Need help with Cycle Analyst/Phaserunner settings, dies on longer hill climbs.

I am running a Cycle Analyst, a Phaserunner and a Bafang G060.750 750w geared hub motor with a 13s8p 2.2ah lg cells 30amp bms.

I set the phaserunner up for 1500w, 30 amp max battery current and 80amps phase current.

The bike works swimmingly, big grins all around until I go up longer hills, short steep hills no problem, longer drag - no sir, the CA just goes blank until I reset the battery.

All connectors are from Grin - on checking everything its connected great. The phaserunner is mounted against my frame -

Running sensorless with just the phase wires connected, not monitoring the temp of the motor right now. The phaserunner is mounted against my frame.

Has anyone run into this with this combo and is there a way to get diagnostics out of the Cycle Analyst?

I'd try raising the LVC a little so that the controller can scale back enough to keep the battery BMS from tripping when the voltage sags.

Thank you could you explain a bit more - looking to understand, thank you so much for replying.

Are you saying when I hill climb I put demand on the battery - this causes a voltage sag in the pack and thus the pack needs to supply more than 30amps in order to maintain the power?

How does LVC work and where is it set, how does it prevent this?

Basically, if your CA is going blank, that's your battery failing at that point. The CA doesn't blank out until you drop below ~12v. So, it's likely that the problem is your battery's BMS cutting you off, for whatever reason.

One potential and likely reason for the BMS to cut you off is that, under a sustained heavy load such as your long hill climbs, the battery's voltage is sagging below the LVC that your BMS has set. And when you drop below the BMS' LVC, it shuts off.

Both the Phaserunner and the CA3 (you only have to set it in one or the other - I recommend setting it in the CA3) have a feature where you can set a soft LVC. So that if the battery drops below a certain voltage, the controller will reduce the current demand to keep the voltage in an acceptable range, instead of simply cutting you off like the BMS does. Typically, you'd set it up so that the LVC Start voltage (the point where it starts to reduce power) is a few volts above your BMS' LVC, and the LVC End voltage (the point at which you're cut off - no more power) is just a bit above the BMS' LVC. But there's plenty of room to adjust the settings to your own needs and desire.

With this setup, you would likely still feel a loss of power during those long hill climbs, but it wouldn't just up and die on you.

Thanks that makes sense.

I did a quick experiment halfing the settings to 750w and I was able to coast up the hill. So if I can set it back to 1500w and have the CA just throttle the demand down for me that sounds awesome.

Where do you set the soft LVC on the Cycle Analyst and what are relevant values to shoot for?

I see LoV Cutoff - which I assumed was used to stop me depleting the battery past a certain point. Essentially you have no battery left stop riding which I set to 42v.

I also see LoVGain which doesn't look well explained anywhere it has an aributrary value of 800.

If I dont want my 48v pack to sag so much things shut off when the CA is set for 1500w, which of these values do I need to change?

I misremembered exactly how the CA3 handles the LVC.

With the CA3, rather than having a rollback start voltage and a rollback end voltage (like the Phaserunner does), it instead simply has that one LVC voltage setting which you found.

However, rather than the CA3's LVC being a hard cutoff like the BMS, the CA3 will instead dynamically limit battery current to maintain at least the minimum value you set.

Here's the relevant exerpt from https://www.ebikes.ca/product-info/cycle-analyst-3.html#display-screens

[ Batt->Vlt Cutoff ]*
Low voltage rollback. When the CA detects the battery voltage falling below VltCutoff, it will gradually scale back the power draw to prevent the voltage from dropping lower. This protects lead acid batteries from sulfation, nickel batteries from cell reversals, and with BMS protected lithium batteries it can keep the battery above the BMS trip point to prevent the battery from abruptly shutting down.

