Archerite
New Member
For nearly a year now I have my DIY-ish self built 88Ah LiFePO4 batterybank. It's made up of 11 smaller 8Ah batteries, joining on a central busbar, individual cell fuses, disconnect switch, 80A main fuse and to monitor it all a Victron BMV-712 Smart. Each battery "cell" has an internal BMS that cuts off power when charged, low voltage and a few other things. These are not super high grade cells or BMS's I am sure...but they at least have something monitoring the internals instead of raw cells.
It's hooked into a Raspberry pi running VenusOS and I have it linked with Home Assistant through a custom NodeRed flow. When the battery is reaching 20% SoC the wall charger is turned on in Home Assistant until it reaches 50%. I also have a "SuperCharger" switch to charge to 80% on cloudy days. All these values are sliders in HA but these are the current settings I use. This is all working great but I thought I should explain the basic setup I have first.
Besides the grid/wall charger I also have 4 MPPT's with only 3 of them connected to panels at the moment. The 4th does not get much sun in winter because of shadow's and other reasons...so I disconnected the solar input. The solar charger are the only way the battery bank charges to 100% SoC most of the time.
My current "problem/situation" is that I would like to add more capacity. I have 2 100Ah batteries ready to install....but it will require a complete redesign of the battery cabinet, wiring, fuses and everything. I was just thinking why it would be a bad idea to have these 100Ah batteries join the system...but with a separate BMV/SmartShunt maybe. Of course before connecting them I would make sure all voltages are equalized and stable. The 100Ah batteries will also get their own fuses matching their limits and cable size of course.
I know it's "bad practice" in general to join cells of different capacity into a battery bank. But what if they are in different banks! it's kind of the same as what Andy from the OffGridGarage shows in his big batteryshelf. Each "bank/shelf" has its own BMS and balancer circuits, disconnects and then one central SmartShunt for the whole cabinet. I think I remember his capacities of the banks are also not matched exactly...280Ah vs 320Ah I think it was at 48v. While mine would then be 88Ah + 100Ah + 100Ah (or 88 + 200) both at 12V.
it would still require some rethinking to make things installed nice and safe...but it would bring my capacity to 288Ah with the batteies I already have! And every "Cell" has it's own internal BMS anyway...including those 100Ah! So when full or at a to low voltage they will disconnect either way. In theory.
Any way...just a thought and I would like to get some feedback if this is "ok", "good", "smart" or "terrible". Thanks in advance
It's hooked into a Raspberry pi running VenusOS and I have it linked with Home Assistant through a custom NodeRed flow. When the battery is reaching 20% SoC the wall charger is turned on in Home Assistant until it reaches 50%. I also have a "SuperCharger" switch to charge to 80% on cloudy days. All these values are sliders in HA but these are the current settings I use. This is all working great but I thought I should explain the basic setup I have first.
Besides the grid/wall charger I also have 4 MPPT's with only 3 of them connected to panels at the moment. The 4th does not get much sun in winter because of shadow's and other reasons...so I disconnected the solar input. The solar charger are the only way the battery bank charges to 100% SoC most of the time.
My current "problem/situation" is that I would like to add more capacity. I have 2 100Ah batteries ready to install....but it will require a complete redesign of the battery cabinet, wiring, fuses and everything. I was just thinking why it would be a bad idea to have these 100Ah batteries join the system...but with a separate BMV/SmartShunt maybe. Of course before connecting them I would make sure all voltages are equalized and stable. The 100Ah batteries will also get their own fuses matching their limits and cable size of course.
I know it's "bad practice" in general to join cells of different capacity into a battery bank. But what if they are in different banks! it's kind of the same as what Andy from the OffGridGarage shows in his big batteryshelf. Each "bank/shelf" has its own BMS and balancer circuits, disconnects and then one central SmartShunt for the whole cabinet. I think I remember his capacities of the banks are also not matched exactly...280Ah vs 320Ah I think it was at 48v. While mine would then be 88Ah + 100Ah + 100Ah (or 88 + 200) both at 12V.
it would still require some rethinking to make things installed nice and safe...but it would bring my capacity to 288Ah with the batteies I already have! And every "Cell" has it's own internal BMS anyway...including those 100Ah! So when full or at a to low voltage they will disconnect either way. In theory.
Any way...just a thought and I would like to get some feedback if this is "ok", "good", "smart" or "terrible". Thanks in advance