Lithium Battery usage

[98st8]

So yesterday I did a Bulk charge on my 2022 Pottery Barn with lithium batteries. I got it charged up to 14.5 volts. I unplug last night, absolutely nothing is on in the AS and the batteries are disconnected and this morning it reads 13.1. What could be causing the drop in volts when nothing is on

[BigAl]

Seems like a lot of discharge but the propane detector is always on even if master switch is off.

[vanderwielen]

Invest in a smart shunt. This will aid you in determining your state of charge as well as showing you current flow in and out of your batteries.

[Crackerman]

Lithium batteries nominally sit around 13.3-13.4v when full.

[field & stream]

Originally Posted by vanderwielen

Invest in a smart shunt. This will aid you in determining your state of charge as well as showing you current flow in and out of your batteries.

Good advice to install a smart shunt, also good to invest a very small amount in a manual true disconnect switch — the only way to ensure that “absolutely nothing is on”.

The factory installed switch definitely leaves some things on, and potentially leaves several things on (e.g. radio presets, subwoofer, tv antenna, inverter).

Still, 13.1 seems lower than normal.

[pcskier]

Originally Posted by 98st8

So yesterday I did a Bulk charge on my 2022 Pottery Barn with lithium batteries. I got it charged up to 14.5 volts. I unplug last night, absolutely nothing is on in the AS and the batteries are disconnected and this morning it reads 13.1. What could be causing the drop in volts when nothing is on

As mentioned, 13.3-13.4 is fully charged, not 14.5. When and how did you measure the voltage? Either the voltage you saw was when it was still charging, and that was the charge voltage; or it was immediately after charging and the batteries were not able to 'rest' yet. (Assuming that Li batteries need to rest like flooded do...if I'm wrong about that, someone feel free to correct me).

[Tyler2you]

I believe 13.6 v is closer to fully charged for a resting LifePO4 battery.

[98st8]

Originally Posted by pcskier

As mentioned, 13.3-13.4 is fully charged, not 14.5. When and how did you measure the voltage? Either the voltage you saw was when it was still charging, and that was the charge voltage; or it was immediately after charging and the batteries were not able to 'rest' yet. (Assuming that Li batteries need to rest like flooded do...if I'm wrong about that, someone feel free to correct me).

[ATTACH][/ATTACH]

One picture of shunt taken last night at 12:21AM at time of charging. I then unplugged it for the night. Second picture of shunt taken at 8:30 this morning showing 13.22 volts.

[98st8]

also strange to me that the shunt would state that I'm at 99% with 13.22 Volts

[field & stream]

Originally Posted by 98st8

also strange to me that the shunt would state that I'm at 99% with 13.22 Volts

OK, one problem here (which I only learned from experience, instead of studying the 712 manual!) is that when the battery is disconnected the 712 needs to be resynchronized with the batteries. Check the manual for how.

Seems to this amateur that when the power is reconnected the 712 reads the existing charge level as 100%. That would explain your 13.22 and 100% readings. I fully charge the batteries then synch the 712.

Hopefully someone more knowledgeable than me can confirm or correct this…..

[GMFL]

Let me try and explain how this all works.
Bulk charging is Amp base. In other words, most amps it can at 13.6 ish volts. 99% of lithium charging is done in the bulk state of charging.
Then come Absorption. Absorption is volts based, for lithium 14.4 ish is the set voltage. The higher voltage allows more pressure. This tops off the batteries and balances the cells. This stage is to maintain the overall health of the batteries.
Float is next. This is to simply maintain the batteries are a fully charged state. Keeps a check on the batteries and does it’s best to keep them in a charged state.

If a lithium battery is left to rest (not on a charger) it will return to its nominal voltage which is 13.1-13.2ish.

The Victron BMV 712 uses 3 factors to determine state of charge (SOC).
#1 Charged Voltage
#2 Tail Current
#3 Charge Detection Time

Charged voltage is a programmed amount that must be exceeded to satisfy the monitor (should be .5 volts less than absorption voltage. (I recommend setting at 14VDC)

Tail Current is the % of total battery capacity allowed to still be entering the batteries at fully charged state. This number is proportional to “your” bank size. Meaning if you have a 400Ah bank at 1% thats 4Amps. If you have a 600Ah bank at 1% would be 8Amps.
(Larger the bank the lower your setting needs to be). I recommend 1% for 400Ah and .5% for anything larger.

Charge Detection Time. This the the amount of time that both Charger voltage must be exceeded and input amp “Tail Current” less than set %.

Example settings for 400 Ah bank.
Charged Voltage 14V
Tail Current 1%
Charge Detection Time 10 min

Thus would mean that the Charged Voltage would need to be above 14V and amps going into the Batteries be less than 4A for a period of 10 min for the monitor to auto sync to 100%

Hope this helps…

[field & stream]

GMFL : Thanks for the information above. Greatly expanded my knowledge.

However, I still have some confusion! Two questions:
1) you say “If a lithium battery is left to rest (not on a charger) it will return to its nominal voltage which is 13.1-13.2ish.” So, why do the published SOC charts for LiFePO4 batteries (like in post #7 above) show that 13.1 - 13.2v is 40-70% SOC? Seems like both can’t be true.

