TSDZ2 750w losing power on hills

[Sasquatch260]

The power just bogged down all the sudden about a mile into a hill. If I kept peddaling, it shut down completely and I got the following on my screen: ERROR O2H POWER PROTECT (motor feels very hot). I have done the hill this happened on dozens of times without issue. (I did have a power problem once before and I needed a new speed sensor but not sure this is the same).
I need some help from any of you experts on here. I've had this setup since 2021 and I really enjoy it and don't want to replace it yet. Thanks.

 

[Slaphappygamer]

Sounds like the battery BMS recognized Low Voltage Cutoff. The battery will sag, in voltage, under heavy loads. This is normal. If the battery repeatedly sags to an unhealthy level (this will be different for different cells within the battery pack), then the cells will get damaged.

A mile ascending seems extreme. What grade is the hill and how long is that climb? Also, how heavy is the bike including you and cargo?

Do you have a voltage read out on your display?

 

[Sasquatch260]

I live at the base of a mountain in Pennsylvania. I would say its a 10% grade but more or less in places. That is one of the reasons I converted my mountain bike - to climb that nasty hill! I usually ascend 1 - 2 miles and then take offshoot trails that somewhat level out.

I have a Giant Talon 29" bike. Approximate weight: 32 lb. Plus accessories est. 8-10 lb. Plus me: 220 lb. So, around 260 pounds total.

I don't have my display set for that, but I'm thinking I can get a voltage read. If I can, what should I look for?

 

[EMGX]

For reference I have a 750w TSDZ2 and live on a small mountain with grades up to >20%. Motor gets warm after long steep climbs but not hot when I've checked. If it's new for yours to be hot when you get the error message maybe something else is going on to strain the motor causing more current drain resulting in battery sag to voltage cuttoff?

 

[Slaphappygamer]

I don't have my display set for that, but I'm thinking I can get a voltage read. If I can, what should I look for?

It would help to know what the pack voltage is before you ascend that hill and the voltage when the bike loses power. 48v packs usually has LVC at 40-42 volts.

Say you had a full pack (54ish volts, assuming a 48v pack). Then the bike shuts down and you measure 38 volts. This would trip the LVC and you can ride again when the battery rests back towards nominal voltage. Still, that is too much sag and your battery may have a bad cell group. Normal sag could be 4-5 volts with a 48v pack. This can happen due to repeated stress, physical damage, or bad charging habits (such as leaving the charger on for extended time after full charge has been achieved).

I know 38 volts may be an extreme case, but cold weather will also affect battery behavior and would sag more than is warm weather. Again repeated stress will age a battery quicker.

 

[spokewrench]

I've had that happen once when I let the battery get pretty low and again when I let the cells get badly out of balance. The motor didn't get hot. I think OH2 means the motor got too hot, as you observed. AFAIK, a battery problem won't cause that.

I believe your kit uses torque sensing. My Abound came with torque sensing and a hub motor. I hated it because it would take off like a rocket even at the lowest level. I was putting too much torque on the pedals. Crocs have fast-twitch muscle fiber which is very powerful but lacks the stamina to pull a wagon up a hill like a horse's slow-twitch muscle fiber. I guess the fast-twitch fibers in my legs were overdeveloped, so my pedaling was driving the motor harder than I liked.

After 4 years, my slow-twitch fiber is improving. I climb at a lower gear because they don't produce as much torque, but their stamina lets me climb hills around here without motor assistance. (Well, I wouldn't attempt a mile at 10% without help!)

If you're using a higher level of assist than before or climbing in a higher gear, that could be the problem. Sometimes a motor that overheats needs cleaning, but I don't know if that applies to yours.

 

[PCeBiker]

,.. I think OH2 means the motor got too hot, as you observed. AFAIK, a battery problem won't cause that.

It is possible if the battery has a Huge Voltage Sag due to a bad cell group.

A fully charged 48 volt battery is 54.6 volts, and the battery puts out (750÷54.6) 13.74 amps to deliver 750 Watts to the motor.

A battery hanging around the LVC under load of say, 40 volts needs to put out (750÷40) 18.75 amps to deliver the same Watts to the motor.

The extra 5 amps does Nothing to help with power or torque because of the lack of voltage, and it all gets turned into heat in the motor.

 

[spokewrench]

A fully charged 48 volt battery is 54.6 volts, and the battery puts out (750÷54.6) 13.74 amps to deliver 750 Watts to the motor.

A battery hanging around the LVC under load of say, 40 volts needs to put out (750÷40) 18.75 amps to deliver the same Watts to the motor.

The extra 5 amps does Nothing to help with power or torque because of the lack of voltage, and it all gets turned into heat in the motor.

An extra 5 amps will help with torque. Torque comes from amps.

The wattage of a motor is a manufacturer's classification. The maximum power delivered to the motor depends on the controller and the battery voltage. I think 24 amps is typical for a bike labeled "750 watts." If a battery with 4 stacks of cells is charged to 54.6 v and delivers 24 amps, that will be 6 amps per stack. The internal resistance of an 18650 cell is about 40 milliohms so a stack of 13 will have about .52 ohm. Terminal voltage will be 51.5, for 1236 watts.

