KT LCD3 - Settings for a 60v motor, 60v battery?

[Mashed Potato]

Hello!

Specs:
KT LCD3
60v 18AH battery that charges up with a 72v (manufacturer supplied) charger
P5: 12
C12: 4

Hopefully someone can shed some light for me as I'm a tad confused about a few things.

1. What sort of minimum and maximum voltage should this battery see, is 72v safe for a 60v battery? At 58v pedal assist still works fine, but the bike dips with high-throttle, however I did have some difficulty getting it to charge yesterday from 58v. For a 60v motor what LVC (low-voltage cutoff) should I expect?

2. How do I get the KT LCD3 to read this battery accurately? I can't see much online stating they can even be used beyond 48v but this bike works, so it.. must, right? My battery indicatory on the display is totally useless currently.

3. How do I calculate P5 and C12 settings for a 60v/72v battery? Current values are above.

4. I've seen people mentioning seeing the live voltage displayed, but not sure how that is done, that would be super handy to know.

Thanks for your help, I'm wary of doing damage to the battery by running it too low and not sure if the bike will cut it off given it's probably looking for a 48v battery and not this one.

 

[amberwolf]

60v 18AH battery that charges up with a 72v (manufacturer supplied) charger

A caution:

A "60v" battery, assuming non-lifepo4, would usually be the average voltage at 3.6 or 3.7v/cell, probably a 16s battery, and so a full charge (assuming 4.2v/cell) would be about 70v. If you know

A 72v charger (assuming actual 72v output) could overcharge it if there is ever a BMS problem. If it's a charger meant for a 72v battery, then it is actually closer to 84v output, and could destroy the battery if the BMS failed to turn off the charge port for any reason.

You may want to verify exactly what the battery is, and exactly what the charger is, to reduce the likelihood of future problems.

1. What sort of minimum and maximum voltage should this battery see, is 72v safe for a 60v battery? At 58v pedal assist still works fine, but the bike dips with high-throttle, however I did have some difficulty getting it to charge yesterday from 58v. For a 60v motor what LVC (low-voltage cutoff) should I expect?

The motor voltage doesn't matter to LVC. The motor voltage rating is only how much voltage it takes to spin it at a certain speed (if they don't state what that speed is, then it's not really a useful rating at all).

For controller's LVC, you'll need to know the details of the battery itself--what is it's actual LVC and HVC, or what chemistry is it and how many series cells? Knowing what the battery LVC is, you can then set the controler's above that so it's not pushing the battery "to dead" every time.

If the controller's LVC is 72v, it can't be a 60v battery, or else it would never operate the motor (the battery should never even reach 72v). So I don't understand what the "is 72v safe for a 60v battery" means; you'll need to explain this.

What specific problem did you have recharging the battery? exact details may help us help you figure out the problem and what you need to repair or replace.

Does "the bike dips with high throttle" mean that the voltage drops with high throttle, or does the system shutdown (motor stop responding) with high throttle, or something else?

In either of those cases, it probably means the battery is not capable of running the bike, and you need a better battery to be able to do the job you are doing with the bike. If the controller has a programmable current limit, you can lower that until the problem doesn't happen, but the bike won't be able to do as much, pull as hard, etc.

 

[E-HP]

2. How do I get the KT LCD3 to read this battery accurately? I can't see much online stating they can even be used beyond 48v but this bike works, so it.. must, right? My battery indicatory on the display is totally useless currently.

I reads accurately; just set the display to show the actual voltage. If you're talking about the goofy battery bar display, then no, it will only work with lithium ion packs, with the common voltages (24V, 36V, 48V), after the controller autodetects the voltage of the pack.

4. I've seen people mentioning seeing the live voltage displayed, but not sure how that is done, that would be super handy to know.

P5=0 displays the real time voltage in the lower middle of the screen (where ODO, DST, and VOL display).

 

[Mashed Potato]

A caution:

A "60v" battery, assuming non-lifepo4, would usually be the average voltage at 3.6 or 3.7v/cell, probably a 16s battery, and so a full charge (assuming 4.2v/cell) would be about 70v. If you know

A 72v charger (assuming actual 72v output) could overcharge it if there is ever a BMS problem. If it's a charger meant for a 72v battery, then it is actually closer to 84v output, and could destroy the battery if the BMS failed to turn off the charge port for any reason.

You may want to verify exactly what the battery is, and exactly what the charger is, to reduce the likelihood of future problems.

First, thanks for your detailed reply! I assume the battery (with some quickmaffs) is a 16 or 17s, it does happily (assuming it has a BMS..) charge to 72.5v which is the max rated output of the charger, it just felt a bit high for a battery pack that states "60v" on the label. Short of taking it apart - mostly brittle plastic with self-tapping screws that may never bite into plastic again - it's hard for me to be certain of the cell configuration.

The motor voltage doesn't matter to LVC. The motor voltage rating is only how much voltage it takes to spin it at a certain speed (if they don't state what that speed is, then it's not really a useful rating at all).

For controller's LVC, you'll need to know the details of the battery itself--what is it's actual LVC and HVC, or what chemistry is it and how many series cells? Knowing what the battery LVC is, you can then set the controler's above that so it's not pushing the battery "to dead" every time.

