July 25, 20223 yr Hello Been scrolling a lot but struggling to get some clarity. so with these Axperts inverters, basically RCT, Mecer, Kodak etc. In order to get them to properly charge lithium which does not have RS or CAN ports you have to manually do the settings such as the USE option and then set the float, bulk voltages etc. But now I understand that lithium uses amps to charge and for a longer time than lead acid, can these Axperts supply the currents for long enough to properly charge the battery ? How does the battery and inverter know how and when to do the current and then less current etc, is it all based off the voltage setting of float, bulk etc ?
July 25, 20223 yr 21 minutes ago, Dylboy said: But now I understand that lithium uses amps to charge and for a longer time than lead acid, ? LFP batteries typically charge at 0.5C, lead acid typically at 0.15C (but it varies a lot). So usually LFP can be charged quicker than lead acid, if you have the charge power. Ah, perhaps you are thinking of the divisor in the charge termination condition. Yes, this does typically mean that the LFP should charge till the current reduces to a low enough value. So this final part of the absorb stage will take a little longer for LFP than lead-acid, yes. But the total charge cycle will typically be quicker for LFP. See below. 22 minutes ago, Dylboy said: can these Axperts supply the currents for long enough to properly charge the battery ? Yes, current is not the problem. 23 minutes ago, Dylboy said: How does the battery and inverter know how and when to do the current and then less current etc, is it all based off the voltage setting of float, bulk etc ? Yes, it just charges as fast as it can, subject to the maximum charge current setting, until the voltage nears the bulk/absorb voltage setting. Then the voltage stays around this value until the termination condition occurs. The termination condition for lead acid is the maximum charge current divided by 5. Weber and I have determined that the equivalent figure for LFP is the maximum charge current setting divided by 12 (used to be 15 or so). So the LFP flavour of the patched firmware does this dividing by 12. But fully patched firmware is only available for 145 V max PV models, and most new models are the higher voltage PV type. If you have a battery with "the cable" (usually an RS-485 port or CAN bus port on the battery) and the inverter or monitoring software can talk to the BMS, then the BMS will sort all that out and tell the inverter what to do.
July 26, 20223 yr Author On 2022/07/25 at 2:23 PM, Coulomb said: ? LFP batteries typically charge at 0.5C, lead acid typically at 0.15C (but it varies a lot). So usually LFP can be charged quicker than lead acid, if you have the charge power. Ah, perhaps you are thinking of the divisor in the charge termination condition. Yes, this does typically mean that the LFP should charge till the current reduces to a low enough value. So this final part of the absorb stage will take a little longer for LFP than lead-acid, yes. But the total charge cycle will typically be quicker for LFP. See below. Yes, current is not the problem. Yes, it just charges as fast as it can, subject to the maximum charge current setting, until the voltage nears the bulk/absorb voltage setting. Then the voltage stays around this value until the termination condition occurs. The termination condition for lead acid is the maximum charge current divided by 5. Weber and I have determined that the equivalent figure for LFP is the maximum charge current setting divided by 12 (used to be 15 or so). So the LFP flavour of the patched firmware does this dividing by 12. But fully patched firmware is only available for 145 V max PV models, and most new models are the higher voltage PV type. If you have a battery with "the cable" (usually an RS-485 port or CAN bus port on the battery) and the inverter or monitoring software can talk to the BMS, then the BMS will sort all that out and tell the inverter what to do. Thank you for the very informative reply ! Apologies it took me long to respond. The termination voltage was most interesting thank you. Will try experiment and do more reading on that.
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