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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
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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
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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
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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.
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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.
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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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paulz
Member
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# Posted: 1 Nov 2025 08:38pm
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Brought a Valance back to the grid to charge. Surprised, as I haven’t moved one in years. 40 lbs. about the same as an FLA. One of my new 100ah LFPs weighs half, 20. To be fair the Valance is advertised as 140ah (U27). Gcrank, pop one of yours on the scale.
More on the testing later, still at it. The other new LFPs are on the cabin solar while away.
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gcrank1
Member
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# Posted: 1 Nov 2025 11:35pm
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Iirc the old 100ah 'marine/rv' deep cycle bats ran 68-72ish #s and my LFP (both at the cabin now) were spaced about 38? For just 'feel' moving them they are more comparable to the little LA garden tractor bats. Last time I moved an old LA marine type to recycling I sure was glad I wasnt messing about with them any more!
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paulz
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# Posted: 2 Nov 2025 06:39am
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Ha, yeah I have a couple of those big batteries around at the cabin for the tractors. Like carrying a ball and chain at our age. Also have one of those garden batteries here, I’ll check it later today. Don’t know why my new 100ah Lfp (Humseink) is only 20lbs. Cheaper materials maybe, they were only $100.
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Steve_S
Member
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# Posted: 2 Nov 2025 08:53am
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Ohh boy, flashback to Manhandling the old Rolls Surette S-550 beasts (56Kg/123Lbs ea).. big & heavy toe crushers...
But, my current 24V/280AH LFP Packs are 45Kg/99Lbs each so what can I complain about LOL...
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paulz
Member
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# Posted: 3 Nov 2025 01:05pm
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All my big FLAs are at the cabin, which I’m returning to today. Mean time, as I mentioned the 40lb Valance sure feels the same as a group 24 FLA. and the new Lfp 100 is only 20. The little garden SLA is 15 but only 35ah.
Anyway I put both LFPs on charger, both went to 14.5 and have settled at 13.38. The cabin has been on the other 3 new batts with the solar going, will se how they’re doing.
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gcrank1
Member
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# Posted: 3 Nov 2025 01:34pm - Edited by: gcrank1
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Maybe Im remembering wrong (seems I do that more now....) and Im not gonna start re-weighing my bats! I just KNOW that lifting my 100ah LFPs is about 1/2 of the lift of my very typical 100ah LA marine bats.
Hope the 'boost' to 14.5 on the grid charger kinda kicks up the performance again for you.
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paulz
Member
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# Posted: 6 Nov 2025 10:40am
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Quoting: gcrank1 Hope the 'boost' to 14.5 on the grid charger kinda kicks up the performance again for you.
Seems to have. Been back and forth on cabin bank a few times. The new ones I ran are the 3 Redodos (named after me) I got earlier this year. But they are 100 amp, the Valance are 140, so with 4 about twice the juice. And it looks that way, about 2 days worth instead of one with no gen charging. The solar going of course but depends on the weather.
So no factual data, but the short story is the 15 year old Valances still work just fine, maybe 14.5 boost they got helped them out.
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paulz
Member
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# Posted: 12 Nov 2025 11:31am
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I’ve had this little 25ah for a long time, done me well but I left a small load on it while away and it died. Shows 5 volts now even after long charge. Doesn’t say Lfp, always figured so. Is there any recovery hope, or does it go in with the dead FLAs?
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Steve_S
Member
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# Posted: 12 Nov 2025 12:04pm
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It can likely be recovered BUT you do need to know which chemistry was used. Make/Model/ any Identifiers on it should make it searchable.
Pending on chemistry, there are differing ways to recover a battery provided it's BMS will allow it. I would try putting a charger on it @ 12.0V to see if it takes it to start with... might need 13V. Start with Low Amps and slowly work up as it takes charge. Too much too fast could have serious side effects from a fully discharged battery.
A Gotcha: If this got drained down that far and sat like that for over 6 months OR frozen in cold or baked in extreme heat, it may not be recoverable easily and may never reach full charge is damaged internally as a result.
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paulz
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# Posted: 12 Nov 2025 02:08pm
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Thanks Steve. Hasn’t been 6 mo or froze. Just clipped it to my cabin bank, after 10 minutes it’s up in the 6s. We will see.
Found exact photo online. Says Lfp.
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Steve_S
Member
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# Posted: 12 Nov 2025 02:47pm
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Your in Luck, 6 months laying flat for LFP will NOT harm it but you might lose a percent or two of capacity. The worst thing is to either freeze them solid in a discharge state or to cook then in high heat when in such a state of discharge.
Start politely to bring it up till it reaches at least 12.0V (3.0Vpc) and then take it up to the top at 3.600Vpc (14.4V) and allow teh amps taken to drop to ZERO ! Then follow that by a rest period of 24+ hrs to allow for natural settle and then charge again to 14.4 and letting amps taken to hit 0.
After the second run, let sit 24hrs and check the voltage, should be somewhere around 3.380Vpc - 13.52V or close. Even if it drops to 3.300Vpc 13.2V your still good but lost a little off the top.
I imagine the BMS cut it off by 2.500Vpc and only allowed a trickle reading but I have no clue on what BMS they may have used, they vary a LOT...
Sit back, take a deep breath as you safely dodged another round.
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paulz
Member
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# Posted: 12 Nov 2025 04:59pm
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It sits at bank voltage, 13.2, but unclipped it drops to 6 immediately. Clip it back on and reads bank voltage again immediately, 13.2. No sparking when the clip touches.
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paulz
Member
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# Posted: 17 Nov 2025 12:14pm
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Quoting: Steve_S Start politely to bring it up till it reaches at least 12.0V (3.0Vpc) and then take it up to the top at 3.600Vpc (14.4V) and allow teh amps taken to drop to ZERO ! Then follow that by a rest period of 24+ hrs to allow for natural settle and then charge again to 14.4 and letting amps taken to hit 0.
Hey Steve, thanks. Back at the grid house, I connected it to my car battery tender. Wouldn’t turn on, so I connected in parallel with the car battery. That turned it on, and this morning green light on the tender. Voltage on the Lfp alone 13.2! But an hour later down in the 9s. Darn. My Meanwells is back at the cabin. Should I bring it back and run up to 14.4?
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gcrank1
Member
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# Posted: 20 Nov 2025 08:33pm - Edited by: gcrank1
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Brought my #2 LFP 100ah back home since I left the inverter and fan going 24hrs......dont ask....
While there today I ran the same for another 4.5hrs before it went into LVD at 11.7v under that load (I was watching it spool down, it was at 11.8 and 'flashed' like it was going to read 11.7 but went black in shut down). Back home I jumped to my little 12v and got the reset, it reads 12.4v (kind of a 'surface charge'? Bet if I run something off it the read will drop like a rock and trigger off at that 11.7 again). Considering that I had given it a good charge before and calc'ing the run time and load it looks like this 100ah bat ran 28.5hrs with ~3.5a load (the inverter overhead and the fan draw) so this inadvertent capacity test indicates to me that the bat makes spec on capacity usable and the LVD voltage. All Good! The run time after 12v wasnt long, that will be a good place to swap bats and save the BMS.
Since I carried the bat in I went right to the bathroom dig-scale and it weighs 22.5# (feels heavier to me) so I cant trust my memory for shutting things off when we leave or how much stuff weighs......Im getting lots of error messages in my head these daze.
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