If the controller's LVC is 72v, it can't be a 60v battery, or else it would never operate the motor (the battery should never even reach 72v). So I don't understand what the "is 72v safe for a 60v battery" means; you'll need to explain this.

Sorry, I may not have been particularly clear. In not knowing the exact makeup of the pack I'm having to make some assumptions so am just trying to get ballpark figures and see how I calculate the rough figures I'd expect to program into the KT LCD3 (and where they are programmed in, as manual doesn't give me much to go on). It being a 60v motor I wondered what the lowest (ballpark) voltage would be expected to run this when the battery is running low. I'm not sure if a 60v motor would run (slowly) on 50v or if something like 58-60v is the expected lower limit. My primary concern isn't being 100% accurate in the figures the controller is expecting, but more not having it be wildly wrong and damaging something.

What specific problem did you have recharging the battery? exact details may help us help you figure out the problem and what you need to repair or replace.

Does "the bike dips with high throttle" mean that the voltage drops with high throttle, or does the system shutdown (motor stop responding) with high throttle, or something else?

In either of those cases, it probably means the battery is not capable of running the bike, and you need a better battery to be able to do the job you are doing with the bike. If the controller has a programmable current limit, you can lower that until the problem doesn't happen, but the bike won't be able to do as much, pull as hard, etc.

When plugged in it just refused to charge, charger was outputting the usual 72v, battery was reading 58.0 and staying there, charging light was green which for this charger means it is in standby, not charging. The morning after, it charged fine, so I put it down to the weather as it was cold in the garage the night before.

When I say it dips I mean a sudden loss of power under heavy throttle i.e. up a hill, but pedal assisted cycling is completely fine, seems that a high draw with the battery relatively low around 58v causes a shutoff. Again, this is only after around 100km of riding, so the battery certainly can run the bike, I'm just trying to ascertain what a rough min and max safe voltage might be for a battery & motor stating 60v paired with a KT LCD3 so that I can program it close enough to ensure it's not thinking a low voltage cutoff of 40v is acceptable, for example, causing the battery pack problems.

I reads accurately; just set the display to show the actual voltage. If you're talking about the goofy battery bar display, then no, it will only work with lithium ion packs, with the common voltages (24V, 36V, 48V), after the controller autodetects the voltage of the pack.


P5=0 displays the real time voltage in the lower middle of the screen (where ODO, DST, and VOL display).

Thanks. Voltage will be super handy, I had expected it to replace the battery symbol as when P5 is set to 0 it just shows an empty battery meter 24/7, but if it's showing in another screen where the odo is that makes a lot of sense, and I will try that again, thanks. Shame the battery bar isn't reliable!

 

[E-HP]

Thanks. Voltage will be super handy, I had expected it to replace the battery symbol as when P5 is set to 0 it just shows an empty battery meter 24/7, but if it's showing in another screen where the odo is that makes a lot of sense, and I will try that again, thanks. Shame the battery bar isn't reliable!

I wouldn't say it's unreliable, but more like undefined. After getting more familiar with ebike, most users will make some decisions about how they want to manage their batteries, frequently opting to charge to 90%-95% of full charge, and discharging to around 20%-10% (or something short of fully discharged). This preserves the longevity of the battery and increase the number of charge cycles before the battery starts to significantly degrade. You could fully charge and then discharge until the pack is dead, and it could have a lot less range in a year, or charge and discharge so the battery doesn't experience the extremes, and it might be good for several years. You don't really know how the manufacturer "calibrated" the bars, but knowing the actual voltage puts you more in control of managing your battery with objective data.

 

[Cockrobin]

I wouldn't say it's unreliable, but more like undefined. After getting more familiar with ebike, most users will make some decisions about how they want to manage their batteries, frequently opting to charge to 90%-95% of full charge, and discharging to around 20%-10% (or something short of fully discharged). This preserves the longevity of the battery and increase the number of charge cycles before the battery starts to significantly degrade. You could fully charge and then discharge until the pack is dead, and it could have a lot less range in a year, or charge and discharge so the battery doesn't experience the extremes, and it might be good for several years. You don't really know how the manufacturer "calibrated" the bars, but knowing the actual voltage puts you more in control of managing your battery with objective data.

Note of caution here.
A lot of components, especially capacitors are rated at 63V, FETs at 60V. Controllers and displays are commodity products and you can bet that minimum allowable component specs apply. The KT series controllers and displays are rated for batteries up to 48V (around 54V fully charged). The electronic parts will stand some over voltage but reliability may be compromised.
I'm running a KT system with a 52V battery, so the system sees 58V at full charge. Even that I find a little edgy.
I have been told that motors will stand higher voltages without much trouble but I'm not sure exactly what "higher voltages" means in context.

 

[amberwolf]

Assuming a brushless outrunner, like a DD hubmotor typically is, a motor can tolerate as high a voltage as it's winding insulation can handle. That is probably at least a couple of hundred volts even for cheap stuff.

An inrunner can only tolerate as high a voltage as will create an RPM at full throttle that does not exceed the ability of the rotor to stay together (and keep it's magnets on if it has PMs), regardless of it's electrical characteristics.

A brushed motor can only tolerate as high a voltage as will create an RPM at full throttle that does not exceed the ability of the commutator to stay together, which is typically much lower than it's insulation rating. A series-wound brushed motor additionally cannot be run unloaded at much higher than it's design voltage or it may "run away", and grenade its commutator.