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gcrank1
Member
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# Posted: 26 Oct 2025 09:43pm
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MW set at 14.5 but what are you getting into the bat terminals?
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paulz
Member
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# Posted: 27 Oct 2025 07:40am
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There are 5’ cables between mw and bank. I got 13.9 at the mw when bank was at 13.7. Taking one batt and mw back to grid today for further testing.
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gcrank1
Member
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# Posted: 27 Oct 2025 09:31am - Edited by: gcrank1
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Why not tweak up the MW so you get maybe 14.2 at the bats for a while, then see where they settle.
Last night I ran my MW at 14.4 to #2bat for 3.5hrs, checking every hour. When I stopped the bat had been reading 14.4 under charge for the prev 1/2hr. Within only a minute it settled to 13.6, after about another 1.5hrs it was 13.5. This morning just now it is 13.48 (higher than Ive ever seen this one settle).
From Steve's chart that looks like 95% (and the charging amps had fallen to too low to read on my cheap gauge for the last 1.5hrs).
Btw, from my charging hash marks on the bat tag this is only the 9th 'full charging' this bat has had with my 2 bat swap out as needed method. It's maybe just breaking in, lol. Pretty sure it will outlive me.
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paulz
Member
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# Posted: 27 Oct 2025 12:25pm
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As i noted earlier, the meanwells are set at 14.5 unloaded. They read 13.9 because the bank was holding them down, bank was at 13.7, as high as they get now. Meanwells will dial up to 16 I think, never ventured there.
Well im back at the grid but didn't bring anything along. At 13.1 this morning with only minimal solar charging yesterday and i didnt want to mess with it. What i will do Wednesday is run the small Honda gas generator on it all day. Only about 20 amps but it doesn't use much gas and its out behind the cabin, can barely hear it.
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Steve_S
Member
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# Posted: 27 Oct 2025 01:07pm
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The common misconception that LFP is "Full" at 3.650 Volts per cell is absolute bunk.
The Allowable Voltage Range (where the battery is operating within a "safe" voltage range without harm/risk/damage) is from 2.500 - 3.650 volts per cell.
The working range is the Voltage Range that they are intended to operate within and what the Manufacturers Test & Validate for the Amp Hour Capacity. This range is from 3.000-3.400. Now we can dip slightly below 3.000 down to 2.800 or even 2.700 without any serious risk (*1) and push over to no more than 3.500 (*2) but when going outside of the working range, you will see the cells deviate quite quickly away from each other. The "Nominal Voltage" is always stated as 3.200V (or 50% of capacity) for this reason BTW.
*1 - Below 2.700 creates some stresses in the chemistries and this is also affected by temps, while not harmful if it is occasionally done, the damage is additive if it's constantly done.
*2 - Anything higher than 3.500 (other than primary initialization/activation) there is absolutely no gain, LFP will not sit there it will always settle to the top of the working voltage range regardless. Above 3.500 cells will again devaiate from each other often triggering BMS shutdowns because one or more cells can "race" up to 3.650 triggering an Over Volt status shutdown.
The Term RUNNER CELL is used for cells that once they get outside of the "Working" range will either discharge faster or race up in voltage quickly.
Example, I have MANY packs out there and in my own system. I have seen packs drop to 2.750VPC internally and all of a sudden 1 or 2 cells rapidly drop to 2.500 under load & trigger Low Volt Disconnect shutting down teh pack, even with soem cells at 2.760 or even 2.900 in the pack. Ther inverse has been seen a LOT, where 1 or 2 cells cross the line after 3.450 and shoot up to 3.650 and shutdown the pack while some cells may still be at 3.425.
Most important to understand is that ALL Lithium batteries are Millivolt & Milliohm sensitive, quite unlike FLA and other chemistries. This is one of the reasons that 3 Decimal Point accuracy for an accurate read is much needed... the more accurate the better read you get on the State of the battery pack & cells within.
I made my own chart based on the settings I use. I use by batts from 2.800 (0% SOC) to 3.400 (100% SOC) which provides a 0.600 volt spread (LFP has a very flat voltage curve)
my 25% SOC = 2.950
my 50% SOC = 3.100
my 75% SOC = 3.250
so 0.060V = 10% capacity and this shows why 3 dec. is important. 13.000 (3.250vpc) would actually be 75%, while 13.240V (3.310vpc) would be 85%
When you look at a Voltage reading of 13.2, is it 13.200 or 13.260(10% more), or 13.290 (15% more) ?
