XP Display "Hack"

Solarman

New Member
One of the features of the XP that I'm not particularly happy with is the way the way the display allows monitoring distance (ODO), trip, voltage, or motor current, but only one at a time. I don't care about the odometer - in my rural area, roads are all in one-mile increments, so I usually know how far I've ridden more accurately than the grossly inaccurate odometer. I've settled on watching the current as I ride, which is the best indication of how much power you're drawing from the battery. But I'd also like to monitor the battery voltage at the same time, as watching the voltage sag as you draw more current is a good indication of remaining charge in the battery.

Watching the voltage for a couple rides I noticed that the "Energy Bar" at the top of the display precisely follows the voltage reading at the bottom (when set to monitor voltage). Today I rode with a partially-charged battery (trying to get it down to "storage voltage" for the winter) and found that it may be able to be "calibrated" to read volts rather than just showing a percentage-of-scale. Half-scale appears to be around 47 volts, where a fully-charged battery showing full scale is around 51. "No bars" would probably correspond to the low-voltage cut-off, either 40 or 41.5 volts (if you have an older XP that you can change that setting). So it appears the "Energy Bar" is simply a graphic voltmeter reading between 40 and 51 volts using a bar graph.

My "hack" is going to be to (temporarily) power the bike with a variable bench power supply (instead of the battery), and annotate the exact voltage required to illuminate each of the bars on the Energy Bar graph. With this "crib sheet" I'll then know the battery voltage based on the number of bars showing and thus be able to achieve my goal of simultaneously watching voltage and current.

I'll post the results for anyone who'd also like to "calibrate" their Energy Bar...

Bud
 

Solarman

New Member
OK, guys & gals, here's the results of my Energy Bar "calibration". After dragging my XP down to my basement ham shack, removing the battery and connecting the bike to a Fluke 301E precision power supply, and varying the voltage while monitoring the voltage display on the XP and a redundant Fluke DVM (which surprisingly verified that the XP's voltage display is quite accurate!), I recorded the following voltages that lit up the corresponding Energy bars:

Bar # (left to right, low to high energy)

1 - Low voltage cutoff to 43.9 volts
2 - 44.0 v
3 - 45.0 v
4 - 46.0 v
5 - 46.5 v
6 - 47.0 v
7 - 47.5 v
8 - 48.0 v
9 - 48.5 v
10 - 49.0 v

While the scale isn't linear, it'll probably better track the battery's discharge curve since the voltage falls off more rapidly towards the end of a charge. Notice that a fully-charged battery is usually about 51+ volts, so you can expect to use quite a bit of energy before seeing the 10th bar disappear - when it does you've already dropped a couple volts. From that point you'll drop a half volt for each bar that extinguishes down to bar #4, then a full volt down to bar #1. And also somewhat surprisingly, bar #1 never extinguishes - the low voltage cutoff starts flashing its warning while it is still lit. This could be somewhat deceiving, as I'd expect with one bar remaining that there would be a bit of energy left in the battery. (Sort of like your car running out of gas while the gas gauge still shows some remaining in the tank.) But not true; you'll run out of juice with that #1 bar still illuminated.

I'm going to see if I can print a clear overlay with these voltages to line up with the respective bar on the display, or at least have the "cheat sheet" clipped close to the display where I can see it.

Btw, the Fluke 301E power supply is variable in hundredths of a volt, and the break point between bars was falling precisely on full or half volt points (.00 or .50) so I'm guessing that the display circuitry in the XP is digitally programmed rather than analog, meaning that barring production changes, all XP's Energy Bars should work the same.

Now I've got to drag the XP up the basement stairs, through the kitchen and laundry and back into the garage...

FWIW. Happy New Year, all!

