DIY Lithium Ion 56 Volt Golf Cart Battery Conversion

Lloyd-ss

Active Member
DIY Lithium Ion 56 Volt Golf Cart Battery Conversion
You know how you've been looking and looking for something, and you finally find a good bargain, but it isn't exactly what you wanted, and you really didn't know any better, but you start working on it and it takes on a life of its own, and you end up having a great time turning it into just what you really wanted, and learning a lot to boot?
If that sentence doesn't strike a familiar note, this thread probably won't be your cup of tea, LOL. But if it does, please read on.
About 2 years ago I bought a used 2002 Club Car DS 36 V-glide rheostat drive. Batteries needed to be replaced but the guy told me that. It was all waxed up and shiny. It was a bargain, and I had been looking for a cart for a long, long time. I got it home and the wife said it was cute, even though she was sure she was going to hate it. She liked the little hub caps. We needed something to get around on the property, back and forth to the garden, thru the woods, up and down steep hills, hauling the grandkids. Fun stuff. No speed needed, just chugging along.

I believe that everything can be made better. My wife says its a sickness. Incurable. And her burden to bear.

The first thing was a new set of six, 6 volt batteries. Only $600, actually less than I was expecting. Then 4 new tires, about $130. Changing little tires has always been such a pain that I finally broke down and bought one of those Harbor Freight lawn tractor tire changers. Money very well spent!! Next was a new D&D High Torque 42A motor for $500. D&D told me a lift kit would be required because the longer motor wouldn't fit between the frame rails. I bought the motor anyway, no lift kit. Wife didn't want a lift kit 'cause it wouldn't be cute anymore. And honestly, maybe more likely to flip on some of the off camber hills we drive on. So instead, I shifted the rear axle a couple of inches to one side, used an offset wheel on the other side, and the new motor fit nicely between the frame rails. Plus the rear track is now 4" wider.
Here's a picture of the middle of that project.



The motor was great, plenty of torque, but man, a little more speed would be nice coming up some of the long hills. The 42A motor has lots of torque and is good for a LOT more than 36 volts, so I considered going to 48 volts. Luckily, my wife pretends not to notice this sort of silliness. She just rolls her eyes, and checks on her flowers. Here it really starts to snowball. If I convert to 48 volts, none of the 36 volt stuff would be usable anymore, its 16 years old, anyway. New controller, solenoid(s), brakes, charger, meters, etc. Oh, and batteries. Hmm, squeeze in 2 more 6 volt batteries at 60 pounds each, or replace all the batts with new 8 volt ones. Neither sounded good.

Not to be hampered by common sense, I started accumulating parts and pieces from eBay for the 48 volt conversion. SPM controller. new heavy duty Curtis 48 v solenoids. One for ON, and one for Forward/Reverse. A little 48volt 6amp charger. Cheap enough where its ok if it doesn't work. Zero to 5 K pot for throttle. Fuse. Meter with shunt to monitor volts, amps, state of charge, watt hours, you name it. Cheap from Hong Kong. A real pedal type parking brake that the grandkids can't accidentally bump loose!

Just when I was about to purchase new lead acid batteries, a buddy of mine visited. He is an avid bicycler, and electric vehicle enthusiast (obsessed!) I was telling him about the new 48volt conversion and needing new Lead Acid batteries. He said, "Why not go to Lithium Ion batteries?" I gave him the deer in the headlights look and muttered something about "too expensive", "too complicated", "set the cart on fire." He said, "None of that is true. I built myself an electric bicycle using Nissan Leaf lithium ion battery modules and I've put over 4,000 miles on it. A hundred mile trip is nothing." The first paragraph in this thread.... he gets it, LOL.

So that was the beginning. With him throwing chunks of information in my direction, and me researching from there, golly, there is a WEALTH of knowledge about DIY Lithium Ion battery powered "vehicles" out there.

Basically, ALL of the parts and pieces I had accumulated for the 48volt conversion would be usable. Maybe not perfect choices, but plenty satisfactory.

