LiFePO4 Low Voltage Damage When in Protection Mode Possible

[TimtheToolMan]

When LFP batteries go into low voltage protection/sleep mode, they need to be activated/jump started soon!

One manufacture said within five days and difficult but maybe possible within 15 days.

I asked if battery was not jump started for 4-6 months (number I just pulled out of the air) what is prognosis, and they said it is hard to say for sure but for this long it would be unlikely that cells would work as intended.​

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So, I asked if this would be covered under warranty, and they said: Damage due to prolonged low voltage disconnect is outside of the manufacturer warranty.​

Copilot wrote:

The time it takes for a LiFePO4 battery to suffer damage after the Battery Management System (BMS) goes into low voltage shut-off can vary. Generally, if the battery remains in a low voltage state for an extended period, irreversible damage can occur within a few hours to a day. Prolonged exposure to low voltage can lead to capacity loss, reduced performance, and potential cell damage.​

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It's crucial to address low voltage situations promptly to prevent long-term harm to the battery.​

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What am I missing since all this is new to me? Should this be stated in user manual and FAQ? I am not complaining at all but want to understand the outcome of an error that I could easily make--accidentally not fully disconnecting battery while in storage or other low voltage possibilities.

Of course, this is way better than lead acid batteries with no BMS. If LA is under the short warranty period, free replacement is expected because supplier does not know how battery was used/abused but with a BMS, it is pretty clear (I think).

 

[Butcher]

I would contact your battery manufacturer. We all have our opinions and some of them do not always align.

I knew nothing about LifePo4 batteries [and some still think I do not]. I spent months researching this technology and I feel after reading many opinions and white papers, I have a grasp about how the technology works. It helps that I have 40+ years of being an automotive mechanic that specialized fixing Mercedes that could not be fixed.

I changed the settings on my BMS to shut off early. That way, I highly doubt if I will ever be over/undercharged. I figure if I needed a couple more amps to get my by a couple hours, I could always change the settings to do that.

I suspect that most good battery manufacturers do not have settings that will ruin the battery or even close to that. Why cause a higher warranty rate?

You are wise to inform yourself. I think you are spending too much time on this. Just make certain the batteries are kept at least 50% and if you drop them down to shut off, charge them up when you can. If you can change the settings, have the low voltage shut off at 2.9v. You will not lose that much capacity. While you are there, change the high voltage shut off to 3.45v. Again, you will not gain much capacity if you go to 3.65v

 

[TimtheToolMan]

I would contact your battery manufacturer. We all have our opinions and some of them do not always align.

I knew nothing about LifePo4 batteries [and some still think I do not]. I spent months researching this technology and I feel after reading many opinions and white papers, I have a grasp about how the technology works. It helps that I have 40+ years of being an automotive mechanic that specialized fixing Mercedes that could not be fixed.

I changed the settings on my BMS to shut off early. That way, I highly doubt if I will ever be over/undercharged. I figure if I needed a couple more amps to get my by a couple hours, I could always change the settings to do that.

I suspect that most good battery manufacturers do not have settings that will ruin the battery or even close to that. Why cause a higher warranty rate?

You are wise to inform yourself. I think you are spending too much time on this. Just make certain the batteries are kept at least 50% and if you drop them down to shut off, charge them up when you can. If you can change the settings, have the low voltage shut off at 2.9v. You will not lose that much capacity. While you are there, change the high voltage shut off to 3.45v. Again, you will not gain much capacity if you go to 3.65v

No doubt, you are quite knowledgeable! I agree that I am spending too much time on this...

Per two manufactures that I contacted, this failure will not be covered by warranty--including Battle Born.

My main concern is if RV is out of my full control, possibly in a shop. Right now, I would turn on solar, remove batteries if shop did not require them, use both battery full shut off and RV shut off, stop by camper on occasion, if possible and hope RV is in sun some and hope for the best. BT could be used to turn off battery and shop would have to ask me to turn them on.

If batteries are left on for extended period of time and not charged, they are not useable (now trash?) in a short period of time (see my original text above) per manufactures. At $600 for batteries, a loss is not great cost but uncomfortable.

I do not have any low voltage disconnect (LVD) that I have control of and considering adding something. My two 100Ah BT LiTime batteries have BMS protection (shutting off at 0%SOC, with some cushion above damage point) and the only information that LiTime would give me is related to how to keep battery properly charged in use and storage.

