Watt Hours and Higher voltages.....confused....

[Tommy L]

Good day gentlemen!

I've been doing some tests with my new build. 9C 2810 with a 6fet 4110 72v/40amp shunt controller, 24S1P(76.8v nom) 38120HP/8ah Headway pack (red cells). Shouldn't this pack be flat at 640whrs?

My CA reports that I used over 700 whrs. and I still was showing a pack voltage of 79v (3.29v per cell) when I completed my ride.

Start:

3.34v per cell 80.2v total
I traveled 16km and the CA reports 45wh/km 16x45= 720whrs......correct?

Under load the pack never went below 76v (approx 3.2v per cell) right in the operating range

Is there a factor that has to be calculated when using higher voltages? I thought that watt hours are watt hours when we calculate amps x volts = Watts....
Therefore.....80v pack x 8 amp = 640watt hours @ 80% 512whrs to be safe.

I appreciated any and all input.
I'm heading out now to do more testing....
I'm totally confused.... but happy to ride!

[dogman]

Odometer calibriated wrong would be one explanation. 45wh/mi is pretty high, 45wh/km is crazy high. Something is out of whack, unless the whole 16k was up a 30% grade.

[Tommy L]

Odometer calibriated wrong would be one explanation. 45wh/mi is pretty high, 45wh/km is crazy high. Something is out of whack, unless the whole 16k was up a 30% grade.

Thank you for your kind response as always Dogman!

It was pretty well WOT all the way elevation changes through out the 16km. I was watching the CA at WOT down slight grade 52kph/1400 watts
and up grades as slow as 35kph at WOT 2800 watts. GPS confirmed that CA is off by only 1 kph.

I guess it's time to put the GoPro Hero 2 on and go for a ride! I'll post YouTube shortly..... Away I Go!


Tommy L sends...

[itchynackers]

Is your Rshunt value calibrated in the CA?

[Tommy L]

Is your Rshunt value calibrated in the CA?

That was going to be my next question
72v 25a controller.....shunt modified to 40amps. It's the only thing I could come up with, but the CA reports peaks of 40.03amps on my
rides.

I have a Direct plug CA..... So do I need to change something in the CA setup?

Thank you kindly....

Tommy L sends.....

Just got back from my ride.... CA reports:

8.5amp/hrs used
13km traveled
50 wh/km

On the previous run.... while charging I used a KiloWatt Meter and it used 0.5kwh to charge the pack. I'm guess that would be 500 wh then there is
"X" amount of loss for the chargers. If the chargers are 85% efficient, then I was using 400whrs on my previous run. This would make sense.
400 whrs / 16km would be 25 wh/km.

So the shunt info needs to be addressed. How? I would appreciate direction.

Tommy L sends....

[Tommy L]

Is your Rshunt value calibrated in the CA?

The voltage, speed and distance work. All the other features (amps, Ah, watt/hr) all show ridiculous numbers.

That's because you haven't calibrated the CA to your controller. The Crystallyte controller should have an rshunt value on a sticker on the back of it. To calibrate the CA follow the manual to go to the Advanced Settings Menu. In the menu there is a variable setting called "rshunt". This is where you need to enter that rshunt value from your controller. Once you enter that value your CA should be calibrated to your controller and should display amps, Ah... ect. properly.

ITCHYNAKCERS..... Thank you for the Rshunt WORD..... I search thru the Forum and found the above quote.

This is a great place!

Tommy L sends....

[Tommy L]

Odometer calibriated wrong would be one explanation. 45wh/mi is pretty high, 45wh/km is crazy high. Something is out of whack, unless the whole 16k was up a 30% grade.

The voltage, speed and distance work. All the other features (amps, Ah, watt/hr) all show ridiculous numbers.

That's because you haven't calibrated the CA to your controller. The Crystallyte controller should have an rshunt value on a sticker on the back of it. To calibrate the CA follow the manual to go to the Advanced Settings Menu. In the menu there is a variable setting called "rshunt". This is where you need to enter that rshunt value from your controller. Once you enter that value your CA should be calibrated to your controller and should display amps, Ah... ect. properly.