The LITHIUM ION BATTERIES.
Lithium Ion modules from the 2013 and later Nissan Leaf are commonly available on the internet and really popular for this type of project. They are reasonably priced and seem to last forever. Each module is about 10 pounds, charges to about 8 volts, and is rated at about 64 AmpHrs. Because the Li batts can be discharged to about 20% of full capacity without any problem, they are pretty much equivalent to a single 8 volt lead acid battery. So, that is a 10 pound battery replacing a 60 pound battery.

The Nissan Leaf uses 48 of these 8volt modules, but I will be using only seven of them.
Cost of the 7 modules was $532, total, with free shipping.
What that gives, is the equivalent of 48 volts of lead acid batteries (approx. 390 pounds?) into a package that is about 10" x 13" x 14" that weighs only 70 pounds. Plus, the max voltage is really 56 volts, so plenty of reserve on the top end. That is a 300 pound weight savings. Plus, the max voltage is really 56 volts, so plenty of reserve on the top end.
Li batteries can also be repeatedly drawn way down and still survive thousands of cycles. But there are tricks to getting long life.

Here is a picture of 7 modules, stacked up for testing. I have been running them thru a discharge and re-charge cycle to see how their performance looks. So far, I am very impressed.



The conversion will be happening during the next few months and I think it will be a lot of fun.

Next time, I promise not to be so wordy, LOL. Lots more to come!!
Lloyd
P.S. If you made it all the way thru this post, thank you for bearing with me.
 

HotRodCarts

Cartaholic
I'm interested in seeing how this DIY Lithium Ion 56 Volt golf cart battery conversion works out. Don't worry about long posts the more details the better and it will help others thinking of doing the same conversion. Also you can attach your pictures directly to your posts if you like instead of having to upload them to photobucket. A couple years ago the forum lost a lot of pictures when photobucket made changes to their photo sharing policy. Either way is fine and keep us updated on this project. :thumbsup:
 

Nubs

Cartaholic
Very interesting, i think you should drop everything else in your life and lock yourself in the garage and push forward:D

Looking forward to this build:hattip:

:waiting:
 

Lloyd-ss

Active Member
Very interesting, i think you should drop everything else in your life and lock yourself in the garage and push forward:D
My wife accuses me of that sometimes. Says when I get on a roll, I only surface for food and bathroom. But this time of year, she is in charge.
 

Lloyd-ss

Active Member
I was curious about the characteristics of the Li batteries and did some reading and finally decided to do some testing of my own. There are enough terminology and test method differences that make it very difficult to do an apples to apples comparison of the capacity of lead acid and Lithium Ion batteries. And as you know, with lead acid batteries, the heavier the current draw is on them, the fewer Amp Hours of capacity they have. That is only very slightly true with Li batts, but not nearly to the degree as with lead acid.

Here is a picture of the battery load test set-up, in progress, for the 56 volt Li batt pack.
A lot of the components shown are just for the testing process. You can see from the meter that the Li pack was putting out 54.37 volts at 35.9 amps at that moment. One of the red coils in the resistance load on the right hand side is also visible.
LoadTestInProgress-a.jpg



Here is a better picture of the resistance load used in the test. It is made from the coils from a pair of milk house heaters. The various Rube Goldberg looking electrical taps, make a load of three 4.5 ohm ni-chrome wire coils, hooked in parallel, to get a final load of only 1.5 ohms. At the 54.37 volts and 35.9 amps shown in the above picture, that is 1952 watts of power (Power in watts = volts x amps) or (Power = voltage squared / ohms). There is a fan blowing on the hot coils to keep things reasonable.
1-4_ohm_Load.jpg

Here is a graph of the volts and amps recorded during the test.
The Lithium Ion battery pack was tested under load for 68 minutes. The 1.5 ohm resistance coail was the load, and average amperage was 36.2 amps. The voltage started to drop off sharply right at 60 minutes. Honestly that was just a coincidence that the 1.5 ohm load would drain the battery in one hour.
LiBattTest.jpg

So here is the real question:
What lead acid AHr rating is this Li battery equivalent too? I have been reading and struggling with this and think that I have a handle on it, but if someone has solid information to the contrary, please let me know. I am thick skinned and am happy to hear constructive criticism. It's all about learning, right?

