MP5 controller problem?

[Michael]

Hello,

I've recently build a customized e-bike around an MP5 rear wheel. I already used this wheel in a previous bike. I was satisfied with the MP5 although I had a controller replaced  after about 1000 km since the wheel was not spinning anymore (it just vibrated).
One of the things I changed along with the bike, was the battery pack. I build the previous one myself and thought it was time for an upgraded battery too.  Previous battery, fully charged was 52V. The new battery, when charged is 60V. However, I only charge it to about 80% of its capacity.
I already tested the whole setup on a bikestand and everything worked fine. The only thing I did not test until two days ago were the brakes. Since I was planning on doing my first real ride with the bike I wanted to tweak the settings of the controller. One of those settings is the regen braking ofcourse. This is when trouble began. First I hooked everything up incl brakes. With full throttle, all seemed fine. But when pullig the brake lever, the wheel started spinning even faster for about two seconds and then started slowing down without regen. I tested this for a few times after checking connectors and measuring them, always with the same results. Another strange thing I noticed was that when the throttle was at about 20% and I pushed the cruise control, the wheel started spinning faster and faster to max speed.
I then disabled regen braking and tested again, no problems here. However the following day I wanted to do the test drive and tested everything again on my bike stand. Regen braking still disabled. I immediately noticed that the wheel was not spinning as fast at full throttle. The PAS worked fine the previous days and now comes on and off with pedals moving at the same speed I tested during the other day.
I read some posts on this forum of people having similar problems after using a battery pack at a voltage around 60V. I assume the controller can't always handle the regen current/voltage.
I tried my previous battery pack at 52V and the regen works just fine. With full throttle the max speed is still down to 30kph (same as at 60V). In the past I got 46 kph at 52V.
My batteries have no BMS since I monitor the battery with cell loggers and use a fuse.
Is it safe to assume my controller is (partially) fried and I need to replace it? If so, would it be better to switch to an external controller or are there some people that use a 60V battery without any problems?

Kind regards,

Michael.

[Bikemad]

The default maximum voltage for the controller programmed for a 48V pack is 62V, so a fully charged battery voltage of 60V should not be a problem under normal use:



My 16 cell LiFePO₄ "48V" GM battery is always charged to 58.4V and I have never had any problem with it.

I have noticed in the past that some of the Vector controllers do occasionally behave strangely when tested with no load, but I have not experienced problems during normal use.

I did have a pre-production version of the Smart Pie which would momentarily brake very slightly when applying the throttle immediately after coasting down hill, or while applying the throttle after riding without motor power on the level.
However, the production version of the Smart Pie did not do this. 

My Magic Pie 4 was set on 24V and would not allow regen to work with my 33.6V fully charged 8S liPo pack until it had been reduced by discharging it.

I later discovered that if I changed the nominal battery voltage setting to 36V and then lowered the undervoltage protection setting to 27V that the regen worked fine:



Unfortunately, I could not lower the overvoltage protection below 48V, and for a 36V battery, that seems way too high.

There have been a few reports on the forum of loss of speed, and most of this was due to a low voltage on the +5V supply to the throttle.

To achieve maximum rpm (full throttle) the signal voltage from the throttle needs to be at least 3.25V. If you don't have a high enough voltage going into the throttle, you won't be able to get maximum rpm.

If you have a plug and socket connector on the pedelec sensor connection, you should be able to easily check the voltage of the +5V supply by measuring across the pins on the red and black wires.

However, your suggestion of converting to an external controller would also allow you to use a much higher voltage battery (60V, 72V, 84V etc.) for a significant increase in top speed (if that's what you really want).

Alan