Jdawg183 said:
Hello all. I have been following this forum for a while and I have finally decided to take the plunge. I have an early 2000s pw80 that I am looking at converting. I am looking for a top speed of about 40 mph give or take, and hoping to get up to 40 miles of range. I think the QS 120 kit should give me the speeds I am looking for right? Initially I was looking at the QS 138 but I think that will be overkill.
Next problem, and this is where I really need help. Where are my USA friends getting their batteries from? I have been looking at some of the posts here and it looks like most people build, but is there anywhere that sells reasonable priced prebuilt batteries? I am guessing I will need probably 2 kWh try get the range I'm looking for. Alternatively, how difficult is it to build a battery and where do you get your parts from? I really apologize, I am a complete noob here and am really struggling to figure this all out. Based on what I have found it sounds like I will want lifepo4 batteries but the prebuilt ones I am finding are all 12v. Could I buy 4 of those too make a 48v battery?
some thoughts to show you some of the interactions between different choices you make. i recommend reading other build threads here (as many as you can) for more of this kind of thing that may help you see some of the things you may not have thought about yet, and help you understand some of the things you'll need to know to figure out everything you'll need for your conversion.
to get 40 miles out of 2000wh, you would have to be using the system in a way that only draws an average of 50wh/mile (2000/40) for the entire trip, and that assumes you will drain the battery completely dead from a completely full state, which gives you no leeway for aging of the battery, detours, headwinds, etc.
40mph is probably going to take more than 50wh/mile. my sb cruiser trike only does 20mph; it's very non-aero and heavy and it uses 40-60wh/mile or more depending on conditions, in traffic, on level city roads, with not much breeze. so it's likely you will use more than that, possibly double that. if you are riding in non-ideal non-flat conditions, you'll probably use even more.
you can go to http://ebikes.ca/tools/simulator.html and play with various setups (or make custom ones; instructions are below the simulator chart), to see what something that will do what you wnat to do will use up for wh/mile, and for watts at various speeds, etc.
at a guess, you'll need at least 3-4kw input power to the system to get 40mph out of it; depends on your system and conditions, and the acceleration you need it to have (if you don't mind taking a long time to get up to speed, you can use less power down to the minimum needed to maintain the max speed you want under the worst case conditions you'll ever ride in, but that might not be safe in traffic depending on where you ride). you might need more (possibly much more, if you want snappy quick acceleration under poor conditions or demanding terrain).
if you're using 48v, then 4000w / 48v = 84a, so your batteyr must be able to supply that much current without voltage sag regardless of it's state of charge (empty or full), to give you the max power (assuming 4000w). if it sags too much in voltage, you get less power (say it sags 8v at half-full, call it 40v under max load, that's 40*84=3360w, so you lose almost 700w to voltage sag on a really saggy battery, and thus can't accelerate as quickly or reach as high a speed.
if you have a 2000wh battery and it has to deliver 4000w, it will only last a maximum of 30 minutes at that rate. most batteries charge (a lot) slower than they discharge, so it could take 4+ hours to recharge that battery, depending on it's specific design/parts.
there are other considerations; if you see my posts in other people's builds in this section, they cover various bits of those.
![ATTACH]](/sphere/proxy.php?image=http%3A%2F%2F%5BATTACH+type%3D%22full%22+alt%3D%22Screenshot_20220311-103447_Chrome.jpg%22%5D313019._xfImport%5B%2FATTACH%5D&hash=fc54ec0687a6f68b09f6a9567e20dc94)
