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gcrank1
Member
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# Posted: 14 Nov 2024 16:44
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Mine don't stay there long at all, just right after a full charge and settle.
They drop quickly to 13.4 then fair quick to 13.3.
They stay longest in the 13.3-13.0 range.
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paulz
Member
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# Posted: 14 Nov 2024 17:55
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Ok, that’s a relief! Mine do the same, unless solar is kicking around. Pretty scarce these days.
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paulz
Member
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# Posted: 14 Nov 2024 20:56 - Edited by: paulz
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Couple more things:
Came inside after a few hours this morning and saw the voltage at 13.4, after 13.1 this morning! Solar says 16 amps coming even though not a patch of blue in the sky, just quit raining matter of fact. Maybe that washed the panels off. or blue sky not necessary, light gray ok.
The Epever Tracer controller display says 13.5 I know, but it always reads higher than a VOM, which matches the 13.4.
Next thing, speaking of Epever solar controllers, I have a second one down at the shop with just a couple panels and FLA car battery hooked to it. Again minimal sun and the battery only supplies a couple led lights and motion detection trail camera. But the fla keeps going dead, tried a couple known good ones. My question is can a controller use that much juice? I do get a decent spark from it when I hook it to a battery. Something wrong with it maybe? I do have a spare little Renogy controller, one of those little black things, maybe I’ll try swapping that in.
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paulz
Member
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# Posted: 15 Nov 2024 19:02 - Edited by: paulz
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Yay! I had left all 3 chargers hooked up after quitting the other night. This morning I figured I would run them one more time. Bank was low, about 13.0-1, sunny day with some solar coming so no big deal. So I fired up just the big genny, plugged in all three and 101 amps! After 5 minutes of that it had dropped to 86, battery resistance going up I guess. Turned off the genny, bank now at 13.2.
Gonna leave em all hooked and test again tomorrow morning.
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gcrank1
Member
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# Posted: 16 Nov 2024 00:18
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Wow!
Im sure no expert, but my gut tells me that the bat-bank voltage is 'reading off' and that your bank isn't near as depleted at it looks like.
Why? Because I would not expect the bats to come up that fast to that reduction of amps; ie, the recharge in 5ish min to that kind of internal resistance doesn't seem right.
Now, where is Steve......
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ICC
Member
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# Posted: 16 Nov 2024 02:05
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Quoting: gcrank1 Because I would not expect the bats to come up that fast......
A battery that seems to recharge very quickly can also be a battery that is failing. If it doesn't have much good capacity left it can seem to recharge fully quite quickly, but when used not have the full rated capacity.
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Steve_S
Member
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# Posted: 16 Nov 2024 12:09
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Snickers snickers... have a seat !
Nothing Wrong there ! No they are NOT worn out.
Here's the deal and this is where MANY get confabulated with the new chemistries.
You charge your batteries to the proper 100% Voltage regularly and the cells within balance out quite nicely (valence always used great cells). The chemistry is "Fully" active since commissioning and you've kept them that way and haven't abused them (frozen, deep discharge to 0% or super high stress loading etc). HAD this not been the case, charging at Higher Amps would take longer.
There is a few things at play which causes some confusion.
- Charging from 2.500 to 2.900 volts per cell is quicker due to the chemistry curve. It's that "cliff fall" segment of the curve.
- Charging from 2.900-3.500 is slower because the curve there is very very flat, it "looks" slower due to the slow incremental gain. Remember 3.0-3.4 is the "delivery segment" of the curve.
- Charging from 3.400 to 3.650 speeds up as that is the other side of the Hockey Stick curve (beyond the working/delivery range). This is also were the Resistance climbs FAST and drops the Amps being taken in.
* This is where it gets a tad confusing if you are "Eagle Eyeing" the charge process because you see the change in Voltages & the Amps taken change fast .
Again, remember that the Deliverable Amp Hours come from that 3.000-3.400 (12.0-13.6) Volts per cell range and most use down to 2.8/2.9 volts per cell (moderate usage profile).
The PARALLEL GOTCHA ! Ohh yeah, like everything, gotcha's lurk to get ya ! Ohhh such fun ! 
-- Assume you have 3 Packs, all identical (age, wear and "tested" AH Capacity).
(A) These will all charge equally and take the same Amperage per pack nicely. They will lower amps taken in unison and top-off balance politely. That would be monitorable at the pack terminals.
(B) Packs with different wear/tear & slight AH Capacity Loss. These will all take full Amps when low, but as the charging progresses, the packs with lower capacity will hit their "full" first and drop amps taken while the Fresher Packs will take more amperage (think of it as saturating a sponge, more capacity = more sponge) and ultimately they will lower the amps taken till Endamps is reached.
