Amp reading discrepancy on a system with no load

Started by Muskoka, March 14, 2020, 10:22:05 PM

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Muskoka

I've noticed the net amp hour reading from the wbjr is incorrect, on a idle system, and under load.

It's night time here, so I did a test, solar panel breakers off, inverter breaker off,  nothing else connected to the system, yet the wbjr is showing a -3.8a draw from somewhere. Batteries are full, sg is to spec.

I've checked the battery bank with 2 different clamp meters and they both show -0.7 to -0.8 amps, certainly not what I'm seeing from the wbjr.

I noticed it when I had a known load on my system, my tv, a light, and internet, and it was showing too high an amp draw, I knew it didn't look right. So I shut the whole system down, and the controller is showing a -3.8(9)amp draw,  when the clamp meters are showing less than 1 amp.

Im pretty sure I've read somewhere here that's there's a pot in the controller that I can adjust, recalibrate. Before doing that, any other thoughts as to why there may be this discrepancy. Batteries are just 2 yrs old so I really doubt it's a battery issue. Bank is 4 Deka 6v  L16's 370ah in series, 24v's.

Shouldn't the wbjr and clamp meters amps read the same, or at least close?

This system was recently changed to 24 volts. The system ran for years at 12v, and I know from years of monitoring that my tv, internet, and light draw around 105w, or in around 8ish amps, and is what the wbjr would show, and was verified with a energy meter.

Well now on 24v the same tv, internet, and light show a draw of 145w, impossible. System voltage is currently 25.3v, and amp draw is showing 5.7a. If the system was drawing 105w at 12v, like it has for at least 5 years, it should still be showing 105w at 24v, yet it isn't, it's now 145w.
Off grid - 24v System - Eco Worthy LiFePO4 12V 280ah x2 - Classic Lite 150 with MNGP wBjr - 1540w solar -  12v System - Antra Power 12v 210ah LiFePO4 - Morningstar Tristar MPPT 60 - 820w Solar - Honda / Firman generators

boB


Interesting...

Did the WB Jr.  used to read correctly when it was on the 12V system ?

There are not adjustments for the WB Jr. in the Classic or on the WB Jr. itself.

You might want to check the tightness of the screws from the WB Jr. to the shunt itself.  If things are loose, that  might show an unreasonably high current reading.

The WB Jr. is mounted directly onto the shunt, right ?  i.e.  No extension wires ?
K7IQ 🌛  He/She/Me

Muskoka

#2
Yes, it appears to have been more accurate at 12v, and everything is tight. That is something that isn't overlooked here, as I have considerable temperature swings from season to season in the battery room, so I'm constantly re-tightening, and or checking the tightness of all connections.

The wbjr is mounted directly to the shunt. Everything was fine until the firmware update, change to 24v, this system has ran fine for years at 12v.

Like I said, I have an energy meter so I know the watts my light, tv, and internet draw from the system, and that wattage has changed since changing to 24v (or the firmware update) , as far as the controller is showing. Those constants haven't changed for years, still the same devices, and they've always used between 100-105 watts.

What concerns me more is the close to 4amp draw the system is showing with nothing connected, that the clamp meters don't agree with. I've done a soft and hard reset using the jumpers since doing the firmware update a few weeks ago, to me the issue has appeared since the firmware update, and not the switch to 24v. The firmware was updated about a week before the change to 24v. I did notice while still on 12v (but the new firmware) in Grahams app that the net amp hours value was negatively increasing throughout the night, again with no "measurable" current through the clamp meters. I'd get up the next day after the system had been off all night, the inverter is not left on, and the net amp value in Grahams app would have decreased by 20-30 amps. I don't ever recall seeing that. Whatever my negative net amp reading was before going to bed, it was always very close to the same number the next morning, not now for some reason.

Only other thing in my mind that would affect this is my shunt, but why would it just suddenly act up. It's been in service for close to 8 years, I don't have another of the proper size here to test.

Ok, here's a couple pic's from Grahams app for the net amp hours, one from last night before I went to bed, and this morning. The system was off for the whole night, inverter off, panels off. Where did those 20 amp hours go on a disconnected system? I was not seeing this prior to the firmware update.
Off grid - 24v System - Eco Worthy LiFePO4 12V 280ah x2 - Classic Lite 150 with MNGP wBjr - 1540w solar -  12v System - Antra Power 12v 210ah LiFePO4 - Morningstar Tristar MPPT 60 - 820w Solar - Honda / Firman generators

Vic

Hi Muskoka,

A few questions:

What DC loads are on the battery,  with the inverter OFF?  Just the Classic?  And,  perhaps,  the energy monitor?   Are ALL other loads,  on the inverter?

Guess that your Classic is a Lite?

There may be a bit of a semantic issue.   To me,  Net Ah,  is the total number of  accumulated Ah that the battery has been discharged,  or charged,   since the last full-charge.

