Conversion questions

New guy here and I am making 2 used and not overly pretty Gem E825’s into one good one, hopefully. One is a 1999 and the other a 2001. Both have the 5hp motor and I will be converting to lithium soon, but will get to those questions after a bit.

To start, if I want to be able to run 35 mph and give it 84 volts with the lithium conversion, should I look at switching to a different motor? Some say the aftermarket motors may not gain me anything over factory, but some of you may know better than others.

I am looking to have a 2" lift at most, later on down the road. I anticipate having close to stock diameter aftermarket rims and tires and have mostly flat terrain with a few good hills to get around anywhere.

One controller had the update by Flight Systems, but may need to be reprogrammed for my goal, as well??

So, with 84 volts and my overall goal for this round, what are your thoughts on the motor and wheel size?


Those years had 8.9 gearboxes. Stay with tires no larger than 21 inches in diameter. Larger tires with this gearbox over torques the motor. Suggest a performance motor. The 3.5 hp will not give you the service you need. These cars have capability of speeds in the high 30s with the T! or T2 controller

HOWEVER you need to upgrade the brakes if you increase the speed capability.


I have the 5hp motor. Would that make a difference in your suggestion? Will more volts (84v with conversion) and less amps to that motor perform well?

The short 5 only has 5/8 brushes thus it’s limited in its current handling ability. unfortunately the long 5 which has 1 1/4 brushes wont fit the early machines. I hot rodded a short 5 and and when it went out it also took out the controller. An expensive lesson.

Look older carts were equipped with 8.9 or 10.35 gear boxes. If you stick with 21 inch tires and add a RFF 7.5 motor your T1 or T2 controller will allow you to travel in the high 30s.

Adding voltage will produce more horsepower out of a given unit. The horsepower applied to the wheels determines the heat generated. Higher voltage does not mean cooler running .

In my opinion your wasting time messing with a 5hp motor. You can buy a RFF or other 7.5hp motor and not purchase any thing else and not have to reinvent the wheel to get good performance.

You know that the brakes on pre 2005 carts were iffy at 25 Mph. If you go faster you need to upgrade.

Lets talk about 84 volts. My next project is to take a post 2005 cart and convert it to pre 2005 electrics. I will also go to 84 volts with the addition of an additional 12volt conventional battery.for more range.

WHY: T2 controllers are now available at 500 amp capability. I buy DEKA size 31 105 amp clones for $97 apiece. They are good for 3/4 years before range is down to 12/13 miles. The cart will ride even better with the addition of another 60 pounds. I wont have the investment of the lithium installation or the extreem amount of wiring and complication of a BMS system. I wont have to modify the cart suspension because of a bad ride. And I end up with a cheap bang bang system that wont require a skilled technician to maintain.

PERFORMANCE: To put things in perspective. My 2002 2 seater in stock form went 25 MPH and climbed the

mini hills in our area at 21 MPH. Presently it does 40 MPH and climbs the same at 32 MPH. It spins the wheels on dry pavement. At 25/26 MPH my range is 22 miles on the flat. Checked this out on a single trip. New batteries not broken in.

Specs are:

10.35 gear box

RFF Advance Black motor (modified by me)

21 inch fat tires on 10 inch rims

7/8 bore master cylinder for more brake pressure.

The things to guard against are excessive tire size for the installed gearbox. 21 inch for 8.9 and 10.35 24 inch for 12.44. Or less.

Installing 24 inch tires on a 10.35 can turn into a poor performance, range eating slug. Braking performance goes down as the tire size goes up.

The sweet spot for performance motors is 6000 RPM +/- Lugging them causes poor acceleration and reduced climbing ability.

Keep us up to date.

In a message dated 7/16/2018 9:12:53 PM US Eastern Standard Time, writes:

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@grantwest has more experience with motors on high voltage than anyone.
And @LithiumGods with lithium and 5hp. He’s happy with 84v and stock motor.
Grant is spoiled and not happy with less than 96v.

