2 Sets of batteries with different behaviour.

[Stokstert]

I have 2 different sets of 2 x12V (24V) Lipo batteries in series on 2 different inverters. After being fully charged with 28,8V and rested at float at 27,4V, the mains as well as the inverters were shut off.

The voltage of the two battery strings were then monitored for 11 hours. The voltage one set, (S120's) then went slowly down to 26,3V - 26,2V within 2 to 3 hours and settled more or less there.

The other set (LiFePO₄WER) was still at 27,4V, being the float voltage after 11 hours.

The second set was then used with a 150-200W load and after 2 hours it was still at 26,7V.

Can anyone explain this behaviour, or is this normal for different battery sets and or manufacturers?

 

[DapperDanMan]

Stokstert, have you not seen any of the posts made by @wingnut771 since the dawn of loadshedding?

Here is an example:

Mecer 5kva inverter battery drain

From page 12. You press and hold the enter button to go into settings mode.

mybroadband.co.za

 

[Stokstert]

Stokstert, have you not seen any of the posts made by @wingnut771 since the dawn of loadshedding?

Here is an example:

Mecer 5kva inverter battery drain

From page 12. You press and hold the enter button to go into settings mode.

mybroadband.co.za

That I have followed, but there the drain is due to the inverter. In this instance the inverters were shut down, with other words no load, not even of the inverter itself.

 

[AlphaJohn]

My 24v100ah LiFePO4

Bulk 28.9
Float 27.7
Rest 26.8

I have yet to see them below 26.4 even after 4 hours of load shedding with 250W - 600W load.

Specs sheet data:

• Normal voltage: 25.6V
• Normal capacity: 2560WH
• Voltage window: 22.4 - 29.2V
• Float charge voltage: 27.6V
• Max continuous discharge current: 100A
• Max pulse discharge current: 200A (30 sec)
• Max continuous charge current: 100A

 

[B-1]

Are the s120 not meant for lead acid replacements?

 

[leon.davibe]

I would measure individual battery voltages not pairs

Spit balling here
If the bms balances cells over 3.4v ie not only when charging

It could cause a voltage drop

Most tend to only balance while charging , but some bms can be configured to balance on cell voltage over 3.4v if imbalance irrespective of charging or not

 

[leon.davibe]

Are the s120 not meant for lead acid replacements?

Technically the reason it can be used for lead acid replacement is because of the cell voltage making a perfect match battery ,ie it is a lifep04 thing not brand thing imo.

Some choose to use it as a marketing tool

 

[leon.davibe]

Just hypothetical ideas take salt

The 28.8 voltage would suggest fully charged as that is a 3.6v average over the 8 cells

But it is possible that the cells are not in perfect balance

Hypothetically
ie lets say 6 of the 8 cells go to 3.7v that would mean the other 2 cells could be 3.3v each ie not totally full

And hence the float could still be pushing charge into the lower cells lifting their voltage
And if removed they settle down dragging down pack voltage until they are in rest

Then Pack voltage settles

I know my pack takes about 1.5hrs for the cell voltages to settle down after charge to stay at stable voltage

 

[Moto Guzzi]

I would not expect any battery comparison to be the same, its a very practical situation from minerals used in manufacturing, manufacturing quality, age before you got it, how it was treated before you got it etc...

 

[Stokstert]

I would measure individual battery voltages not pairs

Spit balling here
If the bms balances cells over 3.4v ie not only when charging

It could cause a voltage drop

Most tend to only balance while charging , but some bms can be configured to balance on cell voltage over 3.4v if imbalance irrespective of charging or not

This is how I read my voltages, every 12V battery apart and then in series, 24V.