Thanks Dogman! I knew something wasn't right. I knew that 25w/hrs km would be a little more reasonable than 50.
I've never owned a CA before and didn't know that the info on the back of the controller needed to be inputted.
Tommy L sends...

[Tommy L]

I set RShunt value in CA. CA reports 15wh/km over same course. A little less wind today and I did pedal.
I used 200w/h over 15km. This now makes more sense.

Dogman..... 15wh/km probably sound a little more like it for the 2810 vise 50wh/km lol.

I have learned about the RShunt value in the CA. I hope this thread helps others.

Tommy L sends...

[cassschr1]

I thought the stand alone didn't need a value put in. Somebody chime in here.

[SamTexas]

I thought the stand alone didn't need a value put in. Somebody chime in here.

The shunt is never a part of the cycle analyst, so the value must be set for both stand alone and plug-in.

CA reports 15wh/km over same course. A little less wind today and I did pedal.

15wh/km could still be wrong, depending on your average speed, your terrain and how much assist you contributed. 15wh/km should result in a speed of around 35kph on flat terrain and no pedaling.

[Tommy L]

15wh/km could still be wrong, depending on your average speed, your terrain and how much assist you contributed. 15wh/km should result in a speed of around 35kph on flat terrain and no pedaling.

I was pedaling for most of the trip to get a work out WOT
CA REPORTS.......
Time: Approx 20min
Throttle: WOT
Watt hours used: 200
Average speed: 40kph

So if I understand the math correctly:
200 wh over 20min = 600 watt hours (200 wh x 3) to put this in hours since km are per hour
600wh / 40kph = 15wh/km

Put Killowatt meter on Battery Charger and it reports:
0.31 kw/h to charge pack...... 310 wh @ 85% = 263 wh (that is if the efficiency of my chargers are 85%)

so now using the killowatt meter:
263wh over 20min = 789 watt hours (263 wh x 3) to put this in hours since km are per hour
789wh / 40kph = 19.7wh/km

The same course with no pedaling and high winds WOT, the Killowattmeter used 0.5kwh to charge pack
425wh @ 85% loss (425 x3 = 1275wh)
/ average speed 36kph = 35 wh/km

With all this info I can safely judge my distance with out straining my pack.

[Tommy L]

I thought the stand alone didn't need a value put in. Somebody chime in here.

This is the DP model

[teklektik]

I thought the stand alone didn't need a value put in. Somebody chime in here.

The SA model comes preset for the matching external shunt sent with the unit. The Rshunt value is still needed by the CA - it was just entered by somebody else . Not a bad plan to read it from the Setup screen and jot it down somewhere...

[Tommy L]

With winds 18kph and gusting to 28kph I pedaled fairly steady.

Here are my stats at WOT:
20 wh/km
average speed 40kph
max speed 52kph
76.8v nom pack LiFePO4 38120HP 24s1p

What is great is understanding your whole Ebike build.
Pack vs controller vs Hub motor and how each one interacts with the other.

Pack: 76.8v 8ah
Controller: infineon based 72v 40amp shunt
Motor: 2810

What is interesting about this set up is that at quick take-offs, she will draw some large watts (2800 or so) but only for a short period.
As you pick up speed, she drops right off. Almost self regulating.... it's probably that KV thing that I've read so much about

So my pack draws around 4 to 5C (2400 to 3000 watts) for a short burst then at full speed 1 to 2.5C (600 to 1500 watts).

Now the HP cells I've tested 4.5C for 80% DOD and they hold their nominal voltage or just slightly under.
So I think that my pack is the minimum for a 40amp controller. If I go to a Lyen, I'd think that I would add a few cells to a 30s1p 96v nom
This would give me around 3800 watts max at 5C and maybe a few more kph with the higher voltage....KV thing again

But the important thing to note here...... ORANGE

Enter OHM numbers from the back of the controller into the CA DP under the advanced RShunt section