Lithium batteries

[dennisvr]

I have a friend that installed two Chins 100AH 12v batteries.  The spec sheet says nominal voltage 12.8v.  When he received them they showed they had 13.2 volts charge.  He used them all night with heater running, "all most continuously, thermostat set at 75deg and 40 deg outside.  This morning woke up to 13.2 volts.  While brewing coffee this morning they dropped to 12.7 then went back to 13.2 when brewing stopped.  I would have thought after the sun went down last night and charging stopped from solar, they would have settled down to 12.8 and then dropped during the night with the consumption.  I'm not that knowledgeable on lithium batteries, so thought I would ask if this is normal.   

Edited February 5, 2022 by dennisvr

[Randyretired]

Yes that is normal.  LFP batteries have a very flat voltage from around 90% charged to 10% charged at around 13v to 13.3v.  By the time these batteries read 12v there isn't a lot of charge left.  When fully charged the voltage will spike up to around 13.4v at rest, not 12.8v like lead acid.  Using voltage as a measurement of state of charge on these batteries doesn't work very well.

[KodiakJack]

Great report and supports the reason my 4 100A 12V Global Power LFP arrived last night.  I am hoping for similar results especially seeing how they will working my limited 610 watts of solar panels.

I do not want to high jack this thread but do have a question as to charging Lithium batteries.  My Magnum inverter/charger does not have a built-in charge profile for LFP batteries so I am looking for advice on how to do this myself. 

Later,

J

[oldjohnt]

Dennis when I received my LiFePo4's after a long shipment they measured 13.1 each (pretty well stay over 13 in my RV when not under charge) were labeled at 12.8 and 14.6 charging volts, yet even when partial discharged or under a heavy load, voltage doesn't drop below 12.8....... Different batteries under different loads and different states of charge may well differ from mine, that's ONLY MY experience with MY batteries

 Instead of only voltage I rely on my shunt based battery monitor when it comes to their State of Charge.

 Im not an expert those are ONLY my findings, see what others have experienced with THEIR batteries under THEIR loads and THEIR States of Charge................ 

 

2 hours ago, KodiakJack said:

My Magnum inverter/charger does not have a built-in charge profile for LFP batteries so I am looking for advice on how to do this myself. 

 

 Jack, I would contact BOTH your battery manufacturer for their charging recommendations and profile and then Magnun to see if your particular model can be programmed or adjusted accordingly I HAVE NO IDEA MAYBE SOMEONE WHO OWNS THE SAME MODEL CAN PROVIDE THE ANSWER ????????? While some modern so called Smart 3 Stage Chargers can still provide a "certain degree" of charging for LiFePo4's, given the cost of the batteries I prefer to use a charger suited specifically for my Lithium batteries BUT THATS JUST ME even if something less can still "work" and provide some degree of charge albeit less than ideal or as recommended by the manufacturer...

John T

 

 

Edited February 5, 2022 by oldjohnt

[Randyretired]

1 hour ago, KodiakJack said:

Great report and supports the reason my 4 100A 12V Global Power LFP arrived last night.  I am hoping for similar results especially seeing how they will working my limited 610 watts of solar panels.

I do not want to high jack this thread but do have a question as to charging Lithium batteries.  My Magnum inverter/charger does not have a built-in charge profile for LFP batteries so I am looking for advice on how to do this myself. 

Later,

J

There are some YouTube videos on how to setup Magnum inverter/chargers.  The one I remember was for Battle Born but I believe the process is the same except for your battery requirements.  I don't have a Magnum inverter and my batteries are diy so my settings are different.  It looked like the settings in the inverter are custom and then user defined.  

[Chad Heiser]

11 hours ago, KodiakJack said:

Great report and supports the reason my 4 100A 12V Global Power LFP arrived last night.  I am hoping for similar results especially seeing how they will working my limited 610 watts of solar panels.

I do not want to high jack this thread but do have a question as to charging Lithium batteries.  My Magnum inverter/charger does not have a built-in charge profile for LFP batteries so I am looking for advice on how to do this myself. 

Later,

J

If you have a remote for your Magnum Inverter/Charger, you can set up any custom charge profile you would like.  Get the specifications for charging from your battery manufacturer and those settings can be programmed into the Magnum Charger through the remote display.

 

15 hours ago, dennisvr said:

I have a friend that installed two Chins 100AH 12v batteries.  The spec sheet says nominal voltage 12.8v.  When he received them they showed they had 13.2 volts charge.  He used them all night with heater running, "all most continuously, thermostat set at 75deg and 40 deg outside.  This morning woke up to 13.2 volts.  While brewing coffee this morning they dropped to 12.7 then went back to 13.2 when brewing stopped.  I would have thought after the sun went down last night and charging stopped from solar, they would have settled down to 12.8 and then dropped during the night with the consumption.  I'm not that knowledgeable on lithium batteries, so thought I would ask if this is normal.   

I don't have specific experience with Chins batteries, but as others have stated voltage is not a good indication of state of charge for lithium batteries.  Their resting voltage will stay pretty constant from full charge down to almost depleted.  The voltage will sag under heavy load (but not quite as much as lead acid/AGM does).  It will then return to a fairly constant voltage when the heavy load is removed.  Light loads cause very little voltage sag in lithium batteries.

