evglobal19 said:
three vendors have a 17" in the 3-5kw versions. I'm leaning towards the NBPower 5kw kit but also looked into the QS. If you're going to build 3kw and the 5kw is not much more why not? if 72v/32Ah is a minimum it is what it is. the NB hub comes with a 100A sine wave programmable controller but I'll check the Savboton too.
I would go with a 3KW QS hub motor, if possible Balanced V3 since they are, in my experience at least, the best compromize.
Your machine is lightweight, a 3KW motor shouldn't heat too much and could give you really good performance. That's what I use on my motorbike actually, so it should be no problem with yours.
In my opinion, a 150A battery 350/phase controller should be more than enough. That would give you around 12KW of power, on such a lightweight machine it will be a blast! Trust me, there is no way you could be disappointed with such a setup.
You don't really want to get too crazy with a too powerful motor, because otherwise you'd have to match your battery and controller to be able to deliver that power. Using an underpowered controller or battery might result in frying them.
evglobal19 said:
If I go with either kit it has disc brake on hub and suppose could swap in matching front wheel with disc setup too. for budget hmm, I'm more inclined to get good pieces one at a time but always worry about being sure they match.
If you go for the kind of power I'm describing, then having a good front brake will not be an option. You really need to be able to stop, it can get to high speeds really fast. You could likely reach more than 100km/h and get there in 7-8 seconds, maybe less if you keep the bike light and if you're not a big fatty yourself XD
But that can be done later, in which case you'd just have to tune down the controller, that's the beauty of having a programmable unit.
evglobal19 said:
without being sophisticated about the electronics I'm tending to rely on the 'kit' being properly matched. If matching the specs isn't as daunting as I think then any suggestions about what to research is quite helpful. like everyone time patience and research always trumps buying things more than once. I'll post the specs on what I'm considering motor wise and look forward to any and all feedback.
Steve
Regarding the RC inboard motor setups, I wouldn't go in that direction. Maybe they could give good performance, but I'm not sure they are reliable enough for a daily driver. If you plan on using your ride often then you might want to go for something with enough real road experience. Those hub motors are widely used on litterally hundreds of millions bikes here in China and they work really well. No real need to reinvent the wheel here
As for dimensioning the battery, you will need to take into account the power draw:
if you go for a standard lithium battery, then most of these will have a 3C discharge rate. With a 150A controller, that means that you will need a 50Ah battery (150A/3C=50Ah).
So what you want here is to find a battery using cells capable of a high discharge rate. In order to live with a 30Ah battery, then you need to make sure that the cells are capable of 5C continuous discharge at least.
You could probably live with 60V, but if you want a bit more speed and power it would be better to go for 72. I don't know the prices of such batteries where you live but that will be a large part of the total cost, so be prepared. Also, make sure that the BMS you will use is capable of delivering at the very least 150A. Better go for at least 200A if possible, to avoid some unwanted cutoffs, especially when your battery will start aging.
Nowadays, some smart BMSs capable of 300A continuous exist, and they are affordable, so it should not be a big issue (the ANT smart BMS is a good value).
There are various lithium chemistries, none of them is perfect, they all have their drawbacks:
-LiFe has a high discharge rate and they last for a long time, so they will keep their capacity rating for several years, but they are big and heavy. Thay are also less sensitive to deep discharge and overcharge so somewhat safer.
-Li-ion is lightweight and takes up less space, but they will quickly lose their capacity, so if you build a 30Ah battery then the next year it might be no more than 25Ah. So in the end you need to overbuild your battery quite a bit, which gets expensive.
Plus they will die earlier, they can handle way less cycles. They are a bit more risky so you need to use state of the art protection to avoid fires.
-LiPo is the lightest, it has a really high discharge capability, plenty of power, but it is very impractical for a daily driver because it needs to be extremely closely watch during both charge and discharge, plus the cells really don't last for long.
-Lead-Acid: it works fine but it is super heavy and it sags quite a bit. Plus they won't last more than a year. But
if you can get them for cheap, then it might be a good option to at least test your setup for a few months, make sure everything works fine, and then upgrade to lithium. It isn't as powerful as a lithium battery, expect to lose around 10-20% of the power. But for testing purpose, it might be a good solution in your case. Just a temporary one and on;y if you can get them for very cheap. In which case, go for seven 12V 20Ah batteries. Expect around 20-25km of range if you drive agressively, maybe 50 if you ride very slowly.
Both LiFe and Li-ion options can work well on your setup, I guess it just comes to whichever you prefer. On my builds I tend to use LiFe because I can live with a bit more weight and I have enough space, but in your case that might be different. I used to run on Lead Acid at the very beginning, it was fine but the beast was very heavy.