48V Conversion - No Speed Gain

[Lee0smond]

Thinking about it though, the math makes sense. If I was expecting a 33% gain, but the batteries are only operating at 75% capacity. That should be close to a wash.

18mph * 1.33 gain = 23.94 theoretical mph

23.94 theoretical mph * 0.75 battery capacity = 17.9 mph

So fingers crossed I actually see some gains after break in.

[Lee0smond]

This was the response I got from D&D. So they expect 3-4 mph. I guess I'll let the batteries break in and see if any improvement. If not, and the log files look good, I guess it would be a motor issue which would seem odd since it was at the higher end of their range on 36V.

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No that is not normal. You should gain around 3-4 mph. I would take it to your local dealer to see what is going on.

Thanks,
Mike
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Hello,

I have a D&D motor installed on my 1992 EZGO Marathon (170-013-0001). I installed it on a 36V cart (with Alltrax SR48500 controller, solenoid, 2AWG cables) and was getting about 18MPH flat ground and ~12MPH uphill.

I recently upgraded to 48V and have seen absolutely no impact to speed or torque. Is that normal? I expected to see at lease some gain.

Model # 170-013-0001
MFg. Date 06/08/20
Serial #: ***
Voltage 36/48.
*******

[JRaf]

Hmm. I'm not an engineer and I'm not particularly smart but even considering battery break-in, something's not right here.
- In going from 36 to 48v, besides replacing the batteries, what else did you do? Did you replace the solenoid? Did you have to address the Alltrax software? Are there boxes in there that need to be checked?
- It certainly seems like the gaggle of mosfets in the controller are doing their job, ramping up the amperage in JohnnieB's freewheeling effect... but where are the results? You're not getting an increase in top speed but what about torque? Is the system behaving the same way under load? On hills?
- I'm not convinced the pack voltage is as high as it should be. How high does it get when it's on the charger? The charger is new, right? Can you see the amperage it's delivering? Is that something you can read on the Alltrax?
- Is it possible there's a dead cell or you're getting a false reading on your meter? Can you test specific gravity on all the cells? Can the Alltrax software read resting voltage?
- Might be very basic but are there any hot wires? Is something bottlenecking the current before it gets to the motor?

[Lee0smond]

Originally Posted by JRaf

Hmm. I'm not an engineer and I'm not particularly smart but even considering battery break-in, something's not right here.
- In going from 36 to 48v, besides replacing the batteries, what else did you do? Did you replace the solenoid? Did you have to address the Alltrax software? Are there boxes in there that need to be checked?
- It certainly seems like the gaggle of mosfets in the controller are doing their job, ramping up the amperage in JohnnieB's freewheeling effect... but where are the results? You're not getting an increase in top speed but what about torque? Is the system behaving the same way under load? On hills?
- I'm not convinced the pack voltage is as high as it should be. How high does it get when it's on the charger? The charger is new, right? Can you see the amperage it's delivering? Is that something you can read on the Alltrax?
- Is it possible there's a dead cell or you're getting a false reading on your meter? Can you test specific gravity on all the cells? Can the Alltrax software read resting voltage?
- Might be very basic but are there any hot wires? Is something bottlenecking the current before it gets to the motor?

1) I replaced the batteries and resistor - I was already running a 36/48v compatible system purchased from Carts Unlimited (Alltrax 48500, HD Solenoid, HD F/R Contactor, 2 AWG cables). Its a series cart so pretty much straight forward. Just adjusted the min voltage up to 38v from 20v, made sure 500amp max allowed, throttle set to 100%, and peak amp enabled.

2) Yeah, still about 18mph flat and 12mph uphill. That was what I was getting before with 36V (checked using phone gps spedometer)

3) I'll have to check but I believe north of 57. Once again, i'll have to check the charger amp but rated for 15. I believe it starts at around there and tapes off to 5amps as it nears full charge. Its set up to deliver 2.40v per cell currently, this can be adjusted up to 2.45

4) Resting voltage is about 50.8 I believe.

5) Nothing hot at all. Also, nothing has been changed in temrs or wiring from 36v to 48v and I was under the impression 48 actually uses less amps so there really should be nothing getting too hot.

I'm at work so I will need to double check the numbers later.

[Lee0smond]

And going up a hill I hold over 45.3V so with my limited knowledge that doesn't really signify a dead cell, correct?