Cutoff voltage per cell varies by chemistry and application; 2.9 to 3.2 V/cell is typical for lithium ion batteries although many users set a higher cutoff to limit how far they drain their pack. The table below shows VltCutoff range for common nominal pack voltages, and applies equally well to lithium, lead, and nickel batteries.

Click to expand...

If setting the CA3's LVC to 42v still results in the battery cutting you off, I'd recommend trying 43v to see if that helps. If 42v is already pretty close to the battery's LVC, the voltage might dip enough for the BMS to cut you off before the CA3 can compensate.

Regarding LoVGain: Increasing that number will cause the power to scale back more abruptly when the voltage falls below the number you set. I have no idea what sort of LoVGain settings would be appropriate if you decide to change it though.

Blacksword said:

Where do you set the soft LVC on the Cycle Analyst and what are relevant values to shoot for?

I see LoV Cutoff - which I assumed was used to stop me depleting the battery past a certain point. Essentially you have no battery left stop riding which I set to 42v.

Click to expand...

That's the setting. 6.3.4 of the manual says to set that value 1-2 volts higher than the battery BMS LVC. I don't mess with the gain setting since it seems to be rolling back the way I'd want.

The plot thickens - the actual battery low voltage cutoff is 36v - I didnt make this pack but checked with my buddy who did.

I've set the Cycle Analysts lvc to 42v and watching the display I can see im just about sagging into that at the point the CA shuts down, so I believe its not throttling things back as it should in that case.

Blacksword said:

The plot thickens - the actual battery low voltage cutoff is 36v - I didnt make this pack but checked with my buddy who did.

I've set the Cycle Analysts lvc to 42v and watching the display I can see im just about sagging into that at the point the CA shuts down, so I believe its not throttling things back as it should in that case.

Click to expand...

First, check the CA Shutdown Voltage setting under Misc Settings. It'll be 'Vshutdown' if you're programming via the CA3's display. If that's set to 42v or thereabout, set it to something way lower - lower than you'd ever see in normal use. 12v or thereabout is good. The CA3 can't regulate anything if it's being told to turn off before it gets the chance.

If your Vshutdown was already low and therefore not the issue, that means your battery's BMS is cutting you off at around that 42v mark. Now, if that's the case, it's worth noting here that the BMS isn't looking at overall pack voltage to determine when to LVC - it's looking at the voltages of the individual cell groups, and it'll LVC when any *one* cell group drops below the voltage setting. Which means that, if you're dealing with one or more weakened cell groups, you could have a pack voltage that looks fine externally, but is in fact the result of adding up several high cell groups and a few low cell groups. That's one possible reason why a BMS might cut you off at 42v pack voltage even though it's not nominally set for that.

Blacksword said:

The plot thickens - the actual battery low voltage cutoff is 36v - I didnt make this pack but checked with my buddy who did.

I've set the Cycle Analysts lvc to 42v and watching the display I can see im just about sagging into that at the point the CA shuts down, so I believe its not throttling things back as it should in that case.

Click to expand...

So the pack BMS is useless for LVC. I'd go a volt or two higher. 3.2V per cell (42V) is where the battery BMS should have been set to. I'd try 43-44V. If you're sagging to 36V, you're killing your pack.

Roger that NCC1941.

Here is what I found VShutdown was 11.0 Volts so non issue as suggested.

I set the CA and Phaserunner to deliver 1800w at 29amps to promote sag . I upped Vlt Cutoff to 45 volts and definitely saw the Cycle Analyst kicking in, it brought my power consumption way down and the bike took the hills no problem.

I think your spot on my Battery is cutting me off at ~42v all roads seem to point there. I just happened to have a coincidence where my battery conking out and my Vlt Cutoff were in the same region.

Thank you so much for your help this bit of experimenting made my day in learning a bit more about my Cycle Anaylst and also helped me practically experience voltage sag for the first time.

All in all I am very happy with my bike build, ill be dumbing things down to 750w to cruise around and save a few parts ill post it on the build forum. Big smiles all around. Thanks all