2) why does my Victron 712 always display 100% SOC after I reconnect the battery no matter what the actual battery voltage is?

Thanks in advance…..

[vanderwielen]

Originally Posted by field & stream

OK, one problem here (which I only learned from experience, instead of studying the 712 manual!) is that when the battery is disconnected the 712 needs to be resynchronized with the batteries. Check the manual for how.

Seems to this amateur that when the power is reconnected the 712 reads the existing charge level as 100%. That would explain your 13.22 and 100% readings. I fully charge the batteries then synch the 712.

Hopefully someone more knowledgeable than me can confirm or correct this…..

You are correct, though i believe a recent firmware update corrected this. I always wire the positive instrumentation feed directly to the battery so the shunt or BMV712 does not reset to 100%. The original poster should verify this.

[GMFL]

Originally Posted by field & stream

GMFL : Thanks for the information above. Greatly expanded my knowledge.

However, I still have some confusion! Two questions:
1) you say “If a lithium battery is left to rest (not on a charger) it will return to its nominal voltage which is 13.1-13.2ish.” So, why do the published SOC charts for LiFePO4 batteries (like in post #7 above) show that 13.1 - 13.2v is 40-70% SOC? Seems like both can’t be true.

2) why does my Victron 712 always display 100% SOC after I reconnect the battery no matter what the actual battery voltage is?

Thanks in advance…..

Sure,
#1. Because the chart is wrong 😑. You cannot determine a lithium battery’s SOC by using voltage. Lithium batteries have a very flat discharge plane. Meaning they tend to maintain the same voltage until they are almost dead.

#2. This is a common setting issue. Follow these steps.
1. Log in to your Victron BMV
2. Enter settings, cog wheel in the top right hand corner.
3. Tap “Battery”
4. Scroll to the bottom of this menu to “Battery SOC on Reset”
5. I would set to Clear so it will have to meet the Programed charge settings to read out a SOC or you can set it to keep the last know SOC.
This will fit your issue.

[field & stream]

Originally Posted by GMFL

Sure,
#1. Because the chart is wrong 😑. You cannot determine a lithium battery’s SOC by using voltage. Lithium batteries have a very flat discharge plane. Meaning they tend to maintain the same voltage until they are almost dead.

#2. This is a common setting issue. Follow these steps.
1. Log in to your Victron BMV
2. Enter settings, cog wheel in the top right hand corner.
3. Tap “Battery”
4. Scroll to the bottom of this menu to “Battery SOC on Reset”
5. I would set to Clear so it will have to meet the Programed charge settings to read out a SOC or you can set it to keep the last know SOC.
This will fit your issue.

Thanks! I will do this when I get ready to go camping again after a Colorado winter.

[98st8]

Originally Posted by GMFL

Sure,
#1. Because the chart is wrong 😑. You cannot determine a lithium battery’s SOC by using voltage. Lithium batteries have a very flat discharge plane. Meaning they tend to maintain the same voltage until they are almost dead.

#2. This is a common setting issue. Follow these steps.
1. Log in to your Victron BMV
2. Enter settings, cog wheel in the top right hand corner.
3. Tap “Battery”
4. Scroll to the bottom of this menu to “Battery SOC on Reset”
5. I would set to Clear so it will have to meet the Programed charge settings to read out a SOC or you can set it to keep the last know SOC.
This will fit your issue.

I can't thank you enough as I've had so many electrical issues that many people with AS have been unable to give clear answers on. Last fall while dry camping the batteries at sea level were reading 13.2 yet the entire electrical system essentially shut down. All of the blue led buttons were blinking 7 times continually. The only thing that worked was DC powered outlets and DC lights. Could not roll in the awning though it started raining. Had to run out to Lowes to get an external battery charger. Complete nightmare

[wwwtractor]

My 400 Amp hour battery has held 13.1 volts since installation. I have a direct monitor on the battery, Victron Solar monitor, Airstream monitor, and power plug monitor. Vehicle and house battery are LiFePO4 plus upgraded the Magnum Inverter/Charger to lithium supporting one when original failed. Have the 2016 Airstream GT and plan to get the Aptera tow vehicle with a massive battery and 700 watts solar charging for backup.

Can charge from alternator, solar, generator, or lithium charger via 110 volt house plug to 14.5 volts to equalize cells.

[soling917]

How cold was it last nite, were the battery heaters on. If it was colder then 40' and the heaters were not on, the batteries got to cold and will not work properly.

[cedonly]

Originally Posted by 98st8

also strange to me that the shunt would state that I'm at 99% with 13.22 Volts

I have installed lithium batteries and also new charge controllers in our previous AS. This is likely the charge controller and not the batteries. Our AGM batteries charge to 13.1. So while charging is probably shows 14.x during charge but when disconnected.. it only charged to 13.1. Either the charge controller does not have a lithium battery setting or.. the charge controller was not set to lithium battery mode from the factory..

Given the stuff I have sen on our 2020 globetrotter I would guess the factory did not set the charge controller correctly… I would start there