Brand new 280ah EVE cells shut off at 43% ah remaining, why?

[timselectric]

Thanks. It took me a while to chew thru the red herrings to figure this out. Glad you agree.

You done all the hard work. Agreeing was the easy part.

 

[Hardergamer1]

The reason you see the drop-off from 25.5v to 23.3v with only a 0.5a load is lifepo4 ah drop off a cliff after 3-3.1v that's why EVE like most other manufacturers state a soc of 10-90%, meaning 280ah cells are really 220ah and as you only charged them to 80% you have lost 10% more.
Did you not do a capacity test on each cell before building the bank?
I would do a full charge to 3.65v 29v and don't go as low, most people I know use around 190-200ah from the 280ah cells.

 

[OffGridIdaho]

The reason you see the drop-off from 25.5v to 23.3v with only a 0.5a load is lifepo4 ah drop off a cliff after 3-3.1v that's why EVE like most other manufacturers state a soc of 10-90%, meaning 280ah cells are really 220ah and as you only charged them to 80% you have lost 10% more.
Did you not do a capacity test on each cell before building the bank?
I would do a full charge to 3.65v 29v and don't go as low, most people I know use around 190-200ah from the 280ah cells.

Ok thanks.
Well that explains a bit more. Should I adjust my ah pack size in my jk and victron to 195ah pack down from 280 to get better % readings?
I did not do a capacity test. I am new and no one told me to do that.

 

[MisterSandals]

I am not disagreeing with anything Hardergamer1 wrote. I'm not even against hitting the battery with one big "full charge to 3.65v 29v" charge once you get your current issues understood (i am too conservative and not inclined/desperate enough to try this on MY cells, yet).

Should I adjust my ah pack size in my jk and victron to 195ah pack down from 280 to get better % readings?

I would not. I am not sure i've heard of anybody doing this, especially without knowing the real, measured capacity.

I did not do a capacity test. I am new and no one told me to do that.

I have about 100 cells in about a dozen different batteries and have never done a capacity test.

I think you should give your new full charge parameters a go and see where you end up. Change one thing at a time, evaluate and adjust.

 

[740GLE]

What’s the connection from SCC and the battery? Are you verifying minimal voltage drop?

SCC maybe think the battery is at ~27v but the pack may be reading around 26.8v.

Also try and use one SCC for fully charging to verify new settings and compare SCC and terminal voltage.

 

[OffGridIdaho]

I am not disagreeing with anything Hardergamer1 wrote. I'm not even against hitting the battery with one big "full charge to 3.65v 29v" charge once you get your current issues understood (i am too conservative and not inclined/desperate enough to try this on MY cells, yet).

I would not. I am not sure i've heard of anybody doing this, especially without knowing the real, measured capacity.

I have about 100 cells in about a dozen different batteries and have never done a capacity test.

I think you should give your new full charge parameters a go and see where you end up. Change one thing at a time, evaluate and adjust.

Ha...... At the 4-6min mark this guy proves what you said about low and slow! The lower the ah charge the higher the pack ah capacity.

 

[MisterSandals]

Ha...... At the 4-6min mark this guy proves what you said about low and slow! The lower the ah charge the higher the pack ah capacity.

His conclusion (and mine too), is not that the "pack Ah capacity" changes at different charge levels.

His point is that with a lower A (amp not amp hour) charge rate, the cells will absorb more during the bulk stage (and need a shorter absorb stage). ** the slower you pour a beer (presumably less foam), the less time you need for foam to settle and top off the glass **

Conversely, charging faster, the cells absorb less during bulk stage (and need a longer absorb stage). ** the faster you pour a beer (presumably more foam), the more time you need for the foam to settle and top off the glass.

Where this applies to your situation that you came here with, is that you did not have ANY absorb stage and a high charge rate did not allow for complete cell charging (lots of foam!). The capacity of the glass did not change, just the amount of beer you put in the glass.

 

[OffGridIdaho]

His conclusion (and mine too), is not that the "pack Ah capacity" changes at different charge levels.