My equipment, Victron BMV-712 battery monitor, Zamp 30A solar controller, 510 W solar, propane frig and no generator or converter--so my power use is low especially if furnace is off.

My minimum plan to reduce risk is to turn on low voltage alarm in battery monitor and remove batteries when RV is stored (quite easy with 23-pound batteries and Anderson quick connect). Camper is not near when stored.

I am considering adding a relay to BMV-712 as a LVD and set to 10-20% SOC to allow more time (BMS provides 5/15 days per Battle Born, LiTime provided no idea how long) to battery failure. Other popular add on LVD (Blue Sea and SureStart) have an upper setting of only 10%SOC. If others have experience doing this, I would appreciate your feedback.

I don't want to spend a lot of time or effort on this.

 

[triplethreat]

I am considering adding a relay to BMV-712 as a LVD and set to 10-20% SOC to allow more time (BMS provides 5/15 days per Battle Born, LiTime provided no idea how long) to battery failure. Other popular add on LVD have an upper setting of only 10%SOC. If others have experience doing this, I would appreciate your feedback.

I don't want to spend a lot of time or effort on this.

I'm curious as to the what and the how to add a LVD to the BMV-712 that you are considering. The only thing that I've seen in the 712 manual would be to use the alarm capabilities to sound an alarm when the low voltage reaches a set point....I've not seen any way to add any type of relay that would actually disconnect the battery from further discharge. Am I missing something there or have you come up with something on your own? Obviously, just sounding an alarm would not help you if the storage location is not near you.

 

[TimtheToolMan]

I'm curious as to the what and the how to add a LVD to the BMV-712 that you are considering. The only thing that I've seen in the 712 manual would be to use the alarm capabilities to sound an alarm when the low voltage reaches a set point....I've not seen any way to add any type of relay that would actually disconnect the battery from further discharge. Am I missing something there or have you come up with something on your own? Obviously, just sounding an alarm would not help you if the storage location is not near you.

Page 9 section 3.7 BMV-712 Smart (any way)https://www.victronenergy.com/uploa...art/9172-Manual_BMV_and_SmartShunt-pdf-en.pdf

Limited to <1A so additional relay is needed.

Possibly https://www.amazon.com/IRHAPSODY-12...=se&keywords=50+amp+12+volt+relay&sr=8-1&th=1

 

[triplethreat]

LOL......thanks. I did not have that manual saved to my computer....but I do now! I had forgotten about that relay functionality, but as it applies to your case, what exactly or how exactly would you use that to functionally shut off the battery to keep it from further discharge?

UPDATE: Sorry, I just saw the edited post above and viewed the 120A relay on Amazon that you linked to. That totally answers my above question....thank you for sharing.

 

[TimtheToolMan]

I expect that Victron Energy BatteryProtect would do a solid job of protecting battery (it is a bit pricey) based on how solid their other products are, but this only allows current in one direction. This is perfect if the goal is to shut off loads when battery voltage is low but not excessively low. Wiring between converter and batteries to add a product like this is difficult for my camper.

What I need to shut off, when battery voltage is very low, is the main positive wire that both charges from converter and receives power come from battery (not the solar cable). Basically, I want to shut off as much of everything as possible to allow battery to survive as long as reasonable until charging can be started.

 

[Butcher]

I agree that I am spending too much time on this...

More people should do this. My brain feels good when I know what is going on or at least thinks it knows what's going on. Sometimes my brain hurts spending all that time.

 

[triplethreat]

More people should do this. My brain feels good when I know what is going on or at least thinks it knows what's going on. Sometimes my brain hurts spending all that time.

I still remember back in late 2021 starting my endless hours of research and discussion on the DIY Solar Forum and trying to learn about LFP batteries so that I could successfully my own battery. One guy must have taken a liking to me and we exchanged multiple PMs and even called and talked on the phone a couple of times. Our first phone call was almost two hours long (we got into details). I learned a lot from him, as well as a few others and the bottom line is that it gave me enough confidence to buy all the materials and assemble my battery.

 

[Butcher]

it gave me enough confidence to buy all the materials and assemble my battery.

And when you flipped the switch to turn it on, gives you that feeling that 'I did that!'

I had a similar journey. Started with thinking that technology was interesting. Thinking I should build a 100Ah battery. As you know, bigger is better, so I ended up building 2 304Ah batteries. Found out after one season, it's better to find more space and build another pair of 304Ah batteries. Finding the space took longer than the actual battery build.

Zero problems to date.