What were  the Firmware versions that were used for the Updates to the Classic?

Later,   Thanks,   Vic
Things do not make too much sense   ...
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!!

ClassicCrazy

When you changed from 12v to 24v did you also change the battery capacity value for the SOC ?

Larry
system 1
Classic 150 , 5s3p  Kyocera 135watt , 12s Soneil 2v 540amp lead crystal for 24v pack , Outback 3524 inverter
system 2
 5s 135w Kyocero , 3s3p 270w Kyocera  to Classic 150 ,   8s Kyocera 225w to Hawkes Bay Jakiper 48v 15kwh LiFePO4 , Outback VFX 3648 inverter
system 3
KID / Brat portable

Muskoka

#5
Thanks for the replies guys.

Vic, loads are a DC-DC buck converter, 2000w 24v inverter, Trimetric TM-2025. At night the buck converter and inverter were off. The Trimetric was still connected, so what little power it was drawing was still present, specs say 30ma. That's it for loads.

Yes, it's a Classic Lite, with a Mngp purchased a few years later.

Ok, system is fully charged by noon, goes to float, Net ah's reset to 0, and hover around 0 for the rest of the afternoon/evening. Unless I do a equalize, then that Net ah figure climbs.

Lets say I don't do an equalize. So the sun has gone down, net ah's are at or very close to 0. I now have my tv, a 5w light, and my internet hub/router on. That for years through testing with a energy meter draws close to 100-105w or 8'ish amps per hour, obviously the amps are at 12v, prior to me switching to 24v. I've measured the draw on the new inverter, and it's basically the same as the 12v unit I was using for years, so no change there. By the time I go to bed the net ah's are usually -30 to -40 depending on how late I stay up, so the system has been discharged that many amps. Odd thing, the watt usage is now around 145-150w, and the inverter draw is basically the same. Working current of the buck converter is 25ma. The difference in watt's doesn't really bother me, and has nothing to do with the ah discrepancy overnight, as everything is turned off, disconnected, so those devices have no effect on what I'm seeing.

When I go to bed the inverter is turned off, as well the buck converter (only had this since switching to 24v). Prior to the firmware update, or change to 24v, when I'd get up the next morning the net ah's were always very close to the number when I went to bed, in other words, the system was off, no loads, very little change in net ah. Now I'm seeing the net ah decrease by 20-30ah's overnight, with all loads off.

Don't know how this factors in, but I'll mention it. The voltage throughout the night normally climbs after I shut the system down. Going by 12v numbers again, when I'd go to bed the voltage on the Trimetric would read 12.5v, get up the next morning and the voltage would read 12.6v. As soon as I'd start turning things back on the voltage would immediately drop back to 12.5v, normal for a resting system, and a healthy battery bank.

Firmware versions I just flashed are, Classic 2193, Mngp 2186.

Larry, yes the battery capacity was changed from 740ah, down to 370ah.

I'll continue to keep an eye on it, and see if the net ah's discrepancy changes over time. I've just switched to 24v, so I'd like to watch it a few more weeks and see if there's a change, or it remains the same.

Glen
Off grid - 24v System - Eco Worthy LiFePO4 12V 280ah x2 - Classic Lite 150 with MNGP wBjr - 1540w solar -  12v System - Antra Power 12v 210ah LiFePO4 - Morningstar Tristar MPPT 60 - 820w Solar - Honda / Firman generators

Vic

Hi Glen,  thanks for the added info.

One thing:  What is the brand name of the Shunt on this system.   Two common ones,  are MidNite's 500 A one,   and the other is the Deltec 500 A.   These are very high quality shunts,  well made and reliable.

The other thought,  would be to disconnect the Trimetric (or whatever the energy monitor is),  from the shunt,  and its V+ connection to the battery,  overnight,  to see what the WbJr/Classic reports for Net Ah.

Also,  did  you need to extend the cable that connects the WbJr to the Classic?   If so,   is this cable shielded?  And,  are there any other wires running in any such extension cable?  How is any shield grounded?

Thanks for the FW version   ...   cannot speak to its behavior,  as we are running one or two versions behind,  here.

Thanks  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!!

boB

Do you have a Fluke handheld meter around ?

IF so...  While the WB Jr. is reading 4 amps or so, try reading how many millivolts are showing across the two shunt measurement screws that the WB Jr. is connected to.  Also check how many mV it reads when the two probes are just connecting to each other.

K7IQ 🌛  He/She/Me

Vic

Glen,

And guess that one should ask just how the DC/DC Converter is being switched Off,  at night.   Guess that you are using a DC circuit breaker as the disconnect (?).

Thanks,   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

Can you draw a simple diagram of where the shunt is in your system and what is connect to each side of the shunt since you changed to 24v system.
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

Muskoka

#10
Let me just start off by saying, everything is connected, setup properly at this end. The system has been running for years. This wasn't a complete system overhaul, I changed the battery cabling, added a buck converter for 12v lights, swapped out the inverter 12v to 24v, flashed firmware, that's it.