His point is that with a lower A (amp not amp hour) charge rate, the cells will absorb more during the bulk stage (and need a shorter absorb stage). ** the slower you pour a beer (presumably less foam), the less time you need for foam to settle and top off the glass **

Conversely, charging faster, the cells absorb less during bulk stage (and need a longer absorb stage). ** the faster you pour a beer (presumably more foam), the more time you need for the foam to settle and top off the glass.

Where this applies to your situation that you came here with, is that you did not have ANY absorb stage and a high charge rate did not allow for complete cell charging (lots of foam!). The capacity of the glass did not change, just the amount of beer you put in the glass.

Im sold!
I lowered the amps and the voltage is staying the same as it continues to charge. Im at meter soc 84% now from 0. Showing negative -49.3ah left to charge to full 280ah pack.

In your advised settings I noticed the bulk and absorb voltages were the same. How does that work then? Isnt it the same with a different charge name?

 

[MisterSandals]

In your advised settings I noticed the bulk and absorb voltages were the same. How does that work then? Isnt it the same with a different charge name?

Yes, i do not rely on absorb because i charge pretty slow and conservatively.
The down and dirty about the bulk vs absorb is that in the bulk stage, the charger strives for constant current (up to bulk voltage as fast as it can).

So during bulk, the tap is wide open pouring as fast as it can, until the top of the glass is reached.

During absorb, the tap pours slowly so that the glass does not overflow yet remains at the top.

The absorb pour continues for your absorb time or until the pour reduces to your absorb tail current (glass is so full and so little foam you can only put in a few drops at a time).

 

[OffGridIdaho]

Yes, i do not rely on absorb because i charge pretty slow and conservatively.
The down and dirty about the bulk vs absorb is that in the bulk stage, the charger strives for constant current (up to bulk voltage as fast as it can).

So during bulk, the tap is wide open pouring as fast as it can, until the top of the glass is reached.

During absorb, the tap pours slowly so that the glass does not overflow yet remains at the top.

The absorb pour continues for your absorb time or until the pour reduces to your absorb tail current (glass is so full and so little foam you can only put in a few drops at a time).

Well the issue I will have with this is that Im charging with a very expensive honda generator and burning a lot of gas and putting a ton of hours on the machine. Both cost $$$$$$

BUT

I ran for 8 days without starting the gen. I got a small amount of solar charge every few days that let me run 8 days without charging.

 

[OffGridIdaho]

Update at 10pm. Ive been running for hours now. Never thought the pack would hold so much extra power. Im currently at 91% and jk bms says Ive charged 255ah -9% shutoff ah gives me a total pack ah rating so far of 280.2 ah pack and still charging.
I lowered the amps from 40 to 30 to 25 and then 20 and then lower to 15 then 13 then 10 and now 7 amps. Im at 27.09 pack and 3.387v cell with a delta of .017.

Update 2

Killed generator. JK shows 257.6ah input and add the 9% shutoff ah remaining to get a pack ah capacity at 92% meter of 282.2 ah at 92% soc.
Looks like your advice paid off. I didnt want to push it any further. I hit the rating ah level so thats good enough. I think it might have held another 10-20ah

Update 3

So the resting volts after killing generator did NOT drop by 20% like before it went from 27.09 under 7a charge to 26.82 pack and 3.352 cell with a 1a drain (inverter in powersave mode) which equates to a 1.01% drop. Delta .006.

Update 4

Now its dropped to 26.74v pack and 3.342 cell with 1a load. Its about 10-15mins after killing generator. Graph shows 3.34cell volts at 87% soc.

 

[MisterSandals]

Graph shows 3.34cell volts at 87% soc.

Mine settle to 3.35Vpc with no load which is same as yours.

Wherever possible, i set 3.35Vpc as my 100% Soc. The voltage above this is surface charge and represents negligible capacity. I think it makes Soc readings more accurate.