Meter matches the voltage in the data log from the controller.

[JRaf]

Well, again, you should wait for the smart guys to check in but 50.7 is a little low (but that could be measurement error). The Cart's Unlimited chart says that's a hair low, they have 12 hour resting voltage at 50.9. Interestingly the USBatteries chart is a little higher at 51.3.
Maybe Interstate publishes their own info? It's worth trying to find it.
The difference between 2.40 volts and 2.45 volts during charge calculates out to 57.6v and 58.8v. Neither seems particularly high.
My 36 volt charger regularly pumps out 18 amps and 46+ volts, which is roughly 130% over nominal voltage. 130% of 48 is around 60 volts. Maybe someone else can confirm that number.
I wonder if that higher voltage wouldn't result in a higher resting voltage.
But would 100% fully charged vs 90-95% charged give you a drop of 3mph or no torque improvement? Maybe, I don't know.

[JohnnieB]

1. Charger

What Make/Model charger?

For a DPI Gen-IV, all flooded Interstate brand batteries use a 2.40V absorption phase.

The final or finish stage is dV/dT (change in Voltage over change in Time), so the batteries ought to end up fully charged, or mighty close to it when the charge shuts off automatically.


2. Batteries

What is full model number?
Interstate has several 8V batteries. Picture of label maybe.

Attached is a SoC chart based on Trojan brand batteries. I cannot find one specifically for Interstates brand batteries, but Trojan is the lowest voltage, so your batteries ought to be at least 50.9V at rest. Maybe a bit higher since they are new.

Storage capacity doesn't have much influence on at-rest voltage. A 2V Lead-acid, Deep-cycle, Wet-cell will have a fully charged at-rest voltage of 2.122V whether it is a 260AH cell in a 6V battery or a 150AH cell in a 12V battery.

How much the voltage drops under load depends on storage capacity and SoC (State of Charge).

On the data log, The at rest voltage was 49.9V and it dropped to 41.8V when 270A were drawn. That indicates weak batteries, not bad, but weak. Maybe not fully charged or possibly just not broken in yet.


3. Controller.

You've mentioned resistor a few times. A XCT in a DCS should not have a pre-charge resistor. It should have a Regen Diode instead. See attached schematic. It is the latest one available on the Alltrax website Rev.-E.

I know the XCT for some Sepex system don't work right with a pre-charge resistor installed, maybe the DCS version is one of those.

[Lee0smond]

1) DPI Gen IV currently on setting 4 (per DPI guidance) - chart attached

2) 9-GC8-UTL - attached specs They are currently resting at 50.8 on full charge (per the installed gauge - i know that can show slightly lower than actual)

Batteries have 2 charge cycles on them so I'm leaning towards not broken in over bad. They were fully charged overnight before that data log.

3) The HD solenoid has a diode and resistor (diode between small terminals, resistor between big terminals). Sized, purchased, and shipped from Scotty B. Diode is same from 36V. Only resistor was increased.

[bronsonj]

Originally Posted by Lee0smond

The interstate GC8 batteries are 8V-170AH, correct. 6 x 8v. Batteries were fully charged (charger shut off).

Often times chargers will have a built in safety timer so if the charger is still charging 16 hours later it'll stop. I don't know about your DPI, but just because the charger turned off doesn't mean that the batteries are fully charged.

Did you verify the electrolyte level in the batteries? Run a charge cycle and if it's still not fully charged run another charge cycle right behind it. 49.9V is about 75% charged.

I would look at that difference. If your dash meter says 50.7V and the controller log says 49.9V that's a big at-rest difference. Use your handheld meter and see what it says.

[Lee0smond]

Originally Posted by bronsonj

Often times chargers will have a built in safety timer so if the charger is still charging 16 hours later it'll stop. I don't know about your DPI, but just because the charger turned off doesn't mean that the batteries are fully charged.

Did you verify the electrolyte level in the batteries? Run a charge cycle and if it's still not fully charged run another charge cycle right behind it. 49.9V is about 75% charged.

I would look at that difference. If your dash meter says 50.7V and the controller log says 49.9V that's a big at-rest difference. Use your handheld meter and see what it says.

I did not check the electrolyte level. Just bought them brand new a week or so ago with a MFG date in Sept 21 so just assumed they were good. I'll need to buy a hydrometer.

I'll throw the voltmeter on it tonight and get an exact pack voltage.