Vic, the shunt is a Deltec 500a, 50mv. I did remove the Trimetric Tm2025 from the system, just for a few minutes, and the reported amp load did not change, in other words it's removal made no difference. Wbjr still reported a -3.9a load at the time, with or without the Trimetric connected. No, the cables for the Wbjr were not extended. The buck converter actually has it's own on/off switch, I haven't installed a dc circuit breaker, yet. To isolate it from the system I'm removing a wire to the buss bar, it's not a high current converter, 160w max.

John, nothing has changed in the layout, nothing was moved, and it's been fine for years. One side of the shunt is connected to the last battery negative with a 18" cable, the other side of the shunt is connected to the negative buss bar with about a 6" cable. The positive and negative buss bars take all the devices cabling, nothing is connected to the battery bank, other than the buss bars.

Bob, yes I have 3 different meters here. A Fluke 87, a Greenlee DM820a, and my Extech Ma220 clamp meter. The Fluke and Greenlee were given to me by a electrician friend, who had purchased new meters, they work fine (?), have seen years of service. Another friend has a clamp meter that I used the other day, it's no longer here.

Here's the numbers, Wbjr was reading -4.1a, idle, isolated system, midnight last night.

Extech probe to probe, 0.0mv. On Wbjr screws it bounced between .1mv and .2mv.

Greenlee probe to probe .02mv. On the Wbjr screws it bounced back and forth, .38mv, .39mv, .40mv. It was always in that order, 38,39,40....38,39,40.

Fluke 87 probe to probe, 0.0mv. On the Wbjr screws it was steady at .2mv.

There's always been a "slight" phantom/ghost load on the system, 1a or less usually. Just throwing this out there, perhaps changing the battery cabling has exposed a problem, or issue with a battery. The bank was configured series/parallel at 12v, now it's all series connections for 24v, so I'm wondering if the old setup was somehow masking/hiding some issue, the way it was wired?

Logic would dictate that going to the higher voltage would decrease any amp readings across the board, they should not be increasing, but perhaps changing the configuration has exposed a "slight" issue? Doesn't make sense that at 12v the ghost load was -1a, and at 24v the load is -4a.

Or am I fishing where there's no fish.
Off grid - 24v System - Eco Worthy LiFePO4 12V 280ah x2 - Classic Lite 150 with MNGP wBjr - 1540w solar -  12v System - Antra Power 12v 210ah LiFePO4 - Morningstar Tristar MPPT 60 - 820w Solar - Honda / Firman generators

ClassicCrazy

The place to start is isolate everything you can - so only controller and batteries in circuit  and have all loads disconnected or switch the breakers or fuses off.
Yes some things can draw power even if their switch is off - depends where in their circuit the switch on device is. So first thing to do is check that buck converter you said you added in . Disconnect it and see what happens - maybe nothing but you have then ruled it out.

If you have every load disconnected and no excessive current - start connecting up each load one at a time.

Larry
system 1
Classic 150 , 5s3p  Kyocera 135watt , 12s Soneil 2v 540amp lead crystal for 24v pack , Outback 3524 inverter
system 2
 5s 135w Kyocero , 3s3p 270w Kyocera  to Classic 150 ,   8s Kyocera 225w to Hawkes Bay Jakiper 48v 15kwh LiFePO4 , Outback VFX 3648 inverter
system 3
KID / Brat portable

Vic

Hi Muskoka,

There is a strong indication,   that there IS something  wrong with your system.

Even though this system has worked for several years @12 V,   would suggest that you focus on what was added/changed after going to 24 V.

The Buck converter seems to be one of those things added/changed..  It may have an electronic Off/On switch  (as Larry noted).   You mentioned that you briefly disconnected it,   and the tare draw did not change.

What brand and model number is your Buck converter?

Perhaps you should leave the Trimetric connected,   but disconnect the Classic from  the battery (switch your circuit breaker Off)  for the entire night.

This is a simple system,   there just cannot be that many things to check/eliminate.

More INFO on the exactness of your system,   like the diagram that John mentioned  would be good info.

Without more INFORMATION about your system,   many of us have probably run out of guesses.

Thanks for added INFO.   Tired 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!!

Muskoka

Are there issues flashing older firmware on top of newer versions, I'll assume not provided a factory reset is done? Would like to go back to the version I was previously on. Is there somewhere I can download older versions, can't seem to find my backups.
Off grid - 24v System - Eco Worthy LiFePO4 12V 280ah x2 - Classic Lite 150 with MNGP wBjr - 1540w solar -  12v System - Antra Power 12v 210ah LiFePO4 - Morningstar Tristar MPPT 60 - 820w Solar - Honda / Firman generators

FNG