I'm trying to put together a portable DIY power bank system for camping and I'm confused about the maximum amperage I have to plan for going through the cables. I've read various posts about sizing cables based on various ampacity charts and formulas, but many of them give conflicting results. I've also read a couple books on DIY PV systems and watched many YouTube videos on the subject, but still have some gaps in my understanding. So, I'm hoping this one question might clear my confusion:
If I have a LiTime 12w 230ah LiFePO4 battery with internal 200BMS and I wire it to a BougeRV 2000w inverter, does the BMS limit the draw to 200a (max continuous current discharge from the battery spec sheet, 5 second max is 600a) or do I have to plan for higher current?
I've seen recommendations to figure the ampacity based on a formula that divides the total watts of the inverter by the lowest voltage draw of the inverter divided by an inverter efficiency factor and finally multiplied by a 1.25 safety factor. For my situation that gives (2000w/9.5v/.85) x 1.25 = 309.6 amps. Other formulas and recommendations just suggest 167amps (=2000w/12v). That's quite a range! I've also seen calculations where the efficiency factor is a multiplier rather than divisor and the would result in a significantly lower amperage (223.7amps). So, I'm very confused as to how to proceed.
I'll also mention that I never plan to draw more than 1500w from the inverter, but I bought it slightly higher than needed since its footprint matches my build better. I'm planning to use 2/0 welding cable from the battery to inverter (<5' total circuit length) and probably 4AWG from the busbar connecting those to a DC fuse box on the DC side of the build. There I have a Redodo 14.4v 40a DC-DC charger and will be purchasing a Victron 100|50 MPPT to charge from 2 (or 3 in the future) Ecoflow 220w bifacial panels (21.8VOC, 13.0 ISC). I'll also be using a 12v Redodo 40a DC-DC (and solar MPPT) charger for hooking into my vehicle alternator system and plan to connect the chargers via SB50 Anderson connectors back to the battery side. Planning on Blue Sea fuses and circuit breakers, LiTime or Blue Sea busbars and welding cable throughout and also have a Victron 500a shunt with 712BMV monitor. I'm building this in 2 modular toolbox enclosures and plan to use an Anderson SB175 connection between the lower battery/invertor box and a separate upper box holding all the chargers and most of the DC stuff. 50amp breakers on the chargers and for a pv cutoff switch, and 120a DC breaker before the 100a fuse panel as the box connecting cable enters the DC side (depending on any feedback I get back about the ampacity values). Probably go with a 300a ANL fuse on the positive coming from the battery unless I hear otherwise. As a complete newbie, my head is spinning from all the specifications and sometimes conflicting equations and online calculators.
So again, can this all be simplified to the battery BMS limiting the amperage to 200amps? If so, maybe my brain can stop hurting...
Thanks in advance for any clarification you can provide. If you see something suspect in my plans, I'd appreciate any additional tips. I'll be creating a diagram to post later once I get the info on max amperage to plan for.
Joe
If I have a LiTime 12w 230ah LiFePO4 battery with internal 200BMS and I wire it to a BougeRV 2000w inverter, does the BMS limit the draw to 200a (max continuous current discharge from the battery spec sheet, 5 second max is 600a) or do I have to plan for higher current?
I've seen recommendations to figure the ampacity based on a formula that divides the total watts of the inverter by the lowest voltage draw of the inverter divided by an inverter efficiency factor and finally multiplied by a 1.25 safety factor. For my situation that gives (2000w/9.5v/.85) x 1.25 = 309.6 amps. Other formulas and recommendations just suggest 167amps (=2000w/12v). That's quite a range! I've also seen calculations where the efficiency factor is a multiplier rather than divisor and the would result in a significantly lower amperage (223.7amps). So, I'm very confused as to how to proceed.
I'll also mention that I never plan to draw more than 1500w from the inverter, but I bought it slightly higher than needed since its footprint matches my build better. I'm planning to use 2/0 welding cable from the battery to inverter (<5' total circuit length) and probably 4AWG from the busbar connecting those to a DC fuse box on the DC side of the build. There I have a Redodo 14.4v 40a DC-DC charger and will be purchasing a Victron 100|50 MPPT to charge from 2 (or 3 in the future) Ecoflow 220w bifacial panels (21.8VOC, 13.0 ISC). I'll also be using a 12v Redodo 40a DC-DC (and solar MPPT) charger for hooking into my vehicle alternator system and plan to connect the chargers via SB50 Anderson connectors back to the battery side. Planning on Blue Sea fuses and circuit breakers, LiTime or Blue Sea busbars and welding cable throughout and also have a Victron 500a shunt with 712BMV monitor. I'm building this in 2 modular toolbox enclosures and plan to use an Anderson SB175 connection between the lower battery/invertor box and a separate upper box holding all the chargers and most of the DC stuff. 50amp breakers on the chargers and for a pv cutoff switch, and 120a DC breaker before the 100a fuse panel as the box connecting cable enters the DC side (depending on any feedback I get back about the ampacity values). Probably go with a 300a ANL fuse on the positive coming from the battery unless I hear otherwise. As a complete newbie, my head is spinning from all the specifications and sometimes conflicting equations and online calculators.
So again, can this all be simplified to the battery BMS limiting the amperage to 200amps? If so, maybe my brain can stop hurting...
Thanks in advance for any clarification you can provide. If you see something suspect in my plans, I'd appreciate any additional tips. I'll be creating a diagram to post later once I get the info on max amperage to plan for.
Joe
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