Sounds like you are learning a lot about your cells and charging. Well done!

I suspect that if you wanted to minimize generator runtime, you could charge at a high amperage until your top charge voltage (3.45Vpc? or experiment a little higher, maybe 3.5Vpc). Then implement an absorb phase of 10A at 3.45Vpc for 15-20 minutes. You will probably discover quickly what works best for YOUR cells.

 

[Quattrohead]

A very enlightening thread, thanks to all involved.
The beer glass analogy is a peach lol

 

[timselectric]

Yes,
I'm very thirsty.

 

[OffGridIdaho]

Mine settle to 3.35Vpc with no load which is same as yours.

Wherever possible, i set 3.35Vpc as my 100% Soc. The voltage above this is surface charge and represents negligible capacity. I think it makes Soc readings more accurate.

Sounds like you are learning a lot about your cells and charging. Well done!

I suspect that if you wanted to minimize generator runtime, you could charge at a high amperage until your top charge voltage (3.45Vpc? or experiment a little higher, maybe 3.5Vpc). Then implement an absorb phase of 10A at 3.45Vpc for 15-20 minutes. You will probably discover quickly what works best for YOUR cells.

OK well.........

Up the next morning and...........according to logs my tiny chest freezer ran once drawing 2 amps for 30 mins. Nothing else ran all night. Inverter draws 1a while in low power mode. Its been 8hrs since charge aprox. My cells now show 3.32v and pack is 26.56 meter shows 87%. According to the cell voltage my pack is now at 75% soc by voltage. So I lost 10% voltage and my meter shows 5% use.

Why the sag again? I ran the dang generator for 8-10 hrs, I lost track it was so long. I know the batteries were getting full as I could see voltage climbing faster so I would lower amps to top off the beer mug. Its kind of frustrating seeing the voltage drop so quickly.

Also while we are talking is there any way to not have to sit and watch the grass grow while charging? I also dont want to charge for 12hrs and destroy an expensive generator. My hopes when I switched over to Lifepo4 were wham-bam-thank-you-mam type charging. Fast and quick!
The old lead acids were slower than molasses. Can I just charge at 30amps until it shuts off and be happy with an 80% pack charge and be done with it? Run between 80-30%?

 

[740GLE]

I’m all for the beer analogy except when pouring a draft you never fill a pint with the tap half open. It’s always full open or full closed. A half open tap will give you all foam.

Carry on with cell charging discussions.

 

[timselectric]

I would only use the generator for bulk (fast) charging. To save on fuel costs. And leave the absorption/float charging to solar.

 

[740GLE]

Or pick up more panels, skip the generator all together.

 

[MisterSandals]

I would only use the generator for bulk (fast) charging.

Yes, at least use max amps while using your generator for bulk.
I would also try to up the bulk voltage a little to perhaps 3.5Vpc (or lower if your cells diverge at 28V total). I think your Samlex EVO 1224 charges up to 40A so I'd try most or all of this for bulk.

When your bulk is over, for a full charge that should be about 80% (224Ah) charged (224Ah)/40A = 5.6h

Also while we are talking is there any way to not have to sit and watch the grass grow while charging?

Yes. That is setting up your bulk as above and your absorb:

Set absorb at 3.45Vpc for an hour, you'd probably be at least 90% full.

Summary:
Start with bulk 35A-40A at 3.5Vpc and absorb at 3.45Vpc for 1 hr absorb time. Let us know how it goes and what you've learned.

 

[OffGridIdaho]

Or pick up more panels, skip the generator all together.

I am 65 miles from Canada in the PNW. We get sun only when the Gods think we need it which is 20 mins every 4 days. More panels wont help when solar amps are zero. I went 60 days once and not a drop of solar charge. Rained the whole time! Im also down in a valley so no wind and I dont have a stream so no micro-hydro. The greedy power company wants 24,000 to run a line down my driveway and I refuse to pay the extortion fee + monthly protection money.

Typical winter day here. Yeah that snow is halfway up my window on the house.