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Old 01-26-2018, 10:35 AM   #11
Furyous
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Default Re: Is our Series Cart a practical application for Lithium Batteries?

I can't get into amperage draw too much, but I would surmise that I have the most similar cart to yours in terms of weight that I have upgraded to lithium. I have a steel framed, stretched, and lifted cart with heavy custom fiberglass body on 23" tires that often carries my wife, 3 kids and I and stuff like lawn chairs and beer (The essentials, I'm not sure what my total weight is but it is a tank). I have an Alltrax AXE500, heavy duty F?R switch from Scotty B, and a custom wound motor from EMP. I did the conversion in July as it was a perfect time- my lead acids were tanked and I was forced to undergo some front end suspension surgery so the cart had to be disassembled.

I bought a 58.8V 62aH DIY Nissan Leaf pack, wifi BMS, and 4A charger from evbatterycenter.com. JohnnieB is right- 400 lbs shaved off from the beginning. Thecost of the conversion was similar to replacing lead acids if you take into consideration selling your old batteries and charger, and you do all the work yourself.

Performance is awesome- it doesn't break a sweat when I stomp on the accelerator and gets to 20mph in 2.5-3 seconds at full charge. It's hard not to put your foot into it when you are used to the acceleration of lead acids- there is not nearly as much voltage drop with lithium upon acceleration. I went from a top speed of 24mph to 28mph full charge. When the batteries were at the end of their range, the lead acids would get me to 18 mph and the lithiums still hit 24mph. Going heavy on acceleration and top speed, just as in lead acid, will decrease your range. If I am always on the throttle, I get about 15 miles of range but have not taken it down to a completely dead charge. I can go about 20 miles on a charge if I am easy on it and it is only me on it.

I need to put an ammeter on the pack when driving to give you a better idea, but I am very happy with the conversion so far. I can tell you that even with the increased voltage I have not seen my motor get warmer than 102F, which tells me that it is not working that hard.
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Old 01-26-2018, 10:44 AM   #12
scottyb
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Default Re: Is our Series Cart a practical application for Lithium Batteries?

The allowable maximum discharge rate I keep finding is 3C. Which translates to 300 amps for a 100ah pack......but there is also a time limit on this high discharge rate. So that may be another thing you need to look into, the duration of this high demand.
Mathematically if 3C is acceptable the pack would have to be 133.3ah to handle a 400 amp draw.
I have a 100ah pack which I will eventually put into a lightweight sepex golf cart. I will have a ammeter in the cart
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Old 01-26-2018, 10:45 AM   #13
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Default Re: Is our Series Cart a practical application for Lithium Batteries?

Quote:
Originally Posted by ThreeCW View Post
I did some current testing on my Cushman using a Fluke 325 Clamp Meter as follows:
- Metering point = 2 AWG battery cable between battery 7 and 8 (see photo)
- Cart Base Weight (with driver) = 1850 lbs
- Cart Loaded Weight = 2800 lbs (loaded with 950 lbs of feed bags - see photo)
- Drive wheels equipped with tire chains (giving traction but added rolling resistance)
- Outside Temperature = 1 C (34 F)
- Cart was previously stored inside garage at 5 C (41 F) … assumed starting battery temperature

DC Amperage Testing Results as follows:

Flat Road (packed snow on plowed gravel road)
- Soft Start = 100 amps at base weight
- Full Acceleration Start = 280 amps at base weight
- Cruising at ~5 mph = 50 amps at base weight / 75 amps at loaded weight
- Cruising at ~10 mph = 100 – 120 amps at base weight / 80 amps at loaded weight

Uphill Road (packed snow on plowed gravel road)
- Soft Start = 120 amps at base weight
- Cruising at ~2 mph = 125 amps at base weight / 150 amps at loaded weight
- Cruising at ~5 mph = 200 amps at base weight / 300 amps at loaded weight
- Flat out (+5 mph) = 250 amps at base weight / 300 amps at loaded weight

Flat Terrain With Snow (6” deep lightly crusted snow on lawn)
- Soft Start = 150 amps at base weight
- Cruising at ~2 mph = 150 - 200 amps at base weight / 180 - 200 amps at loaded weight
- Cruising at ~5 mph = 250 - 400 amps at base weight / 380 - 400 amps at loaded weight

Analysis:
- This amperage testing was done to determine the battery discharge requirements if a lithium battery system was installed in the future.

