June 17, 20233 yr I have a DIY lifepo4 battery and Mecer 24V 3kva inverter. Inverter settings are as follows: 01- UTI 02- 20A 03- UPS 11- 15A 26- 28.4V (bulk) 27- 27V (float) The battery does not reach the set bulk voltage of 28.4V when charging, instead it stops around 27.5V. What could be stopping the battery from reaching the target?
June 18, 20233 yr On 2023/06/17 at 5:12 AM, Tim003 said: I have a DIY lifepo4 battery What bms was used on the diy pack? Do you have comms between bms and inverter? Was the cells of the pack top balanced before connected in series and to the bms?
June 19, 20233 yr On 2023/06/17 at 5:12 AM, Tim003 said: I have a DIY lifepo4 battery and Mecer 24V 3kva inverter. Inverter settings are as follows: 01- UTI 02- 20A 03- UPS 11- 15A 26- 28.4V (bulk) 27- 27V (float) The battery does not reach the set bulk voltage of 28.4V when charging, instead it stops around 27.5V. What could be stopping the battery from reaching the target? Try pushing the float voltage up to 28V... you might be experiencing the premature float bug. You can use the timed absorb or equalize functions to charge to 28.4V if you have them in the menu.
June 19, 20233 yr On 2023/06/17 at 5:12 AM, Tim003 said: I have a DIY lifepo4 battery and Mecer 24V 3kva inverter. Inverter settings are as follows: 01- UTI 02- 20A 03- UPS 11- 15A 26- 28.4V (bulk) 27- 27V (float) The battery does not reach the set bulk voltage of 28.4V when charging, instead it stops around 27.5V. What could be stopping the battery from reaching the target? What lithium chemistry are your batteries? LFP, NMC? If LFP, then 27.5V is perfect to fully charge them. If NMC the charge voltage might need to be lower. Do you have a battery monitor available? When it is charging, check at what voltage the charge current goes to near zero. Once you hit that voltage there is no need to charge any further.
June 19, 20233 yr Author 14 hours ago, GMAC said: Try setting the charge amps up to 30amps if the inverter can It's only limited to 13A on utility power and up to 70A using other sources but the enduser will be using utility only to charge.
June 19, 20233 yr Author 13 hours ago, TaliaB said: What bms was used on the diy pack? Do you have comms between bms and inverter? Was the cells of the pack top balanced before connected in series and to the bms? It's a JBD BMS. I did not have time to top balance cells in parallel but charged them to like 3.5/cell in series (with BMS connected) and topped them individually to 3.65V/cell. They are fairly balanced with about 7-10mV delta.
June 19, 20233 yr Author 2 hours ago, HendrikBigChief said: What lithium chemistry are your batteries? LFP, NMC? If LFP, then 27.5V is perfect to fully charge them. If NMC the charge voltage might need to be lower. Do you have a battery monitor available? When it is charging, check at what voltage the charge current goes to near zero. Once you hit that voltage there is no need to charge any further. It's LFP. You're right, I've since found out from other forums that from 27.5V the battery is full and there's no need to push it beyond 28V. I turned on Equalization just to test that the battery can reach 28.4V but it's off now and set to bulk charge of 27.6V. Below it's a fully charged battery and happily floating at 27V.
June 19, 20233 yr Author 3 hours ago, jumper said: Try pushing the float voltage up to 28V... you might be experiencing the premature float bug. You can use the timed absorb or equalize functions to charge to 28.4V if you have them in the menu. Yes I tried that and working but I just left it at bulk of 27.6V.
June 19, 20233 yr 1 hour ago, Tim003 said: Yes I tried that and working but I just left it at bulk of 27.6V. I found the same. At the below 28V level the current is very low which I take is the battery is close if not full.
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