Bud
 
OK, guys & gals, here's the results of my Energy Bar "calibration". After dragging my XP down to my basement ham shack, removing the battery and connecting the bike to a Fluke 301E precision power supply, and varying the voltage while monitoring the voltage display on the XP and a redundant Fluke DVM (which surprisingly verified that the XP's voltage display is quite accurate!), I recorded the following voltages that lit up the corresponding Energy bars:

Bar # (left to right, low to high energy)

1 - Low voltage cutoff to 43.9 volts
2 - 44.0 v
3 - 45.0 v
4 - 46.0 v
5 - 46.5 v
6 - 47.0 v
7 - 47.5 v
8 - 48.0 v
9 - 48.5 v
10 - 49.0 v

While the scale isn't linear, it'll probably better track the battery's discharge curve since the voltage falls off more rapidly towards the end of a charge. Notice that a fully-charged battery is usually about 51+ volts, so you can expect to use quite a bit of energy before seeing the 10th bar disappear - when it does you've already dropped a couple volts. From that point you'll drop a half volt for each bar that extinguishes down to bar #4, then a full volt down to bar #1. And also somewhat surprisingly, bar #1 never extinguishes - the low voltage cutoff starts flashing its warning while it is still lit. This could be somewhat deceiving, as I'd expect with one bar remaining that there would be a bit of energy left in the battery. (Sort of like your car running out of gas while the gas gauge still shows some remaining in the tank.) But not true; you'll run out of juice with that #1 bar still illuminated.

I'm going to see if I can print a clear overlay with these voltages to line up with the respective bar on the display, or at least have the "cheat sheet" clipped close to the display where I can see it.

Btw, the Fluke 301E power supply is variable in hundredths of a volt, and the break point between bars was falling precisely on full or half volt points (.00 or .50) so I'm guessing that the display circuitry in the XP is digitally programmed rather than analog, meaning that barring production changes, all XP's Energy Bars should work the same.

Now I've got to drag the XP up the basement stairs, through the kitchen and laundry and back into the garage...

FWIW. Happy New Year, all!

Bud
Wow! Great job on your analysis of your findings. Thanks for taking the time and effort to report what you found. Those readings will come in handy. It is great to know about the voltage reading at the last (#1 bar) on the display. I'm thinking that the battery should be charged after the #2 bar has extinguished. You definitely had great equipment to retrieve the voltage readings.

Happy New Year to you and all!
 

GeorgeXP

New Member
And here's what it looks like scotch-taped to the XP display screen above the Energy Bar...
Well Done!!

Here's the Volt/Cell and SOC breakdown for your numbers:
The v/cell is of course the Pack Voltage / 13
The SOC is based on 4.2v/cell Full Charge = 100%, 3.0v/cell End of Charge = 0%

1 - 43.9v 3.38 v/cell 31.41%
2 - 44.0v 3.38 v/cell 32.05%
3 - 45.0v 3.46 v/cell 38.46%
4 - 46.0v 3.54 v/cell 44.87%
5 - 46.5v 3.58 v/cell 48.08%
6 - 47.0v 3.62 v/cell 51.28%
7 - 47.5v 3.65 v/cell 54.49%
8 - 48.0v 3.69 v/cell 57.69%
9 - 48.5v 3.73 v/cell 60.90%
10 - 49.0v 3.77 v/cell 64.10%

Happy New Year to all as well
George
 

GeorgeXP

New Member
bar #1 never extinguishes - the low voltage cutoff starts flashing its warning while it is still lit. This could be somewhat deceiving, as I'd expect with one bar remaining that there would be a bit of energy left in the battery.
Is the point where the Low Voltage Cutoff starts flashing the same point where the controller cuts power to the motor control system? I agree with you, I'd think at 43.9v there should be "some remaining in the tank".

George
 

Solarman

New Member
I expect the two points are the same - I haven't actually run a battery down that far, and my benchtop power supply won't provide enough current to actually run the motor so I wasn't able to test that yet.

The display isn't linear - obviously - so there's a range of voltages associated with each of the 10 bars. I suspect Lectric attempted to "even out" the non-linearity of the "remaining energy vs. battery voltage" in their design. When bar #2 extinguishes and only #1 is lit, you DO have some remaining energy. But as you use it up, LVC will occur when the voltage declines to 40 or 41.5 (depending on which LVC level your bike is programmed for). You just won't know when that last bit of juice is gone, because bar #1 stays lit.

