Is my controller 'bad'? Severe loss of power at low SoC?

[bob2.0]

If your battery drops 7V during acceleration then it is either too cold or you have got a problem with your battery or the wiring or the circuit braker.

It isn't dropping 7V.

My machine follows a derating curve, and I say 'dangerous' because it just would not accelerate. I mean, I actually had to push the bike off from a standstill to get it moving.

I cannot say what your controller is doing, but mine is, and always has, derated as the voltage drops.

It's not clear to me if this is standard. When I mentioned it some time back, the only comment was that the voltage was dropping. That is very much not the case.

I've just adjusted those coefficients to see if I could set it back to 63V and get a good effect. Those numbers did change the derate profile. It was still a bit too weak with it set back to 63V, so I dropped the low volts to 60V (which shouldn't be too unsafe for the battery) and it feels OK now. I will think on it a bit more as to what I want from it.

I don't mind it derating in the last 20%. If I am running out of battery, making me ride more efficiently isn't a bad thing. It is only bad if I cannot accelerate faster than pushing it!

If you get no derating mid SoC then our controllers are working differently.

[bob2.0]

The capcoeff are for the battery SOH Meter and the upper one can also stop regen before your BMS needs to cut.

OK, that makes some sense because I was expecting one less bar.

But what I think is going on, then, I did notice the 'SoC' to the right of those boxes change. So, I think this tortoise mode and the derate is also based on the SoC it is calculating, so it does affect that in an indirect way.

I'll have to do a few more tests yet to figure all this out. I thought the bars on the screen were direct from the battery voltage, but I was not sure. Can they be set to 'actually show' 1 bar when you have only 1 bar, then?!

[dominik]

Have you ever monitored your battery voltage during driving?

Had this exactly that way on a 72450 a 72680 and my 721800.

Set low vol way to 2V and then you have exactly the settings I use and should see the same behaviour.

When my battery is cold and I have a bigger voltage drop during acceleration, I also have a power drop in mid SOC, but during acceleration the voltage drops to the low vol restore value.
When my battery is near 0C I have limited power even at 80% SOC.

In summer the resistance of the battery is lower and you can use full power to lower SOC levels.

[jeff-jordan]

...
I cannot see any issues, apart from the motor temp is reading zero, which I can't see why that would cause a restriction as the battery voltage drops.

There is no temperature sensor in our motor, so you can't read any motor temperatures.

Battery voltage is slightly under what I think it is, but by fractions of a volt.
...

You mentioned a (static) fraction of a volt… but what happens if a current of 120 A flows during acceleration? It would be helpful if you could monitor the battery voltage displayed by the control unit and the actual battery voltage while driving using a multimeter.

Anyway, it would be a good idea to check the contacts of the anderson connector and the terminals of the breaker.
By the way: do you still have your first breaker (120A) inside your thelmoco e-odin 2.0?

Furthermore: it might be that the battery really has a problem.

There may be a significant imbalance. Typical chargers are set to a voltage of 84.0 V and stop charging as soon as the current drops below a certain threshold (e.g., 1 or 2 amps). If the charger cuts off the power supply too quickly, the battery management system (BMS) may not be able to adequately balance all battery packs. The balancing current is usually very low (only a few hundred mA*), especially with inexpensive BMS.

To cure that, you might charge your battery a few cycles with a charger set to 84.2V without any current cut off. This could be done with one or two lab power supplies.

*) just checked the JBD-HP32S001-L8S-150A bms specs, the balancing current is just between 40 and 60 mA. So you need to give the bms a few days time to correct a severe imbalance.

[bob2.0]

You mentioned a (static) fraction of a volt… but what happens if a current of 120 A flows during acceleration? It would be helpful if you could monitor the battery voltage displayed by the control unit and the actual battery voltage while driving using a multimeter.

Anyway, it would be a good idea to check the contacts of the anderson connector

it might be that the battery really has a problem.

*) just checked the JBD-HP32S001-L8S-150A bms specs, the balancing current is just between 40 and 60 mA. So you need to give the bms a few days time to correct a severe imbalance.

I appreciate all the thoughts, but I'll clarify again that I set the low voltage point to 50V and there is no more any current/power restriction at all.

It is all and totally in software, because the restriction can be overcome simply by changing the setting.

I can now see that there is a 'SoC' built into the controller's processing. This is displayed. By adjusting the low voltage, and those two coefficients, I can manipulate the reported SoC.

When the reported SoC is over 70%, there is no restriction that I notice. Current output is scaled back as the reported SoC drops lower.

There is totally and absolutely a ramp-down curve built into my controller as the reported SoC reduces. I can overcome this by manipulating those numbers so the reported value remains high.

