Bafang BBSHD not getting full power

[jellyfish61]

I have a 52V BBSHD with about 8,800km on it, no problems so far. It's programmed to go from 150W in PAS1 to 1000+W (max) in PAS5. Which is what it does except now, when I take the bike with a freshly charged 52V/20A battery, after just a few miles I only get approx. 350W max (which is my PAS2) -- in other words going to PAS3/4/5 does not increase power.

If I stop and let the bike rest for about 15 minutes, it goes to full power again but only for 1 or 2 minutes, then it's 300/350W max again. It's like there is a weird 6/7A current limit kicking in.

The motor is not even warm (cold climate here). Also notice that 1) I replaced the battery with a new one only two weeks ago, and the problem appeared after a week (10 rides/ 400km) with this new battery and 2) the problem appeared the day after I rode the bike pretty hard (25% climbs etc.).

Could this be the battery/BMS, or the controller, or something else??

 

[fechter]

When the power drops, does it show an abnormally low power reading on the display? This sounds like a controller issue.
If I had to guess, I'd be looking at the shunt resistors on the controller board. There are two in parallel. It sounds like what would happen if one had a bad connection. Unfortunately, these are on the bottom side of the board, but it's not super hard to dig out the potting and get to the bottom side of the board. Otherwise, you may need a new controller.

 

[A-DamW]

Sounds like a bad thermistor/temperature reading, does your display have any temperature reading?

 

[jellyfish61]

Tried again today with freshly charged battery, started riding eg in PAS4 and see 600W on the display and after <10 minutes I see 350W (which is my PAS2). I can go lower (PAS1, 200W) but no higher. Cannot imagine how I fried up the controller since I never ride at 100% (PAS5) to conserve battery, but I agree it looks like the controller (and not the new battery) is the culprit.
I have a standard 500C display which does not have a temp reading.

 

[ginekolog]

I had same problems. Turns out that temerature sensor in controller died and showed temp ob 100C. Thats why thermal protection activates and limits to 350W.

I installed open source fw (BBS-FW: Open Source Firmware for BBSHD/BBS02 Controller), disabled temp sensor and it worked great.

 

[jellyfish61]

I don't even have a Windows laptop so just ordered a new controller.

 

[sysrq]

Tried again today with freshly charged battery, started riding eg in PAS4 and see 600W on the display and after <10 minutes I see 350W (which is my PAS2). I can go lower (PAS1, 200W) but no higher. Cannot imagine how I fried up the controller since I never ride at 100% (PAS5) to conserve battery, but I agree it looks like the controller (and not the new battery) is the culprit.
I have a standard 500C display which does not have a temp reading.

Which displays have the temperature reading? I have seen only one such as Bafang C965 and only some of them show some sort of temperature reading.