Critique my plans for my first build!

[heyitsaustin123]

Hey All,
I am in the planning stages of my first build, I've read Micah Toll's book, and I'm getting ready to pull the trigger on some purchases so I'm looking for some oversight from you more knowledgeable E-bikers before I shoot myself in the foot. Just a little background, I plan for this to be my everyday commuter (when the weather is cooperating) in addition to my around town grocery getter etc. My commute is each way according to Google and I live in a fairly hilly place.

Battery
I'll start off with the most controversial... the battery. I've settled on building a 13s5p 18650 pack housed within a 65-cell Hailong case. It seems these are all about the same from the various Alibaba vendors but this one has the most orders. Originally I was going to get the version with nickel strips and USB because I like the custom cut strips but the vendor told me they are nickel plated steel so now I am thinking otherwise. I live in a fairly dry climate (Colorado Front Range) so I'm not too worried about corrosion but more so the extra resistance. Is this a reasonable worry? The pre-cut seems much cleaner than cutting strips by hand. Could I tack on an extra strip of Ni to beef up series connections? As for USB, I plan to use a 48V to 12V regulator to power lights, phones, laptops etc. anyway so not much of an issue.

As for cells, I've settled on the Sanyo NCR18650GA but haven't decided if I am going to purchase from Tumich or QueenBattery. Tumich is a bit cheaper but I'm worried about taxes/import fees. I picked this cell as I love the high capacity, my current draw (4.17A) is well within the 10A it is rated for, and I shouldn't be putting deep cycles on it all too often as my commute is short so should still see pretty good cell life (I think?). As this is the most expensive and crucial component of the build please let me know what you think about this cell! I know this pack is probably a little overkill for such a short commute but I like the added buffer and I will be pushing it time to time while exploring on the weekends. Also, I plan on using the XT60 as my connector.

I plan on picking up one of these Arduino Spot Welders from Malectrics

BMS
This one gets its' own section as I am particularly worried about this destroying my pack. I am thinking about one of these ANT Smart Bluetooth BMSs, the 7S to 16S 100A model without the LCD should be sufficient. I don't think I'll need an LCD if I can get all the data on my phone. I should be able to set a cutoff charging voltage to 4.1V allowing me to use any 'ole 48V charger.

Motor/Controller
As for the motor/controller I am planning on going with a cheap EBay kit like this Voilamart 48V 1000W kit. I figure, the motor will be pretty good and if the controller ends up sucking, I'll just get a new one eventually. AFAIK these Ebay kit motors are all pretty similar.

Yet to figure out/Questions
Charger- I assume I can use any ole 48V charger with the BMS cutoff set correctly. I was thinking something like slow and fanless like this 48V Dolphin Charger from Luna. Maybe there's an even cheaper alternative so I can have one at work/home. If I really want to charge fast, I'll use one of our beefy adjustable power supplies at work and do it by hand.

Spot Welder- I plan on picking up one of these Arduino Spot Welders from Malectrics. Seems pretty sweet but if anyone has anything cheaper/better lmk. Having to lug a car battery is less than ideal but not enough to go for the lipo one. I have access to 120/240V 208/230V at work if needed. I'm splitting this with a co-worker who is also building a pack.

Lights/Accessories- Haven't picked any lights out yet but plan on headlight, tail light, and maybe signals. I was thinking of running these off the 12V regulator as 12V accessories should be cheaper/more common but if you have any other suggestions let me know. May also get a set of 12V heated grips. Eventually I plan on buying another battery receiver to use the battery off-bike for powering an inverter, charging phones/laptops, heated blanket etc. on climbing trips.

Bike- I'm waiting on getting my battery case to go bike shopping as I want to make sure it will fit. Will likely go with a cheap steel-framed mountain bike off Craigslist which should be pretty easy to find in Colorado. Can disc brakes be used with these kits?



Final Purchase List
Hailong case
65x Sanyo NCR18650GA
48V to 12V regulator
ANT Smart Bluetooth BMSs
Voilamart 48V 1000W kit.

 

[thundercamel]

Well thought out! The motor kit you linked is very similar to the two kits I've bought. They do all have the 6-bolt adapter for disc brake rotors, and generally work just fine. I also have the Malectrics spot welder, and it has worked great through the four batteries I've built so far. I was advised to use 0.15x8mm pure nickel strip, and it's not bad at all cutting it yourself. Make sure you use the paper positive end insulators and some sort of cell holders.

