Battery life question

[JohnnieB]

Originally Posted by shrpshtr

...................Knowing now that I can expect good performance out of a good set of batteries, what other steps can I take to get the range, torque, and moderate speed that'll meet my needs with this cart?.............

The first step is defining what the end goal is.
What type terrain?
How far do you need to travel?
How much weight will be carried or towed?
How fast is fast enough?

Range is determined by the Watt-Hours (Wh = AH * Volts) stored in the battery pack, divided by the Wh the cart uses per mile.

Torque is produced by the motor, multiplied by the gear ratio in the differential and reduced by the diameter of the tires.

Speed is determined by motor RPM, divided by the differential gear ratio and increased by tire diameter, which is exactly the opposite of what determines torque, so at the mechanical level (Gear ratio and tire diameter) speed vs torque is a compromise.

How much torque a series motor produces at what RPM is determined by how the motor is wound and they can be wound for low end torque or high speed or something in between.

Increasing the amps the motor is allowed to draw, increases torque.

Increasing the battery pack voltage, increases both speed and torque.

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With the proper upgrades, a golf cart can be built for just about any purpose within reason, but not for all purposes at the same time. IE: A cart that will climb a muddy 45° hill, probably won't do 40 MPH on the road and a cart that will do 40 MPH on the road probably won't climb a 45° incline and neither is very likely to travel 50 miles on a single charge.

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The cart in your avatar appears to be a Clays Cart. There are several guys that indulge in the sport on the BGW forum and might have a few pointers on what works and what doesn't.

[shrpshtr]

ok JohhnieB,

I really would be ecstatic about 20-30 mile range. I can easily ride that far on a work day at the hunt club or turkey hunting. I'd be equally as thrilled if the cart performed in the low-to-mid 20mph range. For the most part, I'd need to be able to get up and down decent hills but not rock climb. I'd say worst case for hilly terrain for me is when my daughter is shooting a sporting clays tournament in upstate SC. Primarily flat or moderate terrain.

Order of importance:
1-range
2-torque
3-speed

I'd like to stay in the 36v range as going to 48v would require a complete overall of the mechanical portion of the cart ($3k probably? not sure).

Thoughts?

[kernal]

48v conversion with first class components including charger approx. $1000+/- plus batteries. Your labor. Not difficult. High current wires could add a couple hundred if needed.

Start here: http://www.cartsunlimited.net/Custom_Options.html

48v will set you free!

For 3K you could do a complete AC conversion (plus batteries).

[JohnnieB]

If the cart in your avatar is the one we are talking about, it looks like the mechanical and cosmetic stuff have already been done, so it is the electrical stuff in the drive system that needs to be upgraded.

Okay, you have a pretty good idea of what you want the cart to do and to get there we have to find out what you have now, for the starting point.

How tall are the tires? Tire height and tire type is a factor in speed and torque and range. (The numbers stamps on the sidewall are approximate at best, so measure the tire height.)

What controller is installed? Stock would be a Curtis 1206 (275A) controller, but the cart is lifted and appears to have over-sized tires, so it may have been upgraded already.

No matter what controller is installed, all the high current cables need to be upgraded to 4Ga or thicker. The cable shown in the picture you posted of the UPS battery is 6Ga and is too small. If you do decided to stay with 36V, 2Ga would be better since the amp flow in a 36V system is higher than it is in 42V and 48V systems.

BTW, your cost estimate might be a bit on the high side.
SMP-48500 controller with Super-Duty (400A/1000A) solenoid = $570
Complete set of 2Ga Silver soldered cables = $250
Heavy-Duty F/R switch = $170
Total = $1,000 + shipping and tax(?) (And, you can back off on the performance some for fewer dollars.)

That would give you roughly the same drive train setup as Sir Nuke except for tires and motor. Your cart wouldn't go as fast since he has a high speed motor, and he might have taller tires, but your cart might have more torque.

A good set of cart batteries will cost a pretty chunk of change also, but battery prices vary from region to region. The trick is to get the highest AH your budget allows at the best price you can find locally.

[shrpshtr]

Originally Posted by JohnnieB

If the cart in your avatar is the one we are talking about, it looks like the mechanical and cosmetic stuff have already been done, so it is the electrical stuff in the drive system that needs to be upgraded.

