It does have user settings and is set to match what Weize includes with the battery
How to determine if Lifepo batteries are bad
- Thread starter Sonnyboy
- Start date
Ok thanks. Easy to switch
MisterSandals
Participation Medalist
Heh heh,
so you're not going to post a pic of your charge settings? :*)
Is that what you are using when you bring it inside to charge?
No, inside I just plug them, one at a time into a Battery Tender…let’s you switch types of batteries
It could take nearly 4 days to charge a 100Ah Lithium battery with a Battery Tender (depending on model). 8 days to charge both of them. So, to start, I suggest a better battery charger. Something 15 or 20 Amps.
The fluctuating voltage, and the voltage dropping to 12V right after charging indicate to me that something is wrong with the battery. It might be recoverable. But first, you need a real charger. What you want to test is the BMS high voltage cutoff. Can you charge the battery to 14.7 volts, or does the battery BMS stop charging before then? You would need to watch *current* to know, not voltage.
What I suspect _might_ be happening, is that the cells are out of balance. You charge to ~12V (which is quite low), then one overvoltage cell causes charging to stop. The charger at this point would read ~14V, but no current. You disconnect the charger, and measure the battery, and it's only 12V. A similar thing could be happening in the video you posted, but maybe a low voltage cut off, and the battery down to 11.2V.
Or a cell might be damaged, or the BMS. Given everything, there is good likelihood this is the case. That could be from the cold, or from charging it with the Battery Tender. Many LFP batteries fail temperature sensing tests, and an insulated box is not enough to keep it from freezing.
The fluctuating voltage, and the voltage dropping to 12V right after charging indicate to me that something is wrong with the battery. It might be recoverable. But first, you need a real charger. What you want to test is the BMS high voltage cutoff. Can you charge the battery to 14.7 volts, or does the battery BMS stop charging before then? You would need to watch *current* to know, not voltage.
What I suspect _might_ be happening, is that the cells are out of balance. You charge to ~12V (which is quite low), then one overvoltage cell causes charging to stop. The charger at this point would read ~14V, but no current. You disconnect the charger, and measure the battery, and it's only 12V. A similar thing could be happening in the video you posted, but maybe a low voltage cut off, and the battery down to 11.2V.
Or a cell might be damaged, or the BMS. Given everything, there is good likelihood this is the case. That could be from the cold, or from charging it with the Battery Tender. Many LFP batteries fail temperature sensing tests, and an insulated box is not enough to keep it from freezing.
I have a 10amp Battery Tender. I can’t imagine that ruined anything. Do you have any reasoning that explains this thinking? It charges one to 13.6v overnight or in 6-8 hours depending how low they are. So both are charged in less than a day. My understanding of the larger amp Battery Tenders is that they charge faster.
If anyone has any testing or diagnostic I could perform to test them, I’d be happy to try it and report back.
sunshine_eggo
Happy Breffast!
First, there's no way a 10A charger can charge an empty 100Ah LFP battery to full in less than 10 hours. If charging peaks at 13.6V, it may take 2-4 hours longer to get to 90-95% - never quite 100%.
Does it ever charge beyond 13.6V?
I’ve never measured more than 13.6-7
sunshine_eggo
Happy Breffast!
Not confident your batteries are being properly charged to anywhere near full. Minimum for maintaining balance is typically 13.8V.
I am suspect of any charger that has an LFP setting, but doesn't tell you or let you adjust what that is. Many cheaper chargers that claim compatibility with LFP will change to LFP voltages (14.4-14.7) but NOT change absorption times or tail-current, or float voltages. These chargers will charge LFP batteries, but over time will damage them and reduce their capacity.
I have not tested the Battery Tender to know one way or another. But they don't seem to publish this information, and conceptually, what the battery tender is (a battery maintainer) is a function that is needed for Lead-Acid, but damaging to LFP.
Further diagnostic requires a charger where you can specifically set the voltage, absorption time, and measure current.
Which charger do you suggest? I am not coming up with any for lifep04 that let you adjust any settings.
Pretty much any Victron Charger will:
BradCagle
Solar Enthusiast
- Joined
- Aug 27, 2021
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Judging from your video, I think what's happening is, when charging gets over 14.3v the BMS is cutting out. Might be from cell imbalance.
Set your charging voltage to max at 14.0v
This will allow the battery to absorb, and balance without the BMS cutting out. It will still fully charge at 14.0
Also I see you're in freezing climate, could be low temp charging protection kicking in.
