XTreme XB700li +7,4V voltage mod

ProDigit

100 W
Joined
May 18, 2012
Messages
153
Ok, there's a lot of bull out there on info on this bike; and a lot I had to wade through by experience.
I want to post some of it here on this thread!

First of all, the XB-700li has a LiMMn or LiPo4 battery. It's not the higher quality LiFePo4 battery.
That means that the bike only has a good 700 recharge cycles; not 2000 like the usermanual may tell you. After 2000 cycles your battery will be completely dead, and no one will drive on a battery with capacity lower than 1/3rd of it's original capacity!
700 recharge cycles mean after 700 cycles the bike should perform less than 80% of new capacity.
However this number is not correct. The bike has regenerative braking, which means that every time you brake, some portion of the cells get charged. The more you drive around in the city, the less long the battery will last, as the more regen braking you'll have to calculate in the recharge cycles!

I've done a good 250 miles on my bike, and already I've noticed the fuel gauge to go to 75% instead of being at 100% with initial acceleration. The voltage under zero load is capped at 54,5V, no voltage mod (the original 48V battery still gives 54,5V when fully charged at ~250mi)

I would strongly suggest to get rid of Xtreme's charger. It's a 5A charger, but charges the batteries just about as fast as BMS' 350W charger. BMS charger seems much more sophisticated, and imho charges the battery much better.
Besides, Xtreme's charger has all kinds of issues. Static could disable it for several hours! I had to return my first charger of XTreme because of static, and my second charger broke within 2 charges too!
A BMSbatteries.com charger is the way to go!

A user on visforvoltage has said that the internal battery gives 35MPC and after a good year and a good 3500 miles, the bike has less than a third of the mileage.

The stock battery is connected with a 'computer cable' to the bike. There's a similar plug found under the seat for charging the bike. On that plug you can plug in another LiPo battery. The battery does not need to be of the same properties. All it needs to have is 48V.
If you find the suspension too hard on the 700, just place the extension battery in the rear trunk. It should put more weight on the rear tire, allowing the suspension to soften a bit.

The bike stock goes ~23MPH, 23,6MPH fresh from the charger, and ~22,2MPH when half empty.
The internal speedometer measures 27,5MPH, an outside meter (or GPS) shows 23,6MPH.
The speedometer is voltage dependent. When opening the throttle but keeping down the bike, it'll show 15MPH, eventhough the bike is not moving. The overall impression is that the speedometer is showing 5MPH too fast, the higher the load, the more the speedometer will measure incorrect; which leads me to believe that they calibrated the speedometer on a workbench without load. Actually, I tested out, the speedometer is only correct at 7MPH. At lower, it shows a slower than actual speed, at higher it shows a faster than actual speed.

The speedometer reads it results from the rear wheel. You can set the bike on a stand, and see the speedometer go up as you engage the throttle, with only the rear wheel rolling.

The bike has an internal limiter in the controller which regulates the amps to 20Ah. Meaning, adding batteries in parallel won't give you more torque. The controller regulates output to 48V, 20Ah. In other words, that's 960Wh. Know that your motor is only rated 700W. You can burn your motor going uphill on long stretches. In most cases the motor has torque enough to push a rider of ~170LBS at 20MPH up a 15degrees bridge or small hill. This is where the motor really starts to heat up! In the beginning, going uphill the motor accelerates much slower, but after a while the controller (with the limiter disabled), pushes the motor to 20,2MPH anyway; regulating the amps so that it will try to get the max speed.
At acceleration the same happens, it takes about 5 seconds before the controller allows maximum torque, that to prevent the motor from overheating at startup.
For this reason I believe the shunt mod is not necessary on this bike, as the motor has everything within itself to perform admirably in most cases where the ground is flat. Like any electric, it's weakness lies in torque; meaning carrying weight uphill.

Going downhill the motor is uncontrolled. I was riding on a sidewalk, with lots of bumps, and could not test the max speed, but the bike rolls downhill 30MPH or faster, if you don't brake.
At 170LBS, and a 20% downhill drive, the regenerative braking can barely keep up with the mass (meaning, it keeps the bike at the same speed rather than slowing down).