Personally, I'd program bar #1 to go off at about 42.5v - so you'd have a bit of warning that LVC is about to occur.

George, I like your "percentage of energy remaining" numbers better than my discrete voltages, even though the lack of discharge linearity makes them somewhat inaccurate. Sorta like a car's gas gauge...still, when MOST cars' gauges are on "E" there is still some gas in the tank. Excellent potential for a future upgrade, Lectric!

Bar #1 illuminates from LVC to 43.99999999 volts, (with #2 coming on at 44.0) and the LVC flashing E006 or something like that - which I believe is simultaneous with the cutoff of power to the motor - happens while bar #1 is still illuminated. DECEIVING, in my opinion. I agree with you - it should extinguish BEFORE LVC happens... Oh, well... Lectric, are you listening???

I have a spare battery now, so I may run one down to LVC while riding and see if the motor cuts off at the same time as the display starts flashing E006... once I get a carrier for the spare battery cobbled up - as they're too big and heavy to carry in a pocket! ;-) Maybe I'll bungee it to the luggage rack with some suitable padding... I'll report what I find.
 

Kimbo

Active Member
Since I only get around 30kms per battery charge now I almost always end up coming home on a dead battery that shows 1 bar and under no assist but I have never seen an E006 code on mine, maybe because I have an older model?
 

Solarman

New Member
Kimbo, it could be that the undervoltage error (E006) actually occurs AFTER the controller cuts off power to the motor...instead of my assumption that they occur simultaneously (remember how to spell "assume").

George asked about that and I haven't tested my assumption yet. Might just be the difference between older and newer model XPs - mine's only a couple weeks old.

Thanks for the input!

Bud
 

GeorgeXP

New Member
I haven't actually run a battery down that far, and my benchtop power supply won't provide enough current to actually run the motor so I wasn't able to test that yet.
I wonder if the F/R lights die when the motor gets shut down. If they did then that would be a way of getting the voltage level (from your supply) without running the motor.

Sorry I don't have anything on this end that can help much. All of my "Tools" are aimed at 13.8v (Hamop also) and the ZKE Load Tester I use is rated at 19.5V 5A 30W so I am a long way from what our XP uses. I did look back at some of ZKE graphs I made of my 10.8v 3s2P Li-ion 18650 pack and 3.38v/cell is ahead of the fast EOC drop off curve, but not by much. Might be that the heat loss in the motor grows rapidly below that so the powers to be decided to error on the safe side. Might be, when the Low Voltage Cutoff flashes it's time to get off and fire up the Walk mode?

I'm snow-bound up here in Minnesota so it will be a while before I can get it on the road (unless I can find a set of chains for this beast).

George
 
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Kimbo

Active Member
I haven't been able to ride my XP in the snow yet due to a really warm winter but my other e-bikes have been a blast in the snow. Here is a video of how someone made their own snow chains.

 

GeorgeXP

New Member
I haven't been able to ride my XP in the snow yet due to a really warm winter but my other e-bikes have been a blast in the snow. Here is a video of how someone made their own snow chains.
Wow... One of these chains on the rear, a ski mounted on the front, we could go out and chase rabbits :)

George
 

GeorgeXP

New Member
Bar #1 illuminates from LVC to 43.99999999 volts
I ran my battery through a discharge cycle yesterday. With no load on the battery it was at 54.21V (97.5%). I started the discharge using a “near” 1.9A constant current load and taking measurement every half hour. The measurement at 4:30 discharge time was 43.78V (a little lower than your 43.99v) at 1.96A load. I continued to monitor the discharge down to 39V (0.00%) at 1.85A where I stopped the discharge at 5:03. So part of the How much is left in the Tank question would depend on at what voltage the motor is shut off or in the case of my numbers if it was 43.78V for example, how far would using throttle only drawing ~1.9amps for 33 minutes get you? I’m assuming that it would be able to run on throttle only at some speed.