Vigo
Solar Addict
Sonnyboy I think a lot of the back and forth here is mostly trying to establish that it 'really is' more complicated than hooking them to a 10a charger meant for lead acid and saying it's good enough. Maybe it could have been established in a better way earlier and things would not have drug on so much, but.. we march on! lol
Basic amp-hour (Ah) math:
100ah battery / 10 amps = 10 hours. So a 10amp supply would need 10 hours under perfect conditions to put 100ah into the battery. BUT... that's if:
Your SCC seems to be somewhere in the, say top 20th percentile of what's out there because it does do multistage charging and lets you adjust a lot of it. Which is all well and good except it's operating from an unreliable power source (sun) into a vague bag of problems (batteries, possibly wiring) while your grid-powered 'reliable' charge source is far from optimal and doesn't let you adjust it any closer to optimal, either.
So i agree with everyone else who said you need to do a more complete charge of the batteries, the only practical way to do it is from the grid, and it will require you to use a different grid-charging source than what you've got now. You can use a 'dumb' power source such as a bench power supply to do this, but it will not protect you from your own mistakes in any way and require careful monitoring in return for dollars saved. It is probably best to bite the bullet on a nice, adjustable, multistage charger on the thinking that it is still cheaper than killing 3 lithium batts and having to buy 3 more.
Basic amp-hour (Ah) math:
- Amps X Hours = Amp-Hours (Ah)
- Ah / Hours = Amps. Ah divided by the hours you got to spend equals the amps you need to do it.
- Ah / Amps = Hours. Ah divided by the amps you got to give equals the hours you need to spend.
100ah battery / 10 amps = 10 hours. So a 10amp supply would need 10 hours under perfect conditions to put 100ah into the battery. BUT... that's if:
- The supply could put out 10amps throughout the entire charge (i.e. against a 'moving target', a battery whose voltage rises).
- The chemical process of charging the battery was 100% efficient (with lifepo4 it's close but not 100%).
Your SCC seems to be somewhere in the, say top 20th percentile of what's out there because it does do multistage charging and lets you adjust a lot of it. Which is all well and good except it's operating from an unreliable power source (sun) into a vague bag of problems (batteries, possibly wiring) while your grid-powered 'reliable' charge source is far from optimal and doesn't let you adjust it any closer to optimal, either.
So i agree with everyone else who said you need to do a more complete charge of the batteries, the only practical way to do it is from the grid, and it will require you to use a different grid-charging source than what you've got now. You can use a 'dumb' power source such as a bench power supply to do this, but it will not protect you from your own mistakes in any way and require careful monitoring in return for dollars saved. It is probably best to bite the bullet on a nice, adjustable, multistage charger on the thinking that it is still cheaper than killing 3 lithium batts and having to buy 3 more.
So assuming I bite the bullet and spring for say a Victron charger, and then fully charge the batteries, how would I then determine whether or not they are faulty? My small setup will never be grid tied so I will need to proceed with that in mind.
sunshine_eggo
Happy Breffast!
At this point, you have what appears to be poorly performing batteries, and it's been established that you don't have suitable equipment for charging. The answer to your subject line is, *YOU* can't. *YOU* lack any diagnostic capabilities whatsoever.
If you don't want to buy a Victron, go cheaper and get the 30V/10A adjustable power supply that Will recommends on his page. You will become master of all voltages and currents between 0-30V and 0-10A. This will enable you to set exact voltage and current limits and observe actual voltage and current real time. This can double as a "dumb" battery charger as well. You just have to set the constant voltage level.
If you want to get the same function and include 3 phase charging, the Victrons are great. You can set most to operate in a constant voltage mode achieving similar functionality as the power supply, but only for voltages more appropriate for 12V. With BT, you can monitor voltage and current on your own.
These things may need to be held at elevated voltage for a week or more if balance is the issue.
Consumerbot3418
Fitting square pegs into round holes... for fun?
I had a whole reply typed out, but @sunshine_eggo beat me to the punch--buy or borrow a bench power supply, set it to 13.8 - 14.0V, and see if you can't get those batteries topped off and balanced. This is the first step you have to take if you want to test the batteries' capacity.
You might also consider picking up a shunt that can count coulombs (something like this), and discharging the batteries one at a time, so you can compare their output.
Thanks and I appreciate the response. I understand everything you are suggesting. But it doesn't answer my question. My question was, assuming I do the very thing you are suggesting, what are the next steps in diagnosing the battery?
Additional info: I have three identical Weize 100ah batteries all claiming(and reinforced by a Will Prowse review) to have temp protection built in, in my model anyway. I just looked at the one installed in my van with a Renogy system(20a Rover scc). The battery was steady at 14.7v. I disconnected it and connected one of the batteries that I am trying to troubleshoot. It was reading 12.4-5 volts. Once I connected it, the scc immediately read 14.6-7 volts. I checked the battery that had originally been in the van, and disconnected it now read 12.5 volts. Does that make any sense?
When I removed the second battery from my shed and now only have one 100ah lifepO4 in there, it seems to charge to 14.1 volts but then bounces up and down between 12.5 and 13 and then 14 again. All with no load.
