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Electric EZGO Electric EZ GO Marathon, Medalist, TXT and RXV.



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Old 12-17-2015, 01:03 PM   #21
rottie
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Default Re: 48 Volt Lithium Project

Nice build. I am watching very closely.
I am doing a similar project but with 16 Leaf cells, Orion jr BMS for 60V at 120ah. Beast motor AMD7124 and Alltrax 72500 controller.
All on a EZGO Marathon.
This should give me super torque but at similar stock speed +/-.

I am not looking for a race car (top speed) but excellent pulling ability and good run time/distance.
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Old 12-17-2015, 04:04 PM   #22
JohnnieB
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Default Re: 48 Volt Lithium Project

Quote:
Originally Posted by rottie View Post
Nice build. I am watching very closely.
I am doing a similar project but with 16 Leaf cells, Orion jr BMS for 60V at 120ah. Beast motor AMD7124 and Alltrax 72500 controller.
All on a EZGO Marathon.
This should give me super torque but at similar stock speed +/-.

I am not looking for a race car (top speed) but excellent pulling ability and good run time/distance.
The high torque AMD 7124 has about 7% less RPM per volt than the standard wind, but you are feeding it about 67% more voltage, so if the stock speed of your Marathon is about 14MPH on 18" tires at 36V, it ought to do about 22.4 MPH at 60V.

A standard 36V (225AH) battery pack stores about 8.1kWh of electrical energy and the proposed 60V 120AH pack only stores about 7.2kWh.

A Lead-Acid pack is not typically discharged more than 50%, so only about 4.05kWH is usable while about 80% of the Lithium battery pack storage is usable, or about 5.76kWh. That works out to something in the neighborhood of 42% greater run-time (range).


FWIW: You actually have 64 Lithium Cells in your proposed battery pack. Each Leaf module (or battery) contains four 3.8V - 33.1AH cells. Two pairs of two connected in series are connected in parallel to create a 7.6V 66.2AH battery (or module). The two sets of eight modules connected in series are connected in parallel to form a 60.8V 132.4AH battery pack.

That is 8.05kWh of storage, so using my numbers for the lithium battery pack, the run-time is 59% greater, rather than just 42%.

Of course, the increased run-time does not take reduced cart weight into consideration, so it ought to be even more.
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Old 12-17-2015, 04:58 PM   #23
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Default Re: 48 Volt Lithium Project

I think In reality it would be a lot worse for the lead acid pack, after all the only way You would get the 8.1kWh stored in the pack would be discharging it at the 0.05C rate for 20 hours.

The Lithium pack will deliver its rated capacity even at the 1C discharge rate.

If You put a load of 120 amps on that lead acid pack (Trojan T-105), it would likely run less than 30 minutes before it is below 50% SOC.

Also, 2 lithium cells in parallel will deliver a little more current than the sum of the individual cells due to the lowered internal resistance.
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Old 12-17-2015, 06:22 PM   #24
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Default Re: 48 Volt Lithium Project

I am going to limit the current to 400Amps for the moment but will have controller to allow 500 amp limit. (SPM72500).

I will be limiting my max voltage to 4.1V charging (multiple reasons) and 3.0 discharge to maximize life out of the batteries $$$$. These things are not cheap but I only want to deal with it ONE time.

I am also adding a Solar panel to it STION 145W so I can extend my run times. It will be in Florida, so I want to make use of that sunshine

Thanks for the speed calcs. That makes me happy as I was shooting for 15-20mph.

If I want more speed then I can add more cells (upto 21 total) for this controller.

The wife is supper happy with this project and will be helping me with it.
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Old 12-17-2015, 06:33 PM   #25
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Default Re: 48 Volt Lithium Project

Quote:
Originally Posted by Sergio View Post
1. I think In reality it would be a lot worse for the lead acid pack, after all the only way You would get the 8.1kWh stored in the pack would be discharging it at the 0.05C rate (20 hours).

The Lithium pack will deliver its rated capacity even at the 1C discharge rate.

2. If You put a load of 120 amps on that lead acid pack (Trojan T-105), it would likely run less than 30 minutes before it is below 50% SOC.

3. Also, 2 lithium cells in parallel will deliver a little more current than the sum of the individual cells due to the lowered internal resistance.
1. You're correct, I did some apples to oranges comparing by not taking the Peukert Effect into consideration.

2. Without doing the math, I suspect that is pretty close.

3. Thanks, I wasn't aware of that. The Li packs mentioned in this thread have a bunch of cells in parallel.
IE: 16S x 4P for the 60V- 120AH Leaf battery pack and 13S x 14P for the 48V 200AH DES battery pack

Look like the Leaf cells are 3.8V 33AH while the DES cells are 3.8V 14AH.


----------
The 48V 100AH DES module with built in BMS is mighty interesting.

Now that my range needs have diminished greatly, I just might get away with just one module instead of two like chewy65 has installed.

Of course it will probably boil down to what has the smallest initial cost, upgrading to a 6 x 8V lead-acid array or a 1(or 2) x 48V DES array plus appropriate charger, etc.
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Old 12-17-2015, 07:31 PM   #26
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Default Re: 48 Volt Lithium Project

I am also working on a 120AH 14 module Lithium solution. The percentage of capacity that you can use is limited by how well you can balance the charging and how well you can monitor the full charge and full discharge. Since over discharge is a bad thing, it is better to make sure that you don't push that. That is why I decided to pay for the 120AH solution even though the 60AH would probably do it for my use. I figure a round of golf including the ride to the course is probably a total of < 10 miles. When I walk the course it measures about 6 miles on my fitbit. The course is less than a mile drive from my home. Once I get a good State of Charge monitor, I plan to get at least 3 rounds in between charges. Unlike FLA, Lithium batteries do not last longer if you charge them often. (As long as you don't over or under charge any of the cells)
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Old 12-17-2015, 07:52 PM   #27
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Default Re: 48 Volt Lithium Project

Lithium ion chemistry based batteries behave very different than anything else we used before.

Not only those AH ratings need to be compared in different ways, but You brought another interesting aspect that will also take time for people to change their long held habits, charging.

Do not charge a lithium pack if the SOC is already above 80%.

When parking a cart with lithium batteries for long term storage, You really want to leave the pack at about 40% SOC, never fully charged.

Last edited by Sergio; 12-17-2015 at 08:05 PM.. Reason: More information
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Old 12-17-2015, 09:49 PM   #28
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Default Re: 48 Volt Lithium Project

Interesting build. Very interesting battery setup. Battery management being self contained is cool.
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Old 12-18-2015, 09:53 AM   #29
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Default Re: 48 Volt Lithium Project

V/A, the 100ah Li systems i build test equally to a 48v "T-875" pack when discharged to 20% by lester discharge tester. That is the baseline i use for comparison.
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Old 12-18-2015, 10:11 AM   #30
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Default Re: 48 Volt Lithium Project

I see You are in Arizona, the original state that caused the class action lawsuit against the leaf.

As I understand from the final settlement, You want to make sure you use the newer type and chemistry of the latest leaf cells in those hot climates.

This graph that was part of the study on how temperature affects the life of the modules shows that the 80% capacity after 5 years claim does not apply to hot climates.

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