D&D motor question

[mrphilf]

I said night but we are talking running at just after dinner time til dusk, 6-9pm temp has been mid-high 70's. I definitely notice better performance when its warmer out.

With the old FNR switch to my best estimates I was losing .7v somewhere outside the batteries, I haven't dug back into the system to see how much of that I "found" because I know I need cables.

In your opinion is 2ga welding wire from the auto parts store sufficient? Or do I need to be getting some type of special wire designed for golf cart cables?

While we are on batteries. Better to run 6 8v Rangers or 8 6v T105s?

[scottyb]

2g cable from the Automobile industry is not sufficient for a 500 amp electric cart with HD aftermarket motor... or any motor for that matter. Get yourself some 2g welding lead with neoprene jacket.

[JohnnieB]

Originally Posted by mrphilf

1. I said night but we are talking running at just after dinner time til dusk, 6-9pm temp has been mid-high 70's. I definitely notice better performance when its warmer out.

2. With the old FNR switch to my best estimates I was losing .7v somewhere outside the batteries, I haven't dug back into the system to see how much of that I "found" because I know I need cables.

3. In your opinion is 2ga welding wire from the auto parts store sufficient? Or do I need to be getting some type of special wire designed for golf cart cables?

4. While we are on batteries. Better to run 6 8v Rangers or 8 6v T105s?

1. Storage capacity for cart batteries is measured at 77°F and for every 10°F increase in temperature, the effective storage capacity increases about 5%. (See first attachment)

When it is about 77°, you have T-875 batteries, when it is about 100° you have T-890 batteries.

2. Good cables and connections will decrease the amount of voltage drop under load.

3. Like Scotty said, the 2Ga cable from an auto parts store might not be what is needed. You want high strand count welding cable. I'm not sure what it is for 2Ga, but I think it is 600 strands or higher for 4Ga, so 2Ga would be quite a bit higher than that.

The trick is that carts don't run on DC, instead they run on pulsed DC and the pulse repetition rate is in the 15kHz to 18kHz range, so the skin effect is very significant. The more strands, the less dynamic impedance due to skin effect.

4. With little exception, eight 6V batteries will give you more run-time (range) than size 8V batteries, but the battery pack will weigh more, so it'll be like carrying another person on the cart with you at all times.

The second attachment compares 48V battery packs made up from various 6V and 8V batteries, without any weight considerations.

The T-875 pack you have now has roughly the same kWh of storage capacity as the standard 36V pack.
A Ranger 160 pack (6 X 8V) would up the storage capacity by 20%.
A T-105 Pack (8 x 6V) would up the storage capacity by 32.4%.

(Since kWh = AH * Volts / 1000 and the volts are staying the same, % AH increases are the same as the % kWh increases shown)

Your 48V T-875 pack weighs 378 pounds.
A 48V Ranger 160 pack will weigh 456 pounds. (78 pounds heavier than now)
A 48V T-105 pack will weigh 496 pounds. (118 pound heavier than now, but only 40 pounds heavier than the Ranger 160 pack)

Either would be an improvement, but I can't say which which is better, other than the T-105 pack would have more storage capacity, so the voltage drop under load would be a little less than the Ranger 160.

The nutty thing is that the T-105 pack may even cost less than the Ranger 160pack.

[mrphilf]

Do you guys have any idea what I should expect to pay for this grade of wire?

I have been poking around for a couple days and I am getting prices anywhere from $1.25 a foot to over $6 a foot. Or is there an actual spec for the correct wire? All I can seem to come up with is wire that is rated for 600A...

Also, if we are under the assumption that 2ga power wire is insufficient but 2ga high strand welding wire is sufficient, how sufficient is it? Especially after reading Scotty's website that he has 600A carts running on 4ga. Any benefit to just running 1/0? I have had car stereo's that ran on 2/0 so 1/0 can't be that far out of the realm of possibilities.

[scottyb]

I want to clarify what was posted here;
... on my website I said that in the past we ran 650 amp controls on 4g welding cable but today engineers tell us we need to use 2g for 500a and up. The engineers determined that the 4g could not provide the peak amperage draws.
Today's controllers have higher peak and sustained output than previous models, their recommendations have improved performance.
Welding lead is the industry standard.

