MisterSandals
Participation Medalist
I could have added this to quite a few different threads but did not want to hijack anybody's thread.
There have been a few conversations about disconnecting batteries from a SCC while the PV array is still hot/connected. There are several scenarios where a battery could be disconnected from a controller such as temperature BMS cutoff, fuse/breaker cutoff or negligent manual battery disconnect. All these have the potential to irreparably damage your SCC (See Morningstar Best Practices, page 20 - my controller is Tristar MPPT 45). I recall folks mentioning Outback and other SCC's having similar warnings.
I REALLY like the idea of the BMS controlling 12v 200A switches. It allows for a small amperage BMS to switch high amperage loads. Not my idea but i expanded on Will's concept and his drawing to use switches to control the PV array load to the SCC.
The problem with this setup which was pointed out in a different thread, failed in the case of the BMS cutting off for low voltage: there would be no solar charging to overcome the low voltage. I am wondering if anybody sees a problem with installing a manual switch, operated at the judgment and peril of the user, to bypass the BMS controlled switch to the PV array in a low voltage cutoff scenario in order to resume PV charging.
See attached, hopefully the schematic explains this better than my words.
I intend to have temperature sensors connected to the BMS to protect the LiFePO4 cells from charging in a freeze condition (temp sensors and wiring not pictured).
And of course if anybody has a way to make this better or even automated with smarts, PLEASE help.
There have been a few conversations about disconnecting batteries from a SCC while the PV array is still hot/connected. There are several scenarios where a battery could be disconnected from a controller such as temperature BMS cutoff, fuse/breaker cutoff or negligent manual battery disconnect. All these have the potential to irreparably damage your SCC (See Morningstar Best Practices, page 20 - my controller is Tristar MPPT 45). I recall folks mentioning Outback and other SCC's having similar warnings.
I REALLY like the idea of the BMS controlling 12v 200A switches. It allows for a small amperage BMS to switch high amperage loads. Not my idea but i expanded on Will's concept and his drawing to use switches to control the PV array load to the SCC.
The problem with this setup which was pointed out in a different thread, failed in the case of the BMS cutting off for low voltage: there would be no solar charging to overcome the low voltage. I am wondering if anybody sees a problem with installing a manual switch, operated at the judgment and peril of the user, to bypass the BMS controlled switch to the PV array in a low voltage cutoff scenario in order to resume PV charging.
See attached, hopefully the schematic explains this better than my words.
I intend to have temperature sensors connected to the BMS to protect the LiFePO4 cells from charging in a freeze condition (temp sensors and wiring not pictured).
And of course if anybody has a way to make this better or even automated with smarts, PLEASE help.