Power station, Electric battery, System What is the best MAX charge voltage for LiFePo4? Tested!
5 volts for all of these tests. Im im gon na build this device using arduino and this microchip, which is going to track how many amps going in or out from a battery and track voltage for the battery information, is going to be stored every 15 seconds. So we will. We can build graphs and see discharge and charge curve for our cell. Also, im going to add this tiny screen to system just to quickly see what is the amps and voltages going into or out from the battery to discharge im going to use this discharger, which is going to track information. How many amp hours we draw from a bathroom okay, if youre interested to see all of these tests and the check results, lets jump to the video Music and here im starting first test. My power supply lab, set to 365 volts battery right now, fully discharged at 2.62 volts and the arduino is tracking uh voltage and amps going in or out from a battery. So now im just going to connect charger to battery and we see that we are charging with 5.3 amps and the arduino start tracking, where the amps going into the battery – and we are about five hours later. We see that our battery at 365 walls fully charged and the power supply web just output in 17, milliamps and now im going to start discharge test and well come back in about five hours and see results and were also storing data.
So we can see this on the graphs so five hours later, we can see that our test is about to finish and from this battery we got 24 844 milliamps, so this is going to be our test data. This is what were going to compare with other tests. Here is a graph for charging curve. If i display voltage for now, we can see that i started test at 2 pm and the voltage was 261 and at just after 2 minutes 21 minute voltage jumped to 327 and its. It was like a big jump and then its just stay relatively flat. Then, after four hours, 30 minutes voltage was 348 volts and it was second jump, so we jump to 3 65 and this jump took another three minutes. So this standard lithium iron phosphate charging curve that you will see on internet. If we look at the current uh with the voltage, so we see that we charging with five amps entire way, till 6 40 pm when our voltage start raising. So, as voltage raising to 365, we dropping amps and at about 7 40 pm, we just charged with 100 milliamps. So we can, we can call batteries full, so entire process took 5 hours and 40 minutes for this charge. Curve lets see how this looks like so for voltage, also standard lithium iron phosphate or lithium batteries curve we start discharging at 367 and it was 11 40 pm and just after, like seven minutes, our voltage dropped to 326 huge drop and then its just stay.
Like almost flat flat line, not of course flat line but almost flat and then when voltage reaching about 310 volts its dropping quickly and current is square like five amps, because lithium can do five amps entire way. Okay, so here is a discharge curve lets jump to the 355 volts tests. Okay, now lets set our charger to 355 volts and charge our battery few hours later. You can see that cell at 355 volts and im pushing just 40 milliamps into the battery. So im going to disconnect chargers and start discharge test lets come back in five hours and see what capacity we got from this cell right now and what is the charging graph and after five hours, heres the results for 355. So we got sixty 24 milliamps from this cell. Okay, and here is a graph for 355 volts charge so lets zoom this graph and um. We started our test at 4, 44 am and we finished charging at about 3 10 14 a.m. So charging took six hours and basically its the same graph that we saw before when a 365 volts charge. So if we look here at about when voltage reached 345 volts, it start decreasing our amps, so amps right here, just like dropping quickly and it dropped less to an amp when we were at at 352 volts. Okay, this charge curve im not gon na even uh check because it is going to be same as a 365 volt discharge, its going to be same for every voltage now lets jump to 345 volts test, so here im about to start 345 volts charge test and Because 345, on the edge of this lithium ion phosphate curve, im setting two charges to 2.
5 volts to eliminate any power loss in the wires. So i want this test to be as much accurate as i can. Okay, so i came back in the morning. We still charging with 130 milliamps, so im gon na leave charging for a few more hours, im just going to disconnect top charger because its not charging anymore. So it shows zero amps and just leave bottom one, which is outputting 134 milliamps into the battery. Lets. Wait a little bit more time and come back later when the charging is finished. Okay – and here we few hours later, you can see that we are putting into the battery 47 milliamps. So at this point, im going just to save uh charging information and we will proceed with the discharge test and five hours later were getting our results for 345 volts. So we got 24 672 milliamps lets jump to the graphs and see where the charging curve was for 345 volts. Okay, and here is the charge curve for 345 volts. Let me zoom into this curve, and we can see that we started our test at about 4 pm and we finished this test at um. What is the last time uh at 2 40 a.m. So our charging, when we did it lets, do 100 milliamps. So it was 2 30. Am so charging time took 10 hours to charge this battery if we see voltage uh? In our case, we dont have this uh spike that we have at at the end for 365 or 345, so our voltage was like flat line and because we stopped at 345, we dont have this spike at the end and current.
If we see for the current we, we were charging at five amps, but then amps start like quickly dropping to four amps three amps, because our battery was like closer to three 345 volts, and we see that for entire entire time. For this battery, we almost didnt charge with the full capacity of power supply. Okay, now lets combine. All of this data in the table. Here is the combined results for all three tests: 365 volts charging time took 5 hours, 40 minutes and weve got capacity of 24.84 amp hours for 355 volts charging time took six hours, which is increase of six percent. If we compared to 365 – and we got capacity as a 24.76 amp hours, which is just 0.3 percent – decrease from original capacity for 345 volts charging time was 10 hours, which is 76 increase of charging, and the capacity weve got 24.67 amp hours. Uh, which is decrease of original capacity of 0.6 percent. Now, when we have all this information its your decision, what is the maximum charging voltage for lithium ion phosphate batteries. In my opinion, it should be anywhere between 345, maybe 350 and 355, and were gon na still have 100 milliamps safety gap uh. If our battery not balanced, then one cell could reach 365 walls, which is still safe. Okay, guys. I hope you like this video.