them parellel at the same time? Are you saying have two packs of batteries to do this.
 

GarageBuilt

Well-Known Member
Andy. With your 925's in series. And if you can run the 1/8 mile in 5 seconds are less. You will get 925 amps from your battery pack. In your case you will be closer to 870 amps. You told me you had a 750 amp controller. Thats why I told you a minimum of 925's

And yes. You take two series battery packs. And then parallel the two packs together.
 
You would simply short circuit the battery pack causing the amps to spike while bypassing the controller. And yes this can be done. I'm just not sure why you would want to. The correct way would be to series your pack till you reach your max voltage. And then parallel the pack untill you reach the max amps that the controller can handle.
weight
 

TDAWG

Member
Andy, since you have both sets of batteries, 925's and 680's, it would be interesting for you to do a real world test whenever you get to the track. See how that 80lb weight difference and lower CA battery affects your 1/8 mile time and post results here. Im sure others would be interested also.
 

GarageBuilt

Well-Known Member
Ok. I will give you that one. We are talking about racing. But if that is your true set up & you are only running a single strand of batteries. Then your gain for amps is not worth the loss of voltage that you get from your batteries. You are pushing your Batteries and your motors to their extreme limits. But you already know that. On the other hand. I for one will not give up power for weight.
 

GarageBuilt

Well-Known Member
Ok. But you are not really getting the numbers on the big end, You are just taking what your set up gives.You are leaving way to much on the table. You are going down the track at half voltage. You are sending way to many amps to the motor. The overabundance of amps is burning up your brushes.

680"S x 2 =1360 usable amps. 180-volts. 1360 amps is more than enough amps to increase power to the max. And by doubling your battery pack. You would have less than a 5% voltage drop.... you have the money, spend it. That would only be a 4000. dollar up grade. Plus 225 lb's more,
 

StreetGlide

New Member
Andy, really better to use AMP Hour CAPACITY to figure current. Cranking AMPS is really not the value I would use (just as FYI).

There is an easy way to read AMPS. There are several very accurate AMP meters on the market.

A shunt is necessary in order to measure high currents. A shunt is an accurate, very low resistance resistor which is placed "in line" with the wire carrying the current to be measured. It is usually placed in the negative wire from the battery string, such that all the current going out of the batteries must pass through it. It should be placed near the negative terminal using the same large gauge wiring (as short as possible) as you main battery. When current flows through the shunt, a small voltage is developed across the shunt which is proportional to the current flow (remember E=I*R). The voltage drop that occurs across the very low resistive resistor for a certain amount of current (for example: "50 millivolts at 500 amperes) is provided through small wires (14 gauge, or so) to a volt meter that is actually calibrated and marked as current. (You can usually purchase this meter to match volt meters on the market.

HOWEVER, when you are talking about a 10 second run, accelerating at a rate or 6 mph per second it wouldn't be the best time to try to read a meter. One could carry a passenger to read it for you, you could video tape it, or, as I had planned to do (before doing my cost analysis) is to buy one of the many available digital versions that connect to a mini or micro computer and records the data. It would be generated on a nice graph and data table for viewing later. Some even send the data live to a remote computer which could be located in the pit! Isn't technology grand? These computer versions usually are designed to be connected to sensors for multiple displays showing computer generated gauges for speed, acceleration, current, voltage, etc. They come in all sizes and colors too!
 
Top