WbSr W/Sense Leads That Measure Battery V?

Started by Vic, June 01, 2015, 08:12:32 PM

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Westbranch

re the difference in actual at battery and What the Classic reads.... there are offsets that you can use to make the Classic send the correct Voltage to the bank...

See page 25  at the bottom here http://www.midnitesolar.com/pdfs/Classic-SL-REV-2056.pdf

hth

KID FW1811 560W >C&D 24V 900Ah AGM
CL150 29032 FW V.2126-NW2097-GP2133 175A E-Panel WBjr, 3Px4s 140W > 24V 900Ah AGM,
2 Cisco WRT54GL i/c DD-WRT Rtr, NetGr DS104Hub
Cotek ST1500 Inv  want a 24V  ROSIE Inverter
OmniCharge3024  Eu1/2/3000iGens
West Chilcotin 1680+W to come

Vic

Quote from: Westbranch on October 31, 2015, 08:09:35 PM
re the difference in actual at battery and What the Classic reads.... there are offsets that you can use to make the Classic send the correct Voltage to the bank...
See page 25  at the bottom here http://www.midnitesolar.com/pdfs/Classic-SL-REV-2056.pdf
hth

Yes,  this could help at a SINGLE given current.  BUT,  it is still all Ohm's Law,  and any of these voltage differences are the result of Resistance  (weather from resistance in cables,  breakers,  fuses,  terminals,  or that ever).  One CAN compensate for voltage drops across a given resistance.  However,  when the current changes,  the voltage drop changes,  and  offset the voltage would need to change,  as well.

So,  when there are varying loads on the system,  and the charge Acceptance of the battery decreases,  as the battery charges,   this FIXED offset is just like any other single-point value of correction/compensation,  it is only correct at a single current value,  NOT over a range of currents.

Kelvin Leads,  or sense leads will allow for accurate measurement of actual battery voltage,  and therefore allow correct readings for a huge range in currents.

FWIW,   Vic
Off Grid - Sys 1: 2ea SW+ 5548, Surrette 4KS25 1280 AH, 5.25 KW PV, Classic 150,WB, Beta Barcelona, Beta KID
Sys 2: SW+ 5548s, 4KS25s, 5.88 KW PV, 2 ea. Classic 150, WB, HB CC-needs remote Monitoring/Control, site=remote.
 MN Bkrs/Bxs/Combiners. Thanks MN for Great Products/Svc/Support&This Forum!!

Resthome

Quote from: Vic on October 31, 2015, 10:01:02 PM
Quote from: Westbranch on October 31, 2015, 08:09:35 PM
re the difference in actual at battery and What the Classic reads.... there are offsets that you can use to make the Classic send the correct Voltage to the bank...
See page 25  at the bottom here http://www.midnitesolar.com/pdfs/Classic-SL-REV-2056.pdf
hth

Yes,  this could help at a SINGLE given current.  BUT,  it is still all Ohm's Law,  and any of these voltage differences are the result of Resistance  (weather from resistance in cables,  breakers,  fuses,  terminals,  or that ever).  One CAN compensate for voltage drops across a given resistance.  However,  when the current changes,  the voltage drop changes,  and  offset the voltage would need to change,  as well.

So,  when there are varying loads on the system,  and the charge Acceptance of the battery decreases,  as the battery charges,   this FIXED offset is just like any other single-point value of correction/compensation,  it is only correct at a single current value,  NOT over a range of currents.

Kelvin Leads,  or sense leads will allow for accurate measurement of actual battery voltage,  and therefore allow correct readings for a huge range in currents.

FWIW,   Vic

+1. Exactly Vic
John

10 x Kyocera KC140, Classic 150 w/WBJr, Link10 Battery Monitor, 850 AH @ 12v Solar One 2v cells, Xantrex PROwatt SW2000
Off Grid on Houseboat Lake Don Pedro, CA

Westbranch

OK, here is the part I focused on

at the moment the system is 66% soc, whizzbang shows 41.6a.  battery midnite says 13.8v.
the actual voltages at the battery is 13.469v, the midnite 13.763.
so when the midnite battery hits 13.9v it hits absorption and starts reducing charging the battery. (actually 14.1v. for some reason when you program absorption 14v, the actual absorption kicks in earlier and then goes up to 14.1v


I may have misinterpreted as I read it as meaning
whizzbang shows 41.6a. (Add:) going to the batteryAdd: and the midnite says 13.8v. 
the actual voltages at the battery is 13.469v, the midnite 13.763. so when the midnite battery hits 13.9v it hits absorption and starts reducing charging the battery. (actually 14.1v. for some reason when you program absorption 14v, the actual absorption kicks in earlier and then goes up to 14.1v


I agree that there is a (bit of a) Battery V delta to get to 13.9V from 13.763V but the Classic can not adjust  by .137V, or can it? { or is the difference at the margin ( 13.763 - 13.469V=) .294V? I am unsure...}
So the adjustment would be .1V,  and that should make the
actually 14.1v. for some reason when you program absorption 14v, more accurate would it not,  assuming that the Amperage would be very slightly changed as the V has only risen by .1V to .2V...