Okay, you have a pretty good idea of what you want the cart to do and to get there we have to find out what you have now, for the starting point.

How tall are the tires? Tire height and tire type is a factor in speed and torque and range. (The numbers stamps on the sidewall are approximate at best, so measure the tire height.)

What controller is installed? Stock would be a Curtis 1206 (275A) controller, but the cart is lifted and appears to have over-sized tires, so it may have been upgraded already.

No matter what controller is installed, all the high current cables need to be upgraded to 4Ga or thicker. The cable shown in the picture you posted of the UPS battery is 6Ga and is too small. If you do decided to stay with 36V, 2Ga would be better since the amp flow in a 36V system is higher than it is in 42V and 48V systems.

BTW, your cost estimate might be a bit on the high side.
SMP-48500 controller with Super-Duty (400A/1000A) solenoid = $570
Complete set of 2Ga Silver soldered cables = $250
Heavy-Duty F/R switch = $170
Total = $1,000 + shipping and tax(?) (And, you can back off on the performance some for fewer dollars.)

That would give you roughly the same drive train setup as Sir Nuke except for tires and motor. Your cart wouldn't go as fast since he has a high speed motor, and he might have taller tires, but your cart might have more torque.

A good set of cart batteries will cost a pretty chunk of change also, but battery prices vary from region to region. The trick is to get the highest AH your budget allows at the best price you can find locally.

The cart in my avatar is the one I am referring to. It is a 2005 EZGo 36v TXT Series cart. Everything (Controller, Solenoid, F&R switch, motor, etc.) is all stock except for the tires. They are 22x10x10. They measure right at 21.75" tall I believe but can verify the details tomorrow. In summation, you're saying if I upgrade to a 500a controller and appropriate components (cables & F&R switch) that will give me the range, speed, and torque I am looking for? A couple of other questions:
1 - What about solenoid?
2 - How would upgrading to a 500a controller help if the motor doesn't change?
3 - Do the 2ga cables really make that much difference? I've heard the resistance is so minuscule between the 6ga & 2ga that it really doesn't make any noticeable difference.

Thanks again for all of the help. You, and the others here, have been a tremendous help.

shrp

[vagabond]

Johnny B can give you a better answer, the larger controller will allow more amps to the motor, look at the 6 gauge cables as a garden hose and the 2 gauge cables as a fire hose more flow through the larger cables.
when I got my cart running I started with 2 gauge cables stock tires, stock controller, and 36v, the cart would hit between 16 and 17 mph, with the dcx 400amp controller I was running between 21 and 22 mph

[JohnnieB]

Originally Posted by shrpshtr

The cart in my avatar is the one I am referring to. It is a 2005 EZGo 36v TXT Series cart. Everything (Controller, Solenoid, F&R switch, motor, etc.) is all stock except for the tires. They are 22x10x10. They measure right at 21.75" tall I believe but can verify the details tomorrow. In summation, you're saying if I upgrade to a 500a controller and appropriate components (cables & F&R switch) that will give me the range, speed, and torque I am looking for? A couple of other questions:
1 - What about solenoid?
2 - How would upgrading to a 500a controller help if the motor doesn't change?
3 - Do the 2ga cables really make that much difference? I've heard the resistance is so minuscule between the 6ga & 2ga that it really doesn't make any noticeable difference.

Thanks again for all of the help. You, and the others here, have been a tremendous help.

shrp

I'll answer the enumerated questions first.
1. The kit mentioned contains both 500A Controller and a Super-Duty Solenoid.

2. The torque a series motor generates is determined by the amps flowing through it and the max RPM a series motor will reach is determined by the voltage applied to it. A slowly spinning motor will draw all the amps the power source can provide and the speed controller controls the motor's speed by limiting the amount of current the motor can draw. The stock controller limits the motor to 275A, so a 500A controller would allow the motor to draw about 82% more Amps, so the same motor would have about 82% more torque.

The 22.75" tires are reducing the stock torque by about 17%, so the net gain in torque would be about 65% over stock where the rubber meets the road.

The max speed is limited by pack voltage, but due to the torque loss of the over-sized tires, the 17% mathematical gain in speed probably is not being seen, so increasing the torque by 6% will most likely take the top speed to about 17 MPH with a 36V battery pack. A 42V or 48V battery pack will increase both speed and torque.

