This is by far the Number one question I get . I will try to answer this to make it easier to understand .
There are 2 parts to make a gem faster .
First is the controller . The controller limits top speed to 25mph . When a Gem starts going faster the controller cuts power and you will get surging . No matter how much power you put in a Gem the controller will limit top speed . So the first thing you have to do is fool the controller so a gem will go faster . Gem’s calculate speed . The controller counts motor rpm’s and multiplies it by the drive ratio and rolling radius parameters in the controller . So to fool the controller you have to modify these parameters . Ride 4 fun’s motor would send ½ the motor rpm’s to the controller . This would make the Gem think it was going slower than it really was . The speedo would report ½ your real speed , so your real speed would be faster .
Inwo came out with the Magic magnet , MM .This would do the same thing , report a slower motor rpm than was really happening . Same effect as a Ride 4 fun motor for a fraction of the price ( a stock Gem motor can do 40+ mph with the proper set up .) So for a small cost and 5 minutes your Gem goes faster . Great addition to the Gem world , Thanks Dave !
The other way you can do it is reprogram the controller . Changing the parameters in the controller will fool it into not knowing your true speed . Different ways to approach it , similar results .You can buy the cable and software to do it for $100 , It takes some time to set it up and learn but it’s not too bad . Ride 4 fun will take your controller and raise its internal limit to allow more than 25mph . With shipping it’s about $350 . Now understand none of this increases your Gem’s power; it just lets it realise the power that it already has .
Next is increasing power . If your Gem is allowed to go faster it needs the power to do it . There are a lot of variables here from year to year and different setups . Most Gems are capable of more than 25 mph if they are allowed . 30 mph is easy for most . But with a high gear ratio , small tires or weak batteries , higher speeds may be difficult . Now if you want to go even faster you will need more power .
First thing to do is lower your field current in the controller . Lowering field current on a Shunt motor will increase its Rpm . You will give up some low end power but you will gain higher rpm and top speed .
Put in a bigger motor . More Hp , more speed . But this only works if your battery pack has the power to supply what the motor needs . Recently had a friend with a 2013 E4 . I had reprogrammed the controller. his Gem would do 35 mph . He wanted more . We swapped out his 5hp for a 7hp , But the Gem didn’t go any faster (told him it wouldn’t) His battery pack was 7 years old and worn out . Added a 80v lithium pack and he easily goes over 40 .
Increase battery pack voltage . Gem’s motors love voltage , More voltage , more power and speed . New Lead batteries help but upgrading to lithium will be a much bigger improvement . In a stock configuration lithium will hold a higher voltage than lead , this leads to higher acceleration and speed . Now increase your battery voltage over stock and the party goes to full swing . A 84v battery , 10.35 gears , Lager diameter tires will hit 40 mph with a 5HP motor ! My personal Gem runs 96v and a 7hp stock motor . I limit it to 42mph , It has more in it . You want 80v minimum to 96v max when designing a lithium pack.
High numeric gear ratios and small tires will limit top speed . They will make your Gem accelerate faster and climb hills better , but limit top speed . Its just like a 10 speed bike . You can be a very strong biker but if you’re in 1st gear you can only go so fast . Adding larger diameter tires usually increases top speed .
Hope this helps those wanting more out of their Gems
The 14.7 gears are like a 5 speed bike stuck in 2nd gear . You can peddle it faster but there is only so fast you can go . With stock wheels I’m guessing 30 max . So for more speed you either use larger diameter tires for a 10% increase , change to a lower ratio gear box or install a high rpm motor . A DC motor wont spin that fast so you would have to do an ac motor install . Go online a do a speed calculation . assume max 6000 rpm for a Dc motor and 9000 for an ac motor . That will get you close . Now you will still need power to push an E6 that hard so a minimum 80v lithium pack will be required , a 96v will be better .
What do I need to do the conversion AC to DC?
And also my car go up to 86v more than that error 16, how to go up to 96v?
Thank You and you post always are very good and helpful
Timoti,
You have a lot of reading to do !!!
We are doing DC to AC conversions not the other way around, There are hundreds of threads on 86 to 96v and error 16.
You would need to do a lithium battery conversion and then look at switching for DC to AC.
Yes I’m doing the lithium battery conversion, I’m waiting for the batteries and yes DC to AC but went the batteries have more than 86v I got -16 error and I have to put the light on for a littler big and then star again
Also in the programming the control there is any option to get the LED display lighter?
that is a big battery pack and should give you great range . 25 cells will work well but it maybe a little low for the quick charger . They are a transformer based charger and have a very narrow range in which they can be tuned for . Calculate your lowest and highest voltage and call them to see if it will work . You may just have to add one more cell . You can run upto 29 in a Gem . If your pack voltage is over 86 volts Inwo can sell you a spoof so that it will work in a Gem . When you convert to AC you wont need it .
Is it yet possible to reprogram the controller on the 2020 GEM models to bypass speedo 25MPH limit?
I have Rodney’s kit, OEM 6.5kW Mtr, Distance AGM Battery which gets to 35MPH.
However, at exactly that same time OEM speedo hits 25MPH and cuts off further acceleration. I’m guessing without the controller limit, the speed would increase to 38-40MPH.
Unfortunately the controller doesn’t control or limit the speed in the new Gems.
The Polaris programmed ecm is the brain. The sevcon control is a slave.
I can program a new controller to take over motor control with custom speed and power maps.
Thanks for the insight.
Can you please provide more detail/cost as to what is involved with programming a new controller as well as the options with “custom speed and power maps”?
My goal is to increase the current MPH from 35 to 38-40 MPH using the current OEM 6.5kW motor and extended range batteries.
It’s probable not worth the effort for only a couple mph. I only have experience going all the way.
80v lithium batteries, dci charger, and new controller.
It would be a learning experience for both of us. Idealy should be near someone who can fine tune the program. Not sure about performance at low voltage. I’m sure the motor will be fine.
Let me think about it, as I know there is demand.