The bike is equipped with drum brakes and regenerative braking. When lightly pulling the brake lever, the electronic circuit gets engaged, and the brake light goes on. It takes about 1-2 seconds before regen braking kicks in. One can use regenerative braking for most travel. Regenerative braking works well with speeds over 5MPH. Below 5MPH the electricity harvested from braking is too low to charge the battery with, and it feels like it's not doing much. At that point the battery BMS just won't recharge anymore, and you're literally braking on the brake light (energy harvested goes to lights).
The more lights are on, the more braking will work. It's a 700W motor, braking lights are 2x~20W; headlights are same. So you'd be braking at 1/10th of the real motor generating capacity.
As soon as you squeeze the brake lever harder, the drum brakes will kick in. Regular drum brakes working together with regen braking.
Braking distance from max speed on regen to 5MPH is about 36-40ft. Min Braking distance with drum and regen braking is about 12ft.

Overvolting 56V:

I Overvolted the bike, without applying any other mod. When overvolting, make sure you connect a battery with BMS.
Without BMS, regen braking won't work; either that, or overvolted the regen voltage is too low to generate enough voltage for the internal batteries to harvest it.
I overvolted the bike with 2x 16A 7,5V RC batteries. I've heard of +12V mods reducing controller lifetime, so I wanted to make sure my controller won't be fried. I deliberately chose a lower voltage, but the math did not match up.
Normally you'd say that the speed would be linear with the power used. at 48V, 20Ah, = 960W the bike can go 23MPH, so it's technically ~40W per mph. Adding the 7,4V should give you 1100W, and a top speed of 26-27MPH. In practice this is not so; not because of wind resistance, no, but because the controller is limiting the RPMs. The controller is merely tricked into believing it's maintaining the 23MPH speed, but due to the overvoltage, probably some internal clock is operating at a faster rate.
Anyway, that's my theory, and about the only thing that can explain why the bike does not accelerate linear with the voltage increase!

At 56V the lights function the way they supposed to.
The voltage meter goes beyond it's limit, and the internal speedometer adds another artificial 5MPH to your speed; showing 35MPH, when in fact the bike only goes upto 25,6MPH.

Adding 7,5V to the stock battery improves speed by a meager 2MPH. Very disappointing!
The shunt mod would have not improved this speed, as the motor has plenty of torque to work with! The shunt mod would only allow more amps to flow to the motor, thus improving it's climbability, or startup speed.
The 700 starts about as fast as a cyclist, much faster than most people on their bikes; but it starts much slower than most cars.

For a reasonable speed increase, you'd have to overvolt the bike with 12V; as the 7,4V speed increase really does nothing worth mentioning; and on top of that, your fuel gauge and speedometer will be totally incorrect, and regen braking will not work! Maybe the same with +12V overvolt mod.

The speed is limited by the controller. If you can hack the controller and mess up the sync clock or perhaps reduce some capacitor's size (to get a shorter timing) or something, it might be possible to increase speed.
I've said it many times before, but the motor has enough in itself to go at least 30MPH, if not 35MPH!
It's just the controller...

Hope this info helps some who are thinking of buying this electric bike.

For me it's a useless bike, as it goes too slow in the place where I live.
I need a bike that goes at least 30MPH, 22MPH is just too slow. If it did 25 or 27MPH I could live with it, but not like this.
I probably will be selling mine soon!
 
Another correction on another user's post, and in correction of my own post concerning the 20Ah limitation on the controller,

The battery of the XB-700 does not have a low voltage shut down, but when driving on a low battery, the controller tries to give the motor the juice it needs to drive. With a lower voltage, automatically the controller tries to increase the amps.
The breaker fuse on the bike shuts down at 20A. That means if the voltage drops too low, the amps might rise above 20A, and the breaker shuts down. It's not the battery's BMS that shuts down at that point.
It could help installing a bigger breaker (like a 30A breaker), or add an extension battery in parallel to keep the high voltage a little longer.

So the controller does not limit the usage to 20A, it regulates the wattage that goes to the motor.
 
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