3. The intrinsic resistance of a 6Ga cable is 2.5 time the intrinsic resistance of a 2Ga cable, so the difference is significant and most certainly noticeable, especially with tall tires and an aftermarket controller and at 36V, since more amps are needed to produce the same performance than what is needed at higher voltages.

With a 400A or smaller controller, 4ga cables will suffice, but for 450A controllers and above, 2Ga is needed.

The total length of the high current cables on a cart is about20 feet, so you are loosing about 1,975 Watts of energy with 6Ga cables when the motor is drawing 500A and about 782 Watts with 2Ga. (1 HP = 746W)

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Will the upgrades suggested give you the Range, Torque and Speed you want? Maybe yes, maybe no.

With a good 36V battery pack, it will give you the Torque you want, the Speed will be about 17 MPH and the Range will probably be acceptable.

To get more Speed and Range, you need to up the pack voltage. (Which will also give you more Torque)

[JohnnieB]

Originally Posted by vagabond

Johnny B can give you a better answer, the larger controller will allow more amps to the motor, look at the 6 gauge cables as a garden hose and the 2 gauge cables as a fire hose more flow through the larger cables.
when I got my cart running I started with 2 gauge cables stock tires, stock controller, and 36v, the cart would hit between 16 and 17 mph, with the dcx 400amp controller I was running between 21 and 22 mph

Apple to Oranges.
He's got a series motor, you've got a sepex motor.
You get a significant speed gain with DCS and PDS cart when you install a DCX controller, but you have to up the pack voltage, change the final drive ratio and/or install a high speed motor to get more speed from a series drive cart.

[shrpshtr]

Just got back from the beach, sorry for the delayed response. (I hate it when vacation ends...) Anyway, like I said before, I am not looking for 50 mile range, 25mph speed, or torque to pull my Sea Ray out of the lake. I am actually getting 16.5-18+ mph now on relatively flat road. I keep the tires inflated just shy of max recommended. If I got 2-5mph consistent improvement there I would happy as long as I didn't lose any of the torque.

So, it sounds like I need to focus on a good battery pack, then upgrade the controller, F&R, and 2ga cables to be in the conversation of what I'd like the cart to do. What would upgrading the motor do then?

Also, (assuming I make the changes above) would I then only need to add additional batteries and charger to go to 42v or 48v?

thanks again for everything.

shrp

[yurtle]

Your stock motor may be more than enough with upgrades. Mine was. I just "needed" to go faster. If you do the upgrades first, you can always get an upgraded motor later, like I did. However, you mentioned hunting. If you plan on driving slowly off-road, especially if the terrain is hilly, muddy, sandy, etc., you may do better with a torque motor than a speed motor. The main thing to monitor is motor temp. I suspect you'll be happy with stock, but if it overheats, you may need a beefier motor. You can also get yours rewound by several companies. To monitor motor temp., you are really doing an indirect measurement. The case is the easiest thing to measure, but it's the copper windings inside the case you are really "worried" about. In fact, it's the insulation on the copper that you need to protect. The simplest way to measure it is wet your finger and quickly touch the case. If it sizzles, time to take a break. The most accurate way is with an inexpensive IR temp. gun.

You mentioned turkey hunting, so probably no need to worry about hauling multiple deer carcasses out of deep woods up steep hills, unless you bag a BUNCH of turkeys.

In my case, in addition to wanting more speed, my stock motor would get border-line hot after hauling 3 buddies around our four subdivisions several times before taking a break. I figured a higher Hp motor was built a little stouter than stock, and it seems to take the minor abuse and run cooler, not to mention faster.

The main thing to decide now is whether to go 48 volts - DO IT! Another decision is reversing contactor or HD FNR. I debated using an industrial reversing contactor before they were available as a plug-n-play option, but stuck with a HD FNR, mainly because of the cost at that time. The ones I have couldn't take the amperage, and the coils were 120 VAC.

The controller, solenoid and cables are a must. I think JohnnyB already said, go with a SD solenoid, and it can take your current voltage, and is compatible with 42 or 48 volts later, if you go that route.

I chose to wait until my batteries were dead and did everything at once. There's no reason you can't do controller, FNR/reversing contactor, solenoid, cables now, then batteries later, and if you need, motor.