new setup with dual motors

[garyv123]

Hey i got an lectric expedition dual batteries just put a direct drive 1000w motor in the front have original geared motor 750w in the back took allot of research and a bit of time to get it wired in. The worst part was getting spokes the size i needed to put the hub in they didnt have kits with my rim size to just plug and play. also with my research i found if you have two motors two controllers but running off of existing batteries the motor that is being added just needs a signal wire from throttle and battery then plug controller to the motor. well i did that but got nothing then i remembered it came with a power console not display but off/on three motor modes and a light button i plugged that in and boom works no problem. so going up hills np level ground constant 30mph when before my norm was 20mph and had trouble but always made it up hills now it hardly looses speed so far definitely worth it. i have to grin torque arms on the front to help it not wreck the drop outs or spin out of them v6 type heavy duty ones . so it powers up separate and has its own power levels everything stock still works stock but it all goes off of the one throttle and the systems using there own interface i can have one or both powered on wich is nice. just wanted to share my build and how it went.

 

[m@Robertson]

Keep your amp draw low on the front motor. Even with torque arms, you have stuff to deal with. Pulling on a fork with a front motor can loosen it. My solution to that was two star nuts inside the steerer but that is not as easy as it seems if the threading is not synchronized right from one to the other. I have at least one fork with a stripped star nut I had to hammer down further to get it out of the way. Also you have probably realized by now that starting from a stop had better happen with the front wheel pointing forward. My 35a fat front controller would pull the bike out from under me if I wasn't careful. That is also a motor/controller combo that will chirp the front tire if I don't go into the controller and set it to slow-start.

Most of my 2wd bikes are cargo bikes. Can't be beat for getting up hills. I have 100 lbs of gravel to go pick up at Home Depot some time today and part of the trip back is over a 16% grade.

Dual Motor AWD Electric Bikes (the good and bad)

I like to build top-quality-component ebikes from the frame up. Quite a few of them are dual motor or AWD or 2WD or whatever you want to call them. Why would you build an AWD ebike?

talesontwowheels.com

 

[garyv123]

Keep your amp draw low on the front motor. Even with torque arms, you have stuff to deal with. Pulling on a fork with a front motor can loosen it. My solution to that was two star nuts inside the steerer but that is not as easy as it seems if the threading is not synchronized right from one to the other. I have at least one fork with a stripped star nut I had to hammer down further to get it out of the way. Also you have probably realized by now that starting from a stop had better happen with the front wheel pointing forward. My 35a fat front controller would pull the bike out from under me if I wasn't careful. That is also a motor/controller combo that will chirp the front tire if I don't go into the controller and set it to slow-start.

Most of my 2wd bikes are cargo bikes. Can't be beat for getting up hills. I have 100 lbs of gravel to go pick up at Home Depot some time today and part of the trip back is over a 16% grade.

Dual Motor AWD Electric Bikes (the good and bad)

I like to build top-quality-component ebikes from the frame up. Quite a few of them are dual motor or AWD or 2WD or whatever you want to call them. Why would you build an AWD ebike?

talesontwowheels.com

thank you for all the valuable info wish i had it before i decided to build my awd ive put over 100 miles on it and i still love it i find putting the front motor in the middle mode as it it has three modes it shares the power and burden with both motors fairly equal and ive been on top of my steering collum seems to take the shock from bumps allot harder now i will look into putting those star nut you mentioned on there but i have found one throttle with front motor at medium power works pretty great no issues so far and my battery range hasnt changed very much but time will tell once again thank you very much for the info im thinking of adding two more 20 ah batteries wich will definitely increase range what are your thoughts on that?

 

[m@Robertson]

im thinking of adding two more 20 ah batteries wich will definitely increase range what are your thoughts on that?

Paralleling packs is something you can't screw up. Using a battery blender qualifies as screwing up. Those are cheap products produced by factories that are completely unaccountable for quality, and the consequences for getting it wrong are catastrophic to the pack and your fire insurance deductible. When I was paralleling, I was doing it directly without a blender, but to do that (mostly) safely you have to build brand-new packs that your builder can certify to be identical, that s/he has tested individual cells of the same type, to ensure they are all at the same end of the voltage range that is acceptable for that cell model. Not possible unless you are having packs custom built.

Also, two packs wired together will roughly simulate the robustness of a single bigger pack, but they won't be as good. By that I mean lets say you take two 14S6P packs (that should make roughly a 20ah pack depending on the 18650 cells you use) and wire the two together in parallel. Each has a BMS with a 30a continuous/50a peak rating. On paper you now have a pack that is 14S12P, and your BMS rating has doubled to 60a/100a. So a 12P pack will suffer from almost no voltage sag unless you have monster controllers, and the 60a continuous rating is pretty much sufficient for twin controllers on a 2wd as well.

Except it doesn't work that way with parallel'd packs. What you have still are 14S6P packs and if you flog them like a real 12P they will suffer (from heat among other things).

I graduated up to single packs with really big BMS' long ago and never looked back. Your continuous power rating should equal the peak ratings on both of your controllers to keep the BMS from popping. So my twin 35a controllers on my 2wd hub bike need 70a. My BMS on my big single battery is 75a continuous (build with a 5a cushion at the least) and 100a peak.

You match the continuous pack rating to the controller peak because if the controller decides to draw at the peak level for a second longer than the BMS is willing to accept as a peak, the BMS will shut off the battery, and it will not turn back on again until you hook it back up to a charger (i.e. you ride home unpowered). Been there/done that/learned the hard way.