To add voltage to the system, you'll probably have to replace the controller with one that is made for the higher voltage, and probably a new DC-DC for the lights/etc as well, if it has one.
Any fuses / breakers / etc on the battery system will also need to be able to handle the higher voltage (or they aren't guaranteed to break the circuit in case of a short, etc).
Then you'll need a new charger for the new full voltage.
Adding a single SLA to a series set of them is very simple, once you have the rest of the parts in the system able to handle it, you simply add a wire from it's negative ot the positive of the most positive SLA that's already in there, and then connect the main positive to it's positive.
Note that the higher speed will take higher power, and drain your battery faster, lowering your range by some (probably significant) amount. Higher torque will do that even more quickly.
You can test for speed limiting by getting the driven wheel off ground. If it runs the same speed off ground as on, it's limited in the controller. If it's faster offground, then it's not limited in the controller (or at least, not limited to what you're presently running at).
You should check to be sure your wheels, tires, brakes, suspension, etc. is all capable of the higher speeds, and replace anything that isn't designed for them, so you don't have failures when you really don't want them.
If you want "a bot (lot?) of extra torque" you're going to need a higher current controller, and a bigger more capable battery that can supply all that extra current.
To find out how much current (amps) / power (watts) you need for the torque you are after, and let you guesstimate the battery you'll need, you can go to the simulators at ebikes.ca and learn how to use them for your specific riding conditions and goals.
I moved the second post out of this thread
Hello from Hamilton Ontario! Long time "lurker", FIRST time poster hoping to get some help. I have an Emmo S6 E-Bike (details to follow). It is powered by a 72v (32 +-1A)(2300W?) controller (again details to follow). I have searched everywhere, including these forums, for as much info as I...
endless-sphere.com
into your original thread about it, so that those helping you won't be scattering their efforts among multiple threads, and all the info is in one place and you won't have to keep answering the same questions over and over (and those helping won't have to keep asking them).