[teecro]

Originally Posted by mrphilf

Do you guys have any idea what I should expect to pay for this grade of wire?

I have been poking around for a couple days and I am getting prices anywhere from $1.25 a foot to over $6 a foot. Or is there an actual spec for the correct wire? All I can seem to come up with is wire that is rated for 600A...

Also, if we are under the assumption that 2ga power wire is insufficient but 2ga high strand welding wire is sufficient, how sufficient is it? Especially after reading Scotty's website that he has 600A carts running on 4ga. Any benefit to just running 1/0? I have had car stereo's that ran on 2/0 so 1/0 can't be that far out of the realm of possibilities.

I paid 100 from Del City for 25 foot of 2 gauge and enough connectors and solder slugs to make new cables plus a a few spares ends/slugs....

[mrphilf]

Originally Posted by scottyb

I want to clarify what was posted here;
... on my website I said that in the past we ran 650 amp controls on 4g welding cable but today engineers tell us we need to use 2g for 500a and up. The engineers determined that the 4g could not provide the peak amperage draws.
Today's controllers have higher peak and sustained output than previous models, their recommendations have improved performance.
Welding lead is the industry standard.

I didn't mean to insinuate something that I shouldn't have, I apologize if I did.

[scottyb]

Originally Posted by mrphilf

I didn't mean to insinuate something that I shouldn't have, I apologize if I did.

No problem, I was quoted a bit out of context and I didn't want readers to be confused. Good luck with the project.

[options89]

I bought number 2 welding cable for about $5-6 Canadian.

[JohnnieB]

Originally Posted by mrphilf

Do you guys have any idea what I should expect to pay for this grade of wire?

I have been poking around for a couple days and I am getting prices anywhere from $1.25 a foot to over $6 a foot. Or is there an actual spec for the correct wire? All I can seem to come up with is wire that is rated for 600A...

Also, if we are under the assumption that 2ga power wire is insufficient but 2ga high strand welding wire is sufficient, how sufficient is it? Especially after reading Scotty's website that he has 600A carts running on 4ga. Any benefit to just running 1/0? I have had car stereo's that ran on 2/0 so 1/0 can't be that far out of the realm of possibilities.

You can get 625 strand 2Ga welding cable with a neoprene jacket for about $1.70/ft and 1650 strand 2Ga for about $2.25/ft.
Any strand count in that range will work, the higher the strand count, the more flexible and the less skin-effect losses.

I suspect you meant to say 600V rather than 600A. Amp ratings are based on gauge while voltage ratings are based on insulation and most welding cable is rated at 600V for all gauges.

Scotty explained what was actually meant by what is posted on his website.

Some car stereos draw more amps than cart motors do, so they need thicker power cables.

That is basically because they typically run on 12V while cart motors typically run on 36V, 42V or 48V.

250 Amps are needed to run a 3,000W car stereo or 3.0 kW cart motor at 12V, while at 36V, only 83.3A are needed, (71.4A @ 42V and 62.5A @ 48V)

The amp load for a car stereo can be more or less continuous, and the ampacity of 2Ga for chassis wiring is only 181A, so 1/0 (245A) or 2/0 (283A) is needed.

The amp draw of a cart motor can go up to whatever the max amps the controller will allow it to draw, no matter what the voltage is, but most of the time the amp draw is less than 100A, so 4Ga (135A) will suffice for a stock cart. However, with tires taller than the 18" stock height, motors more powerful than stock and controllers having more than the stock 275A to 300A max, 4Ga is only marginal.

Regardless of size (gauge), all cables have resistance, amps passing through resistance generates heat and that heat is power not being delivered to the motor, so you want the high current cables to run cool. A good check to see if you cables are heavy enough for your cart is to feel of them after a long, hard run. If they are hot, they are too small for the application, or bad.

They will get warm, but shouldn't get much warmer than about 10°F above the ambient air temperature.

In general terms, overkill is underrated, but thicker cables cost more and are less flexible, so there is a point of diminishing return.

Going from 4Ga to 2Ga is a two step jump, so the is a 37% reduction in resistance and the same with going from 2ga to 1/0Ga.
From 1/0Ga to 2/0Ga is only a one step jump, so the change in resistance is only 20%
Going from 47Ga to 2/0 is a 94% decrease in resistance.