[dennisvr]

Thanks all for the responses.  As I always say, learn something every day.  The guy had to buy a new trailer and solar plus the batteries and is in debt for all, so I dont think he will be buying a shunt to monitor the batteries like he should.  I talked him into going Lithium over the AGM that he wanted to buy, so I'm trying to make sure all goes well.
 One more question, does the BMS shut down the battery if the SOC drops to around 0% to save the battery.  Thinking that if it does at least he cant hurt the battery if he runs it low.

[Randyretired]

I am not familiar with the BMS in that battery but every BMS I have seen will shut down at low voltage in any cell and the battery overall.  That is a basic BMS function.  A few BMS's will not restart automatically and some solar charge controllers will not restart if the BMS has shut down and manual intervention is required.  That isn't  likely but something to keep in the back of your mind.  It is best to set the low voltage shut-off on the inverter above the BMS cutoff.  

[oldjohnt]

3 hours ago, dennisvr said:

One more question, does the BMS shut down the battery if the SOC drops to around 0% to save the battery.  Thinking that if it does at least he cant hurt the battery if he runs it low.

Dennis my BMS will shut down BEFORE any complete full dead discharge but I forget the exact voltage or SOC. I would venture that's (along with over voltage or cold temps etc) one of the important features of any quality BMS but I have no idea of your system. Similar to Randy Ive read some brands ???? if discharged too low require a jump/boost at a certain level prior to activation of recharge.

FWIW this IS ONLY ME, even if you can theoretically discharge Lithium to 90% or even more (BMS and charger settings can come into play) I have an alarm set so Im notified if mine ever reached 20% at which time even if BMS or charger doesn't, IM GOING TO ACTIVATE SOME SORT OF CHARGING (Solar or DC to DC or Converter/Charger) because I choose NOT to discharge mine over 80%........That being said with my Solar and Converter/Charger and my overnight use I have never discharged anywhere near that low yayyyyyyyyyyyyy

Best wishes These are ONLY my preferences, experiences and choices, see what the experts have to say

John T

Edited February 6, 2022 by oldjohnt

[KodiakJack]

Thanks all for your comments.

Yes all of my LFP batteries arrived showing 13.1 - 13.3 volts according to the built in meter; my Klien VTVM agreed. The built in meter also shows individual battery SOC (83-88-90-95%) more than the 50% storage capacity recommended on the batteries label.  (The manufactures charging/discharging information is printed on each battery.)

I have watched a few youtube videos on programing my Magnum using my remote display, with a couple methods available, i.e. CC/CV and Custom as mentioned by Chad.    Turns out I did not have the best length of cables to properly connect to the Magnum, so cables are on order. 

Meanwhile I will use my MTTP solar controller to fully charge the batteries before using (per manufacture) simply because it can be easily changed for LFP batteries.

When I installed the Magnum I retained my PD-9280 converter/charger as a backup but have never used it since.  During the transition I will disconnect it from the batteries and allow it to supply only the 12 volt system.  Soon as the cables arrive it will be back to the Magnum and it's wonderful SOC and additional information display.

Later,

J 

 

Edited February 6, 2022 by KodiakJack

[dennisvr]

22 hours ago, Randyretired said:

I am not familiar with the BMS in that battery but every BMS I have seen will shut down at low voltage in any cell and the battery overall.  That is a basic BMS function.  A few BMS's will not restart automatically and some solar charge controllers will not restart if the BMS has shut down and manual intervention is required.  That isn't  likely but something to keep in the back of your mind.  It is best to set the low voltage shut-off on the inverter above the BMS cutoff.  

Good info, thanks.

 

[dennisvr]

22 hours ago, oldjohnt said:

Dennis my BMS will shut down BEFORE any complete full dead discharge but I forget the exact voltage or SOC. I would venture that's (along with over voltage or cold temps etc) one of the important features of any quality BMS but I have no idea of your system. Similar to Randy Ive read some brands ???? if discharged too low require a jump/boost at a certain level prior to activation of recharge.

FWIW this IS ONLY ME, even if you can theoretically discharge Lithium to 90% or even more (BMS and charger settings can come into play) I have an alarm set so Im notified if mine ever reached 20% at which time even if BMS or charger doesn't, IM GOING TO ACTIVATE SOME SORT OF CHARGING (Solar or DC to DC or Converter/Charger) because I choose NOT to discharge mine over 80%........That being said with my Solar and Converter/Charger and my overnight use I have never discharged anywhere near that low yayyyyyyyyyyyyy

Best wishes These are ONLY my preferences, experiences and choices, see what the experts have to say

John T

Thanks John.  I will see if his system has the ability to have a alarm to be set.

[oldjohnt]

4 minutes ago, dennisvr said:

Thanks John.  I will see if his system has the ability to have a alarm to be set.

Dennis the alarm notification I referred to (which I have set if batteries ever became 80% discharged which they never have likely/hopefully never will) IS ON MY SHUNT BASED BATTERY MONITOR....

John T