A Tale of Two Gems

GEM Forum
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We bought our first GEM begrudgingly back in April of 2020 (insert 4/20 dad-joke here). I say begrudgingly because we were initially looking for a gas-powered golf cart, and didn’t want to spend $$$$’s on batteries every few years. So when this odd-looking thing popped up for a too-good-to-pass-up deal, but had decently new batteries and only a little TLC, we picked it up.

It was an 02 E825, and the majority of the initial work I did can be found here, so I’ll jump to the fun part, lithium!

Thanks to this forum and special thanks to @LithiumGods , I decided I wanted to be one of the cool kids and go down the lithium path.

Here’s what I started with: 96v 24s 74ah BMW (Samsung?) pack w/ DQ charger. Literally had no idea what was up or down about these “batteries” and sweet looking charger.

I figured I needed to mount these somewhere I could easily access them, and read that earlier GEMs drove better with a little weight up front. Some uni-strut, ⅜” all-thread and a foam rubber floor mat to cushion the pack and they were ready to go.

I couldn’t source any ½” spade connectors quickly (this was the height of the lock-down) but did find some in 3/8”, which worked fine for the terminals after a little massaging.

I ended up frying the BMS, even with the dummy-proof board and dummy-proof labels, with a full HD picture as proof! So regardless now that I’m dummy-status, I needed a way to at least monitor voltage until I could get a new BMS, so I found a nice 100v 300a voltmeter that fit perfectly in my gauge pod.

It’s been such a fun, albeit confusing, journey to learn, but so worth it and rewarding when you’re flying past all the “normal” golf cart plebs, with plenty of range to spare!

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But wait, the title says Two Gems:

After a….long…2021 for our family, which included adding a new member to the team, our little E825 wasn’t big enough for our party of 5 now. Insert: an 07 E4.

After a fairly length search, we found this one for a decent enough price with less than 6mo old batteries, and immediately got to work transplanting as much from the E2, and preparing it to sell. This one too needed a little TLC, but less costly compared to our first one: brake pads and bleed, headlights, CV boot repair and motor service (more on that later).

Now that the main maintenance items were addressed, it’s time to move on to the heart transplant. Similar mounting as before, but now under the rear seat AND with a BMS!

I figured out the BMS leads are the same layout as an IDC connector, or a shorter version of an old IDE connector for computer peripherals. So I found an IDC to terminal board, thinking it would make my life easier hooking up the BMS. While it “sorta” was, the limited real estate between the car frame and the battery orientation caused me to have to do a lot of double work. I would probably use them again but definitely re-think the design.

It was now time for the rear seat/cargo bed. I used the cargo bed so much on our old one, I couldn’t imagine not having one on our new one; plus the extra seating capacity is nice.

Problem is, I can’t weld, and didn’t have the help of my brother/father-in-law to weld a frame for me. So I found one of the most universal/modular rear golf cart seats I could find (and one of the least expensive too luckily enough), and got to work figuring out the safest way to bolt it on.

DISCLAIMER I’m not an engineer, nor have I thoroughly tested the load capacity or resilience yet, and no one has ridden back there up to this point. I TAKE NO RESPONSIBILITY IF YOU DECIDE TO TRY THIS ON YOUR OWN.

I loosely assembled the seat and took some measurements, then cut some 1 ½” square steel tube to length.

Test fit just about perfect, with the foot support brackets about 1cm away from the bumper. Drilled some holes to line up with the perforated steel cube, and tightened it down.

Had to notch part of the seat bracket to slide the bolt attaching the square tube to the frame, to allow a flush fit.

I reinforced the front (rear?) of my mount with some extra pieces of square tube, so that any weight in the far rear is supported. I’m most likely going to change this out to a flat ⅝” thick steel plate on both sides of the frame.

I then attached the top of the arm rest rail of the seat directly to the frame behind the seat, using a spare bracket that came in the seat package. I’ve also changed this to a grade 8 bolt since this picture. This is all I had that would fit at the time.

And here’s the finished (for now) product. Still need to add an extra support bar for the step, but overall I’m happy with how it turned out. I’ve bounced on the back of this thing with a few heavy rubbermaid tubs on the back without a creak or groan from anywhere. Still going to do a lot of testing before I’ll let anyone ride back there.

And just when I thought we were ready to take this thing out on the town, this happened:

But thanks to @Inwo , I got a sweet practically (better than) new motor, and the E4 is one step closer to primetime!

Currently troubleshooting and learning the BMS, and still have a few bits to clean up on it before it’s next big transformation: Voodoo Blue!

Just want to shout out to everyone on this forum, with special thanks to @LithiumGods for numerous calls, messages and emails helping me with my lithium setup, and doing his best to keep me from wearing that “dummy” hat. One day I hope to help contribute at least a fraction of what you guys have contributed!

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Great write up jb.

#NeverMind- I first thought these were two parallel builds. Now I see it is a series/successor build and having no BMS issue is being corrected.

Carry-on.

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Thanks.

