I had a 48 volt LiFePO4 Crystalyte 408 rear hub setup for a year now. Loved it.
Just recently I added a 24 volt battery in series, for 72 volt and love the new setup, far more powerful and , for me, safer on the road where I ride.
The super helpful ebikes.ca people sent me the 24 volt battery already wired and labelled. All I had to do was plug and play (Justin, thank you very much for your help.).
The batteries fit in the same original bag that I originally had for the 48 volt setup. Basically I placed the 24 volt battery on top of the 48 volt one, the bag has an additional compartment on top, was very convenient.
The battery bag now weighs around 25 lbs. I'll weigh it when I get a chance and adjust the figure, but that seems about right.
Now, you may think this is weird, but I don't place the battery in the back; I place it at the front. I'l lhave to show you pictures of what I mean. (Imagine the gaz tank of a motor bike, that's where the battery is. I find it a better weight distribution which offsets the rear hub motor. So.. steering, then battery, me behind it, hub motor behind me, yep that works.)
As simple as the upgrade was, there are a few things I have learnt about 72 volt setup, and these are things that you cannot operate without:
Ok, now for the fun stuff:
- You absolutely need the right controller, I blew my 48 volt controller as soon as I plugged the 72 volt battery. We're talking sparks, flames coming out of the power couplings ... . I now have a 72 volt pedal first controller and no smoke is coming out . I was so paranoid from the experience that when I plugged in the 72 volt controller I was wearing gloves and protective glasses, but thankfully that worked out pretty ok and the lesson learnt is: use the right controller for the voltage.
- Torque arm, you MUST have one, no ifs/buts about it. Considering a 72 volt setup? Get a torque arm! This baby packs some huge torque and without a torque arm, you're asking for trouble real quick. Originally I was thinking since my drop out is rectangular in shape and the axle as well, how can the axle possibly twist out? Well, guess what ,without a torque arm, it did!
My brother, super great guy, came over and we went to Canadian Tire, bought steel bar, half inch thick, and a grinder and metal cutting plates and he fashioned a torque arm for me, which I must say has been holding out pretty well!
Did I mention you need a torque arm? because ya do
- Throttle. Be very gentle with the throttle. I have a half twist and in my case I had to add a normal-close pushbutton switch to the power cable going to the controller (red wire) since the battery would shut off when i throttle too quickly, especially when i take off; I'm guessing the BMS on my battery is doing this. I am yet to test this, will keep you posted. The wonderful folks at ebikes.ca have suggested an on/off switch to reset the power going to the controller when battery shutsoff, or add a rampup capacitor to the throttle. I'm guessing also if I were to use a full twist throttle it would be a viable solution, but haven't tested this yet.
You're probably asking, how fast does this thing go?
I don't know, my cycle analyst is yet to be repaired, but I can tell you it's way over 40 kph and as such I rarely twist the throttle all the way (I want to keep my bike and feel that doing 50 kph on the road for a bike is asking for trouble). Going up hill, at full throttle, I'm guessing I'm doing around 32 kph up a 30 degree incline, not bad. Riding against the wind, no problem. Taking off from a dead stop and keeping cars away from my tail, super good. And because I'm not using the full voltage I'm saving my battery, and that I feel great about
Oh yes, I forgot: charging.
And as the funny guy from Hogan's Heroes says : i know nothing. .nothingggg about electronics. I'm just passing along the advice.
- Ok, so yes you do need two chargers. 24 volt and 48 volt.
- You can keep the batteris connected while charging them provided that your chargers are two pronged (the plug that goes from the charger to the wall, needs to have two prongs instead of three, and this for each charger, that was the advice I was given by ebikes.ca), I've been charging them in this fashion and so far no problems.