Please, may I ask this question; do we know, the community, what the cut off voltage is for 100Ah 2.0 batteries is?

The reason I ask is that I have run this to flat and it is the battery that trips first, so it seems a bit pointless to have 63V set as the low voltage when it never gets that low because of the battery settings.

If I can keep the software low voltage above the battery's low voltage setting then it will always remain 'safe', no matter how I tinker with the other settings. Might you know what that voltage is? It must be more than 63V, seeing as it was the battery that tripped first.

[dominik]

You can try by reducing your voltage settings step by step.

Check your battery voltage during acceleration and report back.
This will help finding your problem.

[bob2.0]

I like to know the cut out voltage for the battery.

I don't think there is a problem, it is just that I don't like the rapid derating in my controller (that others don't seem to have). So, I want to work around it.

Surely the low voltage point is wrong anyway, if the battery has shut down before the software stopped it?

[jeff-jordan]

I like to know the cut out voltage for the battery.
...

This depends on the type of battery you have.
My 100Ah / 56kg battery has a relatively high cut off voltage between 64 and 65 V, that's why I had to set the VolProtect value to 66V.
The 120Ah / 43kg battery seems to cut off at about 60V.

But it's not easy to define an over all cut off voltage, because the bms should monitor each cell pack, and as soon as one of the packs drops below it's own cut off voltage (usually set between 2.5 and 3.3V), the whole battery switches off. That's why a proper balanced battery delivers better results.
And if there is one weak cell pack in the whole chain of packs (20S), it severely affects the usability of the battery.

The lower the cut off voltage of the cell packs is chosen, the faster the battery degrades.
The higher it is set, the longer the battery lasts (obviously at the price of capacity/range, it's a trade off).

...
Surely the low voltage point is wrong anyway, if the battery has shut down before the software stopped it?

Yeah, and the silly thing is: if the battery (or a defective breaker) cuts off the power, you can't even activate the warning lights of the bike*. Which is damn dangerous if it happens at night.
*) that's why I'm currently tinkering with a small 12V ups that I like to add to the blinker circuit.

[bob2.0]

Thanks for the replies.

I cannot say if my controller is different to everyone else's, or if there is or is not a fault. But I mentioned this derating with voltage some time back, and no-one commented on having the same problem.

It seems I have been living with a 'neutered' bike for 2 years. I just accepted it as a weird, and negative, feature of the bike; lower than 60% SoC it became dangerously slow.

Anyway, this, below text, is what I have done to my bike, and it is now working so much better.

It is a different bike, and actually more useful now because I do not need to fully charge it for reasonable performance, which will help me manage cheap rate electricity.

Here is what I have done;-

All I have done is drop the 'lowvolprotect' to 58V.

The software does not allow me to adjust many other parameters. I cannot change the 'lovolway', it is stuck at 2V.

I can adjust the reported SoC, but doing this alone does not seem to affect the way it works. I cannot set a 'limitstartsoc' or pretty much any other parameters.

I do not think the battery will get down to 58V before the battery cuts out, but it is set there, just in case it does get that low, it should still just about be OK for the battery and not damage it.

So, that is all I have done, lowvolprotect to 58V (from 63V) and I will see how this goes. This totally changes how the mid SoC derate happens and I get good performance now at ~30% SoC when before it was already well into 'tortoise' mode and just crawling along. I have managed with it, I mean, great range! But those occasions on hills with a queue of cars behind has been stressful.

With the new found performance, I am now wondering if I might install another 40Ah or so into my top box. I mean, before, it'd just take too long to use up a whole battery charge! Now, perhaps I might go further, or, at least, faster!

[bob2.0]

Well ....... I was testing what the bike was like at low SoC, and ended up with the battery cutting out (again).

I turned up the power, and the screen just went blank.

It was still showing 4 bars and I was crawling in '1' after the first battery chop, to inch home. It cut a second time. So I did not risk a 3rd, and possibly damage the battery. I was only a mile from home, I walked it from there.

Same as the 'first time' I experienced the battery cutting out, I re-activated it once after a rest, but won't risk it after a second 'chop'.

I'm nursing the battery back to charge at 2A. Just so it has an easy time. Then I will charge it to full for a balance.

Whatever the 'lowvoltprotect' setting on the controller, I think it's the battery that is more sensitive. It was showing 68.5V when I commenced the charging. What would that drop to in 'speed 1'? I don't think 'speed 1' will pull much current?

I don't know what the battery cuts out at, but, on my pack at least, I don't think it's much less than 65~66V? Of course, it might be one weaker cell rather than total pack voltage.