Yeah I ran it without one for about a year, but only charged it 3 times total (till 100%) and never let it get below around 25%. Also didn’t use it a whole lot for about 6 months of the past year. Pretty crazy because when I did get the BMS hooked up and read the cells, they were all within 0.002 of each other.

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Nice work! You are going to love the 07, serious upgrade to an 02. IF you need any help with the bms let me know.

LG

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The only drawback will be the 12.44 gearbox. Accel will be fun(and needed with a e4+2) but top rpm (~6k?) will come quick.
Bigger tires will help a bit. What are those 25~26 tall?
Don’t get rid of that 02 just yet.

Do you have a target speed you’d like to hit?

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Thanks LG. I was skeptical of how much of a difference the pre and post 05’s were, but man it’s like a completely different driving experience. Seats are softer, suspension doesn’t feel like driving a toaster, double the steering radius. I’m a fan. And yes I believe I’ll need more BMS help per our PM. Enabling DisMOS didn’t seem to do the trick. I’ll have more time later after work to tinker.

Blockquote
AssyRequired
17m
The only drawback will be the 12.44 gearbox. Accel will be fun(and needed with a e4+2) but top rpm (~6k?) will come quick.
Bigger tires will help a bit. What are those 25~26 tall?
Don’t get rid of that 02 just yet.
Do you have a target speed you’d like to hit?

25" tires. A quick test around the block with 30% charge got me to about 31mph by myself. Had to remove the fender for them to not rub. Anything more and I’ll probably have to lift it, which I was trying to avoid. Motor is AMD 7.5 from Inow. My goal was somewhere around 35mph, not really interested in anything faster than that any time soon.

Already sold the 02.

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with tires that large we can get you to 35 mph

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Agree…

12.44@6k

But I’m not sure how those tall squishy things feel in a corner. Probably rides real nice on a slab road.

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They’re amazingly smooth where they belong: on dirt and gravel. On pavement it’s bumpy at crawling speeds but once you’re over 10mph it smooths out. No worse than our 02 with all-terrains and Progressives all around. They’re definitely noisy though, but hey, I look at it as a safety feature, people can hear me coming :slight_smile:

Edit: They’re take-offs from a Polaris side-by-side, which are in no short supply in my neck of the woods. Spend $200 for those and some spacers with the correct bolt pattern, and they were brand-new, so no complaints from me for the price

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96V though a T2 or maybe even a T1 controller and you didn’t blow it up… Damn, that’s award worthy. You rode the razor edge there with those old controllers.

Nice work on the builds.

Can always move the 10.35 from the 02, but those large tires might bog on launch. If they were 22-23 range, it wouldn’t have a problem.

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Ran great actually. It was a T2. I’m a little more surprised about the motor. I doubt it had ever been serviced by the previous owner. I blew it out with air before I sold it.

Are those the only 2 options for transmissions/gears for these?

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Yeah, the short GEs that were in the 99-04 GEMs are ehhh. Not super durable when it comes to heat and overspeed. Some people have decent luck with them though, seems you’re in that group too.

The classic gem gearboxes came in 8.91, 10.35, 12.44 and a 14.76
The 8.91 was on the 99-01’s with the short GE 3ho
the 14.76 was on the eLXD and e6

Ride-4-Fun sells some gear kits, I don’t recall what the ratios are offhand though.

With the 25"+ tires, if it were me, I’d probably should stay with the 12.44 if it carried any kind of load or had hills to deal with.

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You can do this, you just need a spoof on pin 1 to make the controller think you are running less. This used to be commonplace before AC conversions and good battery options.

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I just didn’t realize the T2 could handle that high a voltage on the B side / motor connections without scattering the guts. I knew about putting a spoof on pin 1.

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The crazy thing is, the spoof looks like it only needs to be there when turning on the controller. For my original Leaf battery setup, I was just a volt under with 3 diodes in series for the spoof and I didn’t want to redo the spoof to add one more diode. So I found a Normally Closed momentary push-button switch and wired it in series with the Spoof. But, I put one diode across the two terminals of the switch so when I was fully charged and getting the -16 error(over voltage), I’d turn it off, push the button which opened the switch an injected the extra diode, then turned the GEM on then released the switch. Worked no problem. This was on a T1 controller so I don’t know if a T2, or other, operate the same.

The advantage of a temporary spoof is that the controller sees the real battery voltage so what it’s showing on the display represents the battery, not the battery minus the spoof voltage.

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Did you find the spacers for the polaris wheels locally as well or can I talk you out of a link?!

Nice job, starting a conversion for my boss on an 08 with 105AH lifepo’s, just sent the charger off yesterday for reprogramming and started the top balance on the 24s.

Whats the story on all those Voodoo Blue Toyos? I only ask because I love my FJ80!

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These are the adapters I used.
Amazon.com: EZAccessory 2 Wheel Adapters 4x100 to 4x156 Thickness 1 Inch : Automotive

The story is I’ve loved and wanted a VooDoo Blue TRD Pro Tundra since they came out, including my wife. She also thinks our Gem (all Gems) look dorky, and blue will make it look “less-dorky” :slight_smile:

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Thanks for the link!

I also love the VooDoo blue TRD yota’s, would love to rock any one of those!