George
 

Solarman

New Member
George, having the F/R lights shut off simultaneously with the motor at LVC would be extremely poor design on Lectric's part! I'd be one thing to lose your motor on a night ride, but losing your lights would be a big safety issue. I sure HOPE that's not the way they designed the circuitry on the XP!

Interesting results on your discharge test - shows the battery is really pretty close to the rated 10AH. But with the LVC programmed to 40v you should never see 39v... unless the motor (only) cuts off at 40 and if you have the lights on the voltage may slowly decline to 39.

Looks like I need to do some night riding (staying close to home) with nearly-discharged batteries and see what actually happens at that point...

Bud
 

GeorgeXP

New Member
George, having the F/R lights shut off simultaneously with the motor at LVC would be extremely poor design on Lectric's part!
Yup, I didn't spend much time on thinking that suggestion through. After I posted it I realized it most likely would have to be independent of the motor controller. Type first think later :-(
But with the LVC programmed to 40v you should never see 39v... unless the motor (only) cuts off at 40
On the discharge I posted about above, battery was at 40.83v 11.73% drawing 1.89 amps 77.17 watts and 3 minutes later at 1.85a/72.15w it was down to 39.00v when I stopped the discharge. So with the P15 set at 40 (motor cutout?) there is not much of a usable loss between 40v and 39v.

On a side note. 15 minutes after I stopped the discharge, the battery rebounded to 42.44v 22.05% no load and 2 hrs later it was at 42.91v 25.06% so there may a few minutes left in the tank at that time for maybe the Walk mode but doesn't appear to be much.

George
 

Solarman

New Member
And now I can confirm that the motor cutoff by the electronic speed control (ESC) is independent of the head- and tail-lights. I rode my XP around until the motor cutoff occurred (several times) and the headlight remained on each time.

However, motor cutoff isn't a single event - it happens each time the voltage sags below the cutoff point, and as George pointed out, removing the load from the battery allows the voltage to rebound above the cutoff point, meaning the motor will start again.

At that low voltage, however, the maximum current that is provided to the motor is only an amp or two. Full throttle barely moves the bike. All pedal assist modes behave like PAS1. Normal pedaling on a level surface got me around 4-5 MPH. And as the resting voltage stabilized at around the 41 volt point, any significant motor load would quickly pull it below 40, cutting off the motor -- yet leaving the lights on with no discernible dimming.

The display flashed E 006 briefly before resetting (nearly instantaneously - if you blinked, you missed it!) If you were monitoring voltage or current, you'd notice you were back to the default ODO when the display reset.

I was going to see how long the lights would last with no motor load, but just letting the bike sit with the display and lights on times out and shuts things down. I suspect that if you were riding with PAS turned off, the CPU would detect activity (by the pedal crank rotation) and not time out.

Lesson learned from this experiment: Don't count on getting much power from the motor when there are only 1 or 2 energy bars remaining... but don't worry about your headlight going off when the motor cuts off.

Bud
 

GeorgeXP

New Member
pretty slick getting the information you require the old school way !
In my case the load tests were done using 300w incandescent bulb in parallel with a 3-Way 50/70/100w bulb to allow me to keep near to a 2amp load as the voltage dropped. I have a G.T.Power Power Analyzer but it's not very accurate so for the math based numbers I used a Fluke 77 as the amp meter and a Fluke 177 as the voltmeter. I did log the G.T.Power numbers as well but mainly as for overall health reference; 9.013aH/423.3wH on Full battery Discharge to 39v (0.00%) and 9.756aH/477.9wH on Full Charge 24 hours later.

Lesson learned from this experiment: Don't count on getting much power from the motor when there are only 1 or 2 energy bars remaining... but don't worry about your headlight going off when the motor cuts off.
Thanks Solarman for the numbers you came up with. Glad to hear that the LVC is 40v mark, sounds like a good place to have it at to keep the battery happy and still get good usability. I'm going to have fun with this new toy, but It's going to be a while till the snow clears.

George