I know this is in the weeds a bit and I'm doing it on the fly to provide the example in order to explain it... I hope it makes sense and helps.
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gcrank1
Member
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# Posted: 27 Oct 2025 01:50pm - Edited by: gcrank1
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I guess there must not be any runner cells in this #2 bat since it didn't go into HVD and seeing it settle thus far to 13.48 I think tells me it is fully charged and must be decently balanced?
Now if it wouldnt go into LVD under only a <10amp draw at 12.5ish volts......
I used the higher charging voltage to find out how this bat would respond, now that it shows a good top end settle at 13.48 I can reduce the MW and use lesser voltage to reach that and be done. If it happens with no more than 13.8 v input I will be pleased.
I have now reset the MW to 14.0 (3.5 per cell) as the max and on my next recharge I'll watch that amps fall to -0- on my cheapie a-meter then pull it and watch the settle voltage (likely overnight again).
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gcrank1
Member
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# Posted: 27 Oct 2025 09:51pm - Edited by: gcrank1
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Paul, Im concerned about your MW output of 80 amps Not falling off. Doesnt that mean that you aren't getting a long enough recharge for saturation?
Iirc you upped the voltage setting on those to get the high amps charging for less gen time. Fwiw, mine reads about 25a at best on a low bat when set for 13.8-14.0 but does drop as the bat voltage goes up. Ive never seen the 40amps output even when set to 14.5v and didn't want to go over that.
Your 80amps is being spit between the bats in the bank, isn't that 4? If so that is only 20a per bat so it can take a while for saturation of each.
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paulz
Member
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# Posted: 28 Oct 2025 11:31am
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I don't get it either. Yes its right around 20 amps per battery, as the Valence photos posted above show. This is running two meanwells, set at 14.5 each. And yes I did up the voltage on those from from high 13s awhile ago like you, it did up the amps considerably to near their advertised spec.
In the past, as the bank got to 14 the amps would drop. Now it just stays at 80 and volts dont get over 13.7. Not long enough? Maybe, thats why im going to all day tomorrow. The short story is the bank is working fine, volts drop to 13.2 after the 13.7 charge and stay there ovrnight.
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MtnDon
Member
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# Posted: 28 Oct 2025 06:19pm
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So, if I understand this correctly, nothing has changed in the hardware or the charge settings. However, for some reason, the voltage does not rise as high as it used to, and the amperage remains high, instead of falling.
If that is all correct, then it would seem the batteries or one battery in particular, or most likely, one cell or more, are at fault. Can you read the individual cell voltages? Some BMS permit that.
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paulz
Member
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# Posted: 28 Oct 2025 10:26pm - Edited by: paulz
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Thanks Don,
Here are shots of the 4 batteries under charge (note 20 amp charge per battery) showing each cell voltage.
IMG_5833.jpeg
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IMG_5832.jpeg
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IMG_5831.jpeg
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IMG_5830.jpeg
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paulz
Member
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# Posted: 28 Oct 2025 10:34pm - Edited by: paulz
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And here they are next morning, off charge.
IMG_5879.jpeg
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IMG_5877.jpeg
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IMG_5875.jpeg
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IMG_5876.jpeg
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MtnDon
Member
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# Posted: 29 Oct 2025 11:00am
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Hmmm. What happens with the system if you change from the Valence batteries to the newer ones?
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paulz
Member
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# Posted: 29 Oct 2025 04:11pm
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Trying that now.. we were at the house for two days, got some solar but not much, bank at 13.1 with usual load. So here’s what’s going on: plugged a charger into the inverter, it’s putting out 14.6 unloaded. Clipped it to one of the new 100ah LFPs that was sitting at 13.2.
So I’m charging one of the new batts off the old bank, through the inverter and Meanwell lol. No generator time yet. We’ll see what happens.
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MtnDon
Member
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# Posted: 29 Oct 2025 09:16pm
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Well, we will see what happens.
However, when we try to troubleshoot a system of any kind, we should only make one change at a time. I meant to try swapping out all four Valence batteries for a set of 4 new LFPs. That is basically a single change to the system. If a performance improvement is achieved and two or more changes were made we will not know which change made the difference. (Am I correct in believing you have 4 newer ones? ).
It's the same idea as trying for the quickest 1/4 mile E.T. We shouldn't change to a different set of carb jets at the same time as changing the ignition timing.
But since that test has started, continue and see what happens.
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