Thank you for the information. I did reach out to @LithiumGods for some initial guidance. I got the cars relatively cheap and not running. So, since I have zero good batteries and am somewhat starting from scratch, I plan on going the lithium route after I get the carts put back together and painted. And going to try to stick with the stock 5hp, at least to get it rolling. I have a controller from the 99 that had a update from Flight Systems, but not sure what that entails or I have a stock 2001 controller. Any suggestion on which one works best with lithium and a voltage spoof, if needed?

Rodney is one of the smartest guys on here , period . He has helped me out a few times and knows the mechanical parts of the gem very well . I do disagree with him on the 5 hp motor , 10.35 diff and tire size .

My original lithium conversion cart (2007)from 5 years ago runs 84v , an old short 5hp motor , 10.35 diff and big 24.2" tires . Because of the the higher voltage and the fact the cart is now 350lbs lighter then before it accelerates very fast , slight spin of the tires and go . It did originally have the 12.44 gears , with those it spun the front tires way to easy . This cart will do over 40mph but i limit it to 36 for safety . the factory motor is 16 years old . My 2014 cart also runs a 5hp motor after the 7hp advance motor had a catastrophic failure . It runs an 84v Lto lithium pack with same size tires and 10.35 diff . results are the same . I will be upgrading to a 7hp motor soon because i am trying to build the fast accelerating gem possible .

on a lead cart if you load the motor hard the voltage will drop significantly (called sag) it is a very different experience with lithium , they dont sag much and therefore motors dont lug . lithium is not for everybody , it requires you spend more time with it , have some knowledge and monitor it . If you cruising around in your gated community then stick with lead . For us that take our carts on 35 mph roads are cars are doing 40 mph you will appreciate lithium . Also a gem with a 7hp motor , run at 35 mph wont have a very good range .

so it really depends on what you want out of your gem

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Yes! Rodney seems to have a knowledgable answer for most everyone’s questions on this forum. Insight from any is always appreciated. I do not live in a golf cart community and am building a car to keep up with the surrounding traffic! Having lead golf carts before, I am looking to try something different, with the lithium route. Thank you to all who help get everyone’s questions answered!

If you don’t mind investing in your personal lithium conversion then it’s not for you. These conversions are not turn key quite yet but once they get installed correctley and are running smooth they seem to offer little to no issues. If you don’t mind keeping a eye on things (voltage and cell balance levels) Just to make sure your not damaging your investment you will do well. I think it’s fun to build somthing that is unique and when done right works better then the factory could have ever done is quite rewarding.

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I agree and will have a few more technical questions on it as I get closer to purchasing the battery pack(s). Anyhow, as I was stripping my cart down to build back up, I had a thought. People say the rear shocks are stiffer after removing the batteries. But, looking at the rear end, as it sits there naked :wink:, I thought of my days of riding dirtbikes. Anyone ever thought about cutting off a shock ear and mounting it in the center for a mono-shock set up? You could probably use multiple different shocks, since you could set if up for them. Not sure I will attempt this, yet, but if you are good at welding aluminum, it may be a unique option. Fourwheelers and other vehicles seem to work well with that application.

Would anyone be able to say, in regards to lithium, which factory controller would be better? A 1999 with a flight systems update (not sure what the update entailed) or 2001 factory controller with no signs of being anything other than original. Were there different versions between those years?

Somewhere on here is a really good chronology of the different versions that will give some insight. I know that the early cars were 48V so the first question I would get answered is whether your 99 is one of those. I believe the 2001 has the T1 which I am using with my 96V (24S) lithium setup. I can hit 40 but have 21" OD tires so I limit mine to 36 to protect the motor. The T1 works great with lithium.
If you’ve decided to go lithium, I would definitely do it before considering a larger motor. All the rules change when you go lithium. I live in a hilly community in the mountains and my 5HP GE motor pulls my loaded 4 seater up any hill at 25+ and can do 40MPH on the flats with no problem, no heat issues and ~40+ mile range running a 100AH dual Volt pack. I had lead batteries in my carts prior and was never happy. Constant maintenance and continuous decay in performance. Lithium made it fun again!


High voltage rules…:slight_smile:MVC-004F

108v 2000lbs
I don’t think this one will fit.


I’m sure we could something fabbed over rear axle to hold it :slight_smile: