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Right now we have three 6 cell 6000mah RC batteries in series for 72 volts. I'm a little concerned about run time but haven't been able to test because of rain.
I expected to be down on power compared to the 50cc gas engine so weight savings was a big goal. Using downhill mountain bike pieces I was able to get down to 78.6 which is right at 10 pounds lighter than stock.
Plus the MTB parts a super sweet. The shock is a Fox float x2 air shock with high and low compression and rebound.
The forks are custom lowered Manitou dorado pro's. They have air, compression and rebound and something called TPC. To run the forks we had to use their one off titanium axle, and that's basically awesome.
The brakes are Hope Tech 3 V4's which are cool because you can adjust the lever through and the "bite point" and they come with stainless lines. Had to run a Nihilo oversized rotor to get them to work.
The motor is a stock Oset 1400w it's plenty of power, but i'm not sure it will handle the actual high rpm speed without overheating. We used a Kelly controller that is cool because you can plug it to a laptop and make several power curve adjustments easily.
I'm really looking forward to seeing him ride, but it just wont stop raining...
The Shop
Does the Kelly controller have a low voltage protection or cut off? I don't know how familiar you are with Lipo batteries. I believe the voltage cut off needs to be around 3.3V per cell, I'd have to look back and double check that number. I haven't messed with them in a little while. Anything lower and you can do some serious damage. I have seen Lipos go up in flames from being over discharged. Well, it wasn't the discharge that caused the flames, but trying to charge them after running the voltage too low. I had one personally blow and catch fire on my while charging. A cell decided to take a dump and went poof.
How are you charging them? I'm assuming an RC charger.
I am expecting half the run time of the 20r as my son is not a full throttle ripper (yet).
The kelly does have a low voltage cut out but it is total of all three packs. I have individual battery monitors that alarm if a single cell drops below a set voltage. I usually charge to 4.1 and discharge to 3.2 volts. Some people say the less than full charge allows for many many more charging cycles because the cells are less stressed.
I've got a decent charger from HK that will do 4 6 cell packs. I am actually considering going to 4 three cell packs with higher capacity because the top speed is a little high at 45 mph. So basically trading top speed for run time. Will need to see him ride first.
SHREDDER - I am slightly concerned this motor will not hold up to the heat generated by the added speed. It was designed for about 26mph. If it doesn't, the next step up is a liquid cooled brushless motor. I can plumb in a 12v inline pump and use the stock radiators for cooling. If this motor holds up, I'll probably remove the radiators.
Here is a short video of his Oset we tricked out a few years ago.
Post a reply to: Already posted in Electric Bikes. My sons 50sx