The smart BMS is great peace of mind to verify that all the cell groups are keeping their voltages uniform, and that the BMS is doing it's job. That ANT style is different than the JBD style that I've used three of. I also like the high capacity cells, but chose LG MJ1 for the superior cycle count, verified by Pajda and others on here, but GA should be fine. He also recommends the gmail contact on QueenBattery to get the best price, and I am going to try that the next time I order cells. The XT90 anti-spark connectors will last longer, unless you plan to use the BMS to turn off the battery every time you connect the motor controller.

52v 14s is more popular than 48v 13s, because motor kits that don't have an adjustable low voltage cutoff are usually set around 42 volts, and a 13s battery would still have a fair amount of capacity left. If the kit you linked does actually come with a sw900 display that communicates with the controller, I've successfully used the one with my ebikeling kit to go in the menu and switch from 48v to 36v, and continue riding home. Take a look at the build link in my signature for all the parts I used, and prepare to have fun!

 

[thundercamel]

Oh, and it's generally considered bad practice to use BMS settings to limit charge voltage, though it can be done. The proper way is to vary the voltage that the charger puts out. Some cheap ones (like mine) have a potentiometer that can be slightly adjusted, and better chargers have a programmable voltage.

 

[wturber]

DD hub motor for a durable, low maintenance commuter is sensible. It will need pedal help up hills steeper than around 10%.

It is good to err on the side of an oversized battery IMO.

The same brand freewheel on my similar kit was pretty much junk. And I'm fairly tolerant of mid-quality stuff and not a gear snob. It is likely that you will want to upgrade to a better freewheel with shifting ramps and better overall quality. I'd go in assuming that the freewheel is temporary - though it will be less of an issue if you don't shift much. Wait until you actually buy your bike. There's a fair chance that your bike will have an 8 or 9 speed shifter and freehub. So you may end up changing shifter as well. 8 and 9 speed DNP freewheels have a larger stack height and may require extra spacing. So be prepared that this whole issue may require a bit of fiddling - especially if your base bike is 8 or 9 speed to start. I just went with a 7 speed DNP freewheel and changed to a 7 speed shifter.

I'm unsure about the rim and spokes, but if your wheel comes built with 12 gauge spokes, it is a fair bet that you'll be rebuilding the wheel after a few thousand miles. Mine (different brand and style of rim) lasted about 5000 miles. That could be quite a few years though depending on how much you ride.

A 12v converter works fine. I use one that is very similar to the one you linked to but mine has only a 60 watt capacity. Nonetheless, it runs a motorcycle LED headlight, rear lights and accessories just fine. I run the 12v to a car accessory socket (formerly cigarette lighter socket) that I pack into a 35mm film canister. I then plug a standard USB car adapter into that for my USB powered stuff.

I suggest using an XT90 anti-spark for you main power connection. The anti-spark feature is nice. The DC pop got old after a while and it is hard on the connectors.

Disc brakes generally work fine with those kits. The one potential problem is that the there can be interference between the back of the disc brake caliper and the hub motor case. It all depends on the particular brake caliper and the amount of dish in your wheel build. I ended up going with a 180mm rotor to help with this, but really should have gone with a 203mm to get even better clearance. You can convert a 160 to other sizes with adapters.

I'm a fan of the Trek 820. They are inexpensive, common, all steel and have larger than normal tubes. But any mountain bike from a name brand maker that has decent components and extra beefy frame construction should be good. My commuter is an all aluminum frame but the cargo bike I'm working on will be steel (Trek 820). You should used torque arms on the motor, but it is critical that you do if you have an aluminum frame. A bike with a front shock is worth considering especially if your road quality is poor. The problem with front shocks is that cheap ones can introduce their own issues and better ones usually cost a fair bit more.

 

[j bjork]

I have built practically the same bike that you are planning to.
I think it is alright, I have not ridden it a lot myself. It is mostly my girlfriend that have.
The motor in my kit is 27mm, it would probably be rated 750w. But it has not been a problem so far with my controller, I use a KT 1500w.
I run 13s, it is the best for the battery case that holds 65 18650s. With 14s you would only be able to run 4p, to a total of 56 18560s.
You could go 16s, for a total of 64 cells, but if you go full speed you better go for other cells than GA:s.
The top speed is somewhere in the 50km/h range with 26" wheels, and the range seems to be in the 30km range with GA:s
I have changed the connectors from the battery to andersson, I think I got burn marks on the original ones. I am not sure if they would be a problem, I changed early in the build.You can check my build thread for inspiration.
If i did it again, I would probably get a 35mm motor with 0.35mm lams and sony vtc5A cells, and maybe a 12fet nucular controller.. And a vector light frame.. Well, It is a good commutator as it is.

 

[cheapcookie]

Hey we're not the customer service of Micah's book :lol:

Buy bafang or ebikes.ca if you're smart

Good luck it's a tough world out there