PS , I am thinking this .1V difference also may be due to a cool battery...?
KID FW1811 560W >C&D 24V 900Ah AGM
CL150 29032 FW V.2126-NW2097-GP2133 175A E-Panel WBjr, 3Px4s 140W > 24V 900Ah AGM,
2 Cisco WRT54GL i/c DD-WRT Rtr, NetGr DS104Hub
Cotek ST1500 Inv  want a 24V  ROSIE Inverter
OmniCharge3024  Eu1/2/3000iGens
West Chilcotin 1680+W to come

SolarMusher

Quote from: Vic on October 31, 2015, 10:01:02 PM
Quote from: Westbranch on October 31, 2015, 08:09:35 PM
re the difference in actual at battery and What the Classic reads.... there are offsets that you can use to make the Classic send the correct Voltage to the bank...
See page 25  at the bottom here http://www.midnitesolar.com/pdfs/Classic-SL-REV-2056.pdf
hth

Yes,  this could help at a SINGLE given current.  BUT,  it is still all Ohm's Law,  and any of these voltage differences are the result of Resistance  (weather from resistance in cables,  breakers,  fuses,  terminals,  or that ever).  One CAN compensate for voltage drops across a given resistance.  However,  when the current changes,  the voltage drop changes,  and  offset the voltage would need to change,  as well.

So,  when there are varying loads on the system,  and the charge Acceptance of the battery decreases,  as the battery charges,   this FIXED offset is just like any other single-point value of correction/compensation,  it is only correct at a single current value,  NOT over a range of currents.

Kelvin Leads,  or sense leads will allow for accurate measurement of actual battery voltage,  and therefore allow correct readings for a huge range in currents.

FWIW,   Vic
+20.000 Vic !
Off Grid with 4kw PV | 2x Classic 200/WBjr | 2x Outback VFX3648 Epanel | 3x SPD300 + 1x Schneider HEPD80 | Hub + Mate + PSX-240 | Volthium 400Ah/51.2V LFP battery bank + Trimetric | 1500 watts AC water heater | Kubota 11kw GL diesel generator

australsolarier

westbranch
i am having a lifepo4 battery. (so no cool battery, the temp outside here rarely goes down to 0 degree celsius).  temp compensation is disabled. "sensor not installed".  the outside temp so about 20 celsius.
absorption is programmed to 14.0 volts. however the midnite goes into absorption at 13.9v. and only drops out of absorption when it drops down to 13.7v. and goes up to 14.1v. float is programmed 13.4 volts, but the midnite floats 13.5v. however at the battery terminal sort of average 13.45volt. depending on the usage, that varies, again because of the losses through the cable from the midnite to the positive busbar via breaker.
unless i overlooked some programming feature .....

so what is happening at the battery terminal is sort of acceptable. but not 100%.


i am having a second midnite classic 150 installed and it is doing the same. 0.1v over the programming.
it is not a big problem, however it would be nice if the midnite follows programming and has less of a mind of his own.

Resthome

Quote from: australsolarier on November 12, 2015, 05:10:47 PM
westbranch
i am having a lifepo4 battery. (so no cool battery, the temp outside here rarely goes down to 0 degree celsius).  temp compensation is disabled. "sensor not installed".  the outside temp so about 20 celsius.
absorption is programmed to 14.0 volts. however the midnite goes into absorption at 13.9v. and only drops out of absorption when it drops down to 13.7v. and goes up to 14.1v. float is programmed 13.4 volts, but the midnite floats 13.5v. however at the battery terminal sort of average 13.45volt. depending on the usage, that varies, again because of the losses through the cable from the midnite to the positive busbar via breaker.
unless i overlooked some programming feature .....

so what is happening at the battery terminal is sort of acceptable. but not 100%.


i am having a second midnite classic 150 installed and it is doing the same. 0.1v over the programming.
it is not a big problem, however it would be nice if the midnite follows programming and has less of a mind of his own.

I have seen the same 0.1 V difference from programmed values on my Classic. Some of which maybe just how the Classic is rounding, don't really know the cause, but we all agree voltage sense wires added to the WBjr would be a great addition to the product. The voltage offset is great for calibration but does not take care of voltage drops.
John

10 x Kyocera KC140, Classic 150 w/WBJr, Link10 Battery Monitor, 850 AH @ 12v Solar One 2v cells, Xantrex PROwatt SW2000
Off Grid on Houseboat Lake Don Pedro, CA

CDN-VT

Canadian Solar 350W 37.6 VOC  30.6 VMP 8.22 ISC 7.87 IMP ,-15 c +30c max  4 strings in 2 in Series for 24v Classic 150 -1020 Ah  Freezers & fridges ~~~ Second Array same panels of 3sx3 parallel for 24 V Classic 150 -440 Ah Outback Barns & out blds.
48Vdc almost done,11Strings up of 3s11P same panels

Cniemand

OFF-GRID @ 8500FT : 2000w Array : 8 - CS6P-250P ; VFX 3648 ; WBjr ; MN CL200 #6738 ; FW #2079  
48v LiFePo4 : 16 - CALB CA 100 aH in Series - 5 kWh ; No Active BMS - Bottom Balanced
Charging Parameters : Bulk - 55v, Absorb - 5 EndAmps @ 55v, Float - 54v or 3.375v per Cell : ZERO EQUALIZE

finalman

#24
Looking into this issue now and I am realising voltage sense wires are definitely needed to compensate for the voltage drop at all points of the charging stages.

As others have stated rather than release a new classic revision would be good to get this added to a revised Whiz-Bang Jr or if even possible a revised temp sensor that incorporates voltage sense as it goes to the directly to the battery bank.

Robin

I agree that adding remote voltage sense would be nice, but with everyone working on inverters or other top priority projects, I do not know when we can get to this? We have 14 people in engineering and they are all very busy, so this is a problem at the moment. None of our projects are small ones either. I will discuss this with the group. We might figure out how to squeeze something in if it is as you all think an easy change. I am skeptical that it would be an easy change though.
Robin Gudgel