I haven’t been able to find if it is safe or not to do what I intend to do which is trigger three contactors in parallel instead of just one big one.
Due to reusing packs from a different application, I will have three strings of 32s, which it seems like I can do with just one watchmon core and 6 cellmates.
they are all in parallel so one shunt and shared load, same capacity and all that its perfectly fine.
however, I want to do one contactor for each string, the three strings should share a common negative after the contactors, this way in the event of a fault significant enough to trigger the disconnection, all three strings are isolated from each other and cannot backfeed.
Is this a supported config? is there enough power to trigger three contactors directly or will it pop?
Hello, I have 4 contactors and they have been working perfectly for about 1.5 years, you need to choose contactors with a control current that does not exceed the relay capacity. Usually the control currents of contactors are not high.
This implementation with an individual contactor for each battery composed of 16 series cells was made in the hope of a future upgrade that would disconnect only the battery that has problems by decreasing the charging and discharging currents according to some specifications through the communication protocol with the charger or inverter. You can also use a general contactor, but for 10 such batteries I think you will have a very high cost. The variant in which the contactors are individual and are controlled independently of each other also has the advantage that it disconnects and connects smaller amounts of battery (a bank of 16 cells only) and implicitly modifies the charging and discharging current with smaller values without making the charging/discharging equipment make great efforts to compensate.
