Contoller max amps vs actual draw vs phase amps...

[e-troll]

Hi all. I've been a lurker for some time and just finished building my Surly Troll e-bike. Will post pics soon but had a question. I just purchased a 35 amp Infineon from ebikes.ca. I am running a 15 Ahr Ping at 48V (LiFePO4). Motor is generic Chinese but doesn't even get warm unless ambient temp is over 90F. I read somewhere that a 35 amp controller always provides 35 amps but just for shorter bursts. If the averaged out "continuous" amp draw is only say 10 amps, will the mini 35 amp bursts kill my battery (I believe this chemistry is only good for a max of 2C discharge before one should expect significant reduction in cycle life), or is the continuous amp draw the important number (if that is in fact how a controller works). I rarely accelerate at full throttle, and only do so for a few seconds at a time. I just like having that extra power there for riding in city traffic. It feels so much better to have some acceleration in reserve (as opposed to the 20 amps stock controller). Also can somebody please explain phase amps to me? Why are they so much higher than battery amps and how does that work?

Thanks everybody for such a productive and well informed online community. Look forward to joining in on the conversations from now on.

 

[wesnewell]

The only way I've seen anywhere close to max amps from a controller is by putting the front wheel against a wall before hitting the throttle. With a 30A controller modded for 45A, I couldn't get it to pull more than 30A going up a 20-30% grade and it was accelerating all the way to the top. If you ride sensibly, your max amps should be under 30A for a 35A controller. Ride really conservatively and it probably won't go over 25A.

 

[alfantastic]

Don't worry about the peak amps killing the battery. I've been running a Ping 48v 15Ah for a couple of years now, with plenty of peaks at 32 amps for seconds at a time.
It'll never draw the max amps for long anyway, even up hills. The Ping will cope fine. Just ride and enjoy

BTW, invest in a Cycle Analyst, then you can analyze your power usage in real time. Like air-con, once you've had it, can't live without it lol :wink:

 

[pixelzpusher]

Here's a way of looking at amps for your ebike. My 48v 1000w hub motor draws about 26 max amps with my 190 lb frame and bike loaded with batteries, right from my watt meter. The 26 amps will go up or down based on a number of things. If I have a brand new fresh set of lipos, the amp draw "may" go up because new set of lipos, less resistance, possibly more amps flowing to the motor. I say "may" go up because the motor may not need more amps based on bike load. On an old 3 year lipo pack, definitely amp draw goes down, more resistance, less amp draw from the lipos. I've actually tried this with old set and new set of lipos. How do I know this? I've been flying electric RC airplanes for 8+ years and each time I purchase a new lipo pack in my airplane, it feels like I upgraded the motor. New battery packs are fresher and can "provide" more amps, less resistance in the batteries.

Now, if you load the bike more with weight or your rim brakes are rubbing against the tire, the motor has to labor more and thus, need more power, thus draw more amps. Now this is only the case if your batteries are capable of delivering that power in amps. If not, your motor will just go slower without getting the needed amps from your battery. If it does get the amps from the batteries, then the motor has more power, but will run hotter because more amps. More amps = more heat.

The motor, the controller, or the lipos, could go out or overheat, with the increased amps. Based on my experience, if you draw down too much capacity amps from the batteries, they will go. If your controller runs too many amps for too long, that will overheat and go. Same goes for the motor, too many amps for too long, that will go. Controller can also go out if too many volts. I've done all these things while flying rc airplanes and have had either batteries, controller, or the electric motor go out because of too much heat. Heat is the enemy. A watt meter between your batteries and motor will give you a good reading of what your motor is drawing in terms of amps and the load on your batteries. You can see the voltage sag when the batteries are under load.

Hope that makes sense and not too confusing.