Only thing that can be behind main relay is relay
Solar relays cant be behind relay
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no, BMS is allowed to be behind power switch
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, but…. see BMS section below
Precharge:
precharge ‘behind’ main power switch on positive side; is this ok?
forest: 'its the equivalent
him: every time u add relays in parallel, you double the effect of reliability
you are not allowed to have more than 2 relays that protect the battery pack
precharge is only needed for motors, not solar or other things
steve: “if you put precharge with the motor switch, you’ve done both in one go”
you do need to have a dedicated switch for the motor (and ‘anything else that's needed’ like MOV stuff but doesn’t apply to us)
forest: ‘if we put precharge somewhere else (e.g. isolated DCDC), then can we avoid putting in a relay?’
e.g. on industry EVs, LV
you can’t pre-charge with AUX
in sec 8.2.C.3, it says that ‘supplemental battery cannot provide motive power to the vehicle’
fsfs
‘I haven't seen a car with less than 4 relays’
2 for batt, 1 for solar, 1 for motor
so you can’t have a pre-charge on the main relay, cuz then that reduces reliability of
‘you can’t put pre-charge on the main contactor'
why?
diode could fail
precharge could short out
‘at least doubles the unreliability of the relay you’re working around, because you’ve added a second device that is supposed to be carrying much less current, but is capable of failing'
‘how does adding a second relay in series make anything worse'
steve: 'you can figure that out
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‘the battery protection system shouldn’t be dissipating any power from the battery pack'
‘if your BPS isn’t powered off DCDC or AUX that’s a problem'
Power path:
easiest way to select between DCDC and AUX is to just have DCDC be higher voltage than AUX and use a diode
ICs and stuff is ok, but
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