Ok, so this batt put out a solid 36.2 amps for one hour. And this batt can honestly be drawn down at that rate, to that low a level, over and over again without damage. Drawing a lead acid battery down to that level repeatedly would kill it in short order.

So is it the equivalent of a 36 AHr lead acid battery?
Answer: No, it's capacity is Much Greater than that, more like a 200 AH battery.

Here is why. A lead acid battery with a 200 AH rating means that it can discharge 10 amps for a standard length of time of 20 hours, to give a total of 200 amp hours. BUT, the battery would be totally dead at that point, and manufacturers recommend stopping the discharge at 50% of the capacity, or 100 AH. So that is really 10 amps for 10 hours. But the Lithium battery was tested at a discharge rate that almost drained it (remember, it is ok to almost drain an Li battery) in ONE Hour. With lead acid batteries, the faster you discharge them, the less capacity they are able to give (Peukert's Law). So, if you discharged that remaining 100AH in one hour, you would actually only have about one third of that capacity, or about 34 amp hours, or same as the Li battery.
I hope the discussion makes sense, and please comment if you like. I enjoy doing this kind of stuff and appreciate new information.
Thank you.
 

Lloyd-ss

Active Member
I am just dropping in to let folks know that this topic has not died, even though it might look like it has, LOL. Building projects and air rifle projects have taken priority, but the conversion to Lithium Ion batteries will take place before it warms up this spring. It has to, actually, because the wife will need it for getting back and forth to the garden. But the temp here this morning is 13F. Yuck!
 

oddpowers

Cartaholic
Looks like a cool project. Cant wait to see how it all works out. It will be interesting to see if the .3 C rating will have any drawbacks in an "unregulated" system.
 

Lloyd-ss

Active Member
Too many irons in the fire, but i hope to be getting into this conversion soon.
I believe that the C rating for these modules is 100Ahr, although it seems like that number is often fudged around a bit. The 0.3C value that i tested at (about 33 amps) was done mainly because that worked with the resistor bank that I cobbled up.
I am not exactly sure what you mean by an unregulated system, but I will be using SPM48225 controller. I know that the 225A is a lot lower than some folks like to use, but while running on the old rheostat system, the current seldom climbed above 125A at 36v. I can set the current limit and battery voltage limits in the SPM to stay within safe parameters for the controller and for the Li Ion modules. However, I do not plan on installing a Battery Management System right now, but might need to add one in the future if a problem with cell balancing, etc, occurs. I get conflicting stories on whether or not a BMS is really needed, so I will wait and see. I also have a Cycle Analyst module (all the rage with the electric bike crowd) to monitor voltage and current and battery percentage of charge, so with a little vigilance on my part, all should be ok, I hope, LOL. I also hope that I can operate the cells with a minimum of 25 percent charge to a maximum of 85% charge. That is supposed to greatly increase the life of the modules. I have a couple of friends are electric bike builders and users, so they have been warning me of the pit falls to watch out for.
I am getting eager to do this.
Lloyd
 

oddpowers

Cartaholic
Providing these are the right cells i was looking at, the C rating of those batteries is, 33.1 ah at .3C (per cell) each module would be 4 cells, 7.6 volt, 66.2 ah, I think that means 33.1 amps for 18 minutes per cell (60min X .3=18 min) so 66.2 amps for 36 mins, or 33.1 amps for 72 min.

I mean most controllers only limit the controller current, meaning it will attempt to get all it can from the battery up to the current limit of the controller. Possibly pushing the batteries harder than they should be. I was just thinking the Nissan Leaf (and higher end controllers) may have more capabilities to keep the system from taxing the batteries to much, where as the standard golf cart controller doesn't. Li-ion batteries usually have some sort of circuitry to keep the batteries from discharging over 1C.
I'm not say this IS going to be a problem, Im saying I will be following your build to find out. You have obviously done your homework, so keep it up!
 

