Soldered Shunt more RPM?

[A Monell]

I have a 500 watt 36 volt ebike that I run with 10AH 10s lipos (4 5s packs in 2s-2p). It is an inexpensive Yesscom ebay bike but it runs fine. I was hoping to up the 18 MPH to maybe 20-22 and have seen people adding copper and solder to 1/4 or 1/3 of the shunt. Does this increase the RPM at a given voltage or just enable the controller to run without cutting off (or limiting) at a higher amperage, as when going up a hill? I don't want to go to higher volts as I have 2 lipo packs and one smaller Dewalt pack. I also have a 800 watt version from the same source that works as I like. I just want to have my "guest" bike run at about the same speed.
thanks, Alex

 

[neptronix]

Soldering a shunt ( or otherwise programming a controller to give more amps ) gives you higher amperage, so you will accelerate quicker and hold your speed better on a hill.

Voltage gives you higher RPM.

 

[wesnewell]

I've built a couple of the yescom 48v 500w kits and iirc I got ~25mph on 14s lipo. If I was a little lighter (275lbs) it may have gotten a little more. I hooked a new 40a 72V controller to it and ran it on 20s lipo for a while. Don't remeber exact top speed, but was around 35mph. You just need more voltage for more speed and torque. Controller should support 15s lipo max. I've got a new 48v controller that came with one of the 48v kits if you need one.

 

[d8veh]

If you want to go faster, you have two choices: change the motor or change the batteries. 12S lipos will give the speed you want and should work with your existing controller and motor. A new motor with a higher speed wind will cost about the same and will work with your existing controller and batteries.

Soldering the shunt will cause the controller to supply more amps to the motor, which will give better hill-climbing speed, but be careful not to over-heat the motor by too much full throttle. It's best to use a watt-meter when you do the soldering so that you can see how much extra current you're getting, and go up in stages to see how hot your motor and controller get. A 25% increase should be OK.

 

[iperov]

more amperage -> more economic wheel you get,
because lowest effeciency is keeping low RPM on accelerating.

 

[wesnewell]

I did a shunt mod on one of the yescom 48v 500w controllers and took it from standard 30A to 42A. That was over a year ago and it;s still going strong on 12s lipo with a top speed of about 23mph. And that's what you should get with 12s lipo on your system. But since you already have 5s bricks, I'd just add 2 more for 15s2p. Should give you 25mph, and 50% more range at the same speed as before.

 

[dogman dan]

I wouldn't solder the shunt yet. Try 14s or 15s lipo first. Then after that, solder the shunt.

You'll increase top speed with more volts, and since v x amps is watts, you will even accelerate a bit better with 48v.

You'll have about 160w more power if your controller is 20 amp. Solder the shunt along with the 14s, and you'd have about 1320 watts total. Not enough to melt the motor, but enough to be fun. Oughta get you moving fast, faster.

 

[nechaus]

if you solder the shunt, be sure to test the controller temp to...
it may heat up more

 

[dogman dan]

Yep. The one time I soldered a shunt, the controller began to malfunction soon after. It would do little blips of shut off, then run a few 100 yards, then another short blip of no power. But it is a risk.

Never found out what it was, the controller was returned to HTB so he could look at it, and he sent me a new one.

It wasn't the fets, and may have had nothing to do with the solder, and everything to do with a lot of use for a long time.

 

[John in CR]

This is another common misconception broadly accepted as fact around here. The correct answer is "It depends." On lower powered ebikes it is common to limit max speed through 3 methods other than just battery voltage. One is using a jumper to activate a programmed speed limit in the controller. Another is to use an adjustable pot in the throttle line to limit throttle voltage in a tunable manner to match max speed to fit the laws of that country. The other is through current limiting, where adjusting the resistance of the shunt would increase top speed. It won't increase no-load speed, but the effect on max speed on the road can be dramatic.

Use Justin's simulator at http://ebikes.ca/simulator/. Plug in a nice combo for the motors available from the list such as a 9C 2805 in a 20" wheel. Set the battery as the 66V Dewalt pack, and then try the 20A controller vs the 40A controller and see a 10kph difference in flat land speed.

Current limiting makes for a really nice smooth ride with no jerky throttle response, and in areas with very flat terrain I'd go as far as suggesting the combination of a high speed wind motor with a low current limit on the controller as a bullet proof system resulting in a silky smooth bike that anyone can be allowed to ride.

John

John