HV and LV Contactor help

somfas

Hey guys, thanks for your help so far. I still cannot figure out what I need to get to finish out the plans for this build. Any help is appreciated.

I have a custom 72V EZGO TXT with Alltrax 72500 controller. I am converting to 10 leaf Modules and using an EVMS3 with 2 10 cell BMS modules. The EVMS3 does a few things differently than the BMS16 (or whatever most of you guys have been able to use).

Here are a few things I think I know:

Contactors may work better than relays in my setup due to the higher voltage

MZJ-400A is a cheaper alternative than the Gigavac for the same result

Ian said I MUST use a 12V contactor for the EVMS3

Ian said I MUST use a 80V contactor because the high voltage will burn a 12v

Single contactor is best setup, while using the Alltrax for HV and LV cutoff

LV trigger on single contactor setup will keep charger from charging the pack

EVMS3 must have constant 12v supply, but it goes into auto sleep mode after 5 minutes and shuts down pack power which shuts power to the DC down convertor

So, I am confused. I am sure Ian said it correctly, but the way I read it I am confused if I need a 12v or 80v contactor. Also confused about the other items above.

Again, thanks for your help on this

BGW

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cricketo

Yeah, lots of confusing stuff.

Contactors vs relays is about current, not voltage. You can use a relay (typically rated 40A and less) if you're going to use it to interrupt an existing contactor via its coil circuit. If you're going to wire it in series with the load, then you must use a contactor suitable for that load's current.

You need a contactor or relay that is rated for 12v at coils. Then depending on how you're wiring the thing into the rest of the setup will dictate whether you need a contactor or relay. Basically if you're planning to have your load in-line with it, then you need a contactor that can handle appropriate voltage and current at contacts. If you're going to wire it in-line with your existing contactor's coils, then you can use a relay.