Attachments

Lloyd-ss

Active Member
Unfortunately, much of the terminology that is applied to new battery technology is outdated lead acid marketing buzz from decades ago. It just doesn't fit well with Li Ion batteries because the charge and discharge characteristics of the two technologies is so different. Please take a look at my comparison of the apples to oranges comparison of AHr ratings of LA and Li Ion batteries. I am by no means an expert, but am able to spot the smoke and mirrors. If you read enough material and specs and tests on different sites, its easy to see that there really is little consensus on how to compare battery capacities. The original LA AHr ratings were how many amps you could draw from a lead acid battery to render it dead at the end of the hour. No mention of voltage at all, so how can you even begin to talk about actual power capacity?

So that is why I did the testing myself. Forget the amp hours. I did find specs in several locations that each pouch cell has a maximum capacity of 122 watt hours. No that actually is helpful. We can get amps, volts, and time. But again, end up with a dead battery at the end.

So, for my battery pack there are 7 modules, each with 4 cells each, 28 cells x 122wHr = 3,416 max watt hours for the 7 module pack. Again, that is maximum.

It has been recommended by many, that if you never charge above 80% capacity, and never discharge below 20% capacity, that the Li Ion batts will last almost indefinitely. So lets start by slashing 40% of the capacity, and we end up with 2,050 watt hours of usable power without ruining the batteries. That's 2kWHr.

Again, if you look at my load test in post #5, the total power discharged by the batteries into the resistance load was 2,142 watt hours. If I had stopped the test when each cell had dropped to 3.5 volts, that would have been 2,050 watt hours. So, the test started at 4.05v/cell=56.7 volts, and ended at 3.5v/cell=49.0 volts. Average current draw was about 36.2 amps for the entire test. Could you call that a 1C rating of 36 amps? I don't really know. But I do know that in actual usage in the Nissan Leaf cars, these cells routinely see discharge rates in the 2 to 5 C range. After performing the load tests that I did (more than once!), I am fairly confident that these Li Ion batteries are up to the task.
Lloyd
 

dirtysouth

Cartaholic - Sponsor
Like the idea of the lithium setup but waaaay to many big words and funny numbers for me to follow along.
Best of luck, hope it does what you want it to.
 

Lloyd-ss

Active Member
Ha ha, don't worry, that's just a bunch of engineer BS talk, sand baggin' something that is no more complicated than what you are already doing.
But seriously, the goal of this conversion is to present enough practical DIY information so that other folks with decent skills could do the same conversion if they wanted to. All that engineer talk is just the dirty work that somebody has to wade thru to get to the fun stuff. Call me a sick :censored: if you want (my wife does :oops: , LOL), but I enjoy all the background math and science and testing.
And occasionally, I actually get something that works! ;)
 

John NeSmith

New Member
Ha ha, don't worry, that's just a bunch of engineer BS talk, sand baggin' something that is no more complicated than what you are already doing.
But seriously, the goal of this conversion is to present enough practical DIY information so that other folks with decent skills could do the same conversion if they wanted to. All that engineer talk is just the dirty work that somebody has to wade thru to get to the fun stuff. Call me a sick :censored: if you want (my wife does :oops: , LOL), but I enjoy all the background math and science and testing.
And occasionally, I actually get something that works! ;)
Will you use the 48v lead acid charger to charge the lithium ion batteries?
 

John NeSmith

New Member
Lithium ion. No I’m sick of the lead acid batteries. All of the manufacturers are making batteries that aren’t worth a damn. My last set lasted 9 months. They put in new ones at no charge and I can tell by the charge time that these will be no good in no time
 

Lloyd-ss

Active Member
Lithium ion batteries are very sensitive to proper charging and cell balance. How often do you charge you lead acids?
 
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