If the battery were down to 40 volts when the controller demanded 24 amps, terminal voltage would drop to 37, sending 888 watts to the motor. Actually, I doubt it. Suppose the windings have 1 ohm. 24 amps will be 24 volts, producing 576 watts of heat. I haven't verified this, but I imagine the controller limits current by rapidly switching it off and on.

Maximum amps occur at slow speed, when the motor isn't producing much power. Power depends on torque and speed. A motor producing power acts as a generator, producing back emf, which also depends on torque and speed. If your well-charged battery produces 24 amps at 51.5 amps, the controller can be wide open when the speed reaches a point where, at full torque (24 amps), the back emf will be 27.5 volts, leaving 24 volts to fight winding resistance. At that point, heating will still be 576 watts. As the motor speeds up, current will decline due to increasing back emf. Heating will decline as the square of current.

I've never had a middrive motor, but it seems that downshifting would reduce the torque required and reduce heating as the square of torque (amps).

 

[harryS]

What display do you have? You have to check the manual for that display and see what an error 02 is. I have TSDZ2 and a TSDZ2B, but I use the VLDC5 display. On that display, error 02 is a motor error, which could be anything.

By the way, the stock TSDZ2 circuit card does not contain a temperature sensor as far as I know, There are hackers who have rewritten the firmware, and when those guys want to show temperature, they first have to install their own sensor, You can be sure they would have used it if one were available.

Nonetheless, you do know the motor is too hot. That's serious since most of the TSDZ2 casing has a 1/4" air gap between the shell and any interior heat sinks. If the case is hot, the circuit board and motor are even hotter.

 

[harryS]

So what would cause your TSDZ2 to suddenly lose power and not be able to make the climb?

You've eliminated dragging brakes, and wheel issues? My rear QR skewer used to get loose on my TSDZ2 bike and let the tire sidewall scrape the chainstay. Just a small drag, but might be the final straw on a steep hill?

Could have a bearing fail in the motor. When the motor cools down and is able to run again, can you tell any difference riding w/o power? It shouldn't be really hard to ride w/o power.

Torque sensor problem. You don't get enough assist for the pedal pressure and the motor is only chugging along at 1/2 power. That will overheat. There is a VLDC5 diagnostic to read the torque sensors. I think he is wrong on interpreting the results though,

 

[PCeBiker]

An extra 5 amps will help with torque. Torque comes from amps.

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[spokewrench]

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This will be another live video presentation from Justin Lemire-Elmore that will focus on everything about motor efficiency and system efficiency as it appli...

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I say again. Torque comes from amps. The strength of a magnetic field depends on the amps and determines torque.
I see he uses a 6% hill as a mathematical example. They're fun with the motor off.

 

[Sasquatch260]

You guys are great. I plan to dig into this tomorrow when I have more time. I will update after. Thanks.

 

[Sasquatch260]

I had a little bit of time this evening too look into this. I have a C3 display which allows me to read voltage. My voltage at the start is 50.8 V, but when I try to pedal it goes to 48.5 V or so.

The big problem now is that it has barely any power - even from the start. I can still feel the motor trying to help. I can still hear the normal familiar whine of the motor (although not as loud). I think I can still feel the torque sensor is working to a degree (slightly more as I pedal harder). But the overall power is barely helping. It’s almost nonexistent.

I wonder, is there a way to check the amperage on the battery itself? I wish I knew whether the problem was in the battery or the motor.

 

[spokewrench]

I was thinking of putting one of these on my bike.

Amazon.com

I would expect a 2.3 battery volt drop at 15 or 20 amps, depending on how your battery pack is made. If you're not getting much power, I imagine there's a short in the motor.

I wonder if youtube has a video on how to check your motor with a multimeter.

I don't have a motor like yours, but if it's supposed to turn freely by hand with the power off, and it doesn't, that could be the problem.

 

[Slaphappygamer]

My voltage at the start is 50.8 V, but when I try to pedal it goes to 48.5 V or so.

This is normal. Thanks for checking.

You can get your volt-ohm meter and check the phase wires. I’d first set one lead to the motor housing and (in no particular order) check Blue, Yellow, and Green. You should not have a short between a phase wire and the motor housing. You can also test the hall sensors by checking resistance. There are YouTube’s on that. I don’t have much experience in testing them.

 

[Sasquatch260]

This is normal. Thanks for checking.

Would this being normal cause you to lean more towards the problem being in the motor than the battery?

 

[Slaphappygamer]

Yes. Check out this video. He talks pretty fast, but gives lots of detail on how to test your hall sensors. Only follow as you are comfortable.

 

[spokewrench]

It seems the motor. I'll bet @harryS could tell you how to check for overheated magnets and windings.

 

[EMGX]

I have a C3 display also. In my experience it isn't normal for the voltage to drop as you describe on a fully charged battery. The voltage on my display always understates the fully charged voltage, instead of 54v it will read similar to your 50.8v (I don't recall the number exactly but that sounds close) and the voltage reading doesn't drop until the actual battery voltage drops below that initial value - then it becomes accurate. When the display reaches the point of accuracy the displayed value will sag some on steep ascents, but until then the voltage reading drop doesn't show because the actual battery voltage is 4ish volts above the displayed number. If your voltage drops that rapidly on a fully charged battery then maybe the battery is bad or as mentioned before there is something causing extreme current draw like a mechanical issue or purely electrical as in the controller for example.