- The above testing is not my typical operating conditions but does simulate the maximum continuous amperage that could be experienced during extreme operations.

- Given the above results, a lithium battery continuous discharge requirement of 400 amps would be required to stay within the safe operating capacity of the batteries.

- Given my preliminary review of lithium batteries, it might be difficult to “economically” achieve this 400 amp continuous discharge requirement.

Questions:

Any comments on my testing procedures, results or analysis?

Do any of the BGW members have experience with Lithium Batteries in your Series Carts?

Are Lithium battery users designing their packs to ensure they stay within the Maximum Continuous Amperage rating of their cells?

The Nissan Leaf cells are a popular battery for lithium conversions in golf carts but I have not been able to find any verifiable data for the Amperage Rating for these cells. Can anyone provide this information?

Does anyone know of any lithium cells that will be able to “economically” meet a 400 amp discharge requirement?

Thanks for your feedback!
ThreeCW: Since you are in Canada and I see all the snow in the picture of your cart, where will the cart be stored? The Nissan leaf cells can discharge at 240A continuously and up to 540A short time. You can't charge them if below 32°. You did a nice job of testing and recording data. How far do you travel with these large loads? How long would the constant load be on the battery?

Here is a link to some information on the Nissan Leaf module that Nick has posted on the EV battery website. He passed away on Dec 10. EV Battery is trying to get set up to supply DIY leaf packs again in the near future. Read thru this information on the Leaf cells. Also check out the you tube link at the bottom of the page he has on the fire hazard with the Leaf module, or not..

https://evbatterycenter.com/HAC4/ind...=63&Itemid=196

If I was putting a pack in your cart, I would make it a double pack (14 modules) 7S2P configuration. And I would use a Zeva BMS that E36Racer has used on his pack so that you can montor disscharge rates from the pack and safely disconnect if overload ing the pack. Lots of safety fieature with this BMS.

http://zeva.com.au/index.php?product=122
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Old 01-26-2018, 11:09 AM   #14
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Default Re: Is our Series Cart a practical application for Lithium Batteries?

Quote:
Originally Posted by Furyous View Post
I need to put an ammeter on the pack when driving to give you a better idea,
If you can connect the AXE controller to a laptop, You already have an ammeter connected. Record a data log, it documents the battery amp draw and pack voltage (and some other parameters) several time per second.
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Old 01-26-2018, 11:13 AM   #15
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Default Re: Is our Series Cart a practical application for Lithium Batteries?

Quote:
Originally Posted by JohnnieB View Post
If you can connect the AXE controller to a laptop, You already have an ammeter connected. Record a data log, it documents the battery amp draw and pack voltage (and some other parameters) several time per second.
Good idea.
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Old 01-26-2018, 12:02 PM   #16
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Default Re: Is our Series Cart a practical application for Lithium Batteries?

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Originally Posted by Furyous View Post
Good idea.
Select "Continuous" for the sample rate and you get about 10 samples per second.

Save the logs as .CSV files and they load directly into a spreadsheet were some sorting and number crunching can be done.

You cannot post a .CSV file on BGW, but if you zip them, you can post .ZIP files.

I'd love to add some lithium batteries in a series cart data logs to my collection.
The only lithium data logs I have are from SepEx drives.
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Old 01-26-2018, 03:26 PM   #17
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Default Re: Is our Series Cart a practical application for Lithium Batteries?

Thanks to all for your feedback. Replacing Lead Acid batteries with Lithium in a heavy-duty "SERIES wound" work cart sounds like it may be possible … and I want to ensure that I do it “right” if I go down that road. My objectives with lithium batteries are 1) Safety 2) Meet the performance requirements (sufficient discharge amperage and Amp Hours) 3) Long term battery life to result in a reduced $/battery cycle vs Lead Acid, and 4) Lower Maintenance (quit doing acid!). I am not looking for something to go faster with (my cart is not designed for fast) or looking to increase the range (local farm use only … not going far).

JohnnieB – Adding more cells in parallel will certainly increase the discharge amperage and running a higher voltage is also an option if I renew my controller. These are good points for me to consider.

Furyous – It would be interesting to compare your discharge amperage if you are able to download your controller. Would this be motor amperage or battery amperage … or are these essentially the same? My measurements were made on an interconnecting battery cable.

