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Wbjr -number in float

Started by toothy, February 16, 2016, 07:00:00 PM

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toothy

Hello

I'm trying to do a battery capacity test. I charged the batteries and they are now in float with LOTS of unused charging capacity.

Why with excess charge capacity is my WBjr reading -7 to-10A? The voltage is steady but how can that be with a -A showing across the WBjr?

I thought as long as I have more charge capacity than load and the voltage was relatively steady the Wbjr should be seeing 0+/- amps within reason. How can there be a -number with a steady voltage?

Thanks
Wade

2-Outback vfx3648's, 16 CALB CA400,   solar Classics 2/200's with 5.6kw of panels, WBjr's, Classic 200 with Kestrel 1kw turbine, Northern lights 10 kw back-up,

Vic

Hi Wade,

If the Classics just transitioned to Float,  one will often see negative current,  as the battery voltage comes down from the Absorb voltage.  This negative current should stabilize at zero,  when the Vfloat is reached,  and the quite possibly show some positive current into the battery,  which would probably be needed to keep the batteries at Vfloat.

However,  I know nothing about your Aquion batteries,    how they are charged,  and what the battery voltage does after they are fully charged,  etc.

The only other thought is,  that the shunt might be wired backward ...   but ...

Just some guesses.   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!!

toothy

Thank Vic,

I have seen and understand the negative # after absorb, until it stabilizes around the float voltage. This negative reading goes on for many, 5+ hours, at the float voltage.

As far as being wired backwards I've been accused of that on numerous occasions! However when the sun comes up, the wind blows or the generator kicks on I see a positive value, when I get my butt out of bed and hit the coffee pot it shows a negative #.

I don't know about the Aquion business, I was figuring as with other batteries float sort of means maintain. I wish I could remember what it did on the fla's but I think it was like you described.

Looking on Mymidnite
1118 end absorb go to resting
1220 goes to float -13.5A 52.8V
1720 still in float  -7.5A  52.8V
Always a -# as well as I could tell from 1220 to 1720

During those hours the boss was vacuuming, I was doing stuff and running resistance I looked at the inverter and the load was around 1850W, not an average but we weren't being shy with the power. We go a bit crazy when it finally stops raining, its been doing it pretty much every day since November.

Thanks
Wade
2-Outback vfx3648's, 16 CALB CA400,   solar Classics 2/200's with 5.6kw of panels, WBjr's, Classic 200 with Kestrel 1kw turbine, Northern lights 10 kw back-up,

zoneblue

Because LFP is "stiff" Lithium users do seem to see an extended period where the battery continues to slightly discharge in float. Maybe the sodium is doing something similar?

People have this view that float mode is some kind of magical, stop charging mode. It doesnt work that way, float is just the name for the post absorb voltage setpoint. You could try tweaking the float voltage, however i imagine you have it set per the specs. How do you handle temp comp on those?

6x300W CSUN, ground mount, CL150Lite, 2V/400AhToyo AGM,  Outback VFX3024E, Steca Solarix PL1100
http://www.zoneblue.org/cms/page.php?view=off-grid-solar

Vic

Hi Wade,

OK,  glad that the Shunt is wired correctly.

Have you tried the latest Classic Firmware?   Believe that the latest version,  or perhaps the last two FW versions have the Classic shut off the Converter when Absorb has finished (think that there is a 90 second delay IIRC).   Think that the Classic will Rest,  until Vflt has been reached,  and then the actual Float stage begins,  when some RE power is required to maintain Vflt.

Believe that the above is similar to what the OB CCs have done on the transition to Float,  but the Classic immediately did go to Float,  with the Converter running,  and somehow this could,  or unusual occasions cause some issues,  especially for those with non-Lead Acid batteries.

AND,  zoneblue, you are,  and have been quite correct in your observations that a lot of charging can occur at traditional Vflt,  for a battery that has not just been fully-charged.   Certainly see this on Classic Skip-Days.  Would guess that the FLAs here can be charged to at least 60% of that needed for a full recharge,  or so ...   we do only eyes-on Monitoring,  so do not have real data,  just what is seen by the WBjr.

FWIW,  Opinions,   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!!

toothy

Zoneblue,

Yes I have voltages set per spec. Temp comp temp is 30c instead of 25c like fla's.  The manual says "T-comp......-0.008" I have it at -0.5 mv/c/cell, I think that's close, maybe I should try -1 mv/c/cell. The manual has a "Voltage limits vs Temperature" section that has a # well above anything I've seen. The batts are around 18c.

Vic,

Firmware is 2079 and 2073 I think that is pretty new. I was going to try piggybacking another Wbjr but it looks like I lent/gave it to my neighbor, who I'm sure has never looked at it.

Thanks again
Wade
2-Outback vfx3648's, 16 CALB CA400,   solar Classics 2/200's with 5.6kw of panels, WBjr's, Classic 200 with Kestrel 1kw turbine, Northern lights 10 kw back-up,

Vic

#6
Hi Wade,

Thanks for the added detail.

Too bad about that uncommon Temperature Comp value ...

Am sure that your Classic FW version should be fine.

EDIT:  And,  Wade,  as you know,  Halfcrazy has been running Aquion batteries for a few years,  and he should be able to advise on your situation.  But,  Hc  is often on the road these days,  so he probably has somewhat limited bandwidth.

And for zoneblue,  to me,  the negative battery current represents a battery being discharged,  for hour after hour with good sun, in Wade's case.

Good Luck,   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!!

zoneblue

Quote from: Vic on February 18, 2016, 02:08:17 PM
And for zoneblue,  to me,  the negative battery current represents a battery being discharged,  for hour after hour with good sun, in Wade's case.

Hard to say with out looking at it, but generally if the float voltage is too low (lower than the rest voltage), then the battery will discharge, until such a time as the SOC/rest drops to match the setpoint.

As lithium users here have found out, the recommended float voltage does produce a protracted period of discharge (hours). Thats the cost of actually stopping the battery from continuing to charge, which as is known is fatal for lithium chemistries. But the discharge current in terms of the overall bank capacity is relatively minor, and maybe the bank goes in the post solar period at 98% SOC of whatever it peaked at end absorb.

If we are talking more than that then something is screwy.
6x300W CSUN, ground mount, CL150Lite, 2V/400AhToyo AGM,  Outback VFX3024E, Steca Solarix PL1100
http://www.zoneblue.org/cms/page.php?view=off-grid-solar