Bigreddogs
New Member
- Joined
- May 20, 2021
- Messages
- 14
I'm charging my LFP 12V 170Ah battery with a Victron Blue Smart IP-22 charger on custom setting of Bulk @ 14.6V - constant current at 30A - absorption @ 13.8V with variable current down to 0A - Float @ 13.6V charger shows no current flowing into the battery.
The report at the end of charging shows the battery received 176.3Ah over a 6 hour 4 minute time frame
I connect the battery to a 25A load - voltage drops down from 13.8V to 12.8V and operates at that voltage for about 3 hours before voltage starts to drop off. (that seems like a large drop in the initial voltage to me but I'm new to LifePo4 chemistry)
I discharge the battery down to 10V - that's resting Voltage (shunt shows 9.5V working and based on prior tries I know the BMS will shut the battery down at 9.3V working voltage)
Shunt reads that the battery has provided 95.6Ah at 25amps over 4 hour period - so based on the math and the 2nd shunt on my inverter I believe that to be accurate
(keep in mind that as the voltage drops off the amperage load varies from 25amps down to around 23amps)
I recharge the battery as above and it again accepts 176.3Ah as before...that is 80.7Ah more than was discharged
My inverter is rated at 94% efficiency and my bus is 20 years old so I know I'm going to have some additional loss and I assumed that figuring 10% to 15% total would cover that - so 170Ah rated battery minus 15% for inefficiency should provide 145Ah - operation shows 95.6Ah provided so that still leaves me around 49Ah missing.
What am I missing here...possible that there is more than 15% inefficiency in the system...or a battery that is under performing. How could I test this to find out which is causing my loss. And is a drop of 1V under a load common? I assumed the battery would operate a 13.6V for a bit then drop and operate at 13.4V for a bit then drop again...and so forth. Not go from 13.8V down to 12.8V immediately.
Any insight or advice would be appreciated
The report at the end of charging shows the battery received 176.3Ah over a 6 hour 4 minute time frame
I connect the battery to a 25A load - voltage drops down from 13.8V to 12.8V and operates at that voltage for about 3 hours before voltage starts to drop off. (that seems like a large drop in the initial voltage to me but I'm new to LifePo4 chemistry)
I discharge the battery down to 10V - that's resting Voltage (shunt shows 9.5V working and based on prior tries I know the BMS will shut the battery down at 9.3V working voltage)
Shunt reads that the battery has provided 95.6Ah at 25amps over 4 hour period - so based on the math and the 2nd shunt on my inverter I believe that to be accurate
(keep in mind that as the voltage drops off the amperage load varies from 25amps down to around 23amps)
I recharge the battery as above and it again accepts 176.3Ah as before...that is 80.7Ah more than was discharged
My inverter is rated at 94% efficiency and my bus is 20 years old so I know I'm going to have some additional loss and I assumed that figuring 10% to 15% total would cover that - so 170Ah rated battery minus 15% for inefficiency should provide 145Ah - operation shows 95.6Ah provided so that still leaves me around 49Ah missing.
What am I missing here...possible that there is more than 15% inefficiency in the system...or a battery that is under performing. How could I test this to find out which is causing my loss. And is a drop of 1V under a load common? I assumed the battery would operate a 13.6V for a bit then drop and operate at 13.4V for a bit then drop again...and so forth. Not go from 13.8V down to 12.8V immediately.
Any insight or advice would be appreciated