Scotty – Yes, the 3C maximum discharge rates seems to be the upper end from what I have seen too. Some lithium batteries are rated at a 3C maximum "continuous" (like the GBS-LFMP100AH cells) and other are peak loads (what every that means). A person has to be pretty careful on choosing the right cells if maximum discharge amperage is a consideration in your application.

PingEye3 – The cart is stored in a “heated” garage at 4 to 5 deg C (~40 deg F) in the winter, so charging lithium should not be a problem. I typically only have large loads on the cart perhaps 5% of the time, but I am looking design to this peak load (400 amps driving through deep snow / 300 amps other times). With a large load, I typically could travel a ¼ mile or so … at 2 mph this would be an 8-minute trip, at 5 mph it would be a 3-minute trip for continuous load design purposes. I am sure these times exceed some of the batteries “instantaneous or peak” ratings.

In the past, I have seen the US DOE study for Nissan Leaf batteries that show 240 Amp continuous / 540 instantaneous battery ratings … but I thought that this was for the entire Nissan Leaf battery pack and not the individual cell … I will have to check this out again. I was not able to find any other “valid” reference to the discharge capacity of the Nissan Leaf individual cells. As you also suggest, connecting the cells in parallel will increase the discharge amperage according … an approach that it sounds like I will have to follow with what ever lithium battery pack I decide to go with … at this time, I am leaning to a new lithium battery pack as opposed to a reclaimed pack. I will also have a good look at the Zeva BMS that you suggested.


Again, thanks to all for your valuable feedback … it is always nice to have the BGW members as a sounding board!

Regards, 3CW
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Old 01-26-2018, 05:32 PM   #18
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Default Re: Is our Series Cart a practical application for Lithium Batteries?

Amp draw from my experience is FAR more dependent on terrain than weight of the cart. Loaded and rolling on the road or lanes takes half or less amps than the same surface with 4 or 6 inches of snow or mud, 80 amps vs 160 or more when the going gets tough. On the topic of lithium, the local Chrysler dealer got sent [read stuck with] a new Pacifica hybrid. Wouldn't start or do anything for our 10 day cold snap. They called Chrysler, asked what to do and the reply was,,, nothing. "Sorry, the car is not designed to work in cold temps."
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Old 01-26-2018, 05:43 PM   #19
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Default Re: Is our Series Cart a practical application for Lithium Batteries?

I'v seen a lot of Alltrax files where amp draw spikes to 300 even 400 amps but the duration is usually 5-10 seconds. Peak draws like this usually have a maximum allowable duration when it comes to the manufacture's recommendations.
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Old 01-26-2018, 06:03 PM   #20
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Default Re: Is our Series Cart a practical application for Lithium Batteries?

Quote:
Originally Posted by ThreeCW View Post
--------------------------
Furyous – It would be interesting to compare your discharge amperage if you are able to download your controller. Would this be motor amperage or battery amperage … or are these essentially the same? My measurements were made on an interconnecting battery cable.
--------------------
No aimed at me, but being a Techno-Nerd, I cannot resist answering this.

The output of the controller is PWM (Pulse Width Modulated) DC and the motor's armature/field windings are inductors, so you get a flywheel effect and motor amps exceed battery amps when controller's output is less than 100% duty-cycle and more than 0% duty-cycle.

The attached page from the Curtis 1204/1205 manual explains it fairly well and the higher amps between motor and controller than battery and controller also applies to later generations of both series and sepex controllers.


FWIW:
Also attached is a snapshot of a data log I saved while I was running a DCX controller. The data log from an AXE will look about the same and have almost the same info. (The only difference I know of is the Output Current column is Armature Amps only with the DCX and Motor Amps for the AXE)

The log show about four seconds of me driving across my bumpy lawn at low speed. The columns and row with a green background are ones that I've added to do some number crunching.

There are 48 samples in roughly 4 seconds, so I was getting an average of about 12 samples per second.

Throttle position (duty cycle of the PWM output) varied from 11% to 21%
Battery Current varied from 1.5A to 24.7A while Output Current (Armature Amps) varied from13A to 121A.

The far right column with the green background subtracts the Battery Current column from the Output Current column and show the magnitude of the flywheel effect varies from 11.5A to 97.7A during the 4-second window shown.
Attached Images
File Type: jpg PWM waveshape at motor.JPG (182.4 KB, 0 views)
File Type: jpg Battery vs Motor Amps.jpg (274.0 KB, 0 views)
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