More HP, longer run time?

[auster]

Im rebuilding a 92 marathon. 6 Brand new Trojan 875(8 volt), new 200/800 amp sol, curtis 1204 48 volt 400 amp contoller, new HD FNR from Scotty Bs, but with stock 2hp GE motor. Question is can I expect longer run time on batteries with motor upgrade. Adding a D&D 8 hp tourqe motor next month. This cart will be 80% off road use with 22" tires. At this time it seems like run time is considerably short with current motor. Thanks for any advice in advance.

[ab46501]

My cart is used mostly off road also. I just switched from a rebuilt stock motor by EMP to a D&D. I seem to be getting longer run time with the D&D. I have no real technical data to support this, only what I am experiencing. My guess is the D&D motor is more efficient.

[auster]

At some point in the past Ive seen where someone actually had some technical data but cant find it at this time. Think it was something posted by Johnny b but not sure.

[JohnnieB]

Theoretically, the energy stored six T-875 (8V - 170AH) batteries is roughly the same as the energy stored in six T-105 (6V - 225AH) batteries, about 9.0kWh for both.

On the other hand, a 48V system has more oomph than a 36V system and people tend to used it more, so the run time will very likely be less until the nut behind the wheel gets over the heavy foot syndrome.

Unless the stock 2HP motor is in really, really bad shape, it seems like an 8HP would have the potential of reducing run-time since it is capable of drawing four times the current. Granted, it may be more efficient than the stock motor, but with a heavy foot, 9kWh won't last very long.

[auster]

So Johnny, your saying I should have went with the 890's? Well I was being cheap but wish I would have stepped up now! Didnt realize there was that big of a difference.

[JohnnieB]

T-890's would have given you about 12% more run-time. Whether that is worth the additional expense is the question.

A 48V pack with 8 T-105's would be about 33% more run-time
A 48V pack with 8 T-125's would be about 42% more run-time.
A 48V pack with 8 T-145's would be about 53% more run-time.


What kind of run-time are you getting?

In your first post, you mentioned everything except the cables in your upgrade list.
If any of the cables or connections are getting the hot, or very warm, you are loosing power to the motor, which would be cutting into your run-time.

[auster]

All I knew of were the 875's and 890's. Wish I would have done a little more research, but got impatient. Aprox 3 hours but traversed some extremely hilly terrain during that time period. All cables have been upgraded to 4 awg welding wire. Only wire that gets warm is the bottom cable on the FRN that goes to M-(think thats the right location on the controller). But thats due to a recessed and pitted stud. Have a new HD FNR switch on the way from Scotty bs though. Maybe that will fix that issue.

[auster]

So youre saying if I go to 8 6 volt batteries Ill get that much more run time?

[Foot hill]

That's what Johnny's saying!

Trade off is extra weight and room. Although I've seen eight 6volts fit under the seat it usually requires work.

Good compromise is to look at Johnny's sleeper build 42 volt
7x6volts.

I am curious too how mileage per charge will be affected with up graded motor in real world conditions.
I've got same upgrades as you and next on list will be motor/batt pack.

[JohnnieB]

Originally Posted by auster

So youre saying if I go to 8 6 volt batteries Ill get that much more run time?

Yes.
The percentages of increase are based on a 36V system using six T-105 batteries, but the lower AH capacity of T-875's is offset enough by the higher voltage, that 48V system using six T-875's will have roughly the same run-time, if the cart is driven in the same manner over the same terrain.

It takes the same amount of energy to move a cart from point A to point B and it takes 746 Watts of electrical energy to produce one Horsepower.
Since Watts equals Amps Times Volts, (P=IxE) an electric motor will produce 1HP with either 20.7A @ 36V or 15.5A @ 48V, or any other combination of amps and volts the add up the 746W.

You will get more speed with a 48V pack because the RPM of a series motor is limited by voltage.
You will also get more torque because a 400A controller will deliver more watts to the motor at 48V (19.2kW peak) than it will at 36V (14.4kW peak), but at the expense of run-time.

In order to increase run-time you have to increase the real estate the batteries occupy.
The case size of a T-105 and a T-875 are the same, so the store about the same energy.
By increasing the number of 6V batteries used to make the pack, you increase the amount of real estate used to store the electrical energy.

I wanted more run-time (range actually) and wanted to keep everything under the seat, and I'm a bit on the lazy side, so I compromised.
I went up to 245AH batteries and increased the number of batteries by 1 to give me 42V and about 11.2kWh of storage vs the 9.0kWh I originally had.
If I keep my size 16 foot out of it, or turn down the controller to 300A, that should get me where I want to go and back.