* This can be monitored & replicated. IE put a 100AH & 120AH pack in parallel and you can replicate the effect. 100AH will fill & drop Amps while 120 will take some more & follow suit as it fills.
PSST: remember I was running 1x105AH, 2x175AH & 3x280AH in my bank for quite some time, and other combos & setups as well. Some PITA factors to work out when doing so.
Paul, we do not know the true status of these batteries because you haven't been able to do a full & proper capacity test on each battery individually. They are all likely fairly close but not exactly (you don't know what kind of life they had before). It's likely safe to assume that they likely have slightly different "true" AH capacities, maybe 5AH difference or so.
I suspect, what you saw was they were already 13.0V/3.250vpc (3.200 = 50% SOC) and the 101A was split and delivering 33.6A to each pack. So the Internal Resistance was already in play (@ 12.0V/3,000vpc they would have taken 40A). Now if "A" cell or cells are diminished a bit, they will increase resistance a bit faster & lower the input amps accepted. The Batteries in Parallel will try to share/divide all incoming & outgoing power and by chemistry, they do this proportionately relative to their actual capacity.
Confused yet ? Sorry I think I got a tad circular but letting it stand.
Simple IE using my old bank config mentioned above with regards to Proportional related to Capacity. Assume I am pulling 130A from that bank.
105AH pack dumps 10.5A
175AH packs dump 17.5A ea (35A)
280AH packs dump 28.0A ea (84A)
- 0.5A inefficiency drop.
It works identically but inverse for Charging.
If "Eagle Eyeing" that, at pack level you can actually watch the entire cycle and how the different packs float up/down slightly as they balance the delivery between themselves. You can ONLY SEE this with Advvanced chemistries using BMS'. It's quite a dance really !
CHEATING Capacity Loss Testing !
A fast "Cheat" to give an approximation of Capacity Loss can be done if you want to waste some time & fill your curiosity.
- Charge a single Battery Pack to 14.00V (3.500vpc)
- Allow to "saturate" to Endamps. 100AHx0.05=5A and cutoff charge when down to taking only 5A.
- Allow to sit "disconnected" for 1 hour, note the voltage at the terminals (2/3 decimal accurate)
- Connect inverter and find a load that will pull 0.3C (30A from a 100AH Batt) and let it rip. NOTE the Time of Start & Time of Cutoff.
!!! Set the Cutoff to where you would normally cutoff like 2.800-2.900 vpc 11.2-11.6V
OPTION: You can use something like a Kill-A-Watt meter between inverter & device pulling the 30A and that will give a good read in Wh, kWh & pending on model AH. There is some losses in that process but it's pretty close.
Remember that Battery Temp affects capacity. Optimal Temp is 25C/77F - optimal temp range is 15C-35C, either side of those temps, capacity delivery decreases slightly.
Sorry for the Novella
Hope it helps.
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paulz
Member
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# Posted: 16 Nov 2024 15:38 - Edited by: paulz
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Thanks Steve. I’m headed back to the grid for the weekend (we seem to be doing the opposite of working age cabin folks, quiet cabin life all week and hustle and bustle city life on the weekends). Anyway I will try your single battery test next week. I suspect you’re right though, they will last at least until the day that import duty goes in, hopefully much longer.
In the mean time, I repeated yesterday’s test just now since all still plugged in. Bank was at 13.1, been there all night, didn’t pay attention to second decimal place. As soon as I waddled inside after firing up the genny, less than one minute, it was at 103 amps. Verifies that all three Meanwells are in fact working, and cabling/genny too. In 10 minutes the amperage had dropped to 82. Turn off genny, voltage now at 13.2.
Sunny weekend predicted, should be at 13.3 from solar when I get back Monday. We really didn’t need the genny all week, voltage stayed between 13.0 and 13.2 just from solar. Hit the high 30 degrees this morning, fridge outside stays off a lot I’m sure.
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Steve_S
Member
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# Posted: 16 Nov 2024 15:55
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Gosh... I would really love to see Screen Captures from the Valence BMS Software for PC. I know that software is out there and some folks have it available but not sure where.
Sorry, I spend as Little Time as I can now on DIYSolar, as I am only following 2 threads till the issues are resolved and then I am totally out of there. That placed changed as have some of the people (themselves) and it's not for me anymore.
Possibles ?
https://www.brewskynet.com/valence/
A video on using the tools.
https://www.youtube.com/watch?v=7C3rHbR90I8
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