I am killing my battery bank

[-robw-]

I guess I'm one of the people referred to in "Are you killing your batteries"

Brand new bank of 2 24v strings of CR-305s, and I cannot top it per my refractometer. Best I've done is 1.26 but they're usual at 1.25 (like tonight). And that's charging them lately - hot but sunny days (CL 150 shows 55a max output during sun hours).

2000 watt solar array
Classic shows I sent 338a to bank today
Overnight usage is about 275a
275/338 = 81% which addresses loss accurately for new battery bank and 10ft of 2 awg from Classic to bank and good connectors, so I should be fully charging bank, right?

Wrong

I can't hit 1.275 in these best of (sun) times.

So my question is, I guess, is how high can I go? Absorb is presently at 31v (Crown's recommended equalize) and for 5 hours (I never hit float). Can I go to 31.5? 32? This isn't addressed in sticky but seems to be a solution?

Caveats:
1. Not concerned about off-summer months because 275a is mostly AC.
2. Impractical to add more panels.
3. I think Classic 150 is causing this

[Mike90250]

> 3. I think Classic 150 is causing this

Only if you did not configure it properly.
You could have high resistance in the cables which fool any charge controller with the wrong voltage.
You likely don't have enough panels or are using more power than you can harvest. Deficit charging can really pull a bank way down.
Any daytime loads, subtract from your battery charging

[-robw-]

I've taken my ammeter to primary leads to bank and it shows amps are passing. I guess I could take it to battery interconnects today. Should it show same amperage passing through all 4 batteries?

Low daytime loads, maybe 10a

[Bala]

How new are all the batteries?

What was the SG when they were brand new?

Are you using temp compensation correctly for your readings?

You have two banks so a part parallel system?

Counting you Ah in and out may not be telling you the full usage as Mike suggested.

The parallel may not be helping and you may just need time rather than high V set points to get them up.

[-robw-]

How new are all the batteries?

What was the SG when they were brand new?

Are you using temp compensation correctly for your readings?

You have two banks so a part parallel system?

Counting you Ah in and out may not be telling you the full usage as Mike suggested.

The parallel may not be helping and you may just need time rather than high V set points to get them up.

Three weeks old
1.20ish
Yes
Yes, 2 24v strings
It is. Daytime usage is very, very low.
I've tried absorb setting from Crown recommended (29.04) to 31. 29.04 gets me to 1.20 and 31 gets me to 1.26. The higher absorb voltage keeps controller in bulk mode longer, insuring max amperage. Any setting lower than 31 and controller starts tapering amps down too soon.

The answer I sought has been answered this morning by Crown: Recommended max voltage is 32.04 (equalize) but that's not their recommended absorb setting. Warned I would burn batteries even at 31v. Not sure what to do. Classic logs indicate sufficient amperage being produced but still cannot top batteries, so I either settle with 90-95% SG or replace CL 150 as next step.

[Bala]

As Mike said I also doubt your controller is a problem.

I would be looking for an answer as to why they were 1.20 when you got them, by that reading I would suspect old stock that were dead when you got them.

[Mike90250]

What is your nighttime consumption (in watt hours)
What is your daytime charge ( in watt hours )

Using watt hours is the only reliable way to count inflow/outflow

[-robw-]

My guess is around 6000-7000w but I've ordered a whiz bang/shunt to accurately measure SOC. That still wouldn't explain why CL 150 tapers amperage too soon but it's info I'll need to continue my troubleshooting.

Daytime: presently at .96a AC. Like I said, pretty much nothing. I come in for lunch but otherwise out on ranch all day.

Ha! just realized this cheapo ammeter I got 96a from has a rolling log on kWH too. So tonight all I need to is write down number, then check again in AM. Gotta cancel that WB. Thank you for question!

[-robw-]

So I've forgotten twice now to reset kW meter in the evening, but since I reset it yesterday at about this time I do have a general idea: In 24 hours I use 7600w or (7600/24 +10%) 348 DC amps. That's good to know, not on system size - I'll need solution to draining over 50% of bank each night - but I'll still need specific evening usage.

Figured something else out too: I'm good. Yesterday I worked with Tom, a battery tech with "52 years experience" and he suggested we start from square zero and 1) Let absorb cycle finish and then 2) shut all power in and out of bank down for 24 hours, then check voltage and SG levels. Low and behold, I did just that and SG is 1.27 and voltage at each battery 6.39-6.42. Yes!

It's all counter-intuitive to me. How can batteries show a lower SG when controller is supplying them current (and almost no draw) then at rest? Anyone care to explain?

[Bala]

So I've forgotten twice now to reset kW meter in the evening, but since I reset it yesterday at about this time I do have a general idea: In 24 hours I use 7600w or (7600/24 +10%) 348 DC amps. That's good to know, not on system size - I'll need solution to draining over 50% of bank each night - but I'll still need specific evening usage.

Figured something else out too: I'm good. Yesterday I worked with Tom, a battery tech with "52 years experience" and he suggested we start from square zero and 1) Let absorb cycle finish and then 2) shut all power in and out of bank down for 24 hours, then check voltage and SG levels. Low and behold, I did just that and SG is 1.27 and voltage at each battery 6.39-6.42. Yes!

It's all counter-intuitive to me. How can batteries show a lower SG when controller is supplying them current (and almost no draw) then at rest? Anyone care to explain?

Temp correction, the hotter the electrolyte the lower the SG reading V actual SG.

You had the batteries at a high charge rate so they would have been hotter than they would be after sitting for 24hrs.

http://support.rollsbattery.com/supp...ection-factors

[-robw-]

Temp correction, the hotter the electrolyte the lower the SG reading V actual SG.

You had the batteries at a high charge rate so they would have been hotter than they would be after sitting for 24hrs.

http://support.rollsbattery.com/supp...ection-factors

Good to know but doubtful here. Troubleshooting, a few days ago I took my temp gun to acid and it registered a respectable 84 degrees. Seeing that we're 95+ here and batteries are 1/2" off soil, I suspect AM, PM, on or off absorb, or heat wave would not change that much.

I'm thinking that it has to do with currency draw, which I've estimated as being minimal during day but maybe there's a rogue device causing an issue. I'll know tomorrow because I just reset my ammeter. Will know tomorrow AM exactly how much draw I'm dealing with overnight.

[Bala]

I have found temp gun readings to vary a lot depending on angle and distance.

My original batteries came with a good quality hydrometer, a thermometer to sit in the electrolyte and a chart in the owners manual to calculate SG.

How are you calculating temp compensation?

[-robw-]

The Classic temp gauge does that. I have it set at .3%/C

So, all my concerns were based on assumptions. I assumed SG was low when measuring it improperly, and I assumed a 90+% night time draw on bank. The latter I just found out is not true. Last night only 2800 watts were used, so my concern that Classic could not be topping batteries when its logs showed only 300 ah produced and it tapering too soon was just wrong. For all these days the batteries were most likely topped off, and lower SG and voltage readings were caused by draw when conducting those tests.

Lesson learned: Makes no sense to test if draw on battery bank exists. Disconnect bank from system first, wait an undetermined period of time (to be determined), and then test. Thanks to all who assisted.

[Mike90250]

The waiting time is at least 3 hours.
The temperature correction is for when you measure the battery acid in the hydrometer, warm electrolyte is less dense than cold electrolyte. You use the chart to adjust the temp reading from what the floating element indicates.

[Bala]

To indicate SOC with Voltage you need to rest.

If temp correction is done correctly you can read SOC using SG at any time.