KT-LCD1 battery voltage setting

YonderGod · Apr 23, 2016

Can anyone decipher these poorly translated instructions?
I'm running a 12s(44.4v) battery, so the default setting for a 48v battery shows my battery as low all the time. And I'd prefer 42v lvc if possible.

From the manufacturers manual:

P5 is power monitoring mode, when P5 setting is 0, the power monitoring is the
"real-time voltage" mode. Namely, it is the method to determine the battery capacity
based on real-time battery voltage. When P5 equals to a specified parameter, the power
monitoring is the "smart power" mode (this parameter is determined by the battery
characteristics, ordinary 24V lithium is generally is 4-11, 36V lithium is between 5_15). P5
setting ranges from 0-40

http://www.szktdz.com/en/news_show.php?article_id=374

From BMSbattery website: (they label it the S-LCD1, but I think it's the same thing)

Note: How to determine the value of the parameter P5 ? The formula is LVC+P5/3.77.

For 24V battery, LVC=20V, P5/3.77=1.

For 36V battery, LVC=30V, P5/3.77=1.5.

For 48V battery, LVC=40V, P5/3.77=2.

You can adjust P5 parameter by your own battery discharge curve.

https://bmsbattery.com/ebike-kit/548-s-lcd1-e-bike-lcd-meter-ebike-kit.html

flangefrog · Apr 23, 2016

P5 is for temporal smoothing of the battery voltage.

https://endless-sphere.com/forums/viewtopic.php?f=2&t=62469#p933745
https://endless-sphere.com/forums/viewtopic.php?f=2&t=61562#p919668
https://endless-sphere.com/forums/viewtopic.php?f=3&t=46608&start=75#p811045

YonderGod · Apr 23, 2016

Oh, I see. So the LVC isn't changeable on the LCD1.
P5 was set to 15 for me, I changed it to 0 and it shows full battery now. I'll see if it's more accurate over time and try 10-15 if not.

I still don't understand what they're trying to say how to calculate it.

LVC+P5/3.77
40+P5/3.77
P5/3.77=-40
P5=-150

:?:

And then they say

"For 48V battery, LVC=40V, P5/3.77=2"
soooo
P5/3.77=2
P5=7.54? (round to 7 or 8 )
:?:

flangefrog · Apr 24, 2016

I think the correct equation is (LVC + P5)/3.77

YonderGod · Apr 25, 2016

That isn't an equation. It has to equal something, such as

(LVC + P5)/3.77=1

I don't understand why they are formating it like this, instead of just

P5=xxxxxx

Like if it was (LVC + P5)/3.77=1
then solve for P5 (if LVC is 40)
40+P5=3.77
P5=-36.23

If it was (LVC + P5)/3.77=0
(multiply both sides by 3.77)
LVC+P5=0
P5=-LVC

:roll:

The only thing I can think of that sort of makes sense if if you take where they say
"LVC+P5/3.77"
and
"For 48V battery, LVC=40V, P5/3.77=2"

replace "P5/3.77" with "2" in their "formula"

and you get
LVC+2
40+2
42

jorgedsan · Dec 14, 2016

The formula is useless
At 3.85V the capacity of a li-ion cell is about 50% (source http://www.powerstream.com/lithium-ion-charge-voltage.htm)

3.85V*13=50.05V

How I figure out my P5 setting.

After some trial and error i´ve found that the value of P5 for a 48v li-ion is around 23

I ride the bike until the battery voltage drop to 50V and set P5 for a reading 50% on display.
Continue discharging the battery to reach the lvc and check the lcd

Mumiyoo · Oct 14, 2017

Note: How to determine the value of the parameter P5 ? The formula is LVC+P5/3.77.
For 24V battery, LVC=20V, P5/3.77=1.
For 36V battery, LVC=30V, P5/3.77=1.5.
For 48V battery, LVC=40V, P5/3.77=2.
You can adjust P5 parameter by your own battery discharge curve.

i don't know where the inventer of this formula went to school.
but it look like chinese to me.
How to calculate this formula for a 72v battery ?

What is P5 stand for in this formula ?
72V,lvc=60v, P5 (that the :evil:

i try to figure out) / (= divided by) 3,77 = ???

LVC = 60v

btw, anybody running a qs205 v3 on a kentung 50+A controller ?

Buk___ · Oct 14, 2017

Mumiyoo said:
72V,lvc=60v, P5 (that the i try to figure out) / (= divided by) 3,77 = ???

For 24V battery, LVC=20V, P5/3.77=1. ie. p5 = ( BATV - LVC ) / 3.77 ... (24-20)/3.77 ~= 4/4 = 1
For 36V battery, LVC=30V, P5/3.77=1.5. P5 = (36-30) / 4 = 1.5
For 48V battery, LVC=40V, P5/3.77=2. P5 = (48-40) / 4 = 2

Bat = 72V
LVC = 60V
diff = 12V

P5 = 12 / 3.77 ~= 12 / 4 = 3.

motomech · Oct 14, 2017

Not sure but, I think the first time the display "sees" the pack Voltage, it needs to be high as possible. For fully charged 12S LiPoly, around 50 Volts. This gives the best chance that the values will be close to correct.

wturber · Oct 15, 2017

If the LCD1 is the same as the s-LCD5 and s-LCD3, then you change the low cut0ff value with a "C" setting. The setting "C value no. 12" to a setting of "0" drops the low voltage cuttoff by two volts - which is the maximum amount that it can be lowered from the LCD.

The range of values is 0 to 7 with 0 being -2v, 4 being default cutoff, and 7 being +1.5v

You'll need to check if s-LCD1 uses the same settings as the above two. I don't know if it does or does not.

Mumiyoo · Nov 13, 2017

Thank u guys, sorry for replying late. quite buzy building

docw009 · Nov 14, 2017

wturber said:
If the LCD1 is the same as the s-LCD5 and s-LCD3, then you change the low cut0ff value with a "C" setting.

A lot different. No voltage or watt readout. No LVC adjust. It only has five P settings, and P5 can only be entered as an integer. I dunno how one would enter 1.5.

The intent for it is to have the battery icon match what one expects for battery capacity. I believe a better method is to install a cheap wattmeter and watch the AH usage.

I have an LCD-1 on one bike and I run 36V or 48V on it. It seems to power up and apply a different LVC specific to the battery.

d8veh · Nov 15, 2017

P5 doesn't affect the running of the bike at all. You can make it any number you want. It's just for showing the segments on the battery display to stop it jumping up and down with voltage sag.

KT-LCD1 battery voltage setting

YonderGod

1 W

flangefrog

1 kW

YonderGod

1 W

flangefrog

1 kW

YonderGod

1 W

jorgedsan

1 µW

Mumiyoo

10 µW

Buk___

10 kW

motomech

10 MW

wturber

1 MW

Mumiyoo

10 µW

docw009

1 MW

d8veh

1 GW

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